S. Nagaitsev, A.L. Romanov, A.V. Shemyakin, G. Stancari
Fermilab, Batavia, Illinois, USA
Funding:The work is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Two experiments were carried out to study the statistical properties of undulator radiation in the Integrable Optics Test Accelerator (IOTA) storage ring at Fermilab. The first experiment studied the turn-to-turn fluctuations in the power of the radiation generated by an electron bunch. The magnitude of these fluctuations depends on the 6D phase-space distribution of the electron bunch. In IOTA, we demonstrated that this effect can be used to measure some electron bunch parameters, small transverse emittances in particular. In the second experiment, a single electron was stored in the ring, emitting a photon only once per several hundred turns. In this regime, any classical interference-related collective effects were eliminated, and the quantum fluctuations could be studied in detail to search for possible deviations from the expected Poissonian photon statistics. In addition, the photocount arrival times were used to track the longitudinal motion of a single electron and to compare it with simulations. This allowed us to determine several dynamical parameters of the storage ring such as the rf cavity phase jitter and the dependence of the synchrotron motion period on amplitude.
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C.E. Houghton, C. Bloomer, L. Bobb
DLS, Harwell, United Kingdom
Tungsten blade based photoemission X-ray Beam Position Monitors (XBPMs) are widely used as white beam diagnostics at synchrotrons. Traditionally, the scale factors are determined by stepper motor movements of the XBPM, or by controlled electron beam displacements, and measuring the response. These measurements must be repeated for each ID gap to produce a complete set of scale factors for all operational conditions. This calibration procedure takes time and cannot be done while users are acquiring data. In addition, the scale factors can vary over time due to changes to the storage ring. It is possible for these scale factors to become inaccurate, reducing the accuracy of the beam position measured by the XBPMs. By using the intrinsic kHz electron beam movements and correlating the signals from electron beam position monitors and XBPMs it is possible to have a real-time calculation of the scale factors without the need to disturb user operation. Presented in this paper is a method to non-invasively calculate scale factors during normal user operation. A comparison of the precision of this method versus the traditional stepper motor method is presented.
R.L. Hermann, M. Galonska, Th. Haberer, A. Peters
HIT, Heidelberg, Germany
T. Gehrke
German Cancer Research Center (DKFZ), Heidelberg, Germany
B. Leverington
Universität Heidelberg, Heidelberg, Germany
Funding:Funded by Deutsche Forschungsgemeinschaft (DFG), project number 426970603. The Heidelberg Ion-Beam Therapy Center (HIT) pro-vides proton, helium, and carbon-ion beams with differ-ent energies and intensities for cancer treatment and oxy-gen-ion beams for experimentation. Below the intensities used for therapy, low-intensity ion beams (below 1·105 ions/s) are available for various experiments via manual-ly degrading of the beam. Since there is no built-in beam profile instrumentation device for this intensity region, the development of a transverse ion beam profile monitor for these intensities is therefore of interest. The principle of operation is based on scintillating fibres, particularly those with enhanced radiation hardness. The fibres transform the deposited energy of a traversing ion into photons, which are then converted and amplified via silicon pho-tomultipliers (SiPMs) into electric pulses. These pulses are recorded and processed by a novel and dedicated readout electronics: the front-end readout system (FERS) A5200 by CAEN. A prototype set-up consisting of all the above-mentioned parts was tested in beam and has proven to record the transverse beam profile successfully from intensities of 1·107 ions/s down to 1·102 ions/s.
N. Vitoratou, L. Bobb
DLS, Oxfordshire, United Kingdom
A. Last
KIT, Eggenstein-Leopoldshafen, Germany
G. Rehm
HZB, Berlin, Germany
X-ray pinhole cameras are employed to provide the transverse profile of the electron beam from which the emittance, coupling and energy spread are calculated in the storage ring of Diamond Light Source. Tungsten blades separated by shims are commonly used to form the pinhole aperture. However, this approach introduces uncertainties regarding the aperture size. X-ray lithography, electroplating and moulding, known as LIGA, has been used to provide thin screens with well-defined and high aspect ratio pinhole apertures. Thus, the optimal aperture size given the beam spectrum can be used to improve the spatial resolution of the pinhole camera. Experimental results using a LIGA screen of different aperture sizes have been compared to SRW-Python simulations over the 15-35 keV photon energy range. Good agreement has been demonstrated between the experimental and the simulation data. Challenges and considerations for this method are also presented.
M.T. Switka, K. Desch, D. Elsner
ELSA, Bonn, Germany
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
The Compton Polarimeter at the ELSA 3.2 GeV storage ring has been designed to measure the polarization degree of the stored electron beam by analyzing the profile of the back-scattered gamma-beam with a silicon microstrip detector. Utilizing a scattering asymmetry from interaction with circularly polarized laser light, the electron beam polarization is determined from the vertical shift of the gamma-beam’s center of gravity in respect to the handedness of the laser light. The installation of a new laser source and silicon strip detector has improved the polarimeter’s performance significantly. Additionally, the profile analysis could be enhanced by using a Pearson type peak function fit. The analyzing power was determined through the observation of the Sokolov-Ternov effect and a statistical measurement accuracy of 2 % could be obtained within 5 minutes of measurement time. The polarimeter resolves the expected spin dynamical effects occurring in the storage ring and has shown to be a robust and reliable measurement system for operation with the GaAs source for polarized electrons.
H. Aoyagi, T. Fujita, K. Kobayashi, H. Osawa, 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, 21K12530. This study analyzes a pulse-mode x-ray beam position monitor that enables pulse-by-pulse position measurement in a synchrotron radiation beamline of the synchrotron radiation facility, SPring-8. The monitor is equipped with blade-shaped detection elements utilizing diamond heatsinks to reduce stray capacitance and a microstripline transmission line to improve high-frequency characteristics. The detection elements operate as photocathodes and generate single unipolar pulses with a full width at half-maximum of less than 1 ns, allowing pulse-by-pulse measurement of the synchrotron radiation beam. We confirmed the basic operation of the monitor at the SPring-8 bending magnet beamline*. The detection element’s heat resistance consequently improved. An evaluation test was carried out at the SPring-8 undulator beamline with significantly high synchrotron radiation intensity. We aim to report the evaluation results of the sensitivity and resolution of the monitor measured by exciting a betatron oscillation in the horizontal/vertical direction using beam shakers of the SPring-8 storage ring and the observation results of the pulse-by-pulse photon beam dynamics induced by beam injection. * https://journals.aps.org/prab/pdf/10.1103/PhysRevAccelBeams.24.032803
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N. Baboi, H.T. Duhme, B. Lorbeer
DESY, Hamburg, Germany
The superconducting FLASH user facility (Free electron LASer in Hamburg) accelerates 10 electron bunch trains per second, which are mostly used to produce high brilliance XUV and soft X-ray pulses. Each train usually contains up to 600 electron bunches with a typical charge between 100 pC and 1 nC and a minimum bunch spacing of 1 us. Various types of beam position monitors (BPM) are built in three electron beam lines, having a single bunch resolution of 2-100 um rms. This paper presents multi-bunch position measurements for various types of BPMs and built in at various locations. The dependency of the resolution on the beam offset is also shown.
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J.C. Dooling, M. Borland, A.M. Grannan, C.J. Graziani, Y. Lee, R.R. Lindberg, G. Navrotski
ANL, Lemont, Illinois, USA
N.M. Cook
RadiaSoft LLC, Boulder, Colorado, USA
D.W. Lee
UCSC, Santa Cruz, California, USA
Funding:Work supported by Hard X-ray Sciences LDRD Project 2021-0119 and by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The reduced emittance and concomitant increase in electron beam intensity in Fourth Generation Storage Ring (4GSR) light sources lead to the challenging machine protection problem of how to safely dispose of the circulating charge during unplanned whole-beam loss events. Two recent experiments conducted to study the effects of 4GSR whole-beam dumps showed that damage to candidate collimator materials can be severe. This is a paradigm shift for SR light source machine protection. Typically the biggest threat to the machine is from CW synchrotron radiation. The choice of collimator material is important. High-Z, high-density materials such as tungsten may appear effective for stopping the beam in static simulations; however, in reality, short radiation lengths will cause severe destructive hydrodynamic effects. In our experiments, significant damage was observed even in low-Z aluminum. Thus unplanned, whole-beam dumps cannot be stopped in a single collimator structure. In this tutorial, alternatives such as multiple collimators and fan-out abort kicker systems will be discussed. Collimator design strategy and foreseen diagnostics for their operation will also be presented.
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O. Sedláček, M. Ady, C. Castro Sequeiro, A.R. Churchman, S. Mazzoni, G. Schneider, K. Sidorowski, R. Veness
CERN, Meyrin, Switzerland
P. Forck, S. Udrea
GSI, Darmstadt, Germany
M. Sameed
European Organization for Nuclear Research (CERN), Geneva, Switzerland
O. Sedláček, O. Stringer, C.P. Welsch, H.D. Zhang
The University of Liverpool, Liverpool, United Kingdom
O. Sedláček, O. Stringer, C.P. Welsch, H.D. Zhang
Cockcroft Institute, Warrington, Cheshire, United Kingdom
In a gas jet monitor, a supersonic gas curtain is injected into the beam pipe and interacts with the charged particle beam. The monitor exploits fluorescence induced by beam-gas interactions, thus providing a minimally invasive transverse profile measurement. Such a monitor is being developed as part of the High Luminosity LHC upgrade at CERN. As a preliminary study, the fluorescence cross section of relevant gases must be measured for protons at 450 GeV and 6.8 TeV (i.e. the LHC injection and flat top energies). In these measurements, neon, or alternatively nitrogen gas, will be injected into the LHC vacuum pipe by a regulated gas valve to create an extended pressure bump. This work presents the optical detection system that was installed in 2022 in the LHC to measure luminescence cross-section and horizontal beam profile. Preliminary measurements of background light and first signals are presented in this paper.
B. Alberdi-Esuain, J.-G. Hwang, T. Kamps
HZB, Berlin, Germany
T. Kamps
HU Berlin, Berlin, Germany
Plasma-based accelerator technology is reaching a mature state, where applications of the beam for medical sciences, imaging, or as an injector for a future large-scale accelerator-driven light source become feasible. Particularly, the requirements for beam injection into a storage-ring-based light source are very strict with regards to beam quality and reliability. A non-invasive diagnostics greatly helps to reduce the commissioning time of the machine. We present a device suitable for online, non-destructive monitoring of the transverse spot size of the injected beam. In order to measure lateral beam sizes with a few-micrometer resolution, the technique uses an interferometric regime of coherent synchrotron radiation that is enabled by a sub-femtosecond short bunch-length. Simulations of the photon flux and the retrieval of the beam spot-size are performed for different bandwidth filters in order to define the bandwidth acceptance. Results show the potential of the proposed system that achieves precise retrieval of the complex degree of coherence at an extremely low photon intensity similar to those expected towards the plasma-acceleration injectors.
M. Labat, A. Bence, A. Berlioux, B. Capitanio, G. Cauchon, J. Da Silva, N. Hubert, D. Pédeau, M. Thomasset
SOLEIL, Gif-sur-Yvette, France
SOLEIL storage ring is presently equipped with three diagnostics beamlines: two in the X-ray range (pinhole cameras) and one in the visible range. The visible range beamline relies on a slotted copper mirror extracting the synchrotron radiation from one of the ring dipoles. The extracted radiation is then transported down to a dedicated hutch in the experimental hall. Up to now, this radiation was split into three branches for rough monitoring of the beam transverse stability, bunch length measurements and filling pattern measurements. In the framework of SOLEIL’s upgrade, we now aim at developing a new branch for high resolution beam size measurement using polarized imaging. This work presents the various modifications recently achieved on the beamline to reach this target, including a replacement of the extraction mirror, and preliminary results towards transverse beam size measurement.
D.S. Levin, C. Ferretti, A. Kaipainen, N.A. Ristow
University of Michigan, Ann Arbor, Michigan, USA
P.S. Friedman
Integrated Sensors, LLC, Ottawa Hills, Ohio, USA
T.N. Ginter
NSCL, East Lansing, Michigan, USA
Funding:This work is funded by SBIR Phase-II Award No. DE-SC0019597, DOE Office of Science to Integrated Sensors, LLC. A high performance Scintillator Ion Beam Monitor (SBM)provides diagnostics across a range of isotopes, energies, and intensities. It uses a machine-vision camera and a magazine of thin scintillators, movable into the beam without breaking vacuum. Two proprietary scintillators are used: a semicrystalline polymer material (PM) tested over a thickness range of ~1 to 190 µm. The PM yields stronger signals than other commercial plastic scintillators tested and is radiation damage resistant; a 100-400 µm opaque wafer consisting of inorganic crystals in a polymer hybrid matrix (HM). Both PM and HM are non-hygroscopic and produce minimal secondary reflections. HM produces significantly larger signals than CsI with excellent radiation damage resistance. The SBM was staged at the FRIB (East Lansing) ion beam, demonstrating real-time beam profile and rate analysis spanning more than five orders-of-magnitude including visualization of single ion signals with ~10-20 µm spatial resolution. It is superior to and may replace the reference detectors: Faraday cup, silicon strips and a CCD camera beam imager. A proton test beam extended the dynamic range by four orders-of-magnitude.
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C. Bloomer, L. Bobb
DLS, Oxfordshire, United Kingdom
W. Freund, J. Grünert, J. Liu
EuXFEL, Schenefeld, Germany
M.E. Newton
University of Warwick, Coventry, United Kingdom
The European XFEL can generate extremely intense, ultra-short X-ray pulses at MHz repetition rates. Single-crystal CVD diamond detectors have been used to transparently measure the photon beam position and pulse intensity. The diamond itself can withstand the power of the beam, but the surface electrodes can be damaged since a single pulse can already exceed the damage threshold of the electrode material. Presented in this work are pulse intensity and position measurements obtained at the European XFEL using a new type of all-carbon single-crystal diamond detector developed at Diamond Light Source. Instead of traditional surface metallisation, the detector uses laser-written graphitic electrodes buried within the bulk diamond. There is no metallisation in the XFEL X-ray beam path that could be damaged by the beam. The results obtained from a prototype detector are presented, capable of measuring the intensity and 1-dimensional X-ray beam position of individual XFEL pulses. These successful measurements demonstrate the feasibility of all-carbon diagnostic detectors for XFEL use.
M. Marongiu, G. Kube, M. Lantschner, A.I. Novokshonov, K. Wittenburg
DESY, Hamburg, Germany
The PETRA IV project will be a Diffraction Limited Light Source designed to be the successor of PETRA III, the 6 GeV 3rd generation hard X-Ray synchrotron light source at DESY in Hamburg. It will operate at a beam energy of 6 GeV with a design emittance of 20/4 pm rad. For a precise emittance online control, two dedicated diagnostics beamlines will be built up to image the beam profile with synchrotron radiation in the X-Ray region. With two beamlines, it will be possible to extract both the transverse beam emittances and the beam energy spread. Both beamlines will be equipped with two interchangeable X-Ray optical systems: a pinhole camera system to achieve high dynamic range and a Fresnel Diffractometry system for high resolution measurements in the range 1-18 um. This paper describes the planned setup and deals with the possible limitations.
P. Casolaro, S. Braccini, G. Dellepiane, A. Gottstein, I. Mateu, P. Scampoli
AEC, Bern, Switzerland
P. Scampoli
Naples University Federico II, Napoli, Italy
Funding:This project was partially funded by the Bern Center for Precision Medicine (BCPM) of the University of Bern, and by the Swiss National Science Foundation (SNSF) [Grant: CRSII5180352] A new radiotherapy modality, known as FLASH, is a potential breakthrough in cancer care as it features a reduced damage to healthy tissues, resulting in the enhancement of the clinical benefit. FLASH irradiations are characterized by ultra-high dose-rates (>40 Gy/s) delivered in fractions of a second. This represents a challenge in terms of beam diagnostics and dosimetry, as detectors used in conventional radiotherapy saturate or they are too slow for the FLASH regime. In view of the FLASH clinical translation, the development of new dosimeters is fundamental. Along this line, a research project is ongoing at the University of Bern aiming at setting-up new beam monitors and dosimeters for FLASH. The proposed detection system features millimeter scintillators coupled to optical fibers, transporting light pulses to a fast photodetector, readout by high bandwidth digitizers. First prototypes were exposed to the 18 MeV proton beam at the Bern medical cyclotron. The new detectors have been found to be linear in the range up to 780 Gy/s, with a maximum time resolution of 100 ns. These characteristics are promising for the development of a new class of detectors for FLASH radiotherapy.
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F. Roncarolo, P.A. Arrutia Sota, D. Belohrad, E. Calvo Giraldo, E. Effinger, M.A. Fraser, V. Kain, M. Martin Nieto, S. Mazzoni, I. Ortega Ruiz, J. Tan, F.M. Velotti, C. Zamantzas
CERN, Meyrin, Switzerland
M. Bergamaschi
MPI-P, München, Germany
At the CERN Super Proton Synchrotron (SPS) the proton beam is supplied to the fixed target experiments in the North Area facility (NA) via a slow extraction process, taking place at 400 GeV. The monitoring of the spill quality during the extraction, lasting 4.8 seconds with the present SPS setup, is of high interest for minimising beam losses and providing the users with uniform proton-on-target rates. The monitor development challenges include the need for detecting, sampling, processing and publishing the data at rates ranging from few hundred Hz to support the present operation to several hundreds of MHz to serve future experiments proposed within the Physics Beyond Collider (PBC) programme. This paper will give an overview of the ongoing studies for optimizing the existing monitors performances and of the R&D dedicated to future developments. Different techniques are being explored, from Secondary Emission Monitors to Optical Transition Radiation (OTR), Gas Scintillation and Cherenkov detectors. Expected ultimate limitations from the various methods will be presented, together with 2022 experimental results, for example with a recently refurbished OTR detector.
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