Inclined X-ray Beam Position Monitors to Reduce Influence of Filling Pattern for the SPring-8 Photon Beamlines
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H. Aoyagi, Y. Furukawa, S. Takahashi
JASRI/SPring-8, Hyogo, Japan
Funding:This work is partly supported by Japan Society for the Promotion of Science through a Grant-in-Aid for Scientific Research (c), No.18K11943. The X-ray beam position monitors (XBPMs) equipped with blade-type detector heads in SPring-8, which operate in photoemission mode, are required to withstand severe high heat loads. In addition, they must work in a variety of several-bunch mode operations. However, as bunch current in the storage ring increased, influence of bunch filling patterns on XBPM performance increased year by year. We have performed a systematic evaluation of the influence of the filling patterns. We found that the cause of the influence is suppression of the XBPM current signal due to the space charge effect, and that it can be quantified by observing the behavior of the current signal while changing the voltage of a photoelectron collection electrode*. We have designed and manufactured new blade-type detector heads in inclined configuration for the purpose of mitigation the space charge effect**. It has been demonstrated that the influence of filling patterns is reduced to a few um. We also report that, as a result of a series of efforts against existing XBPMs for all ID beamlines, the influence has been reduced to about 5 um RMS. * IPAC2019 WEPGW027, https://ipac2019.vrws.de/papers/wepgw027.pdf ** PASJ2019 THPI029, https://www.pasj.jp/webpublish/pasj2019/proceedings/PDF/THPI/THPI029.pdf
Funding:Work supported by the US Department of Energy, Office of Science, High Energy Physics under Cooperative Agreement award number DE-SC0018362. Capacitive pickups such as beam position monitors (BPMs), are sensitive to the electric field distribution produced by the beam. For relativistic fields, the fields are flattened therefore they well represent the longitudinal bunch shape. However, for non-relativistic beam, ß<0.1, the field at the pickups can extend past the bunch which affects the measurements from the BPM. This effect from non-relativistic fields is currently accounted for with theory and simulations, however a test stand is also desired that can replicate the field distribution and the bunch velocity. To accomplish this a test stand using a helical transmission line was designed and constructed which propagates with phase velocity of ~0.03c. Presented are measurements of the phase velocity, dispersion, and impedance of the helical transmission line and compared to simulations and theory. Also demonstrated is the ability for the helical transmission line to propagate pulses with minimal deformation and the fields from the helix well represent a particle bunch.
Multiplexer System for the SPEAR3 Booster BPM Upgrade
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F. Toufexis, P. Boussina, L. Campana, W.J. Corbett, J.J. Sebek
SLAC, Menlo Park, California, USA
Funding:Work sponsored by US Department of Energy Contract DE-AC02-76SF00515. BPM measurements in booster synchrotrons are often only critical during accelerator commissioning or when a problem occurs. As a result, many facilities do not make large investments in booster BPM signal processors; they either have very few BPMs and/or use older generation processors. The SPEAR3 booster BPM processor system, for instance, has operated since 1990 with commercial multiplexers to switch between BPM button signals into a single dated analog BPM processor that was developed at SLAC*. This system has reached its end-of-life so we are in the process of upgrading to modern multiplexers that feed a pair of turn-by-turn Libera SPARK-ERXR processors. This low-cost solution gives us the ability to arbitrarily multiplex between BPM signals during the energy ramp with modern BPM processors. The system can either measure 2 BPMs turn-by-turn in parallel during the entire energy ramp, or sequentially measure all BPMs (2 at a time) at different time slices within the ramp. Here we show measurements of the MiniCircuits switch we chose as well as our architecture for the upgrade. *W. Lavender et al., "The SSRL injector beam position monitoring systems," 1991 IEEE Particle Accelerator Conference, San Francisco, CA, USA, 1991, pp. 1151-1153 vol.2, doi: 10.1109/PAC.1991.164563.
X-Ray Beam Position Monitor Silicon Photodiode Measurements for the Advanced Photon Source Upgrade
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K.P. Wootton, H. Cease, M. Erdmann, S.M. Oprondek, M. Ramanathan, B.X. Yang
ANL, Lemont, Illinois, USA
Funding:This research used resources of the Advanced Photon Source, operated for the U.S. Department of Energy Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. To best leverage the orders of magnitude average brightness increase of multi-bend achromat synchrotron radiation storage rings, ambitious beam stability requirements are imposed. One system that will be employed at the Advanced Photon Source Upgrade in support of photon beam stability will be X-ray beam position monitors. In the present work, electrical characterisation of several types of photodiodes are evaluated for potential use in X-ray beam position monitors.
Analysis of the Bunch Position Monitoring in Long Bunch Trains at FLASH
N. Baboi, B. Lorbeer
DESY, Hamburg, Germany
Multi-bunch beams are routinely being accelerated at the FLASH Free Electron Laser at DESY, Hamburg. More than hundred Beam Position Monitors (BPMs) measure the transverse offset of every single bunch in each train with a bunch repetition frequency of up to 1 MHz and a length of several hundreds of microseconds. Various types of monitors are being used: button, stripline and cavity BPMs, each type with several designs. The performance differs from type to type, with resolutions from one to tens of micrometers. However so far only the first bunch in the train was investigated in detail. In this paper we study every bunch along long bunch train for several BPM designs and locations.
Simulation of the Signal Processing for the New Interaction Region BPMs of the High Luminosity LHC
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D.R. Bett
JAI, Oxford, United Kingdom
A. Boccardi, M. Krupa, M. Wendt
CERN, Geneva, Switzerland
New stripline beam position monitors (BPMs) will be installed at the Interaction Regions of the ATLAS and CMS experiments as part of the High-Luminosity upgrade to the LHC. These BPMs will be located in sections of the beamline where the two counter-propagating proton beams co-exist within a single pipe, such that the signal observed on each output port is a combination of the signals generated by each beam. The use of the BPMs as the input for a possible luminosity feedback system places a demanding requirement on the long-term accuracy of the BPMs. Accurate measurement of the position of each beam requires a method for isolating the individual beam signals. A simulation framework has been developed covering all stages of the measurement process, from generation of the signals expected for beams of a given intensity and orbit through to digitization, and has been used to evaluate several candidate methods for extracting the position of each beam in the presence of the unwanted signal from the other.
S.S. Cao
Private Address, Zhangjiang, Shanghai, People’s Republic of China
R. Jiang, Y.B. Leng, R.X. Yuan
SSRF, Shanghai, People’s Republic of China
SHINE (Shanghai High repetition rate XFEL aNd Extreme light facility) is designed to be an extremely high-performance hard X-ray free-electron laser facility located at Zhangjiang, Shanghai. As one of the key parameters of the facility, the resolution of the beam position measurement in the undulator section is required to be under 200 nm at a low bunch charge of 100 pC and better than 10 um at 10 pC. To achieve this, a pre-study based on cavity beam position monitors is under development. Four sets of cavity monitors with different frequencies or load quality factors have been designed and are now manufactured by four different companies. It aims to select the cavity with the best performance and select the most capable company. This paper will briefly introduce the motivation, cavity design considerations, and cold test results.
BPM Studies and Prototype Design for the SOLEIL Upgrade
M. El Ajjouri, F. Alves, A. Gamelin, N. Hubert
SOLEIL, Gif-sur-Yvette, France
Synchrotron SOLEIL is preparing a machine upgrade with a reduction by more than a factor 10 the horizontal electron beam emittance (< 100 pm.rad)., the future multibend achromat lattice will be composed of a large number of magnet elements. Quadrupole and sextupole strengths will impose a drastic reduction of the vacuum chamber dimensions and in particular its diameter that will be reduced to 10 mm. One of the challenges for the beam position monitors will be the mechanical integration of the 4 buttons and feedthroughs on such a small beam pipe. In this context we have realized a first prototype with Component Off The Shelf 3 mm buttons diameter, to validate this mechanical integration and are starting the 3D electromagnetic simulations to study the impedance characteristics, the RF parameters, the heating and thermal issues.
Experiments With a Quadrated Dielectric-Filled Reentrant Cavity Resonator as a Beam Position Monitor (BPM) for a Medical Cyclotron Facility
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S. Srinivasan, P.-A. Duperrex, J.M. Schippers
PSI, Villigen PSI, Switzerland
Funding:This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 675265. Low beam currents (0.1-10 nA) are used for tumour treatment in the proton radiation therapy facility at PSI. The facility houses a superconducting cyclotron with extraction energy of 250 MeV pulsed at 72.85 MHz. Online measurement of the beam position is traditionally performed with the help of ionisation chambers (ICs), however, at the expense of reduced beam quality and scattering issues. There is a strong demand to have this measurement performed with minimal beam disturbance since the beam position is directly associated with the dose-rate applied. A cavity resonator, working on the principle of an electric dipole mode resonance, whose frequency is coupled to the second harmonic of the pulse rate, has been built to measure beam position in a purely non-invasive manner. Followed by a reasonable agreement between the test-bench and the simulation results, the cavity is installed in one of the beamlines. Here, we report on the measurement of the cavity BPM as a function of beam current and position and its shortcomings. The cavity BPM can deliver position information within the accuracy and resolution demands of 0.50 mm, when measured with a spectrum analyzer.
Properties of Cherenkov Diffraction Radiation as Predicted by the Polarisation Currents Approach for Beam Instrumentation
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D.M. Harryman, K.V. Fedorov, P. Karataev
JAI, Egham, Surrey, United Kingdom
M. Bergamaschi, R. Kieffer, K. Łasocha, T. Lefèvre, S. Mazzoni
CERN, Geneva, Switzerland
L. Bobb
DLS, Oxfordshire, United Kingdom
A. Potylitsyn
TPU, Tomsk, Russia
A. Schloegelhofer
TU Vienna, Wien, Austria
Cherenkov-Diffraction Radiation (ChDR) appears when a charged particle moves in the vicinity of a dielectric medium with velocity higher than the phase velocity of light inside the medium. As the charged particle does not contact the medium, the emission of ChDR is a phenomenon that can be exploited for a range of non-invasive beam diagnostics. Experimental tests are underway on the Booster To Storage-ring (BTS) test stand at Diamond Light Source to explore the use of dielectric radiators as Beam Position Monitor (BPM) pickups by measuring the incoherent ChDR emission. In order to compliment the experiments on the BTS test stand, ChDR simulations have been performed using the Polarisation Currents Approach (PCA) model. This paper explores the PCA simulations for the BTS test stand, and the application for future diagnostics.
Development of Abnormal Beam State Monitoring Processor on SSRF Storage Ring
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L.W. Lai, Y.B. Leng, Y.B. Yan
SSRF, Shanghai, People’s Republic of China
An abnormal beam state monitoring processor has been developed on SSRF, which is based on the hardware of self-developed digital BPM processor. By applying digital signal processing algorithms in the on-board FPGA, the processor keeps monitoring the beam running state. Once abnormal event is detected, the processor will record the abnormal event type and store the turn-by-turn beam position data before and after the event for later analyzing. The abnormal events including beam loss and beam position jump.
A cavity beam position monitor acts for the detection of the beam location within a pipe with high precision and best resolution. Some of them are used as a fixed point to refer the other parts of the beamline. To be able to fix the monitor against the other vacuum components bellows need to be adapted next to the monitor to relax the other part of the vacuum chamber. The bellow itself can create a resonance which would influence the resonator of the cavity beam position monitor. In this study the influence of a the bellow to a cavity beam position monitor is investigated with simulations for a SINBAD project. The result is that the influence to the dipole resonator is below 0.1%.
New beamlines will be installed at the AS in the next few years and photon BPMs will be part of the front end design. A theoretical study of the potential benefits of a multi-bladed photon BPM design has been simulated using beam profiles from SPECTRA. The results show that it is possible to remove the gap/field dependence of the photon BPM by a least squares fit of the distribution, in this test case a Gaussian distribution, to the beam profile sampled by the multiple blades.
Characterization Study of a Button BPM with an Approach to Automated Measurements
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Y. Verma
Indian Institute of Science Education and Research, Mohali, India
M. Aggarwal, V.J. Joshi, A. Sharma
IUAC, New Delhi, India
Beam position monitors (BPMs) are one of the very im-portant diagnostic components of any accelerator systemgiving information about beam position. It is a class of non-intercepting devices which use the coupling of the EM fieldaround a charged particle bunch to some sort of conductorelectrodes to recover beam position information from thebeam-induced signals. In this paper, a characterization studyof an in-house developed Button BPM including sensitivitymeasurement and transfer impedance studies is presented. Sensitivity measurement was done using the stretched wiremethod by passing current pulses through the wire of differ-ent diameters like 0.5 mm and 1 mm, thus mimicking thebehavior of the actual beam. Sensitivity information wasthen used to reciprocate the 2-D position map of the device. Owning to the time taken for such huge measurements, anautomated BPM test bench approach of the whole setup isdeveloped by remote interfacing over LAN. A substantialdecrease in measurement time was observed along with areduction in measurement error.
Funding:Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 As light source electron beam sizes shrink, orbit stability demands increase. There are many factors that contribute to orbit stability. This paper will focus on beam position monitor (BPM) electronics and describe a self-calibration technique implemented at the ALS. The ALS commissioned new BPM electronics about 3 years ago. The electronic design is similar to that of the NSLS-II BPMs. For instance, the digital front end is the same as the NSLS-II design. The ALS team changed the analog front end (although conceptually similar) and the FPGA firmware to further the pilot tone calibration method begun at NSLS-II. The choice of bandpass filters is critical to the success of a pilot tone calibration scheme, as is the digital processing applied to the beam signal and pilot tones. The initial goal was to accurately track and calibrate slow thermally induced position errors. This capability has been expanded to track and remove differences between the BPM channels up to the system bandwidth of about 5kHz.
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Commissioning of the Beam Energy Position Monitor System for the Superconducting RIKEN Heavy-ion Linac
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T. Watanabe, N. Fukunishi, H. Imao, O. Kamigaito, T. Nishi, K. Ozeki, N. Sakamoto, A. Uchiyama, Y. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan
K. Hanamura
Mitsubishi Electric System & Service Co., Ltd, Tsukuba, Japan
A. Kamoshida
National Instruments Japan Corporation, MInato-ku, Tokyo, Japan
R. Koyama
SHI Accelerator Service Ltd., Tokyo, Japan
T. Toyama
KEK, Tokai, Ibaraki, Japan
The beam commissioning for the RIKEN Heavy-ion Linac (RILAC) upgrade, including the new Superconducting Linac (SRILAC) has been successfully completed. These RILAC upgrade aims at promoting super-heavy element searches and the radioactive isotope (RI) production for medical use. When we accelerate the beam by the SRILAC, we must definitely reduce the beam loss under 1 W/m. To constantly monitor the beam nondestructively, we have developed the new system (BEPM) measuring simultaneously not only the beam position but also the beam energy by measuring the time of flight of the beam. This system has the great advantage that can handle time-chopped beam by synchronizing the measurement system with the beam-chopping signal. At the beginning of the commissioning, the beam was chopped to 3% duty to make the SRILAC cavity protected from the beam loss. Even though the beam intensity was 15 enA, the beam position and energy were accurately measured. We measure the beam position to an accuracy of ±0.1 mm and the beam energy to that of several 10-4. Here, we present details concerning the BEPM system and commissioning results.
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S.J. Wei, J.S. Cao, Y.Y. Du, H.Z. Ma, Y.F. Sui, J. Yang, Q. Ye, J.H. Yue, X.E. Zhang
IHEP, Beijing, People’s Republic of China
Beam Position Monitors BPM is the most important and frequent non-destructive diagnostics used at nearly all synchrotrons. In HEPS project, the BPM electronics have been developed all by the BI group staffs. There are 4 main parts are involved in development: the hardware of AFE (RF analog circuit) and DFE (Digital signal processing circuit), the firmware of algorithm, the data acquisition software (DAS), and the BPM testing system. In order to get a better performance, the RF analog circuit (AFE) is design carefully, and the algorithm (HDL in DFE) has been designed and optimized. At the same time, several related techniques are studied to improve the system long-term resolution, such as the thermally controlled racks, 2-way analog switching, the thermal compensation algorithm, etc. Moreover, testing system for BPM is a very important during the BPM electronics development, in manufacturing stage, it can provide the testing tools for the hardware and firmware. And in system running stage, it can be used for a diagnose tools, calibration tools, and monitoring tools for the BPM system. So the BPM testing system can make the system more robust.
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