| Paper | Title | Other Keywords | Page |
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| MOPMR031 | Investigation of Injection Losses at the Large Hadron Collider with Diamond Based Particle Detectors | injection, kicker, proton, detector | 310 |
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| During the operation of the Large Hadron Collider (LHC) in 2015, increased injection losses were observed. To minimize stress on accelerator components in the injection regions of the LHC and to guarantee an efficient operation these losses needed to be understood and possible mitigation techniques should be studied. Measurements with diamond particle detectors revealed the loss structure with ns-resolution for the first time. Based on these measurements, recaptured beam from the Super Proton Synchrotron (SPS) surrounding the nominal bunch train was identified as the major contributor to the injection loss signals. Methods to reduce the recaptured beam in the SPS were successfully tested and verified with the diamond particle detectors. In this paper the detection and classification of LHC injection losses are described. The methods to reduce these losses and verification measurements are presented and discussed. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR031 | ||
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| TUPMR039 | The Development of a New High Field Injection Septum Magnet System for Main Ring of J-Parc | injection, septum, operation, power-supply | 1337 |
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| We are improving the Main Ring (MR) for beam power of 750 kw which is the first goal of J-PARC. The repetition period of the fast extraction must be short to 1.3 second from the current period of 2.48 second for the improvement of the beam power. It is necessary to exchange a high field injection septum magnet which will be installed at the injection line from RCS to MR and its power supply, because the current injection septum system can not be operated with 1.3 second repetition. Since confirmed the large leakage field around current circling beam line of the injection magnet, we must improve the shielding structure which make low leakage field. We started the development of the new injection septum magnet and its power supply in 2013. It can operate with 1 Hz repetition and the low leakage field which its order is 10-4 of the gap field. The new Injection septum magnet and the new power supply were constructed in Winter of 2014. We had many improvement of the magnet and power supply. We will install the new injection septum magnet system in this summer. In this presentation, we will report the detail of the results of its performance. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMR039 | ||
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| TUPMR049 | Feasibility Study of the PS Injection for 2 GeV LIU Beams with an Upgraded KFA-45 Injection Kicker System Operating in Short Circuit Mode | simulation, injection, kicker, operation | 1363 |
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| Under the scope of the LIU project the CERN PS Booster to PS beam transfer will be modified to match the requirements for the future 2 GeV beams. This paper describes the evaluation of the proposed upgrade of the PS injection kicker. Different schemes of an injection for LIU beams into the PS have been outlined in the past already under the aspect of individual transfer kicker rise and fall time performances. Homogeneous rise and fall time requirements in the whole PSB to PS transfer chain have been established which allowed to consider an upgrade option of the present injection kicker system operated in short circuit mode. The challenging pulse quality constraints require an improvement of the flat top and post pulse ripples. Both operation modes, terminated and short circuit mode are analysed and analogue circuit simulations for the present and upgraded system are outlined. Recent measurements on the installed kickers are presented and analysed together with the simulation data. First measurements verifying the performance of upgrade options have been taken during the last end of the year stop. The paper concludes with an upgrade plan and a brief overview of implementation risks. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMR049 | ||
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| TUPOR009 | Single Bunch Longitudinal Instability in the CERN SPS | impedance, simulation, synchrotron, emittance | 1670 |
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| The longitudinal single bunch instability observed in the SPS leads to uncontrolled emittance blow-up and limits the quality of high intensity beams required for the High Luminosity LHC and AWAKE projects at CERN. The present SPS impedance model developed from a thorough survey of machine elements was used in macro-particle simulations (with the code BLonD) of the bunch behavior through the acceleration cycle. Comparison of simulations with measurements of the synchrotron frequency shift, performed on the SPS flat bottom to probe the impedance, show a reasonable agreement. During extensive experimental studies various beam and machine parameters (bunch intensity, longitudinal emittance, RF voltage, with single and double RF systems) were scanned in order to further benchmark the SPS impedance model with measurements and to better understand the mechanism behind the instability. It was found that the dependence of instability threshold on longitudinal emittance and beam energy has an unexpected non-monotonic behavior, leading to islands of (in)stability. The results of this study are presented and can be used to define possible parameter settings for the future CERN projects. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR009 | ||
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| WEPOY019 | Beam Optimization Study for an X-ray FEL Oscillator at the LCLS-II | electron, emittance, FEL, linac | 3020 |
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The 4 GeV LCLS-II superconducting linac with high repetition beam rate enables the possibility to drive an X-Ray FEL oscillator at harmonic frequencies *. Compared to the regular LCLS-II machine setup, the oscillator mode requires a much longer bunch length with a relatively lower current. Also a flat longitudinal phase space distribution is critical to maintain the FEL gain since the X-ray cavity has extremely narrow bandwidth. In this paper, we study the longitudinal phase space optimization including shaping the initial beam from the injector and optimizing the bunch compressor and dechirper parameters. We obtain a bunch with a flat energy chirp over 400 fs in the core part with current above 100 A. The optimization was based on LiTrack and Elegant simulations using LCLS-II beam parameters.
* T. J. Maxwell et al., Feasibility study for an X-ray FEL oscillator at the LCLS-II, IPAC15, TUPMA028. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY019 | ||
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| THPMW014 | High Voltage Supply for Particle Accelerators Based on Modular Multilevel Converters | high-voltage, operation, power-supply, controls | 3567 |
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Modular Multilevel Converters brought a paradigm shift in very high voltage and high power applications with the replacement of high voltage valves by multiple series-connected, low-voltage modules that can be by-passed in case of fault. The reliability and precision in output waveform generation make it a potential candidate in accelerator power conversion. This work demonstrates operation of MMC-based high voltage magnet supply for a transfer line application. The output current regulation precision and the total power losses are examined. Finally, the challenge of the control optimization combined with the passive components dimensioning is highlighted.
* R. Marquardt and A. Lesnicar, "An innovative modular multilevel converter topology suitable for a wide power range", in Proc. IEEE Bologna Power Technol. Conf., Jun. 2003, pp. 1-6. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW014 | ||
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| THPMW022 | The RF Design of a Compact, High Power Pulse Compressor with a Flat Output Pulse | cavity, klystron, FEL, linac | 3591 |
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| An X-band, high-power pulse compressor, which can produce a flat pulse and a power gain of 4.3, has been designed. The device is compact, with the dimensions of within 1m, and is designed for CLIC first energy stage based on klystrons. We also discuss about a two stage pulse compressor with power gain of 9.18, which may be a candidate of the X-FEL using CLIC X-band linacs and klystrons with low peak power. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW022 | ||
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| THPMW029 | Feasibility Study of the Fast SPS Ion Injection Kicker System | simulation, injection, ion, kicker | 3607 |
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| As part of the upgrade project for ions the rise time of the injection kicker system into the SPS needs to be improved. The changes being studied include the addition of a fast Pulse Forming Line parallel to the existing Pulse Forming Network for the fast kicker magnets MKP-S. With the PFL an improved magnetic field rise time of 100 ns is targeted. Two different configuration utilizing a 2nd thyratron or two fast diode stacks have been outlined in the past. This paper presents the recent progress on the analogue circuit simulations for both options as well as measurements carried out on a test system. Modelling, optimization and simulation of the entire system with diodes and a second configuration with two thyratron switches are outlined. Measurement results are given and the feasibility of the upgrade is discussed. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW029 | ||
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| THPMW032 | Measurements on Magnetic Cores for Inductive Adders with Ultra-Flat Output Pulses for CLIC DR Kickers | kicker, damping, collider, emittance | 3619 |
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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 CLIC 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 flat, high-voltage, pulses. The specifications for the DR extraction kickers call for 160 ns duration flattop pulses of ±12.5 kV, with a combined ripple and droop of not more than ±0.02 % (±2.5 V). An inductive adder is a very promising approach to meet the specifications. Two five layer, 3.5 kV, prototype inductive adders have been built at CERN, and used to test passive and active analogue modulation methods to compensate droop and ripple of the output pulses. Recently, magnetic core materials and full-scale magnetic cores have been evaluated for the 12.5 kV prototype inductive adders. These results are presented in this paper and conclusions are drawn concerning the design of the full-scale prototypes. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW032 | ||
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| THPOW059 | UV Pulse Shaping with a-BBO Crystals for the Photocathode RF Gun | laser, electron, gun, optics | 4079 |
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| Recently, manipulation with the drive laser plays a significant role in high brightness electron beam production by the photocathode RF gun. The method based on pulse stacking with birefringent crystal serials was tried to longitudinally shape ultraviolet laser pulse. Using four or five pieces of a-BBO crystals to stack an input UV pulse with appropriate initial duration into 16 or 32 sub-pulses to form quasi flattop UV laser pulse, which can be applied for emittance optimization of the electron beam based on the photocathode RF gun. Moreover, the negative slop of the energy transmittance of a-BBO serials is also revealed to be a passive stabilization mechanism for energy jitter reduction in the driving laser. With appropriate design of a-BBO serials, this method can fulfill the requirements for driving laser in a broad scope of applications such as x-ray FELs and high-power Terahertz(THz) radiation production. | |||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW059 | ||
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