Q. Wang, Q.Y. Dong, L.T. Huang
DICP, Dalian, Liaoning, People’s Republic of China
Q. Luo
USTC/NSRL, Hefei, Anhui, People’s Republic of China
A nondestructive method to measure beam energy spread using the quadrupole modes within a microwave cavity is proposed. Compared with a button beam position monitor (BBPM) or a stripline beam position monitor (SBPM), the cavity monitor is a narrow band pickup and therefore has better signal-to-noise ratio (SNR) and resolution. In this study, a rectangular cavity monitor is designed. TM220 mode operating at 4.76 GHz in the cavity reflects the quadrupole moment of the beam. The cavity plans to be installed behind a bending magnet in Dalian Coherent Light Source (DCLS), an extreme ultraviolet FEL facility. In this position, the beam has a larger dispersion, which is beneficial to measure the energy spread. A quadrupole magnet, a fluorescent screen, and a SBPM with eight electrodes is installed near the cavity for calibration and comparison. The systematic framework and simulation results are also discussed in this paper.
B. Lorbeer, H.T. Duhme, I. Krouptchenkov, T. Lensch, D. Lipka, M. Werner
DESY, Hamburg, Germany
The European X-ray free-electron laser (E-XFEL) and the FLASH2020+ project for the free electron laser Hamburg (FLASH) at DESY in Hamburg, Germany foresee several machine upgrades in the years to come. At FLASH a whole undulator section in a shutdown starting in summer 2024 and finishing in autumn 2025 is going to be rebuild. Existing button beam position monitors installed in this section of the machine do not deliver sufficient signal strength for future required resolution specification and orbit feedback optimization for machine operation. The resolution limitations will be overcome by replacing the button-based beam position monitors with in-house developed cavity beam position monitors and compact microTCA based radio frequency receiver read-out electronics. The measurement system has been tested and evaluated in a test setup at FLASH.
Funding:Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy Coherent Electron Cooling experiment carried out at RHIC requires small slice emittance of 15 MeV electron beam with high peak current. In this paper we describe the system for slice emittance measurement utilizing transverse deflecting cavity and slit. The image of the beam passing through the slit is used to measure slice intensity and angular divergence. Beam size at slit location is measured using scan of the beam across the slit with trim. The angular kick by the trim is taken into the account during calculations. Data processing and the experimental results are presented.
T. Lensch, D. Lipka, Re. Neumann, M. Werner
DESY, Hamburg, Germany
The SINBAD (Short and INnovative Bunches and Ac-celerators at DESY) facility, also called ARES (Acceler-ator Research Experiment at SINBAD), is a conventional S-band linear RF accelerator allowing the production of lowcharge ultra-short electron bunches within a range of currently 0.01 pC to 250 pC. The R&D accelerator also hosts various experiments. Especially for the medical eFLASH experiment an absolute, non-destructive charge measurement is needed. Therefore different types of monitors are installed along the 45 m long machine: A new Faraday Cup design had been simulated and realized. Further two resonant cavities (Dark Current monitors) and two beam charge transfomers (Toroids) are installed. Both, Dark Current Monitors and Toroids are calibrated independently with laboratory setups. At the end of the accelerator a Bergoz Turbo-ICT is installed. This paper will give an overview of the current installations of charge monitors at ARES and compare their measured linearity and resolution.
S. Kiy, P.M. Jung, T. Planche, O. Shelbaya, V.V. Verzilov
TRIUMF, Vancouver, Canada
A time-of-flight measurement system has been in use at ISAC-II since 2006 for the phasing of cavities and accurate ion beam velocity measurements across the nuclear chart. This system is heavily relied upon as the primary energy-time domain diagnostic downstream of the ISAC-II linac. Ongoing High Level Applications (HLA) development at TRIUMF has enabled the use of methods that are being applied to these measurements - both for processing and automation of data acquisition. An update will be provided on operational experience with the system over the past 10 years including its recent re-calibration and error analysis. A brief summary of the current HLA framework will be given, including a database for beam measurements and the ability to carry out sequential measurement processes. Finally, the way in which these developments enable beam-based calibration of cavity parameters and a shift to model-based tuning methods is discussed.
W.L. Huang, X.J. Nie
IHEP CSNS, Guangdong Province, People’s Republic of China
M.Y. Liu, X.Y. Liu, Y.F. Sui
IHEP, Beijing, People’s Republic of China
Q.R. Liu
UCAS, Beijing, People’s Republic of China
Funding:Natural Science Foundation of Guangdong Province, 2021A1515010269 National Natural Science Foundation, 11475204 During the upgrade of linac in CSNS-II, the beam in-jection energy will increase from 80.1MeV to 300MeV and the beam power from 100kW to 500kW. A com-bined layout of superconducting spoke cavities and ellip-tical cavities is adopted to accelerate H− beam to 300MeV. Due to a ~10ps short bunch width at the exit of the spoke SC section, the longitudinal beam density dis-tribution will be measured by bunch shape monitors using low energy secondary emission electrons. As the most important part of a bunch shape monitor, a prototype 324MHz RF deflector is designed and tuned on the basis of a quasi-symmetric λ/2 325MHz coaxial resona-tor, which was fabricated for the C-ADS proton accelera-tor project. Preliminary parameters of the bunch shape monitor are presented. Simulation of the RF deflector and test results in the laboratory are described and analysed.
M.W. Bruker, J.M. Grames, J. Guo, J. Musson, S.A. Overstreet, G.-T. Park, T.E. Plawski, M. Poelker, R.A. Rimmer, H. Wang, C.M. Wilson, S. Zhang
JLab, Newport News, Virginia, USA
M.H. Pablo, B.F. Roberts, D. Speirs
Electrodynamic, Albuquerque, New Mexico, USA
Funding:Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. Multi-Harmonic driver development supported by SBIR DE-SC0020566. A harmonically resonant kicker cavity designed for beam exchange in a circulator cooler* was built and successfully tested at the Upgraded Injector Test Facility (UITF) at Jefferson Lab. This type of cavity is being considered for the injection scheme of the Rapid Cycling Synchrotron at the Electron-Ion Collider, where the spacing of neighboring bunches demands very short kicks. Operating with five transversely deflecting modes simultaneously that resonate at 86.6 MHz and consecutive odd harmonics thereof, the prototype cavity selectively deflects 1 of 11 electron bunches while leaving the others unperturbed. An RF driver was developed to synthesize phase- and amplitude-controlled harmonic signals and combine them to drive the cavity while also separating the modes from a field-probe antenna for RF feedback and dynamic tuning. Beam deflection was measured by sweeping the cavity phase; the deflection waveform agrees with expectations, having sub-nanosecond rise and fall times. No emittance increase is observed. Harmonically resonant cavities like the one described provide a new capability for injection and extraction at circulators and rings. * G.T. Park et al., "Beam exchange of a circulator cooler ring with an ultrafast harmonic kicker", Phys. Rev. Accel. Beams 24, 061002
D. Lipka, T. Lensch, Re. Neumann, M. Werner
DESY, Hamburg, Germany
The ARES facility (Accelerator Research Experiment at SINBAD) is an accelerator to produce low charge ultra-short electron bunches within a range of currently 0.5 pC to 200 pC. Especially for eFLASH experiments at ARES an absolute, non-destructive charge measurement is required. To measure an absolute charge of individual bunches different types of monitors are installed. A destructive Faraday Cup is used as reference charge measurement device. To measure the charge non-destructively 2 Toroids, 1 Turbo-ICT and 2 cavity monitors are installed. The latter system consists of the cavity, front-end electronics with logarithmic detectors and µTCA ADCs. The laboratory calibration of the cavity system is performed by using an arbitrary waveform generator which generate the same waveform like the cavity with beam. This results in a non-linear look-up table used to calculate the ADC amplitude in charge values independent of beam-based calibration. The measured charges from the cavity monitors agree very well within few percent in comparison with the Faraday Cup results.
L.W. Lai, S.S. Cao, X.Q. Liu, Y.M. Zhou
SARI-CAS, Pudong, Shanghai, People’s Republic of China
J. Chen
SSRF, Shanghai, People’s Republic of China
R. Meng
SINAP, Shanghai, People’s Republic of China
Funding:Work supported by The National Science Foundation of China (Grant No.12175293). Youth Innovation Promotion Association, CAS (Grant No. 2019290) A RF direct sampling beam signal processor has been developed in SSRF. It mainly consists of four channels RF direct sampling ADCs and a SoC FPGA. The ADC is 9GHz bandwidth and 2.6GHz sampling rate. A prototype of RF module contains band pass filter, low noise ampli-fier and step attenuator has been designed for SHINE cavity BPM system. Then a novel cavity BPM electronic including the processor and the RF module has been built for SHINE. The performance of the electronic has been analyzed and evaluated in lab. The amplitude relative error is 2.0×10-4,which is better than the required 1×10-3 on cavity BPM system. The phase error is 14fs, also bet-ter than the requirement of RF BAM system. The algorithm and the implementation in FPGA have been introduced. Corresponding author: lailw@sari.ac.cn
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