IBIC2013 - Classification: BPMs and Beam Stability

Paper

Title

Page

Development of the Sirius RF BPM Electronics

63

D.O. Tavares, R.A. Baron, F.H. Cardoso, S.R. Marques, J.L.B. Neto, L.M. Russo
LNLS, Campinas, Brazil
A.P. Byszuk, G. Kasprowicz, A.J. Wojenski
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland

A BPM system has been developed for the new low emmitance 3 GeV Brazilian synchrotron light source, Sirius. The Sirius BPM electronics is a modular system based on a PICMG(R) MicroTCA.4 platform using ADC mezzanine cards in ANSI/VITA 57.1 FMC form factor and standalone RF front-end boards. It has been designed under the CERN Open Hardware License (OHL) in a collaboration between Brazilian Synchrotron Light Laboratory (LNLS) and Warsaw University of Technology (WUT). This paper presents: i) overall architecture of the BPM system; ii) performance evaluation of the first prototype of the BPM electronics comprehending beam current, filling pattern and temperature dependencies as well as resolution vs. beam current; and iii) preliminary results with beam at LNLS's UVX storage ring.

Poster MOPC09 [1.451 MB]

MOPC10

Optimization of NSLS-II Blade X-ray Beam Position Monitors: From Photoemission Type to Diamond Detector

67

P. Ilinski
BNL, Upton, Long Island, New York, USA

Optimization of blade type X-ray Beam Position Monitors (XBPM) was performed for NSLS-II undulator IVU20. Blade material, conﬁguration and operation principle were analyzed. Optimization is based on calculation of the XBPM signal spatial distribution. Along with standard photo-emission blades, Diamond Detector Blade (DDB) was examined as XBPM signal source. Analyses revealed, that Diamond Detector Blade XBPM would allow to overcome drawbacks of the photo-emission type XBPMs.

MOPC12

Development of the New Electronic Instrumentation for the LIPAc/IFMIF Beam Position Monitors

71

A. Guirao, D. Jimenez, L.M. Martinez Fresno, J. Molla, I. Podadera
CIEMAT, Madrid, Spain

Funding: Work partially supported by the Spanish Ministry of Science and Innovation under project AIC10-A-000441 and AIC-A-2011-0654.
Among all the LIPAc/IFMIF accelerator diagnostics instrumentation, the Beam Position Monitors are a cornerstone for its operation. A new approach for the LIPAc/IFMIF beam position monitors acquisition electronics is proposed for the twenty BPM stations distributed along the accelerator. The new system under development is a fully digital instrumentation which incorporates automatic calibration of the monitors' signals and allows monitoring of both fundamental and second signal harmonics. The current state of the development and first experimental results of the system on the test bench will be presented.

MOPC13

Design of Cold Beam Position Monitor for CADS Injector II Proton LINAC

75

Y. Zhang, X.C. Kang, M. Li, J.X. Wu, G. Zhu
IMP, Lanzhou, People's Republic of China

Cold beam position monitor based on capacitive buttons are designed for Chinese Accelerator Driven System (CADS) Injector II proton LINAC. This LINAC is aiming to produce a maximum design current of 15 mA at the 10 MeV energy with an operating frequency of 162.5 MHz. Cold button BPM will be installed in the Cryomodule, which will be in the middle of the superconductor cavity and the superconductor magnet. Some special issues must be considered when designing a cold BPM: low-beta beam in the cryogenic environment, strong rf-field from the superconductor cavity and high magnetic field from the superconductor magnet. In this contribution, the status of cold BPM will be presented, focusing on the electromagnetic response for low-beta beams and mechanical design in the cryogenic environment.

MOPC14

Beam Position Monitors R&D for keV Ion Beams

78

S. Naveed, A.A. Nosych, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
S. Naveed, A.A. Nosych, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
A.A. Nosych, L. Søby
CERN, Geneva, Switzerland

Funding: Work supported by the EU within the DITANET and oPAC projects under contracts 215080 and 289485, HGF and GSI under contract VH-NG-328 and STFC under the Cockcroft Institute core grant ST/G008248/1.
Beams of cooled antiprotons at keV energies shall be provided by the Ultra-low energy Storage Ring (USR) at the Facility for Low energy Antiproton and Ion Research (FLAIR) and the Extra Low ENergy Antiproton ring (ELENA) at CERN's Antiproton Decelerator (AD) facility. Both storage rings put challenging demands on the beam position monitoring system as their capacitive pick-ups should be capable of determining the beam position of beams at low intensities and low velocities, close to the noise level of state-of-the-art electronics. In this contribution we describe the design and anticipated performance of BPMs for low-energy ion beams on the examples of the USR and ELENA orbit measurement systems. We also present the particular challenges encountered in the numerical simulation of pickup response at very low beta values and describe an experimental setup realized at the Cockcroft Institute for BPM callibration. Finally, we provide an outlook on how the implementation of faster algorithms for the simulation of BPM characteristics could potentially help speed up such studies considerably.

MOPC16

FPGA Based Fast Orbit Feedback Data Acquisition System for Electron and Hadron Storage Rings

82

G. Schünemann, P. Hartmann, D. Schirmer, G. Schmidt, P. Towalski, T. Weis
DELTA, Dortmund, Germany

In the course of a BMBF supported development of a fast orbit feedback system for electron and hadron storage rings, in prospect of the upcoming FAIR facility, this paper presents the developed data acquisition system, based on Field Programmable Gateway Array (FPGA) technology, as well as the first results of in-situ measurements. Data was successfully taken at the TU-Dortmunds synchrotron light source DELTA as well as hadron storage rings COSY of the Forschungszentrum Jülich (FZJ) and SIS18 of the GSI Helmholtzzentrum für Schwerionenforschung GmbH (GSI).

MOPC17

Calibration of a Non-Linear Beam Position Monitor Electronics by Switching Electrode Signals

85

M. Gasior
CERN, Geneva, Switzerland

Button electrode signals from beam position monitors embedded into new LHC collimators will be individually processed with front-end electronics based on compensated diode detectors and digitized with 24-bit audio-range ADCs. This scheme allows sub-micrometre beam orbit resolution to be achieved with simple hardware and no external timing. As the diode detectors only operate in a linear regime with large amplitude signals, offset errors of the electronics cannot be calibrated in the classical way with no input. This paper describes the algorithms developed to calibrate the offset and gain asymmetry of these nonlinear electronic channels. Presented algorithm application examples are based on measurements performed with prototype diode orbit systems installed on the CERN SPS and LHC machines.

MOPC18

Development of a High Dynamic Range Beam Position Measurement System Using Logarithmic Amplifiers for the SPS at CERN

89

J.L. Gonzalez, T.B. Bogey, C. Deplano, J.-J. Savioz
CERN, Geneva, Switzerland

A new Front-End electronics, based on Logarithmic Amplifiers, is currently being developed for the CERN SPS Multi Orbit POsition System (MOPOS). The aim is to resolve the multi-batch structure of the beams and cope with their large intensity range (> 70 dB). Position and intensity signals are digitized in the Front-End electronics installed in the tunnel. The data are then transmitted over a serial fibre-optic link to a VME Digital Acquisition board located in surface buildings. A first prototype, equipped with a calibration system, has been successfully tested on the SPS under different beam conditions, including single bunch, 25ns and 50ns bunch trains. The system architecture and the first beam measurements are reported in this paper.

Poster MOPC18 [4.013 MB]

MOPC19

Status of the Beam Position Monitors for LIPAc

93

I. Podadera, F.M. De Aragon, A. Guirao, D. Jimenez, A. Lara, L.M. Martinez, J. Molla
CIEMAT, Madrid, Spain

Funding: Work partially supported by the Spanish Ministry of Science and Innovation under project AIC10-A-000441 and AIC-A-2011-0654.
The LIPAc accelerator will be a 9 MeV, 125 mA CW deuteron accelerator which aims to validate the technology that will be used in the future IFMIF accelerator. Several types of Beam Position Monitors BPM’s- are placed in each section of the accelerator to ensure a good beam transport and minimize beam losses. Prototypes of almost all the BPM’s have been already fabricated. Acceptance tests have been carried out on each device. The output of the vacuum leak tests and electrical tests will be analyzed in this contribution. In addition, the test bench to characterize the BPM’s has been upgraded and validated using some prototypes in order to obtain a better global measurement accuracy of the electrical center offset. The test bench can be used to crosscheck the simulations with the real response of each BPM. The result of the comparison will be discussed in detail.

MOPC20

Application of Metal-Semiconductor-Metal (MSM) Photodetectors for Transverse and Longitudinal Intra-Bunch Beam Diagnostics

97

R.J. Steinhagen
CERN, Geneva, Switzerland
M.J. Boland
SLSA, Clayton, Australia
T.G. Lucas, R.P. Rassool
The University of Melbourne, Melbourne, Australia
T.M. Mitsuhashi
KEK, Ibaraki, Japan

The performance reach of modern accelerators is often governed by the ability to reliably measure and control the beam stability. In high-brightness lepton and high-energy hadron accelerators the use of optical diagnostic techniques for this purpose is becoming more widespread as the required bandwidth, resolution and high RF beam power level involved limit the use of traditional electro-magnetic RF pick-up based methods. This contribution discusses the use of fibre-coupled ultra-fast Metal-Semiconductor-Metal Photodetectors (MSM-PD) as an alternative, dependable means to measure signals deriving from electro-optical and synchrotron-light based diagnostics systems. It describes the beam studies performed at CERN's CLIC Test Facility (CTF3) and the Australian Synchrotron to assess the feasibility of this technology as a robust, wide-band and sensitive technique for measuring transverse intra-bunch and bunch-by-bunch beam oscillations, longitudinal beam profiles, un-bunched beam population and beam-halo profiles. The used amplification schemes, achieved sensitivities, linearity, and dynamic range of the detector setup are presented.

Poster MOPC20 [3.065 MB]

MOPC21

Layout of the BPM System for p-LINAC at FAIR and the Digital Methods for Beam Position and Phase Monitoring

101

M.H. Almalki, G. Clemente, P. Forck, L. Groening, W. Kaufmann, P. Kowina, C. Krüger, R. Singh
GSI, Darmstadt, Germany
W. Ackermann
TEMF, TU Darmstadt, Darmstadt, Germany
M.H. Almalki
IAP, Frankfurt am Main, Germany
M.H. Almalki
KACST, Riyadh, Kingdom of Saudi Arabia
B.B. Baricevic, R. Hrovatin, P.L. Lemut, M. Znidarcic
I-Tech, Solkan, Slovenia
C.S. Simon
CEA/DSM/IRFU, France

The planned Proton LINAC at the FAIR facility will provide a beam current from 35 to 70 mA accelerated to 70 MeV by novel CH-type DTLs. Four-fold button Beam Position Monitor (BPM) will be installed at 14 locations along the LINAC and some of these BPMs are mounted only about 40 mm upstream of the CH cavities. The coupling of the RF accelerating field to the BPMs installed close to the CH cavities was numerically investigated. For the digital signal processing using I/Q demodulation a 'Libera Single Pass H' is foreseen. The properties of this digitization and processing scheme were characterized by detailed lab-based tests. Moreover, the performance was investigated by a 80 μA Ne⁴⁺ beam at 1.4 MeV / u and compared to a time-domain approach and successive FFT calculation. In particular, concerning the phase determination significant deviations between the methods were observed and further investigations to understand the reason are ongoing.

Poster MOPC21 [1.622 MB]

MOPC22

A New High-Dynamic Range BPM for ELBE with Integrated Differential Current Monitor (DCM)

104

A. Büchner, B. Lange
HZDR, Dresden, Germany

ELBE is a LINAC electron accelerator for small energies (12 to 50 MeV). It serves as a beam source for many quite different experiments. The recent ELBE upgrade allows electron beams with bunches in the range of single electrons to 1 nC. The maximum beam current is 1.6 mA CW and the repetition rates covering the range from one shot single bunch pulses to 26 MHz CW. The existing BPMs and especially the DCMs which are used for the Machine Protection System cannot handle this wide parameter range. To improve this situation the development of new BPMs / DCMs was necessary. The DCMs measure the difference of the beam current between two stripline sensors and produce an interlock for differences greater 10 microamps. The new BPM electronics system has been designed including the DCM functionality because both BPMs and DCMs use the same stripline sensor signals at 1.3 GHz.

MOPC24

Design Of The Stripline BPM For The Advanced Photoinjector Experiment

108

S. De Santis, M.J. Chin, D. Filippetto, W.E. Norum, Z. Paret, G.J. Portmann, F. Sannibale, R.P. Wells
LBNL, Berkeley, California, USA

Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
We describe the design, bench testing, and initial commissioning of the shorted striplines beam position monitors used in the Advanced Photoinjector Experiment (APEX) at Lawrence Berkeley National Laboratory. Our BPM's are characterized by extreme compactness, being designed to fit in the vacuum chamber of the quadrupole magnets, with only a short portion including the RF feedthroughs occupying additional beam pipe length. In this paper we illustrate the design process, which included extensive 3D computer simulations, the bench testing of prototype and final components, and the first measurements with beam. The readout electronics is also described.

MOPC25

About BPMS to be Used for PAL-XFEL

112

H. J. Choi, H.-S. Kang, C. Kim, S.H. Kim, S.J. Lee, S.J. Park, H. Yang
PAL, Pohang, Kyungbuk, Republic of Korea

Pohang Accelerator Laboratory (PAL) has been building the X-Ray Free Electron Laser (XFEL), a fourth-generation accelerator, and the construction will be complete in 2015. To successfully construct the XFEL, PAL built an injection test facility (ITF) in 2012, and the facility is in operation. The ITF examines the efficiency of various diagnostic units through extended tests. A BPM is a diagnostic unit that measures the position of an electron bunch. There are various kinds of BPM, and they have different merits and demerits. A user can select any kind of BPM that is appropriate for their purpose, and install it after going through various design and production processes. In order to measure the position of an electron bunch, a cavity BPM is installed at an undulator of PAL-XFEL and a stripline BPM is installed at an accelerator. The efficiency of the stripline BPM was tested at the ITF. The X-band cavity BPM was produced and is being tested at the ITF. This paper aims to introduce the specification and properties of the cavity BPM and stripline BPM to be installed at PAL-XFEL, and explain the physical concept and the way of measuring necessary for designing a stripline pickup.

MOPC26

Optimization of Bunch-to-Bunch Isolation in Instability Feedback Systems

116

D. Teytelman
Private Address, San Jose, USA

Bunch-by-bunch feedback formalism is a powerful tool for combating coupled-bunch instabilities in circular accelerators. Imperfections in the analog front and back ends lead to coupling between neighboring bunches. Such coupling limits system performance in both feedback and diagnostic capacities. In this paper, techniques for optimizing bunch-to-bunch isolation within the system will be presented. A new method for improving the performance of the existing systems will be described. The novel approach uses a "shaper" filter in the digital signal processor to compensate for the imperfect response of the power amplifier and kicker combination. An objective optimization method to derive the optimal back end configuration will be presented and illustrated with measurements from several accelerators.

Poster MOPC26 [0.851 MB]

MOPC27

Cavity Beam Position Monitor System for ATF2

120

S.T. Boogert
Royal Holloway, University of London, Surrey, United Kingdom
S.T. Boogert, F.J. Cullinan, Y.I. Kim, A. Lyapin, J. Snuverink
JAI, Egham, Surrey, United Kingdom
T. Tauchi, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
G.R. White
SLAC, Menlo Park, California, USA

The Accelerator Test Facility 2 (ATF2) in KEK, Japan, is a prototype scaled demonstrator system for the final focus required for a future high energy lepton linear collider. The ATF2 beam-line is instrumented with a total of 38 C- and S- band resonant cavity beam position monitors (CBPM) with associated mixer electronics and digitizers. The current status of the BPM system is described, including a study of the CBPM performance over a three week period, including systematic effects such as charge, bunch length and beam offset dependence. The BPM system is routinely used for beam based alignment, wakefield kick measurements and dispersion measurements, the operational experience and example measurements are also reported.

MOPC28

The Hardware Implementation of the CERN SPS Ultrafast Feedback Processor Demonstrator

124

J.E. Dusatko, J.M. Cesaratto, J.D. Fox, J.J. Olsen, C.H. Rivetta
SLAC, Menlo Park, California, USA
W. Höfle
CERN, Geneva, Switzerland

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research program ( LARP)
An ultrafast 4GSa/s transverse feedback processor has been developed for proof-of-concept studies of feedback control of e-cloud driven and transverse mode coupled intra-bunch instabilities in the CERN SPS. This system consists of a high-speed ADC on the front end and equally fast DAC on the back end. All control and signal processing is implemented in FPGA logic. This system is capable of taking up to 16 sample slices across a single SPS bunch and processing each slice individually within a reconfigurable signal processor. This demonstrator system is a rapidly developed prototype, consisting of both commercial and custom-design components. It can stabilize the motion of a single particle bunch using closed loop feedback. The system can also run open loop as a high-speed arbitrary waveform generator and contains diagnostic features including a special ADC snapshot capture memory. This paper describes the overall system, the feedback processor and focuses on the hardware architecture, design and implementation.

Poster MOPC28 [1.684 MB]

MOPC29

Realization of Transverse Feedback System for SIS18/100 using FPGA

128

T. Rueckelt
Technische Universität Darmstadt (TU Darmstadt), Signal Processing Group, Darmstadt, Germany
M. Alhumaidi, T. Rueckelt, A.M. Zoubir
TU Darmstadt, Darmstadt, Germany

Higher beam intensities in particle accelerator are usually prevented by beam instabilities. To cure these instabilities, additional active system must be used besides passive damping. For this purpose, we have developed a distributed low-latency Transverse Feedback System (TFS) using FPGAs. Data acquisition takes place on multiple BPMs with individual FPGAs and ADCs around the accelerator ring. Acquired data is compressed and sent over broadband fiber optic wires to a central unit. For synchronization, data is tagged using timestamps from a reference time, which is distributed by a specially constrained network time protocol to obtain cycle accuracy. The central unit provides an FIR filter for system bandwidth limitation, and an adaptive IIR filter for stable beam signal rejection. Feedback is given using a linear combination of the pre-processed BPM signals. The system provides substantial flexibility, due to the possibility to configure most parameters online. Filters, feedback sources and parameters, compression rate and more can be adapted via Ethernet interface, which also supplies analysis data. First results are shown.

Poster MOPC29 [1.842 MB]

TUBL1

NSLS-II BPM and Fast Orbit Feedback System Design and Implementation

316

O. Singh, B. Bacha, A. Blednykh, W.X. Cheng, J.H. De Long, A.J. Della Penna, K. Ha, Y. Hu, B.N. Kosciuk, M.A. Maggipinto, J. Mead, D. Padrazo, I. Pinayev, Y. Tian, K. Vetter, L.-H. Yu
BNL, Upton, Long Island, New York, USA

The National Synchrotron Light Source II is a third generation light source under construction at Brookhaven National Laboratory. The project includes a highly optimized, ultra-low emittance, 3 GeV electron storage ring, linac pre-injector and full energy booster synchrotron. The low emittance requires high performance beam position monitor systems, providing measurement to better than 200 nm resolution; and fast orbit feedback systems, holding orbit to similar level of orbit deviations. The NSLS-II storage ring has 30 cells, each deploying up to 8 RF BPMs and 3 fast weak correctors. Each cell consists of a "cell controller", providing fast orbit feedback system infrastructure. This paper will provide a description of system design and summarize the implementation and status for these systems.

Slides TUBL1 [5.225 MB]

TUBL2

A 4 GS/s Feedback Processing System for Control of Intra-Bunch Instabilities

323

J.D. Fox, J.M. Cesaratto, J.E. Dusatko, J.J. Olsen, K.M. Pollock, C.H. Rivetta, O. Turgut
SLAC, Menlo Park, California, USA
W. Höfle
CERN, Geneva, Switzerland

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research program ( LARP)
We present the architecture and implementation overview of a digital signal processing system developed to study control of Electron-Cloud and Transverse Mode coupling instabilities in the CERN SPS. The system is based on a reconfigurable processing architecture which samples vertical bunch motion and applies correction signals at a 4 GS/s rate, allowing 16 samples across a single 5 ns SPS RF bucket. The system requires wideband beam pickups and a vertical kicker structure with GHz bandwidth. This demonstration system implements a general purpose 16 tap FIR control filter for each sample. We present results from SPS machine studies showing the impact of wideband feedback to excite/damp internal modes of vertical motion as well as stabilize an unstable beam. These results highlight the challenges of intra-bunch feedback and show proof of principle feasibility of the architecture.

Slides TUBL2 [12.154 MB]

TUBL3

A Multiband-Instability-Monitor for High-Frequency Intra-Bunch Beam Diagnostics

327

R.J. Steinhagen
CERN, Geneva, Switzerland
M.J. Boland, T.G. Lucas
The University of Melbourne, Melbourne, Australia

To provide the best possible luminosity, even higher beam intensities are needed in the Large Hadron Collider (LHC) and in its injector chain. This is fundamentally limited by self-amplifying beam instabilities, intrinsic to unavoidable imperfections in accelerators. Traditionally, intra-bunch or head-tail particle motion is measured using fast digitizers, which even using state-of-the-art technology are limited in their effective intra-bunch position resolution to few tens of um in the multi-GHz regime. Oscillations at this scale cause partial or total loss of the beam due to the tight transverse constraints imposed by the LHC collimation system. To improve on the present signal processing, a prototype system has been designed, constructed and tested at the CERN Super-Proton-Synchrotron (SPS) and later on LHC. The system splits the signal into multiple equally-spaced narrow frequency bands that are processed and analysed in parallel. Working with narrow-band signals in frequency-domain permits the use of much higher resolution analogue-to-digital-converters that can be used to resolve nm-scale particle motion already during the onset of instabilities.

Slides TUBL3 [3.165 MB]

TUPC07

Design and Impedance Optimization of the SIRIUS BPM Button

365

H.O.C. Duarte, S.R. Marques, L. Sanfelici
LNLS, Campinas, Brazil

Design of several BPM Buttons is presented with detail impedance, heat transfer and mechanical analysis. Special attention is given to the application of ceramics as materials with low relative permittivity inside of the BPM Button and to the geometric shape of the BPM Button. The heat dissipation is evaluated based on the loss factor calculated for a 2.65mm bunch length. The narrow-band impedance is discussed and its dependence on applied ceramic materials is compared.

Poster TUPC07 [1.715 MB]

TUPC08

Design and Impedance Optimization of the LNLS-UVX Longitudinal Kicker Cavity

369

L. Sanfelici, H.O.C. Duarte, S.R. Marques
LNLS, Campinas, Brazil

Performance evolution of parameters achieved during the electromagnetic design of the longitudinal kicker cavity for the LNLS UVX storage ring is presented. The effort on the electromagnetic optimization process of the heavily loaded cavity has been made to reach the required electrodynamic parameters of the kicker. The results for three different geometries are compared and a good compromise between the longitudinal shunt impedance and the effect of the longitudinal Higher Order Modes (HOM’s) on beam stability has been found.

Poster TUPC08 [1.365 MB]

TUPC09

Longitudinal and Transverse Feedback Systems for the BEPCII Storage Rings

373

J. Yue, J.S. Cao, L. Ma, Y.F. Sui, L. Wang, X.Y. Zhao
IHEP, Beijing, People's Republic of China

In order to cure the transverse and longitudinal coupled bunch instabilities caused by higher order modes of RF cavities and resistive wall impedance in the BEPCII storage rings, two type bunch by bunch feedback system – a longitudinal feedback system and a transverse feedback system are used. The LFB system are digital system produced by Dimtel Company, the longitudinal kicker is drift-tube type borrowed from SLAC. An analog bunch-by-bunch transverse feedback system was designed and used*. The main components are two sets of beam oscillation detectors, betatron phase adjuster, notch filter and stripline kicker. This paper will describe the achieved results of curing the coupled bunch instabilities by using the LFB and TFB together with current status.
* Performance of the Transverse Coupled-Bunch Feedback System in the BEPCII Storage Ring, Proc. of 40th ICFA ABDW, 2008

Poster TUPC09 [0.356 MB]

TUPC10

Operation of Diamond Light Source XBPMs with Zero Bias

376

C. Bloomer, G. Rehm
Diamond, Oxfordshire, United Kingdom

Tungsten blade X-ray Beam Position Monitors (XBPMs) have been used at Diamond Light Source since 2007, however a long-standing problem with these devices has been the growth of leakage current through the ceramic insulation within the XBPMs over time, often becoming greater than 10% of the signal current after a few years of operation. The growth of these leakage currents has been found to be exacerbated by the application of a negative bias (-70V) to the tungsten blades, a bias suggested for optimum position sensitivity. This bias is applied in order to accelerate free electrons away from the surface of the blades and to prevent cross-talk, however, we have found that the operation of the XBPMs without bias has negligible impact on our measurements. Removal of the bias has been found to prevent the growth of leakage currents over time, and can also significantly reduce the cost of our signal acquisition by removing the need for a low-current amplifier with a bias supply.

Poster TUPC10 [0.455 MB]

TUPC11

Beam-Based Measurement of ID Taper Impedance at Diamond

380

V.V. Smaluk, R. Bartolini, R.T. Fielder, G. Rehm
Diamond, Oxfordshire, United Kingdom

New insertion devices (IDs) are being designed now for a Diamond upgrade. One of the important topics of the design is the coupling impedance of the ID vacuum chamber movable tapers. To get a complete and reliable information of the impedance, analytical estimations, numerical simulation and beam-based measurement have been performed. The impedance of an existing ID taper geometrically similar to the new one has been measured using the orbit bump method. It turns out that in spite of the small magnitude (a few um) of orbit distortion to be observed in this case, the BPM resolution is sufficient for this measurement. The measurement results in comparison with simulation data are discussed in this paper.

TUPC12

Status of the Stripline Beam Position Monitor Development for the CLIC Drive Beam

384

A. Benot-Morell, L. Søby, M. Wendt
CERN, Geneva, Switzerland
A. Benot-Morell, A. Faus-Golfe
IFIC, Valencia, Spain
J.M. Nappa, S. Vilalte
IN2P3-LAPP, Annecy-le-Vieux, France
S.R. Smith
SLAC, Menlo Park, California, USA

Funding: MINECO contract FPA2010-21456-C02-01, SEIC-2010-00028, U.S. Department of Energy contract DE-AC02-76SF00515
In collaboration with SLAC, LAPP and IFIC, a first prototype of a strip-line Beam Position Monitor (BPM) for the CLIC Drive Beam and its associated readout electronics has been successfully tested in the CLIC Test Facility linac (CTF3) at CERN. In addition, a modified prototype with downstream terminated strip-lines is under development to better suppress any unwanted RF signal interference. This paper presents the results of the beam tests, the most relevant design aspects for the modified strip-line BPM version and its expected performance.

Poster TUPC12 [1.729 MB]

TUPC13

System Overview and Design Considerations of the BPM System of the ESS Linac

388

H. Hassanzadegan, A. Jansson, R. Zeng
ESS, Lund, Sweden
A.J. Johansson
Lund University, Lund, Sweden
K. Strniša
Cosylab, Ljubljana, Slovenia
A. Young
SLAC, Menlo Park, California, USA

The ESS Linac will include in total more than 140 Beam Position Monitors of different sizes and types. The BPM system needs to measure the beam position, phase and intensity in all foreseen beam modes with a pulse rate of 14 Hz, duration of 2.86 ms and amplitude ranging form 5 mA to 62.5 mA. With respect to the BPM connection to the Machine Interlock System, the total response time must be less than 10 us. The signal level variations from one BPM to another along the Linac should be as small as possible to meet the requirements on the analog gain of the front-end electronics and the dynamic range of the digitizer card input. The other requirement is that the BPM system needs to give at least a rough estimation of the beam position and phase, even if the beam is significantly debouched, ex. during the Linac tuning phase. These requirements and their impact on the design of the BPM detector, the analog front-end electronics and the selection of the digitizer card are discussed in this paper along with a general description of the BPM system.

Poster TUPC13 [3.050 MB]

TUPC14

Development of a Low-Beta Button BPM for PXIE Project

392

A. Lunin, N. Eddy, T.N. Khabiboulline, V.A. Lebedev, V.P. Yakovlev
Fermilab, Batavia, USA

The button BPM is under development for a low beta section of the Project X Injector Experiment (PXIE) at Fermilab. The presented paper includes an analytical estimation of the BPM performance as well a direct wakefield simulation with CST Particle Studio (on a hexahedral mesh). In addition we present a novel approach of a low beta beam interaction with BPM electrodes realized with ANSYS HFSS TD-solver on unstructured tetrahedral mesh. Both methods show a good agreement of BPM output signals for various beam parameters. Finally we describe the signal processing scheme and the electronics we are going to use.

Poster TUPC14 [1.051 MB]

TUPC15

BPM Electronics Upgrade for the Fermilab H⁻ Linac Based Upon Custom Downconverter Electronics

396

E.S.M. McCrory, N. Eddy, F.G.G. Garcia, S.U. Hansen, T. Kiper, M.Z. Sliczniak
Fermilab, Batavia, USA

As part of the Fermilab Proton Improvement Plan, the readout electronics for the Fermilab H⁻ Linac has been upgraded. The new custom electronics provide a low cost solution to process the 2nd harmonic of the RF at 402.5MHz. A single 4 channel NIM-bin module is used to readout each 4 plate stripline BPM pickup with each module being locked to an external 805MHz machine reference from the low level RF. For each BPM a number of measurements are provided including average horizontal and vertical position, average intensity, and average relative phase for variable pulse lengths from a few μs up to 50~usec. The system is being exploited in a number of ways with new operations applications.

Poster TUPC15 [1.731 MB]

TUPC16

Bunch-by-Bunch Feedback and Diagnostics at BESSY II

399

A. Schälicke, F. Falkenstern, R. Müller
HZB, Berlin, Germany

At the light source BESSY II new digital bunch-by-bunch feedback systems have been put into operation in January 2013, replacing the existing analog as well as the obsolete digital systems. From the first days of operation the new system successfully suppresses transverse and longitudinal beam instabilities in wide range of machine parameters. The system offers also many new diagnostics opportunities, these include the analysis of instability modes, measurement of the feedback loop gain, and determination of the transfer function. A method to systematically optimise the output amplifier response function with the help of shaper coefficients for the optimal bunch separation has been developed. In addition the analysis of the input data stream allows a passive determination of machine properties like betatron and synchrotron frequencies as well as the longitudinal phases for every bunch. The integration of external triggers permits the analysis of postmortem data, the characterisation of beam-loss events, and monitoring of the injection process. In this contribution first operational experience, the developed data analysis techniques and experimental data will be presented.

Poster TUPC16 [56.767 MB]

TUPC17

A Multiconductor Transmission Line Model for the BPMs at the 3-50 Beam Transport Line in J-PARC

403

T. Toyama, D.A. Arakara, M. Tejima
KEK, Ibaraki, Japan
K. Hanamura
Mitsubishi Electric System & Service Co., Ltd, Tsukuba, Japan
Y. Hashimoto, K. Satou
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

We have developed an accurate and efficient analysis method with a multi-conductor transmission line model. This method combines the two-dimensional electrostatic analysis including beams in the transverse plane and the transmission line analysis in the longitudinal direction. The loads are also included in the boundary condition of the transmission line analysis. Calculation of 2D electrostatic fields can be easily performed with the boundary element method. Taking low frequency limit of the formula, we have obtained an accurate expectation of the BPMs of 200 mm diameter at the 3-50 Beam Transport Line in J-PARC.

TUPC18

Development of a Highly Efficient Energy Kicker for Longitudinal Bunch-by-Bunch Feedback

407

M. Masaki, T. Fujita, K. Kobayashi, T. Nakamura, H. Ohkuma, M. Oishi, S. Sasaki, M. Shoji
JASRI/SPring-8, Hyogo-ken, Japan

A highly efficient energy kicker has been developed for longitudinal bunch-by-bunch feedback to suppress synchrotron oscillation of a high-current single electron bunch, and to cure possible longitudinal multi-bunch instability if lower beam energy is to be adopted for emittance reduction and electric power saving in a future upgrade plan of SPring-8. Through the performance test using a prototype kicker, a new water-cooled copper kicker was designed and fabricated, and it has been installed in the storage ring. The new kicker consists of three cells with each cavity length of 96 mm, its resonant frequency of 1.65 GHz, which is 3.25 times of RF frequency of the storage ring, and low Q-factor of 4.2. In beam kick test, the synchrotron oscillation amplitude of 0.64 ps was excited by kick voltage with continuous amplitude modulation at synchrotron frequency when the RF input power was 132 W/3cells. The kick voltage evaluated from the experimental result is 920 V/3cells. Shunt impedance of each kicker cell is estimated as 1.1 kΩ. As we intended, the shunt impedance per length is about three times higher than those of widely used waveguide overloaded cavity type kickers.

Poster TUPC18 [9.117 MB]

TUPC19

First Beam Tests of a Prototype Cavity Beam Position Monitor for the CLIC Main Beam

411

F.J. Cullinan, S.T. Boogert, A. Lyapin, J.R. Towler
JAI, Egham, Surrey, United Kingdom
W. Farabolini, T. Lefèvre, L. Søby, M. Wendt
CERN, Geneva, Switzerland

Beam position monitors (BPMs) throughout the CLIC (Compact Linear Collider) main linac and beam delivery system must routinely operate at 50 nm resolution and be able to make multiple position measurements within a single 156 ns long bunch train. A prototype cavity beam position monitor, designed to demonstrate this performance, has been tested on the probe beamline of CTF3 (the CLIC Test Facility). Sensitivity measurements of the dipole mode position cavity and of the monopole mode reference cavity have been made. The characteristics of signals from short and long bunch trains and the dominant systematic effects have also been studied.

TUPC20

Technologies and R&D for a High Resolution Cavity BPM for the CLIC Main Beam

415

J.R. Towler, T. Lefèvre, L. Søby, M. Wendt
CERN, Geneva, Switzerland
S.T. Boogert, F.J. Cullinan, A. Lyapin
JAI, Egham, Surrey, United Kingdom

The Main Beam (MB) LINAC of the Compact Linear Collider (CLIC) requires a beam orbit measurement system with a high spatial (50 nm) and high temporal (50 ns) resolution to resolve the beam position within the 156 ns long bunch train, traveling on an energy-chirped, minimum dispersive trajectory. A 15 GHz prototype cavity BPM has been commissioned in the probe beam-line of the CTF3 CLIC Test Facility. The performance and technical details of this prototype installation are discussed in this paper, including the 15 GHz analog down-converter, the data acquisition and the control electronics and software. An R&D outlook is given for the next steps, which requires a system of 3 cavity BPMs to investigate the full resolution potential.

TUPC22

Cavity Beam Position Monitor in Multiple Bunch Operation for the ATF2 Interaction Point Region

419

Y.I. Kim, D.R. Bett, N. Blaskovic Kraljevic, S.T. Boogert, P. Burrows, G.B. Christian, M.R. Davis, A. Lyapin, C. Perry
JAI, Oxford, United Kingdom
J.C. Frisch, D.J. McCormick, J. Nelson, G.R. White
SLAC, Menlo Park, California, USA
Y. Honda, T. Tauchi, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

The Accelerator Test Facility 2 (ATF2) at KEK, Japan, is a scaled test beam line for the international linear collider (ILC) final focus system. There are two goals: firstly, to demonstrate focusing to 37 nm vertical beam size; secondly, to achieve a few nanometer level beam orbit stability at the focus point (the Interaction Point (IP)) in the vertical plane. High-resolution beam position monitors around the IP area (IPBPMs) have been developed in order to measure the electron beam position in that region with a resolution of a few nanometers in the vertical plane. Currently, the standard operation mode at ATF2 is single bunch, however, multiple bunch operation with a bunch spacing similar to the one foreseen for the ILC (around 300 ns) is also possible. IPBPMs have a low Q value resulting in a decay time of about 30 ns, and so should be able to measure the beam position of individual bunches without any significant performance degradation. The IPBPMs in the ATF2 extraction beam line have been tested in multibunch regime. This paper analyses the signals, processing methods and results for this mode.

Poster TUPC22 [1.050 MB]

TUPC24

The Design Strategy of Orbit Feedback System in the TPS

423

C.H. Kuo, J. Chen, Y.-S. Cheng, P.C. Chiu, K.T. Hsu, K.H. Hu, C.Y. Wu
NSRRC, Hsinchu, Taiwan

TPS (Taiwan Photon Source) is a 3 GeV synchrotron light source which is being constructed at NSRRC. The BPM electronic is based on uTCA platform, is used for various request and function reasons. The orbit feedback system design is based on open structure, modularization and highly integration. There are many advantages that orbit feedback system is embedded in the BPM crate with FPGA modules. High throughput backplane, data transfer and processing support rich function for waveform record, diagnostic, beam study and transient analysis. The design and implementation result of the system will be reported in this conference.

TUPC25

Design of the SwissFEL BPM System

427

B. Keil, R. Baldinger, R. Ditter, W. Koprek, R. Kramert, F. Marcellini, G. Marinkovic, M. Roggli, M. Rohrer, M. Stadler, D.M. Treyer
PSI, Villigen PSI, Switzerland

SwissFEL is a Free Electron Laser (FEL) facility being constructed at PSI, based on a 5.8GeV normally conducting main linac. A photocathode gun will generate two bunches with 28ns spacing at 100Hz repetition rate, with a nominal charge range of 10-200pC. A fast beam distribution kicker will allow to distribute one bunch to a soft X-ray undulator line and the other bunch to a 0.1nm hard X-ray undulator line. The SwissFEL electron beam position monitor (BPM) system will employ three different types of dual-resonator cavity BPMs, since the accelerator has three different beam pipe apertures. In the injector and main linac (38mm and 16mm aperture), 3.3GHz cavity BPMs will be used, where a low Q of ~40 was chosen to minimize crosstalk of the two bunches*. In the undulators that just have single bunches and 8mm BPM aperture, a higher Q will be chosen. This paper reports on the development status of the SwissFEL BPM system. Synergies as well as differences to the E-XFEL BPM system** will also be highlighted.
* F. Marcellini et al., "Design of Cavity BPM Pickups For SwissFEL", Proc. IBIC'12, Tsukuba, Japan, 2012.
** B. Keil et al., "The European XFEL BPM System", Proc. IPAC'10, Kyoto, Japan, 2010.

Poster TUPC25 [1.074 MB]

TUPC26

Beam-line Diagnostics at the Front End Test Stand (FETS), Rutherford Appleton Laboratory, Oxfordshire, UK

431

G.E. Boorman, S.M. Gibson
Royal Holloway, University of London, Surrey, United Kingdom
G.E. Boorman, S.M. Gibson
JAI, Egham, Surrey, United Kingdom
R.T.P. D'Arcy, S. Jolly
UCL, London, United Kingdom
C. Gabor
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
S.R. Lawrie, A.P. Letchford
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

The H⁻ ion source and beam-line at FETS will require the beam current and beam position to be continually monitored. Current transformer toroids will measure the beam current and beam position monitors (BPM) will determine the beam position. The ion source delivers pulses at a rate of 50Hz with a current up to 60mA, each pulse is 2ms long, and a 324MHz micro-bunch structure imposed by the radio frequency quadrapole (RFQ) accelerating structure. The toroid outputs will be acquired on a fast oscilloscope. The BPM design is still under consideration (shorted strip-line or button type) but the processing for both types is similar and has been designed, with simulated measurements made. Each BPM uses four pickups, at a frequency of 324MHz, which are mixed using RF electronics to an intermediate frequency of 10.125MHz. The resulting signals are then digitized at 40.500MHz and processed in an FPGA to produce the position and phase of the beam at each BPM location, with a precision of better than 100μm and 0.05rad. The measurements from the toroids and BPMs will be via EPICS servers at every pulse.

Poster TUPC26 [0.660 MB]

TUPC28

Strip Line Monitor design for the ISIS Proton Synchrotron using the FEA program HFSS

435

S.J. Payne
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

This paper reports the development of a strip line monitor for the ISIS accelerator main ring. The strip line is still in the design phase and the work reported here is the results of the FEA programme HFSS. The strip line will eventually form part of a beam instability feedback system and will be used to control instabilities both in the current ISIS machine and for all future ISIS upgrades where higher intensities and energies could be realised. The strip line consists of two pairs of 550mm by 160mm broad flat electrodes configured to allow damping in both the horizontal and vertical planes. The paper describes the efforts to achieve a bandwidth of >260MHz which will allow the feedback system deal with instabilities such as those caused by electron clouds. Design of the electrodes including matching of the feed throughs to the electrodes , concerns of materials for the electrode supports are considered. Also considered are methods used to improved inter-electrode decoupling (to better than -30db) . Results in the form of scattering parameters, smith charts, time domain reflectivity and shunt impedances will be presented.

TUPC29

Grounded Coplanar Waveguide Transmission Lines as Pickups for Beam Position Monitoring in Particle Accelerators

438

A. Penirschke, A. Angelovski, R. Jakoby
TU Darmstadt, Darmstadt, Germany
C. Gerth, U. Mavrič, D. Nölle, C. Sydlo, S. Vilcins
DESY, Hamburg, Germany

Funding: The work was supported by the MSK group at DESY Hamburg. The authors would like to thank the CST AG for providing the CST Software Package.
Energy beam position monitors (EBPM) based on grounded co-planar waveguide (GCPW) transmission lines have been designed for installation in the dispersive sections of the bunch compressor chicanes at the European XFEL. In combination with beam position monitors at the entrance and exit of the bunch compressor chicanes, measurements of the beam energy with single bunch resolution are feasible. The EBPM consists of transversely mounted stripline pickups in a rectangular beam pipe section. The signal detection for the measurement of the phases of the pulses at each end of the pickups is based on the standard down-conversion and phase detection scheme used for the low-level RF-system. A measurement resolution within the lower micrometer range can be achieved for input signal reflections at the pickup of less than -25 dB at 3 GHz. In this paper, simulation results of a novel pickup geometry utilized with GCPW pickup structures and optimized transitions to perpendicular mounted coaxial connectors are presented. The simulation results exhibit small reflection coefficients with reflected signal components having less than 2% of the peak voltage signal.

TUPC30

Design of Strip-Line BPM for Large Thermal Stress Conditions

442

P.E. Evtushenko, F.E. Hannon
JLAB, Newport News, Virginia, USA
B. Wustmann
HZDR, Dresden, Germany

Jefferson Lab FEL operates DC photo gun and GaAs photocathode. Operation with average current of several mA and sufficiently long cathode lifetime requires pressure in the gun region at least at the 10^-11 Torr level or better. To achieve such low pressure the gun chamber and the adjacent beam line are baked for an extended period of time. This imposes an additional requirement of withstanding the bake on all diagnostic elements. Additionally, analyzing beam line temperature in a high current energy-recovering linac as ones considered for future light sources, it was found that due to the short bunch length the resistive wall losses can be very high, which can cause large thermal stress to the beam line elements. With these in mind we have designed a modified strip-line beam position monitor with a flexible connection between the stip-line electrode and the central pin of conflate mounted SMA feedthrough. The design is based on a BPM previously developed for radiation source ELBE. To make manufacturing of the BPM more precise and less costly, brazing is used in place of welding. Mechanical and microwave design of the BPM is presented with initial microwave characterization.

TUPC31

New Design of High Order Modes Electronics in MTCA.4 Standard for FLASH and the European XFEL

443

S. Bou Habib, A. Abramowicz
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
N. Baboi, H. Schlarb
DESY, Hamburg, Germany

At free-electron linear accelerators, various High Order Modes (HOM) - both monopole and dipole - are excited. Extensive studies at DESY have shown that monitoring and analysis of some of these modes can be used for different applications including Beam Position Monitors (BPMs) and the reduction of wake-fields, the measurement of the beam phase with-respect-to RF signal in cavities, and the measurement of cavity alignment in the 1.3 GHz cryo-modules. Three frequencies were chosen for further experiments: the 1.3 GHz base frequency from the klystron, the 1.7 GHz dipole mode and the 2.4 GHz monopole mode. In order to realize the monitoring and analysis requirements, very high resolution measurements in amplitude, phase and shape (time resolution) are required for all three frequencies simultaneously. In this paper, we present the new HOM electronics prototype including a microstrip and stripline RF tri-passband filter design and measurements and the specialized MTCA.4 Rear Transition Module for HOM measurements with an ultra-fast high-resolution AMC digitizer.

Poster TUPC31 [1.226 MB]

WEBL1

Beam Position Monitors: How to Meet the Specifications of Most Recent Accelerators

623

G. Decker
ANL, Argonne, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, under Contract No. DE-AC-02-06CH11357.
Modern particle accelerators must operate with increasingly restrictive beam stability requirements. Synchrotron light sources require sub-micron stability for time periods extending to one week and for frequencies up to 1 kHz and beyond, and FELs need similar levels of shot-to-shot reproducibility. A variety of beam position monitor (BPM) technologies used at synchrotron light sources, FEL facilities, and other accelerators will be reviewed and future areas of development outlined. This will include an overview of analog vs. digital downconversion, including data acquisition and processing techniques. Orbit and trajectory feedback systems using modern field-programmable gate array technology and dedicated fast data networks have been developed to take advantage of high-speed BPM data streams and will be described.

Slides WEBL1 [7.638 MB]

WEBL2

Applications of Stripline and Cavity Beam Position Monitors in Low-Latency, High-Precision, Intra-Train Feedback Systems

630

M.R. Davis, D.R. Bett, N. Blaskovic Kraljevic, P. Burrows, G.B. Christian, Y.I. Kim, C. Perry
JAI, Oxford, United Kingdom

Two, low-latency, sub-micron beam position monitoring (BPM) systems have been developed and tested with beam at the KEK Accelerator Test Facility (ATF2). One system (‘upstream’), based on stripline BPMs uses fast analogue front-end signal processing and has demonstrated a position resolution as low as 400nm for beam intensities of ~1 nC, with single-pass beam. The other (‘IP’) system, based on low-Q cavity BPMs and utilising custom signal processing electronics designed for low latency, provides a single pass resolution of approximately 100nm. The BPM position data are digitised by fast ADCs on a custom FPGA-based feedback controller and used in three modes: 1) the upstream BPM data are used to drive a pair of local kickers nominally orthogonal in phase in closed-loop feedback mode; 2) the upstream BPM data are used to drive a downstream kicker in the ATF2 final focus region in feedforward mode; 3) the IP cavity BPM data are used to drive a local downstream kicker in the ATF2 final focus region in closed-loop feedback mode. In each case the beam jitter is measured downstream of the final focus system with the IP cavity BPMs. The relative performance of these systems is compared.

Slides WEBL2 [1.934 MB]

WEBL3

Wake Field Monitors in a Multi Purpose X Band Accelerating Structure

634

M.M. Dehler, S. Bettoni, B. Beutner, G. De Michele
PSI, Villigen PSI, Switzerland
G. De Michele
EPFL, Lausanne, Switzerland
G. De Michele
CERN, Geneva, Switzerland

In a collaboration between CERN, PSI and Sincrotrone Trieste (ST), a series of four multipurpose X-band accelerating structures has been designed and fabricated. These feature integrated wake field monitors (WFMs), which are used to measure the alignment (offset and tilt) between structure and beam. One structure has recently been installed in the SwissFEL Injector Test facility (SITF) at PSI. The WFM front end electronics will be developed within the EuCard2 framework, so for the measurements described in this paper we used the raw WFM signals. We compare these measurements to the theoretical results obtained via an equivalent circuit model used in the design and numerical calculations. The beam tests show that by minimizing the WFM signals, the emittance dilution given by the transverse wakes, crucial because of the small aperture of the structure, is minimized as well.

Slides WEBL3 [1.668 MB]

WEPC07

Development of the RF Front End Electronics for the SIRIUS BPM System

670

R.A. Baron, F.H. Cardoso, S.R. Marques, J.L.B. Neto
LNLS, Campinas, Brazil
J.-C. Denard
SOLEIL, Gif-sur-Yvette, France

Tight stability requirements for new low emittance light sources, such as SIRIUS being built in Brazil, strongly depend on the BPM RF Front-End performance. Small nonlinearities, uneven temperature drifts and excess noise can spoil the performance of the whole digital BPM system and orbit correction. Calibration and temperature control schemes have been tested in order to suppress position measurement drifts during user beam delivery down to a fraction of micrometer. A method for measuring electronic component nonlinearities at mdB scale is also presented.

Poster WEPC07 [1.236 MB]

WEPC08

Vibration Measurement and its Effect on Beam Stability at NSLS2

674

W.X. Cheng, A.K. Jain, S. Krinsky, S.K. Sharma, C.J. Spataro
BNL, Upton, Long Island, New York, USA

Vibration measurements have been carried out at NSLS2. The floor has more than 100nm RMS vertical motion during workdays (>1Hz). This motion reduces to 30nm RMS during night and weekends. Traffic on the nearby expressway is considered to be the major source of ground motion. Weather (wind) and utility system induced vibrations are other possible factors on floor motion. Vibrations have been measured at various locations, like the tunnel and experiment floor, HXN long beamline satellite building floor, high stability BPMs, Quadrupole magnets etc. Assume a typical un-correlated motion of Quadrpole magnets of 100nm, beam orbit jitter is around 4-7 microns. Fast orbit feedback will control the orbit stability within 10% of beam size.

WEPC09

Performance of NSLS2 Button BPM

678

W.X. Cheng, B. Bacha, B.N. Kosciuk, S. Krinsky, O. Singh
BNL, Upton, Long Island, New York, USA

Several types of button BPMs are used in NSLS2 complex. Coaxial vacuum feedthroughs are used to couple the beam induced signal out. The feedthroughs are designed to match the external transmission line and electronics with characteristic impedance of 50 Ohm. Performances of these BPM feedthroughs are presented in this paper.

WEPC10

Capability Upgrade of the Diamond Transverse Multibunch Feedback

682

M.G. Abbott, G. Rehm, I.S. Uzun
Diamond, Oxfordshire, United Kingdom

We describe an upgrade to the Transverse Multi-Bunch Feedback processor used at Diamond for control of multi-bunch instabilities and measurement of betatron tunes. The new system will improve both feedback and diagnostic capabilities. Bunch by bunch selectable control over feedback filters, gain and excitation will allow finer control over feedback, allowing for example the single bunch in a hybrid or camshaft fill pattern to be controlled independently from the bunch train. It will also be possible to excite all bunches at a single frequency while simultaneously sweeping the excitation for tune measurement of a few selected bunches. The single frequency excitation can be used for bunch cleaning or continuous measurement of the beta-function. A simple programmable event sequencer will provide support for up to 8 steps of programmable sweeps and changes to feedback and excitation, allowing a variety of complex and precisely timed beam characterisation experiments including grow-damp measurements in unstable conditions.

Poster WEPC10 [0.427 MB]

WEPC11

Radiation Resistance Testing of Commercial Components for the New SPS Beam Position Measurement System

686

C. Deplano, J. Albertone, T.B. Bogey, J.L. Gonzalez, J.-J. Savioz
CERN, Geneva, Switzerland

A new Front-End (FE) electronics is under development for the SPS Multi Orbit POsition System (MOPOS). To cover the large dynamic range of beam intensities (70dB) to be measured in the SPS, the beam position monitor signals are processed using logarithmic amplifiers. They are then digitized locally and transmitted via optical fibers over long distances (up to 1km) to VME acquisition boards located in surface buildings. The FE board is designed to be located in the SPS tunnel, where it must cope with a radiation dose rate of up to 100 Gy per year. Analogue components, such as Logarithmic Amplifiers, ADC-Drivers and Voltage regulators, have been tested at PSI for radiation hardness, while several families of bidirectional SFP, both single-fiber and double-fiber, have been tested at both PSI and CNRAD. This paper gives a description of the overall system architecture and presents the results of the radiation hardness tests in detail.

Poster WEPC11 [3.299 MB]

WEPC12

Evaluation of Strip-line Pick-up System for the SPS Wideband Transverse Feedback System

690

G. Kotzian, W. Höfle, R.J. Steinhagen, D. Valuch, U. Wehrle
CERN, Geneva, Switzerland

The proposed SPS Wideband Transverse Feedback system requires a wide-band pick-up system to be able to detect intra-bunch motion within the SPS proton bunches, captured and accelerated in a 200 MHz bucket. We present the electro-magnetic design of transverse beam position pick-up options optimised for installation in the SPS and evaluate their performance reach with respect to direct time domain sampling of the intra-bunch motion. The analysis also discusses the achieved subsystem responses of the associated cabling with new low dispersion smooth wall cables, wide-band generation of intensity and position signals by means of 180 degree RF hybrids as well as passive techniques to electronically suppress the beam offset signal, needed to optimise the dynamic range and position resolution of the planned digital intra-bunch feedback system.

WEPC13

Optimisation of the SVD Treatment in the Fast Orbit Correction of the ESRF Storage Ring

694

E. Plouviez, F. Epaud, L. Farvacque, J.M. Koch
ESRF, Grenoble, France

The ESRF fast orbit correction system has been in operation since May 2012. The orbit correction scheme relies classically on the calculation of a correction orbit based on the SVD analysis of the response matrix of our 224 BPMs to each of our 96 correctors. The rate of the calculation of the corrections is 10 KHz; we use a PI loop achieving a bandwidth of 150Hz completed with a narrow band pass filter with extra gain at 50Hz. In order to make the best use of the correctors dynamic range and of the resolution of the calculation, it can be useful to limit the bandwidth of loop for the highest order vectors of the SVD, or even to totally remove some of these vectors from the correction down to DC. Removing some of the eigen vectors while avoiding that the loop becomes unstable usually increases a lot the complexity of the matrix calculations: we have developed an algorithm which overcomes this problem; The test of this algorithm is presented. We present also the beneficial effect at high frequency of the limitation of the gain of the correction of the highest SVD eigen vectors on the demand of the peak strength of the correctors and on the resolution of the correction calculation.

Poster WEPC13 [0.974 MB]

WEPC14

Development of High Precision Beam Position Monitor Readout System with Narrow Bandpass Filters for the KEKB Injector Linac Towards the SuperKEKB

698

R. Ichimiya, K. Furukawa, F. Miyahara, M. Satoh, T. Suwada
KEK, Ibaraki, Japan

The SuperKEKB accelerator complexes are now being upgraded to bring the world highest luminosity (L=8x10³⁵/cm²/s). Hence, the KEKB Injector Linac is required to produce: electron: 20 mm mrad (7GeV, 5nC), positron: 10 mm mrad (4GeV, 4nC). To achieve this, the accelerator components have to be aligned within ± 0.1mm (1 σ). BPM is essential instrumentation for Beam Based Alignment, and is required one magnitude better position resolution to get better alignment results. Since current BPM readout system using oscilloscopes has ~50um position resolution, we decided to develop high precision BPM readout system with narrow bandpass filters. It handles two bunches with 96ns interval and has a dynamic range between 0.1nC (for photon factory) to 10nC (positron primary). To achieve these criteria, we adopt semiconductor attenuators and optimized two-stage Bessel filters at 300MHz center frequency to meet both time and frequency domain constraints. To correct position drift due to gain imbalance during operation, calibration pulses are output to the BPM between beam cycles (20ms). The beam position and charge calculations are performed by onboard FPGA to achieve fast readout cycle.

Poster WEPC14 [3.039 MB]

WEPC15

Development of the Beam Position Monitors System for the LINAC of SPIRAL2

702

P. Ausset, M. Ben Abdillah, J. Lesrel, E. Marius
IPN, Orsay, France
T. Ananthkrishnan, S.K. Bharade, G. Joshi, P.D. Motiwala, C.K. Pithawa
BARC, Trombay, Mumbai, India
V. Nanal, R.G. Pillay
TIFR, Mumbai, India

The SPIRAL 2 facility will deliver stable heavy ion and deuteron beams at very high intensity, producing and accelerating light and heavy rare ion beams. The driver will accelerate between 0.15mA and 5 mA deuteron beam up to 20 MeV/u and q/A=1/3 heavy ions up to 14.5 MeV/u. It is being built on the site of the Grand Accelerator National d’Ions Lourds at CAEN (France) The accurate tuning of the LINAC is essential for the operation of SPIRAL2 and requires from the Beam Position Monitor (BPM) system the measurements of the beam transverse position, the phase of the beam with respect to the radiofrequency voltage and the beam energy. This paper addresses the advancement made during the last twelve months on the realization of the 22 BPM required for the SPIRAL 2 LINAC. The BPM sensors are now completed and tested. The design of the acquisition card for the BPM is given and will be described. The prototype card is now under test and the first results are given. The aim is to verify the main parameters: sensitivity, position and phase measurement and the appropriate behavior of the BPM acquisition card in all cases (pulsed, electrode signal reconstruction, interlock, post mortem)

WEPC16

The Design of BPM Electronic System for CSNS RCS

706

W. Lu, H.Y. Sheng, X.C. Tian, J.W. Zhao, Y.B. Zhao
IHEP, Bejing, People's Republic of China

A Beam Position Monitor (BPM) system has been designed for the Rapid Cycling Synchrotron (RCS) at the China Spallation Neutron Source (CSNS) to acquire beam position information. This article introduces the design and implementation of the BPM electronic system. The challenge of designing the BPM electronics is to acquire and process the signal with large dynamic range (5.8mV~32V) and changing width (80ns to 500ns). The analog circuit described in this paper, which is constructed of a single-stage operational amplifier and an analog switch, can cover the input signal with large dynamic range. Because of the minimum bunch length (80ns) and the requirement of position resolution, a 14 bit 250MHz ADC is adopted to digitize the signal. Besides, for BPM system, the demand of an accurate real-time position monitoring is mandatory. The algorithm developed in an FPGA is able to make Bunch-by-Bunch position calculation and Closed Orbit position calculation in real time. Also, some preliminary test results will be presented and discussed, which show that the resolution of Bunch-by-Bunch position is 0.8mm when the input signal is 5.8mV and the resolution of Closed Orbit position is 50um.

Poster WEPC16 [0.937 MB]

WEPC17

Design and Simulation of Beam Position Monitor for the CADS Injector I Proton Linac

710

Y.F. Sui, J.S. Cao, H.Z. Ma, Q. Ye, J. Yue
IHEP, People's Republic of China

Funding: Work supported by the National Natural Science Foundation of China (NO. 11205172)
Beam Position Monitors (BPM) based on both capacitive and stripline pick-ups are designed for the China Accelerator Driven Subcritical system (C-ADS) Injector I proton LINAC. The BPM will be installed to measure the transverse beam position in the LINAC, of which the beam parameters are listed as current 10mA, energy 10MeV and the repetition frequency 325MHz. This contribution presents the status of the BPM design development and focuses on the design of the pick-ups and CST Particle Studio simulation results, including impedance, sensitivity, time domain, frequency domain response, etc. The main goal of the simulation is optimization of the mechanical design.

WEPC18

Development of Compact Electronics Dedicated to Beam Position Monitors in Injectors and Boosters

713

G. Jug, M. Cargnelutti
I-Tech, Solkan, Slovenia
K.B. Scheidt
ESRF, Grenoble, France

The need for state-of-the-art electronics for data-acquisition and processing of BPM signals in Injector and/or Booster Synchrotrons is being addressed in a development that aims at making such system available with less complexity and yet fulfilling precisely the needs of such specific BPMs. The ESRF Booster Synchrotron uses 75 BPMs in its 300m circumference to measure the orbit along its acceleration cycle of 50 milliseconds for the electron beam from 0.2 to 6GeV. The 25 year old electronics of these BPMs are in need of replacement. While BPM developments in recent years have focused on devices for Storage Rings that face extreme requirements like sub-micron drift with time, beam intensity, etc. that result in complicated implementation schemes. This new development combines both the simplification in the measurement concept and the implementation of novelties like compact design integrating RF electronics, with power-over-Ethernet supply and passive cooling, a powerful System-on-Chip engine and easy communication via SCPI commands. This paper will present the full design concept and its aimed functionalities as a BPM device that should offer an excellent price/performance ratio.

WEPC19

Performance of Injection Beam Position Monitors in the J-PARC RCS

716

N. Hayashi, P.K. Saha
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
T. Toyama
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

It is important to monitor the injected beam trajectory and position into a synchrotron ring. In the J-PARC RCS, there are two specialized beam position monitors (BPM) in the first arc section in order to perform continuous monitoring. They detect the linac RF frequency 324 MHz or its second harmonics, these contributions quickly decrease after a few turns in the ring. Therefore, they are sensitive only just injected beam. The RCS adopts the multi-turn injection and transverse painting. These monitors are useful to check the beam behavior on-line.

WEPC20

Bunch Extension Monitor for LINAC of SPIRAL2 facility

720

R.V. Revenko, J.L. Vignet
GANIL, Caen, France

Funding: This work is funded in frame of CRISP project.
Measurements of the bunch longitudinal shape of beam particles are crucial for optimization and control of the LINAC beam parameters and maximization of its integrated luminosity. The non-interceptive bunch extension monitor for LINAC of SPIRAL2 facility is being developed at GANIL. The five bunch extension monitors are to be installed on the entrance of LINAC between superconducting cavities. The principle of monitor operation is based on registration of x-rays induced by ions of accelerator beam and emitted from thin tungsten wire. The monitor consists of two parts: system for wire insertion and positioning and x-ray detector based on microchannel plates. The prototype of detector has been developed and was tested using protons and heavy ions beams.

Poster WEPC20 [9.366 MB]

WEPC21

Design and Beam Test Results of Button BPMs for the European XFEL

723

D.M. Treyer, R. Baldinger, R. Ditter, B. Keil, W. Koprek, G. Marinkovic, M. Roggli
PSI, Villigen PSI, Switzerland
D. Lipka, D. Nölle, S. Vilcins
DESY, Hamburg, Germany

Funding: Swiss State Secretariat for Education, Research and Innovation
The European X-ray Free Electron Laser (E-XFEL) will use a total ~300 button BPMs along the whole accelerator, as well as 160 cavity BPMs. The pickups for the button BPMs have been designed by DESY, whereas the electronics has been developed by PSI. This paper gives an overview of the button BPM system, with focus on the RF front end electronics, signal processing, and overall system performance. Measurement results achieved with prototypes installed at FLASH/DESY and at the SwissFEL Injector Test Facility (SITF) are presented. The position noise obtained with button pickups in a 40.5 mm aperture beam pipe is as low as ~11 um at 20 pC bunch charge.

Poster WEPC21 [1.595 MB]

WEPC22

First Steps Towards a Fast Orbit Feedback at ALBA

727

A. Olmos, S. Blanch-Torné, Z. Martí, J. Moldes, M. Muñoz, R. Petrocelli, X. Serra-Gallifa
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
A. Gutierrez-Milla
UAB, Barcelona, Spain

An optimum performance of the ALBA facility requires a beam orbit stability on the sub-micron level up to frequencies in the 100 Hz range. The Fast Orbit FeedBack system (FOFB) is designed to achieve such a stability. After investigation of possible system architecture, a decision has been taken that exploits the available in-house hardware. This “low-cost” first stage FOFB will be an ideal test-bench to learn about beam stabilization and find possible problems and improvements on it. This report explains the current lay-out and status of the FOFB at ALBA.

Poster WEPC22 [3.107 MB]

WEPC23

Design of an Ultra-Compact Stripline BPM Receiver using MicroTCA for LCLS-II at SLAC

731

C. Xu, S. Babel, S. L. Hoobler, R.S. Larsen, J.J. Olsen, S.R. Smith, T. Straumann, D. Van Winkle, A. Young
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy under Contract Numbers DE-AC02-06CH11357 and DE-AC02-76SF00515
The Linac Coherent Light Source II (LCLS II) is a free electron laser (FEL) light source. LCLS II will be able to produce 0.5 to 77 Angstroms soft and hard x-rays. In order to achieve this high level of performance, the electron beam needs to be stable and accurate. The LCLS II stripline BPM system has a dynamic range of 10pC to 1nC beam charge. The system has a 3.5 micrometer resolution at 250pC beam charge in an one inch diameter stripline BPM structure. The BPM system uses the MicroTCA physics platform that consists of analog front-end (AFE) and 16-bit analog to digital convertor (ADC) module. The paper will discuss the hardware design, architecture, and performance measurements on the SLAC LINAC. The hardware architecture includes bandpass filter at 300MHz with 15 MHz band-width, and BPM calibration process without communicating with the CPU module. The system will be able to process multibunch beams with 40ns spacing.

Poster WEPC23 [1.769 MB]

WEPC24

Performance Measurements of the New X-Band Cavity BPM Receiver

735

A. Young, J.E. Dusatko, S. L. Hoobler, J.J. Olsen, T. Straumann
SLAC, Menlo Park, California, USA
C. Kim
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: Work supported by U.S. Department of Energy under Contract Numbers DE-AC02-06CH11357 and DE-AC02-76SF00515
SLAC is developing a new X-band Cavity BPM receiver for use in the LCLS-II. The Linac Coherent Light Source II (LCLS-II) will be a free electron laser (FEL) at SLAC producing coherent 0.5-77 Angstroms hard and soft x-rays. To achieve this level of performance precise, stable alignment of the electron beam in the undulator is required. The LCLS-II cavity BPM system will provide single shot resolution better than 50 nm resolution at 200 pC*. The Cavity BPM heterodyne receiver is located in the tunnel close to the cavity BPM. The receiver will processes the TM010 monopole reference cavity signal and a TM110 dipole cavity signal at approximately 11 GHz using a heterodyne technique. The heterodyne receiver will be capable of detecting a multibunch beam with a 50ns fill pattern. A new LAN communication daughter board will allow the receiver to talk to an input-output-controller (IOC) over 100 meters to set gains, control the phase locked local oscillator, and monitor the status of the receiver. We will describe the design methodology including noise analysis, Intermodulation Products analysis.
* Commissioning and Performance of LCLS Cavity BPMs, Stephen Smith, et al., Proc. of PAC 2009

Poster WEPC24 [0.251 MB]

WEPC25

Optimisation of a Split Plate Position Monitor for the ISIS Proton Synchrotron

739

C.C. Wilcox, J.C. Medland, S.J. Payne, A. Pertica, M.A. Probert
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

A new Beam Position Monitor (BPM) has been designed for the ISIS proton accelerator facility at the Rutherford Appleton Laboratory in the UK. The new monitor, which will be installed in the beam line to Target 1, is of a ‘split plate’ design which utilises two pairs of electrodes to allow the beam position to be measured simultaneously in the horizontal and vertical planes. Simulations carried out using the CST low frequency solver have highlighted the inaccuracies in the measured beam position caused by strong inter-electrode coupling in such a monitor. This coupling, along with imbalanced electrode capacitances, leads to reduced sensitivity to changes in beam position as well as producing a positional offset error. This paper describes how the problems associated with inter-electrode coupling have been removed with the addition of grounded rings placed between each of the four electrodes. The design and positioning of the rings also ensured that the four electrode capacitances were matched. The results are presented both as CST simulations of ‘thin wire’ beam position measurements and results from bench measurements of a prototype dual plane BPM.

WEPC26

Pickup Electrode Electrodynamics Investigation

742

A. Kalinin
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Waves induced in a pickup by beam were investigated on a large scale model, using 10ps step in coaxial line as beam, and a differentiating capacitive probe. The probe signal was observed at 20GHz oscilloscope. In each of the front and rear transverse gaps between pickup electrode and wall (button pickup), a shorter-than-gap bunch excites a ‘plain-wave’ packet which length is of the order of gap length over c. Two packets are spaced by electrode length over c. The packets propagate along the electrode to a coaxial connector. At this low impedance common point each of the packets partially reflects back and partially passes into the opposite gap. The voltage appearing on the impedance excites two TEM-wave packets: one propagates backwards, another one propagates forward through connector. The connector output is sum of two such packets spaced the same as two incident packets. The packets propagating backwards reflect from the electrode open end, come back to the summing point and generate output in similar way. The same processes occur in a pickup with single gap electrodes (stripline pickup). This phenomenological picture can be used as a guide in pickup design and simulation.

Poster WEPC26 [0.647 MB]

WEPC28

Bunch By Bunch Transverse Beam Position Observation and Analyze During Injection at SSRF

746

Y.B. Leng, Y.B. Yan, Y. Yang, R.X. Yuan, N. Zhang
SSRF, Shanghai, People's Republic of China

Funding: Work supported by National Science Foundation of China (No. 11075198)
Top-up operation has been performed at SSRF since Dec. 2012. Orbit disturbance every 10 minutes decreased the quality of synchrotron radiation. In order to minimize this disturbance the tilts and the timing of injection kickers need to be tuning carefully based on real beam information. A set of button type pick-up and a scope based IOC were employed to capture the transient beam movement with bunch by bunch rate during injection. Several sets of observation and analyze will be discussed in this paper.

FRWMJ1

SLAC LCLS Cavity BPM Upgrade Project

P. Krejcik
SLAC, Menlo Park, California, USA

Patrick summarized the experience of the SLAC LCLS X-Band (11.4 GHz) cavity BPM system, which has been in operation for several years. Even though the system meets the requirements, some of the original design ideas proved to be not optimal in practice, e.g. the ridged waveguide coupling between pickup and receiver, the pickup support structure, complex tuning of the BPM resonators, etc. Based on this experience Patrick presented a redesigned cavity-BPM pickup, with a loaded-Q ~2000. It now utilizes a waveguide-to coaxial transition, and semi-flexible coaxial cables to connect to the RF electronics. Detailed EM simulations, including an analysis of mechanical tolerances has been performed at SLAC, a prototype has been produced in collaboration with PAL (Pohang Accelerator Laboratory, South Korea). The new pickup design is also more relaxed on tolerances, thus the tight tuning requirements could be reduced. A prototype has been installed at LCLS, and the first beam tests are underway. There was a question addressed to the material, copper vs. Cu-plated stainless steel: SLAC has got years of experience brazing copper, so this is preferred material. The answer to another question, the x-y cross talk: 20dB before, 30dB after tuning.

Slides FRWMJ1 [1.023 MB]

FRWMJ2

LCLS-II Cavity BPMs Electronics

A. Young
SLAC, Menlo Park, California, USA

Andrew presented the related read-out electronics for the new LCLS X-Band cavity BPM pickup. It turned out that the waveguide mixers in the current system suffer from a bias voltage degradation, which alters the overall gain. These components are not anymore available, and start to cause a serious issue. The new read-out system with coaxial inputs is based on the same classical heterodyne RF downconverter schema and a digitizer to convert the IF to baseband, which actually is used in most cavity BPM implementations. The 3-channel (X, Y, REF) RF section is located in the tunnel, and includes a commercial communication interface for remote operations on attenuators, etc. A 4th spare channel is also located on the PCB. The LO, based on a commercial PLL board (?), and is phase-locked to the accelerator RF system. The 14-bit digitizer from Struck rests in a μTCA crate, located outside the tunnel. The RF board is made from a multilayer PCB, made from FR4, with embedded Rogers Duroid layers for the high frequency sections. The RF front-end provides ~80dB dynamic range, plus attenuator settings, and a NF=3dB. The IF section provides 34dB gain. In the following we shortly mentioned the pros and cons of a downconverter schema versus a simple diode detector. The common opinion is that the direct diode baseband detection results in substantially higher noise floor. It also was mentioned that the limited return loss of diodes (or input filters in case of a downconverter) might cause an unwanted asymmetries between the two arms of the cavity BPM outputs. Other discussion points where on the PLL. Great care has to be taken on the loop filter design, particular in case of fractional PLLs. A high frequency for the PLL should be considered, this would result in a lower phase noise. Is phase-locking to the accelerator RF beneficial? It may result in a better resolution measurement, but the resolution stops reacting to some systematic effects, and it is beneficial to keep it sensitive to have an indicator of the system health. In addition, unlocked LO is beneficial for model-independent methods applied to waveforms as the whole phase space is covered in that case.

Slides FRWMJ2 [0.745 MB]

FRWMJ3

Cavity Design Questions

M. Hansli
TU Darmstadt, Darmstadt, Germany

Matthias presented two cavity designs. His waveguide loaded 3 GHz monopole mode resonator is optimized as phase detector for low charge beams in a plasma wakefield experiment. We discussed his questions on the options of the waveguide-to-coaxial coupling, which often are very pragmatic, personal engineering solutions, sometimes just a matter of “taste”. His 2nd design was a dipole mode resonator, to be used as a Schottky pickup for FAIR (GSI). He shared some details on the optimization of the geometry, e.g. to maximize the R/Q. We agreed that he did a good job, and addressed most design issues very systematically.

Slides FRWMJ3 [0.191 MB]

FRWMJ4

Beam Position Monitors for the LUNEX5 Project

N. Hubert
SOLEIL, Gif-sur-Yvette, France

Nicolas presented the LUNEX5 project, a FEL, driven by either a conventional 400 MeV linac, or in future by a laser wakefield accelerator in a tuneable energy range 0.31GeV (called the COXINAL project). Both projects require BPMs for the orbit measurement. The requirements, presented by Nicolas, initiated a little discussion on stripline/button BPMs vs. cavity BPMs. In this case, with a required 530 um resolution (at 500 resp. 10pC bunch charge) in a 20mm diameter beam pipe, we suggested to go with striplines or even buttons. With respect to the laser wakefield acceleration, experience at CERN shows a high EMI near the experimental setup, from which any beam diagnostics may suffer.

Slides FRWMJ4 [0.502 MB]

FRWMJ5

Production of Cavity BPMs for the European XFEL

D. Lipka, D. Nölle, S. Vilcins
DESY, Hamburg, Germany

The DESY colleagues gave a comprehensive presentation of the large-scale cavity BPM system required for the XFEL (DESY), with most details are self-explaining by the slides. The XFEL cavity BPM pickup is based on a design from T. Shintake (Spring-8), a compact setup of waveguide loaded dipole mode and reference cavities, both utilizing a “magnetic”(loop) waveguide-to-coaxial transition for the signals. Both XFEL cavity BPM variants, for the beamline and the undulator, are made of stainless steel, to ensure a low-Q of ~70 (3.3GHz operating frequency), ensuring single bunch detection (bunch spacing 222ns). Details on the performance and manufacturing of the N-type feedthrough were given, which is based on a design of Shintake. Dirk went through the entire production process of the cavity BPMs, starting from the first prototypes until the full production series, which included some surprises. This contribution was very comprehensive, and most questions were answered by the presentation. On the cross coupling between the planes, Dirk mentioned better than 40dB!

Slides FRWMJ5 [1.025 MB]

FRWMJ6

Cavity BPM Activities at PSI

B. Keil
PSI, Villigen PSI, Switzerland

Boris reported on cavity BPM activities at PSI for various projects: Read-out electronics for FLASH and XFEL, and an entire cavity BPM system for the SwissFEL. He compared the requirements of the BPMs in the different areas of the accelerator, and presented the anticipated cavity BPM pickup and read-out solutions. Boris also showed the results from the prototype R&D at the SwissFEL Injector Test Facility, which included a different concept, with a direct analog downconversion to baseband, and a novel technique of ADC clock phase feedback to align ADC samples to the peak on the signal waveform. The resolution of the different prototype BPMs, achieved during the beam tests, range within a few 100nm, far better than the requirement. A very interesting side aspect mentioned by Boris, was the investigation of UHV coaxial feedthroughs for high frequencies. As everyone observes, the known niche companies increased their prices to the extreme, forcing the community to search for alternatives. Boris found a Swiss manufacturer, who now provides custom feedthroughs with acceptable UHV and RF properties (return loss >30dB@3GHz) at moderated to low costs. Very interesting!

Slides FRWMJ6 [2.044 MB]

FRWAJ1

The FERMI@Elettra Cavity BPM System

R. De Monte
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Raffaele gave a short introduction on the FERMI@Elettra FEL project and the related cavity BPM diagnostics system, most used along the two undulator areas. As of limited manpower resources, the 6.5GHz cavity BPM system builds as much as possible upon industrial components. The analog front-end solution is somewhat untypical, and generated some interesting discussion. Instead of the usual heterodyne downconverter, a hybrid based RF detector rectifies the signals in front of the μATCA-based digitizer. Phase shifters are used to zero calibrate the channels, as well as a calibration tone feed through the reference channel. The measured resolution is ~1.4μm, however, efforts to improve the resolution <0.5μm are underway. These include adding a downconvertor section into the signal processing. The pros and cons of this improvement were discussed rather controversial.

Slides FRWAJ1 [1.741 MB]

FRWAJ2

Low vs High Q Cavity BPMs

S.R. Smith
SLAC, Menlo Park, California, USA

Steve summarized the pros and cons of high vs. low Q cavity BPM pickups very comprehensively. He included a few real-world examples on mode-leakage, dynamic range and expected resolution by acquiring multiple samples of the waveform. The latter favors a high-Q BPM resonator, which he claims will improve the resolution, i.e. effective number of bits, by using more ADC samples n on the waveform by ln(n)/2. Other arguments of Steve on the Nyquist theorem and signal aliasing also favors the use of a high-Q BPM. Most colleagues followed his view: try to use a high-Q cavity BPM!

Slides FRWAJ2 [0.273 MB]

FRWAJ3

How short should the cavity resonator be?

V. Vogel
DESY, Hamburg, Germany

Vladimir discussed this question analytically, to better understand the resolution limit of a pill-box cavity BPM with respect to the bunch length and operation frequency. A good rule of thumb seems to be, try to make the length of the cavity resonator comparable to the bunch length. However, for accelerators with very short bunch length <<1mm, e.g. FEL drivers, this seems to be not applicable. In this case the presence of the signal component due to a beam angle cannot be avoided. Vladimir also presented the required suppression of unwanted modes to achieve 1nm resolution, which is in the order of 125135dB.

Slides FRWAJ3 [0.222 MB]

FRWAJ4

Experience on the ATF2 Cavity BPM System

S.T. Boogert
JAI, Egham, Surrey, United Kingdom
S.T. Boogert
Royal Holloway, University of London, Surrey, United Kingdom

Steward focused on the ATF2 cavity BPM relevant parts of his IBIC ATF2 beam diagnostics presentation. He summarized the experience on the BPM system over long operational periods, e.g. calibration, drifts, but discussed also the problems of large beam offsets, which are limiting the resolution. Of particular interest was his comparison of calculated and measured wakefield effects.

Slides FRWAJ4 [0.299 MB]

FRWAJ5

CBPM Waveform Deconvolution

F.J. Cullinan
JAI, Egham, Surrey, United Kingdom

Francis presented simulations on the deconvolution of the cavity BPM response to a single bunch from signals obtained for a bunch train stimulus, based on the CTF3 beam parameters. In this case the bunch spacing is always short compared to the decay time τ of the BPM resonator. He tried to resolve individual bunches by the deconvolution method. Applying a random position jitter along the bunch train, he compared a simple downconversion procedure and a combination of downconversion and deconvolution to the original beam position. The DDC/deconvolution method seems to better resolve the beam position along the bunch train. He finally presented his method on measured ATF2 data.

Slides FRWAJ5 [0.217 MB]

FRWAJ6

CBPM Principal Component Analysis

Y.I. Kim
JAI, Oxford, United Kingdom

Young-Im gave a short introduction on the principal component analysis (PCA). It makes use of an SVD analysis on the sampled waveform data on a single bunch measurement, and can explain the variance of the signal contents. She discussed some results obtained for heterodyne and homodyne receivers in a test setup at ATF2.

Slides FRWAJ6 [0.528 MB]