Keyword: flattop
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TUPOST006 Frequency-Dependent RF Voltage Calibration Using Longitudinal Tomography in the CERN PSB cavity, synchrotron, extraction, injection 845
 
  • D. Quartullo, S.C.P. Albright, H. Damerau
    CERN, Meyrin, Switzerland
 
  Longitudinal phase-space tomography reconstructs the phase-space distribution from a set of bunch profiles and the accelerator parameters, which includes the RF voltage. The quality of the reconstruction depends on the accuracy to which these parameters are known. Therefore, it can be used for beam-based RF voltage calibration by analysing oscillations of a mismatched bunch. The actual RF voltage may be different from the programmed one due to uncertainties of the electrical gap voltage measurements and intensity effects. Tomography-based RF voltage calibration was systematically performed with low-intensity bunches in all four rings of the PS Booster (PSB) at injection and extraction energy. For each of the three RF cavities present in a given ring, the calibration was performed separately to extract the voltage errors while avoiding any influence of phase misalignments. The number of synchrotron oscillation periods available for the voltage calibration was constrained by the short duration of the PSB flat-bottom and top. Longitudinal beam dynamics simulations using the full PSB impedance model were performed to benchmark the results provided by the calibrations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST006  
About • Received ※ 30 May 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 14 June 2022
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WEPOTK028 Implementation of RF Channeling at the CERN PS for Spill Quality Improvements cavity, extraction, resonance, simulation 2114
 
  • P.A. Arrutia Sota, H. Damerau, M.A. Fraser, M. Vadai, F.M. Velotti
    CERN, Meyrin, Switzerland
  • P. Burrows
    JAI, Oxford, United Kingdom
 
  Resonant slow extraction from synchrotrons aims at providing constant intensity spills over timescales much longer than the revolution period of the machine. However, the extracted intensity is undesirably modulated by noise on the machine’s power converters with a frequency range of between 50 Hz and a few kHz. The impact of power converter noise can be suppressed by exploiting a Radio Frequency (RF) technique known as empty bucket channelling, which increases the speed at which particles cross the tune resonance boundary. In this contribution the implementation of empty bucket channelling in the CERN Proton Synchrotron (PS) is described via simulation and measurement. The technique was tested with both a resonant RF cavity and an inductive Finemet cavity, which can produce non-sinusoidal waveforms, to significantly reduce the low frequency noise observed on the extracted spill.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK028  
About • Received ※ 07 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 22 June 2022
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WEPOTK046 Improved Longitudinal Performance of the LHC Beam in the CERN PS feedback, extraction, emittance, cavity 2165
 
  • H. Damerau, V.D. Desquiens, A. Huschauer, A. Jibar, A. Lasheen, B. Mikulec, M. Morvillo, C. Rossi, B.J. Woolley
    CERN, Meyrin, Switzerland
 
  At the end of the 2018 run the intensity target for the High-Luminosity LHC (HL-LHC) had just been reached at extraction from the Proton Synchrotron (PS). In the framework of the LHC Injectors Upgrade (LIU) project additional RF improvements have been implemented during the 2019/2020 long shutdown (LS2), mainly impacting the impedance of the 10 MHz, 40 MHz, and 80 MHz RF systems. With the upgraded injection energy of 2 GeV (kinetic), also the intermediate plateau energy for RF manipulations has been increased. Following a campaign of beam studies throughout the 2021 run, a bunch intensity of up to 2.9·1011 p/b in trains of 72 bunches is achieved with the required longitudinal beam quality, surpassing the LIU target of 2.6·1011 p/b. The threshold of longitudinal quadrupolar coupled-bunch instabilities is increased during acceleration, but they are again observed at the flat-top. While dipolar coupled-bunch oscillations are well damped by a dedicated feedback system, the quadrupolar modes are suppressed by operating a 40 MHz system as an active higher-harmonic Landau cavity. The main commissioning steps are outlined, together with the key contributions to the improved beam performance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK046  
About • Received ※ 07 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 16 June 2022  
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THPOTK005 The New High Field Septum Magnet for Upgrading of Fast Extraction in Main Ring of J-PARC operation, extraction, septum, proton 2778
 
  • T. Shibata, K. Ishii, S. Iwata, H. Matsumoto, N. Matsumoto, T. Sugimoto
    KEK, Ibaraki, Japan
  • K. Fan
    HUST, Wuhan, People’s Republic of China
 
  Upgrading the beam-power of the J-PARC Main Ring to 750 kW is underway by reducing the cycle from 2.48 s to 1.3 s. Required upgrade of the four High Field (HF) Septa will be completed in 2022. The operation test of a new HF SM31 was conducted in 2020. First was 1 Hz operation test. The power supply had no problem in the operation, and the joule heating at the magnet coil was lower than limit. We found a good linearity between the current and the gap field which has no saturation. The field integral in the magnet gap was measured to calculate the appropriate current for beam operation, and we found it was 3,400 A. We compared the gap field of the neutrino side with that of the beam abort side. The magnitude of gap field had no significant discrepancy larger than its measurement accuracy. The end-fringe field was measured and the we found large leakage field still existed around the end-fringes. We are producing an additional magnetic shield which will be mounted in the circulating beam duct, and it will finished in Feb. 2022. In next March we will install the inner shield and measured the leakage field. After that we will install the new SM31 in MR.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK005  
About • Received ※ 20 May 2022 — Revised ※ 10 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 28 June 2022
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