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| WEPIK087 | Measurement and Characterization of Cable Losses for High Voltage Coaxial Cables Used in Kicker Systems | 3131 |
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| In the framework of CERN's LHC Injector Upgrade, simulation models for kicker pulse generators have been improved. A key element in the conventional pulse generators, among many others, are the high voltage coaxial cables. Since they can have significant impact on the waveform characteristics, an accurate cable model for simulation is crucial for reliable results during development. For this purpose, precise measurements of scatter parameters have been carried out in order to improve existing simulation models. Specialized high voltage cables, sometimes SF6 gas filled, used in various CERN kicker systems are usually large, heavy, not very flexible and often only one end is easy accessible. In addition, the impedance of these cables is rarely of 50 Ohms, which presents an extra difficulty. This paper describes the methods that have been defined and used to measure any kind of coaxial structures relying on S11 parameters exclusively. Measurements for various specialized cable types are presented and compared with their improved models. The implications for overall kicker system performance are briefly discussed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK087 | |
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| WEPIK098 | Resonant Kicker System With Sub-part-per-million Amplitude Stability | 3174 |
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| High stability resonant kicker magnet systems have been developed as part of the fast electron beam switching system of Swiss Free Electron Laser (SwissFEL). They are designed to separate two closely spaced electron bunches (28 ns apart) accelerated in one RF macro-pulse and to send them to two separate undulator lines. High shot-to-shot amplitude stability is required to minimize the disturbance of the electron beam trajectories and to ensure stable X-ray lasing. The stability and speed was unlikely to be achieved by standard pulsed systems and a novel 18 MHz, lumped-element resonator deflector with high Q was developed. It is driven into resonance by a specialized pulsed RF driver. At resonance, the circulating currents can approach 300 A and the resulting magnetic field gives the required deflection to the electron bunches. The advanced DC offset measurement system is also described in this paper. The measured stability reached less than 1 ppm (10e-6) rms, well within the project requirements. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK098 | |
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| WEPVA023 | Performance of the PS Injection Kicker System Short Circuit Mode Upgrade for Operation with 2 GeV LIU Beams | 3308 |
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| In the framework of the LHC Injector Upgrade (LIU) project an upgrade of the existing PS proton injection kicker system for 2 GeV operation is in progress. The upgrade is based on the operation of the existing kicker system in short circuit mode. This paper briefly reviews the deployed modifications to the system to obtain the specified reduction of pulse reflections unavoidably induced by such a configuration. The implementation of improvements to the magnet entry box, transmission cables and the short circuit plug with integrated LC-filter are described as well as tests and measurements during the 2016/17 annual shutdown. The impact of the residual pulse shape structure on the beam performance for the reference LIU beam is quantified. The paper concludes with a performance analysis, a comparison of measurements vs. simulations and an outlook to the remaining modifications during the next long shut down. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA023 | |
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| WEPVA024 | Design of an Inductive Adder for the FCC Injection Kicker Pulse Generator | 3312 |
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| The injection system for a 100 TeV centre-of-mass collider is an important part of the Future Circular Collider (FCC) study. Due to issues with conventional kicker systems, such as self-triggering and long term availability of thyratrons and limitations of HV-cables, innovative design changes are planned for the FCC injection kicker pulse generator. An inductive adder (IA) based on semiconductor (SC) switches is a promising technology for kicker systems. Its modular design, and the possibility of an active ripple suppression are significant advantages. Since the IA is a complex device, with multiple components whose characteristics are important, a detailed design study and construction of a prototype is necessary. This paper summarizes the system requirements and constraints, and describes the main components and design challenges of the prototype IA. It outlines the results from simulations and measurements on different magnetic core materials as well as on SC switches. The paper concludes on the design choices and progress for the prototype to be built at CERN. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA024 | |
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| WEPVA047 | Input Signal Generation for Barrier Bucket RF Systems at GSI | 3359 |
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| At the GSI facility in Darmstadt, Germany, Barrier Bucket RF systems are currently designed for the SIS 100 synchrotron (part of the future FAIR facility) and the Experimental Storage Ring (ESR). The purpose of these systems is to provide single sine voltage pulses at the cavity gap. Due to the high requirements regarding the gap signal quality, the calculation of the pre-distorted input signal plays a major role in the system development. A procedure to generate the input signal based on the dynamic properties in the linear region of the system has been developed and tested at a prototype system. It was shown that this method is able to generate single sine gap signals of high quality in a wide voltage range. As linearity can only be assumed up to a certain magnitude, nonlinear effects limit the quality of the output signal at very high input levels. An approach to overcome this limit is to extend the input signal calculation to a nonlinear model of the system. In this contribution, the current method to calculate the required input signal is presented and experimental results at a prototype system are shown. Additionally, first results in the nonlinear region are presented. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA047 | |
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| WEPVA056 | Development of an Induction Accelerator Cell Driver Utilizing 3.3 kV SiC-MOSFETs | 3388 |
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A novel synchrotron called an induction synchrotron (IS) was developed at KEK in 2006*. In the IS, charged particles are accelerated by pulse voltages driven by switching modulators employing high-speed semiconductor switches. As the switches are turned on and off by gate signals corresponding to the revolution frequency of the ion bunches, switching frequency reaches up to MHz order. The switching power supply (SPS) that generates bipolar pulses is one of the key technologies for the DA. The rating of SPS is roughly 2.5kV-20A-1MHz. To accomplish these requirements, we adopted 7 series connected Si-MOSFET for the switching devices of the 1st generation SPS. However it was too large and complicated for the future practical accelerator driver. Therefore we started to develop the next generation of SPS utilizing silicon carbide (SiC) devices, since they have inherently excellent properties such as high breakdown electric field high drift velocity, and high thermal conductivity**. In this paper, we describe the pulse switching test results of a prototype SiC-MOSFET and the test results of the prototype SPS.
* K. Takayama et al., Phys. Rev. Lett., 98, no.5, pp.054801(1)-054801(4) (2007). **H. Okumura, Japanese J. Appl. Phys. vol.45, no.10A, pp. 7565-7586, Oct. 2006. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA056 | |
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| WEPVA059 | Construction of the New Septum Magnet Systems for PF-Advanced Ring | 3398 |
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| From July 2016 we are constructing a new beam transport (BT) line for the Photon Factory Advanced Ring (PF-AR). The new BT line was designed to transport the full energy 6.5-GeV beam directly from the LINAC, and the top up injection will be possible for the PF-AR. We designed and produced new pulsed septum magnet systems for this project. Two pulsed septum magnets are used for the injection of the 6.5-GeV beam. The septum magnets were constructed with a passive type magnet, a copper eddy current shield and a silicon steel magnetic shield. The magnetic fields of these magnets have been measured by the search coil method. We paid attention to evaluating eddy current losses of the SUS beam duct in the magnetic field measurement. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA059 | |
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| WEPVA060 | Construction of the New Kicker Magnet Systems for PF-Advanced Ring | 3401 |
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| From July 2016 we are constructing a new beam transport (BT) line for the Photon Factory Advanced Ring (PF-AR). The new BT line was designed to transport the full energy 6.5-GeV beam directly from the LINAC, and the top up injection will be possible for the PF-AR. We designed and produced new kicker systems for this project. Three kicker magnets are used for the injection of the 6.5-GeV beam. The kicker magnets were designed as a window frame type ferrite core magnet. The magnetic fields of these magnets have been measured by the search coil method. We paid attention to evaluating eddy current losses of the metal coated ceramic duct in the magnetic field measurement. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA060 | |
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| WEPVA064 | The Pulsed Power Supplies of the SESAME Booster and Storage Ring | 3415 |
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| SESAME the Synchrotron Radiation Light Source in Allan (Jordan) consists of an 800 MeV injector (original from BESSY I, Berlin, Germany) and a 2.5 GeV Storagering. Injection into the Booster is done by an electrostatic Septum and one stripline kicker. Extraction out of the Booster is done by means of a bumper magnet, a strip-line-line kicker and a direct driven in-vacuum septum. Injection into the Storagering is done by a direct driven out-off vacuum septum and one kicker. The pulses of all septa are full sine, the ones of the kicker half sine with exception of the extraction kicker (flat-top). Extraction Kicker and Storage ring injection kicker are switched by Thyratron, all others via transistors. This report describes the injection and extraction optics and the results of the commissioning. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA064 | |
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| WEPVA077 | Design of the Control System of Pulsed Power Supplies for WHMM Injection Bump Magnets | 3442 |
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| The injection bump system of the synchrotron of the Wuwei Heavy-ion Medical Machine(WHMM) consists of four horizontal bump magnets to merge the injection beam with the circulating beam. In order to control the injection beam with sufficient accuracy, the bump mag-nets need four pulsed power supplies with high speed, precision, reliability. The power supplies, whose IBGT (Insulated Gate Bipolar Transistor) are working in the linear area, are required to output the maximum current of 2900A. Furthermore, the current pulse is activated by synchronous triggering events, the current pulse frequen-cy is required about 30Hz, and that the pulse current falling edge should be less than 60us. In this paper, a control system for the pulsed power supplies was described in details. The commissioning results showed that the control system owned high reliability and flexible and that beam could be injected effectively into the synchrotron of the WHMM. In addition, one on-line current pulse waveform is shown in the result section. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA077 | |
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| WEPVA094 | Study of an Improved Beam Screen Design for the LHC Injection Kicker Magnet for HL-LHC | 3471 |
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| During Run 1 of the LHC, one of the injection kicker magnets (MKIs) occasionally exhibited an excessively high ferrite temperature, caused by coupling of the high intensity beam to the real impedance of the magnet. Beam-screen upgrades have been very effective in reducing beam coupling impedance during Run 2. However, temperature measurements during LHC operation have shown that one end of the MKIs ferrite yoke is consistently hotter than the other: this effect is due to highly non-uniform beam induced power deposition along the kicker. Electromagnetic and thermal simulations show that part of the ferrite yoke will be above its Curie temperature when the LHC is operated with HL-LHC beam parameters, which could increase the turn-around time between fills of the LHC. An impedance mitigation study is presented in this paper with emphasis on the effect of the beam screen layout upon both total beam induced power deposition and its longitudinal distribution. Results of complex thermal simulations, to benchmark the effectiveness of the proposed schemes, are reported. To validate the proposed modification a test bench measurement was performed and preliminary results are discussed | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA094 | |
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| WEPVA095 | Preliminary Estimate of Beam Induced Power Deposition in a FCC-hh Injection Kicker Magnet | 3475 |
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| The Future Circular Collider for hadrons (FCC-hh) will require a fast injection kicker system that is highly reliable and that does not limit accelerator performance. Important considerations in the design of such a system are machine protection constraints, collider filling factor and hence rise and fall times of the kicker magnet field. Fast rise time kicker magnets are generally ferrite loaded transmission line type magnets with a rectangular shaped aperture. The beam coupling impedance of the kicker magnets is crucial, as this can be a dominant contribution to beam instabilities. In addition, beam-induced heating of the ferrite yoke due to the real component of the longitudinal beam coupling impedance needs to be controlled: if the ferrite temperature exceeds the Curie point this impacts the ability to inject beam and hence the availability of the machine. This paper presents estimates for the beam induced power deposition in the ferrite yoke, based on a calculated FCC beam spectrum and an analytical model of longitudinal impedance for unshielded kicker magnets. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA095 | |
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| WEPVA096 | Thermal Analysis of the LHC Injection Kicker Magnets | 3479 |
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Funding: Research supported by the HL-LHC project. The CERN Large Hadron Collider LHC is equipped with two fast pulsed magnet systems (MKIs) that inject particle beams coming from the injector chain. Operation with high intensity beams for many hours can lead to significant beam induced heating of the ferrite yokes of the MKIs. When the ferrite exceeds the Curie temperature of 125°C it loses its magnetic properties, preventing further injection until the ferrite cools down, potentially causing a delay of several hours. Hence important upgrades of the beam-screen were implemented after Run 1 of LHC. However, the High-Luminosity (HL) LHC will be operated with significantly higher intensity beams and hence additional measures are required to limit the ferrite temperature. These magnets operate under ultra-high vacuum conditions: convection is negligible and, as a result of low emissivity of the inside of the vacuum tanks, thermal radiation is limited. A detailed study of the thermal behaviour of these magnets is reported and compared with measurements. In addition several options to improve cooling of the ferrites are presented and analysed. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA096 | |
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| WEPVA097 | Upgrading the SPS Fast Extraction Kicker Systems for HL-LHC | 3483 |
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| The CERN SPS has two fast extraction systems, each consisting of travelling wave kicker magnets (MKEs). The beam induced heating in the ferrite yoke of these magnets was historically kept to an acceptable level by implementing water cooling of the kicker magnets: in addition serigraphy was applied on the surfaces of the ferrite yoke facing the beam. Nevertheless, high intensity beams needed in the future for HL-LHC will significantly increase the beam induced heating, potentially raising the MKE ferrite yoke temperature to its Curie point. Hence detailed studies of longitudinal beam coupling impedance were carried out to identify simple but effective methods of further reducing beam induced power deposition. Based on the results of these studies, and in the framework of the LHC Injectors Upgrade (LIU) project, an upgraded MKE kicker magnet was installed during the 2015-2016 shutdown. This paper reports and compares results of predictions, laboratory measurements, temperature measurements during SPS operation, and machine development studies. Measurements of both dynamic pressure rise in the upgraded magnet and Secondary Electron Yield, on samples, are also reported. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA097 | |
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| WEPVA098 | Measurements on a 12.5 kV Prototype Inductive Adder for the CLIC DR Extraction Kickers | 3487 |
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| The CLIC study is investigating the technical feasibility of an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The pre-damping rings and damping rings (DRs) will produce ultra-low emittance beam with high bunch charge. To avoid beam emittance increase, the DR kicker systems must provide extremely stable field pulses during injection and extraction of bunches. The DR extraction kicker system consists of a stripline kicker and two pulse modulators. The current specifications for the modulators call for pulses with 160 ns or 900 ns flattop duration of ±12.5 kV and 305 A, with ripple of not more than ±0.02 % (±2.5 V). An inductive adder is a very promising approach to meeting the specifications because analogue modulation methods can be applied to adjust the output waveform. Recently, the first full-scale, 20-layer, 12.5 kV prototype inductive adder has been assembled at CERN and testing has commenced. The goal is to tailor the output waveform of the prototype to the waveform required for the DR extraction stripline kicker. The results of the initial tests and measurements are presented. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA098 | |
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| WEPVA099 | Influence of Conducting Serigraphy Upon Field Pulse Shape of the SPS Extraction Kicker Systems | 3491 |
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| Fast pulsed magnets with ferrite yokes are used for beam extraction from the CERN SPS accelerator. These kickers are transmission line type magnets with a rectangular shaped aperture through which the beam circulates. Unless special precautions are taken, the beam impedance of the yoke can provoke significant induced heating, especially for high intensity beams. Previous upgrades of the SPS extraction kicker magnets have included silver fingers serigraphed on the surface of the ferrite facing the beam, to help shield the ferrite yoke from circulating beam. Beam based measurements of the extracted beam indicated that the serigraphy may influence the shape of the field pulse, causing it to increase slightly in magnitude during the flat-top. Hence theoretical studies have been carried out to determine whether the serigraphy influences the field pulse: these studies are reported in this paper. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA099 | |
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| WEPVA100 | Operational Experience of the Upgraded LHC Injection Kicker Magnets During Run 2 and Future Plans | 3495 |
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| During Run 1 of the LHC, one of the injection kicker magnets caused occasional operational delays due to beam induced heating with high bunch intensity and short bunch lengths. In addition, there were also sporadic issues with vacuum activity and electrical flashover of the injection kickers. An extensive program of studies was launched and significant upgrades were carried out during Long Shutdown 1 (LS 1). These upgrades included a new design of beam screen to reduce both beam coupling impedance of the kicker magnet and the electric field associated with the screen conductors, hence decreasing the probability of electrical breakdown in this region. This paper presents operational experience of the injection kicker magnets during the first years of Run 2 of the LHC, including a discussion of faults and kicker magnet issues that limited LHC operation. In addition, in light of these issues, plans for further upgrades are briefly discussed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA100 | |
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| WEPVA141 | Ion Cyclotron Resonance Heating Transmitter Opening Switch Upgrade | 3600 |
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| Diversified Technologies Inc. (DTI) has installed a high-power solid-state opening switch upgrade package to replace the mercury ignitron crowbars in the Ion Cyclotron Resonance Heating (ICRH) Transmitters at MIT Plasma Fusion Science Center's (PFSC) Alcator C Mod, a Tokamak-type fusion experimental device. The speed of the series opening switch avoids the large fault currents on the transformer and power feed inherent with a crowbar. This improvement enables re-optimization of the Transformer/Rectifier (T/R) set, ultimately allowing increased power output and increased tetrode reliability. The ratings of the prior high voltage power supply are a compromise between high output power (lower impedance required from the T/R set) and crowbar reliability (higher impedance required from the power supply to limit fault current). DTI's opening switch upgrade safely allows the use of significantly reduced transformer impedance and lower droop, giving increased power as well as improved tube protection. DTI's opening switch kit can readily be adapted to any similar transmitters as an upgrade from a crowbar. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA141 | |
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| WEPVA150 | New Controller for High Voltage Converter Modulator at Spallation Neutron Source | 3621 |
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Funding: This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. We have developed a new control system for the high voltage converter modulator at the Spallation Neutron Source to replace the original control system designed by Los Alamos National Laboratory which is approaching obsolescence. The new controller, based on national instruments PXI/FlexRIO FPGA hardware, offers enhancements over the original system such as modular construction, flexibility and non-proprietary software. The new controller also provides new capabilities like modulator pulse flattening, waveform capture & first fault detection. This paper will discuss the design of the system, including the human machine interface, based on lessons learned at the Spallation Neutron Source and other projects. It will also discuss performance and other issues related to operation in an accelerator facility which requires high availability. To date half of the high voltage converter modulators have been upgraded with the new controller with the remainder scheduled for completion by mid-2017. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA150 | |
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