Synchrotron Ring Research Articles

Performance of the CERN Proton Synchrotron internal dump: numerical simulation studies and comparison with beam measurements

In the framework of the LHC Injector Upgrade project, a new internal dump for the CERN Proton Synchrotron (PS) ring has been designed, installed, and successfully commissioned. This device is designed to move rapidly into the beam and stop charged particles over several thousand turns to provide protection to PS hardware against beam-induced damage. Due to its design, the internal dump absorbs only a fraction of the secondary particles shower produced by the beam particles that impinge on it. The performance of the dump should ensure efficient use throughout the PS energy range, i.e. from injection at 2 GeV (kinetic energy) to flat top at 26 GeV (total energy). This paper presents comprehensive numerical simulations that combine advanced beam dynamics and beam-matter interaction codes to analyse the behaviour of stopped or scattered particles. Based on the impacts computed by multi-turn beam dynamics simulations, detailed shower simulations with FLUKA were performed to assess the impact of the radiation field on downstream equipment, with a particular emphasis on the dose measured by Beam Loss Monitors. The results of these numerical simulations are compared with the data collected during the routine operation of the PS and its internal dump.

Development of the Continuous Readout Digitising Imager Array detector

The CoRDIA project aims to develop an X-ray imager capable of continuous operation in excess of 100 kframe/s. The goal is to provide a suitable instrument for Photon Science experiments at diffraction-limited Synchrotron Rings and Free Electron Lasers considering Continuous Wave operation. Several chip prototypes were designed in a 65 nm process: in this paper we will present an overview of the challenges and solutions adopted in the ASIC design.

New Injection Controls Environment for the Taiwan Light Source

Taiwan Light Source (TLS) has been service for user service since 1993. Several legacy systems have recently been updated in order to remove obsolescent parts and provide higher operating efficiency. Proprietary designed timing modules were recently replaced by an event based timing system. The magnets of the booster synchrotron were configured as three White circuits and driven by resonance excitation. The original control of the White circuits, which included an analogue amplitude loop and digital phase loop for regulation, has been replaced by full digital regulation loops. The successful upgrade of both systems has led to easy and smooth injection control with enhanced functionality and flexibility. The injection control includes foreground and background processes that coordinate the operation of e-gun, linear accelerator, booster synchrotron, and storage ring with the help of timing system. The injection control GUI provides an intuitive operation interface that includes parameter setting and all necessary information displays, such as various timing value, stored beam current/lifetime, injection efficiency, filling pattern, kickers waveform and so on. Energy saving mode of White circuits operation are supported and embedded into injection control to save electricity. Lifetime calculation of the storage ring is also synchronized with the injection process. Implementation details and operation experience will be presented.

A torus source and its application for non-primary radiation evaluation

Objective. Non-primary radiation doses to normal tissues from proton therapy may be associated with an increased risk of secondary malignancies, particularly in long-term survivors. Thus, a systematic method to evaluate if the dose level of non-primary radiation meets the IEC standard requirements is needed. Approach. Different from the traditional photon radiation therapy system, proton therapy systems are composed of several subsystems in a thick bunker. These subsystems are all possible sources of non-primary radiation threatening the patient. As a case study, 7 sources in the P-Cure synchrotron-based proton therapy system are modeled in Monte Carlo (MC) code: tandem injector, injection, synchrotron ring, extraction, beam transport line, scanning nozzle and concrete reflection/scattering. To accurately evaluate the synchrotron beam loss and non-primary dose, a new model called the torus source model is developed. Its parametric equations define the position and direction of the off-orbit particle bombardment on the torus pipe shell in the Cartesian coordinate system. Non-primary doses are finally calculated by several FLUKA simulations. Main results. The ratios of summarized non-primary doses from different sources to the planned dose of 2 Gy are all much smaller than the IEC requirements in both the 15–50 cm and 50–200 cm regions. Thus, the P-Cure synchrotron-based proton therapy system is clean and patient-friendly, and there is no need an inner shielding concrete between the accelerator and patient. Significance. Non-primary radiation dose level is a very important indicator to evaluate the quality of a PT system. This manuscript provides a feasible MC procedure for synchrotron-based proton therapy with new beam loss model. Which could help people figure out precisely whether this level complies with the IEC standard before the system put into clinical treatment. What’ more, the torus source model could be widely used for bending magnets in gantries and synchrotrons to evaluate non-primary doses or other radiation doses.

Progress report on Muon Source Project at CSNS

A Muon station for sciEnce, technoLOgy and inDustrY (MELODY) has been listed in the China Spallation Neutron Source upgrade plan, and the infrastructure construction is scheduled to start by the end of 2022. The 1.6 GeV double-pulsed proton bunch will be extracted from the Rapid Cycling Synchrotron (RCS) ring to a stand-alone target station. One surface muon and one decay muon beamline are designed to provide multi-terminals for applications. In this report, we describe the design of MELODY and prospect for future applications.

An FEA Investigation of the Vibration Response of the BEATS Detector Stage

The Synchrotron-light for Experimental Science and Application in the Middle East (SESAME) facility is in the process of designing, procuring, and installing a new beamline for tomography (BEATS). The BEATS experimental hutch, hosting sample and detectors, will be located 43 m away from the undulator in the synchrotron ring. Noise in the form of vibration originating from different sources transferred to the detector stage can be a source of poor image quality thus it is important that the detector stage is analysed for its vibration transmission properties. In this study, the result of a three-dimensional random vibration analysis using Finite Element Analysis (FEA) for the detector stage is presented which leads to an estimate of the severity of the vibrations. The random vibration source is that of the ground which was measured exactly where the detector stage will be mounted. The random vibration analysis is conducted in two stages; the modal frequencies of the structure are calculated, thereafter, the random vibration analysis is conducted and the response power spectrum density (PSD) of the structure is calculated along with the root mean square (RMS) displacement values. Since the beamline BEATS is under installation, an existing structure installed at beamline ID28 of the European Synchrotron Radiation Facility (ESRF) was used to validate the model. The model used on the ID28 structure deviated from the experimental results on modal analysis by 2% - 4% on random vibration analysis. This suggested that the model is valid. The analysis as applied to the BEATS detector stage design predicts that the RMS displacement values are less than the pixel size of the detector which is 1 μm. Thus, the structure is sufficiently engineered to moderate the floor vibrations.

Development of CoRDIA: an Imaging Detector for next-generation Synchrotron Rings and Free Electron Lasers

An x-ray imager is being developed for use in diffraction-limited synchrotron rings and continuous wave free electron lasers. The imager is named CoRDIA (COntinuous Readout Digitising Imager Array) and aims at achieving continuous operation at a frame rate in excess of 100kHz. Other goals include single-photon sensitivity at 12 keV (or below), a full well in excess of 10k photon/pixel/image, and a 100μm pixel pitch. The detector ASIC will be compatible with multiple sensor materials to cover different energy ranges. Exploratory prototypes of the readout ASIC (basic circuital blocks) have been manufactured in TSMC 65nm technology: they are presently under test.

Modelling the effects of optical vibrations on photon beam parameters using ray-tracing software.

A method to simulate beam properties observed at the beamline sample-point in the presence of motion of optical components has been developed at Diamond Light Source. A series of stationary ray-tracing simulations are used to model the impact on the beam stability caused by dynamic motion of optical elements. Ray-tracing simulations using SHADOW3 in OASYS, completed over multiple iterations and stitched together, permit the modelling of a pseudo-dynamic beamline. As beamline detectors operating at higher frequencies become more common, beam stability is crucial. Synchrotron ring upgrades to low-emittance lattices require increased stability of beamlines in order to conserve beam brightness. By simulating the change in beam size and position, an estimate of the impact the motion of various components have on stability is possible. The results presented in this paper focus on modelling the physical vibration of optical elements. Multiple beam parameters can be analysed in succession without manual input. The simulation code is described and the initial results obtained are presented. This method can be applied during beamline design and operation for the identification of optical elements that may introduce large errors in the beam properties at the sample-point.

A pulsed high-voltage decelerator system to deliver low-energy antiprotons

The GBAR (Gravitational Behavior of Antihydrogen at Rest) experiment at CERN requires efficient deceleration of 100 keV antiprotons provided by the new ELENA synchrotron ring to synthesize antihydrogen. This is accomplished using electrostatic deceleration optics and a drift tube that is designed to switch from -99 kV to ground when the antiproton bunch is inside – essentially a charged particle “elevator” – producing a 1 keV pulse. We describe the simulation, design, construction and successful testing of the decelerator device at -92 kV on-line with antiprotons from ELENA.

Measurements of 73-keV X-ray time spectrum with avalanche-photodiode scintillation detector using Bi2O3-nanoparticle-doped plastic scintillator

Time spectra of 73-keV X-rays were successfully observed with a scintillation detector using a Bi2O3-nanoparticle-doped plastic scintillator (PLS) and silicon avalanche photodiode (Si-APD). A 5 wt% Bi2O3-nanoparticle-doped PLS was fabricated and cut out to be ∼3.0×3.0 mm and 0.9 mm thick, and it was mounted on a Si-APD operating in proportional mode. An organic scintillator of [2-(4-tert-butylphenyl)-5-(4-phenylphenyl)]-1,3,4-oxadiazole was used for the PLS by 1.68 mol% of polystyrene solvent. When the PLS and Si-APD were cooled to −30° C, a good time resolution of 0.35 ns (full width at half maximum) was obtained for 73.04-keV X-rays when measuring a time structure of the multibunch mode in synchrotron ring operation. The Si-APD scintillation detector mounting a Bi2O3-nanoparticle-doped PLS can be applied well to research fields that need both a high detection efficiency and a subnanosecond time resolution with a photon energy of more than 70 keV, such as synchrotron radiation nuclear resonant scattering on 193Ir.

Present status of HIRFL complex in Lanzhou

Heavy Ion Research Facility in Lanzhou (HIRFL) is a cyclotron, synchrotron and storage ring accelerator complex, which accelerates ions of hydrogen to uranium from low to medium energy. Since the complete of HIRFL-CSR project in 2008, under the support from CAS, efforts have been put to improve the infrastructure for machine performance, including improvement of EMC environments, power distribution stations, PS stations, cooling water system, RF system of cyclotrons and adoption of EPICS control system, etc. New generation SC ECR source (SECRAL-II) with high performance is put into operation. Experiments of electron cooling with pulsed electron beam are performed for the first time. Stochastic cooling and laser cooling are realized in CSRe. The performance of RIBLL2 and CSRe are gradually improved. The isochronous mode of CSRe for precise atomic mass measurements is well studied and reaches state-of-art mass resolution of storage rings. The operation status and enhancement plan of HIRFL will be briefly reported in this paper.

In Situ X-Ray Diffraction Analysis of Face-Centered Cubic Metals Deformed at Room and Cryogenic Temperatures

The present study concerns the cryogenic processing of metals with simultaneous analysis of x-ray diffraction in a synchrotron ring. The mechanical properties improvement related to cryogenic processing of metals is attributed to the partial suppression of dynamic recovery. Thus, commercially pure metals with different stacking fault energies (silver, copper and aluminum) were deformed by uniaxial tensile tests and characterized by in situ x-ray diffraction, at room (293 K) and cryogenic (77 K) temperatures. The cryogenic processing allows a simultaneous improvement in ductility and strength for silver and copper and an improvement in strength for aluminum. This difference in mechanical properties was investigated by means of variations in crystallite size, microstrain and also the amount and size of dimples on the fracture surface. The microstructural refinement at cryogenic temperatures shows a tendency related to the stacking fault energies.

Pulse picking in synchrotron-based XPEEM

We report on a simple and cost-effective device for high-speed gating in photoemission electron microscopy (PEEM) with pulsed photon sources. This device is based on miniaturized electrode plates, which deflect the photoelectron beam inside the imaging column of the microscope so that it is either accepted or blocked in its path towards the detector. The gating device is optimized for installation on the Elmitec SPELEEM III microscope. Due to the compact design, it can be driven by voltage pulses of low amplitude (few volts), delivered by commercially available signal generators. Most notably, our device allows for stroboscopic data collection with on-time of less than 10 ns and at a rate in the range from 1 MHz to 250 MHz, making it suitable for usage in both hybrid and standard multi-bunch operation of the synchrotron ring. We demonstrate applications of pump-probe imaging at high lateral resolution, namely magnetic imaging and PEEM imaging of surface acoustic waves.

SU‐F‐J‐190: Time Resolved Range Measurement System Using Scintillator and CCD Camera for the Slow Beam Extraction

Purpose:To investigate the time structure of the range, we have verified the rang shift due to the betatron tune shift with several synchrotron parameters.Methods:A cylindrical plastic scintillator block and a CCD camera were installed on the black box. Using image processing, the range was determined the 80 percent of distal dose of the depth light distribution. The root mean square error of the range measurement using the scintillator and CCD system is about 0.2 mm. Range measurement was performed at interval of 170 msec. The chromaticity of the synchrotron was changed in the range of plus or minus 1% from reference chromaticity in this study. All of the particle inside the synchrotron ring were extracted with the output beam intensity 1.8×108 and 5.0×107 particle per sec.Results:The time strictures of the range were changed by changing of the chromaticity. The reproducibility of the measurement was sufficient to observe the time structures of the range. The range shift was depending on the number of the residual particle inside the synchrotron ring.Conclusion:In slow beam extraction for scanned carbon‐ion therapy, the range shift is undesirable because it causes the dose uncertainty in the target. We introduced the time‐resolved range measurement using scintillator and CCD system. The scintillator and CCD system have enabled to verify the range shift with sufficient spatial resolution and reproducibility.

Energy compensation of slow extracted beams with RF acceleration

In a conventional carbon-ion radiotherapy facility, a carbon-ion beam is typically accelerated up to an optimum energy, slowly extracted from a synchrotron ring by a resonant slow extraction method, and ultimately delivered to a patient through a beam-delivery system. At Japan’s Gunma University, a method employing slow-beam extraction along with beam-acceleration has been adopted. This method slightly alters the extracted-beam’s energy owing to the acceleration component of the process, which subsequently results in a residual-range variation of approximately 2mm in water-equivalent length. However, this range variation does not disturb a distal dose distribution with broad-beam methods such as the single beam-wobbling method. With the pencil-beam 3D scanning method, however, such a range variation disturbs a distal dose distribution because the variation is comparable to slice thickness. Therefore, for pencil-beam 3D scanning, an energy compensation method for a slow extracted beam is proposed in this paper. This method can compensate for the aforementioned energy variances by controlling net energy losses through a rotatable energy absorber set fixed between the synchrotron exit channel and the isocenter. Experimental results demonstrate that beam energies can be maintained constant, as originally hypothesized. Moreover, energy-absorber positions were found to be significantly enhanced by optimizing beam optics for reducing beam-size growth by implementation of the multiple-scattering effect option.

Electron cooling system in the booster synchrotron of the HIAF project

The High Intensity heavy ion Accelerator Facility (HIAF) is a new accelerator complex under design at the Institute of Modern Physics (IMP). The facility is aiming at the production of high intensity heavy ion beams for a wide range of experiments in high energy density physics, nuclear physics, atomic physics and other applications. It consists of a superconducting electron-cyclotron-resonance ion source and an intense proton ion source, a linear accelerator, a 34Tm booster synchrotron ring, a 43Tm multifunction compression synchrotron ring, a 13Tm high precision spectrometer ring and several experimental terminals. A magnetized electron cooling device is supposed to be used in the booster ring for decreasing the transverse emittance of injected beams. The conceptual design and main parameters of this cooler are presented in this paper.

Energy transfer in the high-voltage electron cooler for the COSY synchrotron ring

An electron cooler produced by the Budker Institute of Nuclear Physics was put into operation at the COSY synchrotron (Julich, Germany) in 2013. This electron cooler has been designed for suppressing the effect of beam scattering by an internal target at energies as high as the maximum proton beam energy of 3 GeV. As the electron cooler was developed, many complicated electrotechnical problems were solved. One of these problems was the transfer of the electric power to many electronic consumers kept at a high electric potential. Several practical methods for solving this problem are described. These variants were analyzed and tested while designing the cooler construction. The final decision is based on the principle of operation of the cascade transformer containing 33 sections connected in series. The described design solutions can be used not only for future electron coolers in projects NICA-JINR (Dubna, Russia), FAIR (Germany), and MEIC (United States), but also for other high-voltage facilities requiring power transfer to devices held at a high potential. After decommissioning of the electron cooler at Fermilab (United States), the described facility has become the highest-voltage electron cooler worldwide.

Use of combined sputter ion and NEG pumps in the heavy ion medical machine

The Heavy Ion Medical Machine (HIMM) is the first medical accelerator being built in China using heavy ion beams for cancer therapy. The accelerator complex, developed by IMP (the Institute of Modern Physics, Chinese Academy of Sciences), has several innovative features, including the use of a synchrotron ring as the main ion accelerator. To guarantee a sufficient storage lifetime of the heavy ions, the average pressure for the entire synchrotron ring must be lower than 5 × 10−7 Pa. This has been achieved integrating a sputter ion and a NEG pump in a suitably designed combination pump. The compact size of the combination pump (CP) allows its easy mounting in spite of the severe space limitations of the machine. The overall CP pumping speed exceeds 1000 l/s (H2), a factor 2 larger than a standard ion pump of comparable size. This feature allows achieving lower ultimate pressure in shorter time, this being beneficial to increase the beam time for patient treatment at HIMM. The CP was also tested under very high gas loads to assess its usability at higher pressure (10−5–10−6 Pa). Preliminary data indicate that long term stable pumping performances of the CP can be achieved also under these more demanding conditions. The result is of more general interest for compact accelerators operating in this pressure range and requiring very compact pump design solutions.

Towards the heavy-ion program at J-PARC

A future heavy-ion program at J-PARC has been discussed. The QCD phase structure in high baryon density regime will be explored with heavy ions at the beam momenta of around 10 A GeV/c at the beam rate of 1010–1011Hz. For this quest, a large acceptance spectrometer is designed to measure electrons and muons, and rare probes such as multi-strangeness and charmed hadrons/nuclei. A heavy-ion acceleration scheme is under study with a new heavy-ion linac and a new booster ring, which accelerate and inject beams into the existing Rapid-Cycling Synchrotron and Main Ring synchrotron. An overview of the heavy-ion program and an accelerator design, as well as physics goals and a conceptual design of the heavy-ion experiment are discussed.

Position and flux stabilization of X-ray beams produced by double-crystal monochromators for EXAFS scans at the titaniumK-edge

The simultaneous and active feedback stabilization of X-ray beam position and monochromatic beam flux during EXAFS scans at the titanium K-edge as produced by a double-crystal monochromator beamline is reported. The feedback is generated using two independent feedback loops using separate beam flux and position measurements. The flux is stabilized using a fast extremum-searching algorithm that is insensitive to changes in the synchrotron ring current and energy-dependent monochromator output. Corrections of beam height are made using an innovative transmissive beam position monitor instrument. The efficacy of the feedback stabilization method is demonstrated by comparing the measurements of EXAFS spectra on inhomogeneous diluted Ti-containing samples with and without feedback applied.