BNL, Upton, Long Island, New York, USA
Stony Brook University, Stony Brook, USA
Two SRF photoemission electron guns are under development at BNL. The first gun operates at 704 MHz and is design to deliver high bunch charge and high average current beams for the R&D ERL accelerator. Its cavity is of an elliptical geometry. The gun cryomodule has been commission without a cathode up to the design voltage of 2 MV. The experiments with a copper cathode are underway. The second gun utilizes a quarter wave resonator geometry with coaxial cathode insert and beam tube RF power coupler. It will be used to produce high bunch charges, but low average beam currents for the coherent electron cooling proof-of-principle experiment. This 112 MHz SRF gun was first tested two years ago. Since then it was rebuilt in a new cryomodule and cryogenically re-tested in late 2012/early 2013, reaching the accelerating gap voltage of 0.9 MV. This paper describes main design features of two SRF guns, presents test results and discusses future plans.
BNL, Upton, Long Island, New York, USA
Stony Brook University, Stony Brook, USA
Niowave, Inc., Lansing, Michigan, USA
SBU, Stony Brook, New York, USA
A short 22-MeV linac under development at BNL will provide high charge, low repetition rate beam for the coherent electron cooling demonstration experiment in RHIC. The linac will include a 112 MHz SRF gun and a 704 MHz five-cell accelerating SRF cavity. The paper describes the two SRF systems, discusses the project status, first test results and schedule.
BNL, Upton, Long Island, New York, USA
Stony Brook University, Stony Brook, USA
ANL, Argonne, USA
A search for the QCD Critical Point has renewed interest to electron cooling ion beams in RHIC at energies below 10 GeV/nucleon. The electron cooling will utilize bunched electron beams form an SRF linac at energies from 0.9 to 5 MeV. The SRF linac will consist of two quarter wave structures: a photoemission electron gun and a booster cavity. In this paper we present preliminary design consideration of this SRF linac.
Muons, Inc, Illinois, USA
SLAC, Menlo Park, California, USA
A high brightness superconducting radio frequency (SRF) photoinjector gun cavity has been developed to a level ready for construction. The design aims to prevent operational limitations encountered with existing concepts.
HZDR, Dresden, Germany
JLAB, Newport News, Virginia, USA
In order to improve the gradient of the cavity and the beam quality of the gun, a new design for the SRF photo injector at the Helmholtz-Zentrum Dresden-Rossendorf has been developed. Apart from the special design of the cavity itself – as presented at SRF09, Berlin – the next update will include a separation of input and output of the liquid nitrogen supply system. This is supposed to increase the stability of the nitrogen pressure and enable a better monitoring of its temperature. The implementation of a superconducting solenoid inside the cryomodule is another major improvement. The position of this solenoid can be adjusted with a high precision using two independent step motors, which are thermally isolated from the solenoid itself. The poster will present the progress of turning the first design models into reality.
HZDR, Dresden, Germany
JLAB, Newport News, Virginia, USA
MBI, Berlin, Germany
A lot of the future electron accelerator projects such like ERLs, high power FELs and also some of the new collider designs rely on the development of particle sources which provide them with high average beam currents at high repetition rates, while maintaining a low emittance. SRF photo injectors represent a promising concept to give just that, offering the option of a continuous wave operation with high bunch charges. Nevertheless, emittance compensation for these electron guns, with the goal to reach the same level as normal conducting sources, is an ongoing challenge. The poster is going to discuss several approaches for the 3-1/2-cell SRF gun installed at the accelerator facility ELBE at the Helmholtz Center Dresden-Rossendorf including the installation of a superconducting solenoid within the injector’s cryostat and present the currently used method to determine the beam’s phase space.
BNL, Upton, Long Island, New York, USA
Stony Brook University, Stony Brook, USA
The 704 MHz superconducting RF gun for the R&D ERL project is under comissioning at BNL. Since last November, the SRF gun has been conditioned and demonstrated an operational accelerating voltage of 2 MV (an accelerating gradient of 23.5 MV/m). Preparations for the cathode insertion are in final stages and we expect the gun to generate the first electron beam this summer. This paper discusses the BNL SRF gun system,and the results of the SRF gun commissioning.
Bergische Universität Wuppertal, Wuppertal, Germany
JLAB, Newport News, Virginia, USA
Enhanced field emission (EFE) from particulate contaminations and surface irregularities is one of the main field limitations of the superconducting Nb cavities required for XFEL and ILC. While the number density of particulate emitters can be reduced by dry ice cleaning (DIC) and clean room assembly, the optimum choice of crystallinity and polishing are still under discussion [1]. For the future ILC cavities, large or even single crystal Nb with a combination of BCP and EP is considered. Therefore, we have systematically investigated the EFE of single crystal Nb samples which got the same total polishing depth 136-138 μm but a different EP/BCP ratio (5.80, 2.40, 0.73, 0.15) and DIC by means of correlated optical/AFM profilometry, field emission scaning microscopy (FESM) and high-resolution SEM. Depending on the surface roughness (Ra < 200 nm), field enhancement factors b of 12 – 42 and emitting areas S up to 0.1 μm² were obtained. High current conditioning (μA - mA) of these emitters usually resulted in a slight reduction of b (factor < 2) but a strong increase of S. The influence of the surface roughness on the EFE and conditioning of the remaining emitters will be discussed.
[1] Reschke et al., Phys. Rev. ST Accel. Beams 13, 071001-1 (2010)
BINP SB RAS, Novosibirsk, Russia
HZB, Berlin, Germany
KEK, Ibaraki, Japan
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
HZDR, Dresden, Germany
Electron multipacting is still observed in the Rossendorf SRF gun which limits the cavity fields (accelerating gradient). To better understand this process, a three-cell 1.3 GHz elliptical-shape cavity with cathode was modeled in CST Studio Suite® 2013 at the University of Rostock. All parameters are provided by Helmholtz-Zentrum Dresden-Rossendorf. The multipacting simulations have been performed with CST Microwave Studio® (CST MWS) [1] and CST Particle Studio® (CST PS) which is suitable and powerful for 3D electromagnetic designs and provides the most advanced model of secondary emission. The radio frequency fields are calculated using the frequency domain solver of CST MWS, whereas the CST PS is used for particle tracking simulation [2]. The purpose of these numerical simulations is to better comprehend multipacting in the Rossendorf SRF gun and make a detailed analysis. The midterm goal is to find a new cavity shape, which might suppress the electron amplification so that the SRF Gun will be able to operate up to an accelerating gradient of 50 MV/m.
#eden.tulu@uni-rostock.de
[1] CST AG, Bad Nauheimer Str. 19, D-64289 Darmstadt, Germany
[2] F. Hamme, U. Becker and P. Hammes, Proc. of ICAP 2006, Chamonix, France
BNL, Upton, Long Island, New York, USA
HZB, Berlin, Germany
Stony Brook University, Stony Brook, USA
The Brookhaven Energy Recovery Linac (ERL) is operated as R&D setup for high-current, high charge electron beams. It is comprised of a superconducting (SC) five-cell cavity and a half-cell SC photoinjector electron RF gun. Achieving the performance objectives requires effective HOM damping in the linac and gun cavity. Among the HOM dampers being developed is a beam-tube type HOM load for the electron gun consisting of a ceramic break surrounded by ferrite tiles. This design is innovative in its approach and achieves a variety of ends including broadband HOM damping and protection of the superconducting cavity from potential damage of the separately cooled ferrite tiles. The damper properties are described by the coupling impedance to a beam and the external Q to constrain the unloaded mode Q’s. Measured results for the gun damper at room and superconducting temperatures are presented