bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring Fcc-ee Optics Designs with Combined Function Magnets
Authors: García-Jaimes C , Pieloni T , van Riesen-Haupt L , Seidel M , Tomás R
Published: January 2024

The FCC-ee project takes a step forward towards the discovery of new physical phenomena beyond the frontier of the standard model, by aiming at unprecedented center of mass energies and luminosities in a double-ring lepton collider. In order to explore potential improvements to the current lattice design, this paper examines the use of combined function magnets within the short straight sections of the arc cells. The use of High Temperature Superconductors (HTS) with an operating temperature of 12 K and maximum field of 18.2 T for the combined function magnets allows increasing the bending radius and decreasing the synchrotron radiation. A first design is presented with comparisons to the current baseline.
An Experimental Study of X-Y Emittance Repartitioning in KEK-STF
Authors: Kuriki M , Liptak Z J , Mukherjee S , Power J , Sakaue K , Guo L , Hayano H , Jin X , Kashiwagi S , Yamamoto N , Yamamoto Y , Kim S , Piot P
Published: January 2024

In a linear collider, the colliding beam has to be flat in the transverse plane to suppress energy spread by Beamstrahlung and to maximize the luminosity, simultaneously. In the current design of ILC, the flat beam is realized by the asymmetric emittance generated by the radiation-damping effect. We propose to generate the equivalent beam directly in the injector linac employing the emittance repartitioning technique. As an experimental demonstration, a beam experiment was carried out at KEK-STF. We present the experimental results.
Low-Level Radio-Frequency system integrated with feed-forward control and vector modulation
Authors: Xiao C. C. , Fang W. C. , Zhang J.Q. , Wang C. , Tan J. H.
Published: January 2024

To provide a more accurate and stable Radio-Frequency (RF) signal in conditioning and processing test progress, it is necessary to design a Low-Level Radio-Frequency (LLRF) control system which can provide high precision RF driving signal based on meeting the amplitude and phase stabilization requirement. Through Feed-Forward operation, accurate phase adjustment and amplitude adjustment are realized inside the pulse, to realize the precision and automation of phase-inversion, amplitude stabilization, phase stabilization, and wave-form adaptation matching. An LLRF System integrated with feed-forward control and vector modulation output was designed and built, and the long-term working stability of the LLRF system was verified during a new 50MW S-band Klystron conditioning progress.
Study and simulation of cryogenic bi-periodic accelerating structure with TM02 mode
Authors: Gao Z , Fang W , Wang C
Published: January 2024

To further enhance the accelerating gradient of accelerators, we designed a cryogenic C-band standing wave bi-periodic accelerating structure for the Shanghai Soft X-ray Free Electron Laser Facility (SXFEL). According to the low-temperature environment, material characteristics and technological conditions, the design is completed and it is decided to design the accelerating structure into a bi-periodic magnetic coupling structure. It is a 17-cell structure consisting of 9 accelerating cavities and 8 coupling cavities. To guarantee the symmetry of the field, the structure is doubly-fed. Operating with the π/2 mode standing wave, it is much less sensitive than the standing-wave structure of π-mode. Additionally, the microwave mode is TM02 in coupling cavities that are larger and even less sensitive than the traditional bi-periodic structure. The shape of the coupling cavity can be redesigned to make it tunable.
Estimated heat load and proposed cooling system in the FCC-ee interaction region
Authors: Novokhatski A , Boscolo M , Fransesini F , Lauciani S , Pellegrino L
Published: January 2024

We discuss the beam power loss related to the heating of the beam pipe walls of the FCC-ee interaction region. We analyse the excitation of trapped modes, which can accumulate electromagnetic energy and determine the locations of these modes. We study the unavoidable resistive-wall wake field, which is responsible for the direct beam pipe walls heating. We show the distribution of the heat load along the central part of the interaction region. We also present the cooling system design and results for temperature distribution in interaction region in the operational mode.
Modification of Beam Transport Line Design for Simultaneous Top-up Injection to PF and PF-AR
Authors: Higashi N , Mitsuda C , Nagahashi S , Harada K , Nogami T , Uchiyama T , Nakamura N , Honda T , Satoh M , Okayasu Y , Enomoto Y
Published: January 2024

The High Energy Accelerator Research Organization (KEK) has two light sources: Photon Factory (PF, 2.5 GeV) and Photon Factory Advanced Ring (PF-AR, 6.5 GeV). In 2017, the operation of a new beam transport line (BT) of PF-AR was started, and the simultaneous top-up injection for both PF and PF-AR was realized. These days, there have been strong demands for the reduction of the operating cost of accelerators, and its importance is greater in PF-AR with higher ring-energy of 6.5 GeV. In 2019, the 5 GeV operation was started in PF-AR. However, the new BT of PF-AR (ARBT) was designed for the energy of 6.5 GeV, then the simultaneous top-up injection is no longer available under the condition of 5 GeV operation of PF-AR and 2.5 GeV operation of PF. In order to mitigate this impact, the pseudo-top-top injection has been employed by fine-tuning the current of a common DC bending magnet placed at the intersection of ARBT and the BT of PF (PFBT) within a given time frame. However, this scheme reduces the flexibility of the operation schedules, and will not be able to respond adequately to low emittance optics of PF-AR that may bring the shorter beam lifetime. In order to realize true-top-up injection, a modification of BTs’ optics design was carried out to add new horizontal steering magnets and a flattened-duct. The beam commissioning succeeded and the application to the user-run will start in this May. This time, details of modification and its extended plan will be presented.
Studies on a Triple-Turn Energy-Recovery Mode at the S-DALINAC
Authors: Schliessmann F , Arnold M , Brauch A , Dutine M , Fischer M , Grewe R , Juergensen L , Meier M , Pietralla N , Schneider D
Published: January 2024

The electron accelerator S-DALINAC at TU Darmstadt was successfully operated in single- and double-turn energy-recovery mode. The latter was realized using a shared beam-transport where two beams are superimposed in the first recirculation beamline. Due to its current design, the S-DALINAC can be upgraded with reasonable effort to be operated in triple-turn energy-recovery mode with shared beam-transport. Here, two beams are superimposed in both the first and the second recirculation beamline. This mode is particularly challenging since it does not allow for on-the-fly beam tuning compared to a triple-turn energy-recovery mode with individual beam-transport. Therefore, the triple-turn energy-recovery mode requires precise determination of the accelerator setup obtained from beam-dynamics simulations prior to beam-tuning. First results of the necessary beam-dynamics simulations for this mode are presented.
Fully coherent soft X-ray pulse generation based on ERL
Authors: Cao L , Cai M , Feng C , Wang Z , Chen S , Zhao Z T
Published: January 2024

Energy recovery linacs (ERLs) possess the bright prospect of fully coherent X-ray generation. Recently, we designed a 600 MeV energy recovery linac capable of producing high power fully coherent radiation pulses at 13.5 nm with a relatively low-intensity 256.5 nm seed laser profiting from the employment of angular-dispersion-induced microbunching (ADM) technology. We also designed a matched multiplexed system that can deflect each radiator by 8 mrad with a carefully choreographed multi-bend achromat (MBA) scheme. As a result of downstream MBA’s dispersion compensation, bunching factors will be enhanced both at the fundamental wavelength and high harmonics. The bunching factor of the 19th harmonic increased from 10% to 26%, and that of the 57th harmonic became 8.4%, which is sufficient to generate fully coherent radiation in the soft X-ray range.
Emittance Growth Study of an Electron Beam in a Double-Alpha Magnet Compressor Used in an Inverse Compton Scattering X-Ray Source
Authors: Pires A , Chauchat A , Collet M , Le Flanchec V , Delerue N
Published: January 2024

An Inverse Compton Scattering (ICS) X-ray source is under development at the ELSA (Electrons Laser X-Sources and Applications) electron RF linac of CEA DAM (Commissariat à l’Energie Atomique et aux Energies Alternatives, Direction des Applications Militaires). X-rays are emitted by the interaction of 30 MeV electron bunches with Nd:YAG laser pulses. The electron bunches duration is 30 ps rms before compression in two alpha magnets. In such a system, electron trajectories are curved with a short radius, resulting in a noticeable degradation of the beam emittance. In the specific case of strongly curved trajectories, the straight trajectory and beam shape assumptions used for space charge calculation in most simulation codes are questionable. Two different approaches to the simulation of electron beam dynamics within the alpha magnets are compared. A specific method to deal with changes from the reference particle frame to the laboratory reference frame, which does not imply any trajectory and beam shape assumptions, is proposed. Calculation results are presented. Along with an important emittance growth, they show that more physical effects can be taken into account in the latter simulation.
Bending Magnet Photon Absorber Design and Calculations for the Elettra 2.0 Storage Ring
Authors: Scrimali G , Cudin I
Published: January 2024

To harness the major advances that have been done in the field of synchrotron light research, Elettra synchrotron radiation facility is being updated. Presently in its design phase, the Elettra 2.0 project will allow new and better research to be performed at the facility. In the upgrade of the storage ring, the new 6BA lattice brings challenges in terms of available space and radiated power. This paper presents the bending magnet photon absorber designed to cope with the new requirements. The absorber concept created for ESRF-EBS has been revised and re-engineered to make it suitable for the specific features of Elettra’s sources. To reduce the high-power densities induced by the short source-absorber distance, the one-jawed, toothed profile was obtained via a robust optimization, considering possible misalignments or beam miss-steering. Novelty of the approach is the absorber insertion in the vacuum chamber from the inside of the ring. Finally, presented are the thermo-mechanical and computational fluid dynamics simulations (ANSYS) performed to validate the design, comprehensive of a Monte-Carlo, ray-traced simulation to evaluate photon reflections (SYNRAD) and their effects.
Photoelectron spectroscopy of CsK2Sb photocathode at Synchrotron Radiation Facility using vacuum transport system
Authors: Shiohara K. , Guo L. , Yamaguchi H. , Takashima Y.
Published: January 2024

As accelerators and electron microscopes become more advanced, high-performance photocathodes are required. In particular, Cesium potassium antimonide (CsK2Sb) photocathode is of interest because of its low emittance, excitability in visible light, and high quantum efficiency (QE). The challenge is its high susceptibility to environment that lead to low operating vacuum pressure and short lifetime/low extraction charge. To resolve these issues, it is necessary to understand the molecular structure of the cathode and its degradation mechanism. In this study, we transported CsK2Sb photocathode to a beamline of synchrotron radiation facility using a vacuum transport system for molecular structure analysis. Specifically, the cathode was deposited in an evaporation system at Nagoya University. We transported it to Aichi Synchrotron Radiation Center (Aichi SR) located 15 km away, and analyzed it in the depth direction by X-ray photoelectron spectroscopy (XPS) at BL7U. Based on the results, we quantitatively evaluated the composition ratios and stoichiometry of the cathode elements (Sb, K, Cs). A Cs ex-cess state of surface was observed at the surface, and it is consistent with previous studies. The intended atomic structure of CsK2Sb was formed only at a few nanometres of the surface on the Mo substrate. On the other hand, the CsK2Sb cathode structure on the graphene substrate was preserved further in the depth direction.
Test of a DC-photogun injector for the Lighthouse facility
Authors: Blokesch G , Grewe M , Keune B , Krämer J M , Kümper V , Piel C , Quitmann C , Trinh T , Hoffstaetter G
Published: January 2024

Worldwide there is a push for producing medical isotopes using particle accelerators rather than fission reactors. Here we report on the operation of the beam test facility (BTF), set up and operated at the RI site in Bergisch Gladbach, Germany, comprising a dc-photogun designed for producing 99Mo in the Lighthouse facility and commissioned by the Institute for Radio Elements (IRE, Belgium) [1]. The gun is based on the successful CBETA design by the Cornell University[3]. The existing design has been reworked and integrated with a fully automatable photocathode production facility (PPF) designed for series production and exchange of photocathodes (PC).
Dynamics of off-axis injection near the coupling resonance at PETRA IV
Authors: Cortés García E.C. , Agapov I.V.
Published: January 2024

The PETRA IV project will have a storage ring with an ultra-low natural emittance of 20 pm rad. For an off-axis injection scheme with working points at the difference resonance, it is critical to ensure that the vertical excursion caused by transversal coupling does not affect injection efficiency. In this contribution, we present simulation results of an off-axis injection near the coupling resonance, which provides equal equilibrium emittances. The advantages and disadvantages of such a scheme are discussed.
Calibration of the 2-Phase Bubble Tracking Model for Liquid Mercury Target Simulation with Machine Learning Surrogate Models
Authors: Lin L , Tran H , Radaideh M , Hoover A , Winder D , Cousineau S
Published: January 2024

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is one of the most powerful accelerator-driven neutron sources in the world. The intense protons strike on SNS’s mercury target to provide bright neutron beams, which also leads to severe fluid-structure interactions inside the target. Prediction of resultant loading on the target is difficult particularly when helium gas is injected into mercury to reduce the loading and mitigate the pitting damage on vessel walls. A 2-phase material model that incorporates the Rayleigh-Plesset (R-P) model is expected to address this multi-physics problem. However, several uncertain parameters in the R-P model require intensive simulations to determine their optimal values. With the help of machine learning and the measured target strain, we have studied the major uncertain parameters in this R-P model and developed a framework to identify optimal parameters that significantly reduce the discrepancy between simulations and experimental strains. The preliminary results show the possibility of using this mercury/helium mixture and surrogate models to predict a better match of target strain response when the helium gas is injected.
AISHa: an ECRIS for nuclear-physics, new clinical protocols and material experiments
Authors: Celona L. , Leonardi O. , Castro G. , Gammino S. , Neri L. , Costanzo G. , Chines F. , Siliato D. , Passerello S. , Russo F. , Calabrese G. , Marletta S. , Vercesi V. , Lanza A. , Kourkoumeli A , Ramos R. L. , Scagliotti C. , Vercellati F. , Falbo L. , Maugeri C. , Monferrato R. , Sironi S. , Vigon A.
Published: January 2024

The Advanced Ion Source for Hadrontherapy (AISHa) is an ECR ion source operating at 18 GHz, developed with the aim to produce multiply charged ion beams with low ripple, high stability and reproducibility. Due to its unique peculiarity, it is the most suitable choice for medical applications, but also for nuclear-physics and material experiments. Two sources have been realized: the first at INFN-LNS and the second at the Centro Nazionale di Adroterapia Oncologica (CNAO). The first one, fully commissioned at INFN-LNS, will be used as test-bench for development of new beams and several R&D activities are planned within the IONS experiment to increase plasma confinement and to refine techniques of non-invasive plasma diagnostics to correlate plasma and beam parameters. The second one recently produced the first beam and it will allow to increase the CNAO potential in the field of experimental and industrial research, with the long-term goal of introducing new ionic species into clinical practice such as helium, oxygen and later also iron and lithium, useful for bio-spatial research. In this work, the key peculiarities and the experimental results of the two Aisha ion sources will be presented.
Beam Dynamics Studies for the Target Beamlines of the High Brilliance Neutron Source
Authors: Lehrach Andreas , Baggemann Johannes , Felden Olaf , Gebel Ralf , Gutberlet Thomas , Podlech Holger , Zakalek Paul
Published: January 2024

The High Brilliance Neutron Source (HBS) belongs to the class of High Current Accelerator based Neutron Sources (Hi-CANS). The driver Linac for the HBS must be able to reliably accelerate a 100 mA proton beam to an energy of 70 MeV [2, 1, 3]. The beam is sent pulse-by-pulse to three different targets via a multiplexer in the High Energy Beam Transfer (HEBT) section. Each individual proton pulse behind the multiplexer has a specific time structure in order to optimally serve the different instruments grouped around one target station. The main development steps of the HEBT are the development of a three-field septum magnet, which is an essential part of the multiplexer magnet system, the beam dynamics integration of the multiplexer magnet system into the beamline, and the ion-optical layout of the individual target beamlines.
Simulation and measurement of beam loading effects in magnetic alloy rf cavity of CSNS RCS
Authors: Liu Hanyang , Huang Liangsheng , Liu Yang , Xu Shouyan , Wang Sheng
Published: January 2024

Different from the ferrite cavity, the Q value of magnetic alloy cavity in CSNS RCS is only about 1.25, the frequency band of impedance is wide, and the beam loading effects is strong. Based on the impedance measurement results, the influence of the beam loading effects on the longitudinal distribution of the magnetic alloy cavity in CSNS RCS is studied by simulation, and the induced voltage measured on the machine is consistent with it.
Fabrication progress of the prototype spoke cavity for the JAEA-ADS linac
Authors: Tamura J , Kondo Y , Yee-Rendon B , Meigo S , Maekawa F , Kako E , Umemori K , Sakai H , Dohmae T
Published: January 2024

The Japan Atomic Energy Agency (JAEA) has been proposing an accelerator-driven nuclear transmutation system (ADS) as a future nuclear system. In preparation for the actual design of the CW proton linac for the JAEA-ADS, we are now prototyping a low-β (≈ 0.2) single-spoke cavity. The cavity fabrication started in 2020. Most of the cavity parts were shaped in fiscal year 2020 by press-forming and machining. In 2021, we started welding the shaped cavity parts together. By preliminarily investigating the optimum welding conditions using mock-up test pieces, each cavity part was joined together with smooth welding beads. So far, we have fabricated the body section and the beam port sections. By measuring the resonant frequency of the temporarily assembled cavity, it was confirmed that there were no significant problems with the cavity fabrication.
Accelerator and beam physics challenges in support of FRIB experiments
Authors: Ostroumov P N , Fukushima K , Hwang K , Maruta T , Plastun A , Wei J , Zhang T , Zhao Q
Published: January 2024

The Facility for Rare Isotope Beams (FRIB), a major nuclear physics facility for research with fast, stopped and reaccelerated rare isotope beams, started operation in May 2022. Since then, a dozen nuclear physics experiments have been successfully accomplished. Typically, the experiments with rare isotope beams last a week or two. Each experiment requires a different primary beam species and energies. Shortening the accelerator and fragment separator setup time is critical to meet the demands of the FRIB Users community. Currently, the primary focus in the linac is reducing the accelerator setup time and beam power ramp-up. Many physics applications have been developed and used to set up the accelerator and beamlines. The simultaneous acceleration of multiple charge states of heavy ion beams is routinely used to minimize the beam power deposition on the charge selector slits after the stripper. This paper discusses the challenges of linac tune development for the acceleration of various ion species.
Future ESS upgrade to Medium Pulse Length – What are the technical challenges for the accelerator and target?
Authors: Lindroos M. , Arai M. , Danared H. , Deen P. , Eshraqi M. , Jones B. , Milas N. , Miyamoto R. , Odén U. , Plostinar C. , Santoro V. , Schweika W. , Zanini L. , Carlile C. , Ekelöf T. , Olvegård M. , Machida S. , Prior C.
Published: January 2024

A compression of the ESS proton pulse from the present 2.86 milliseconds to a medium pulse length of a few tens of microseconds which is better matched to the moderator time-constant of thermal neutrons would considerably boost the performance for many instruments at ESS. Generating such a proton pulse with preserved instantaneous beam power requires a storage ring to be added to the ESS accelerator. Such a ring has been studied within the ESSnuSB neutrino super-beam study. The proton pulse length extracted in single turn extraction from this ring would be approximately 1 microsecond long which could be destructive for the present ESS target and is very short compared to the moderator time constant. The more desirable medium length pulse could possibly be generated by multi-turn extraction and a new concept using a cyclotron like extraction scheme in a synchrotron or a FFA. Another way to generate the longer pulses is to extract a bunch train using fast strip line kickers but this would require a larger storage ring. Using a “bunch train” has been successfully applied at the CERN ISOLDE facility to avoid destruction of sensitive liquid metal targets used for Nuclear Physics experiments. Other challenges are linked to the injection into the storage rings and the understanding of the target, moderator and neutron extraction systems with short and medium pulse length.
Operational tests of CRYRING@ESR without electron cooler solenoid compensation
Authors: Krantz C , Andelkovic Z , Dimopoulou C , Fedotova S , Geithner W , Herfurth F , Heß R , Kraus I , Khammee S , Lestinsky M , Reiter A , Roβbach J , Trotsenko S , Vorobyev G
Published: January 2024

We have tested operation of FAIR’s low-energy ion storage ring CRYRING@ESR with uncompensated electron cooler solenoid. With its standard working point on the lowest-order difference resonance, a second solenoid is normally used to cancel betatron coupling introduced by the cooler’s magnetic field. In operation with a D+ test beam, we found that omission of the compensation solenoid did not lead to a notable deterioration of beam intensity, quality, or cooling time, though the expected coupling of betatron motion is then clearly observed.
Tailoring transverse beam characteristics with the new CERN PS Booster charge-exchange injection system
Authors: Renner E , Albright S , Antoniou F , Asvesta F , Bartosik H , Bracco C , Di Giovanni G P , Mikulec B , Prebibaj T , Skowronski P , Velotti F M
Published: January 2024

A key aspect of the LHC Injectors Upgrade project is the connection of the PSB to the newly built Linac4 and the related installation of a new 160 MeV charge-exchange injection system. The new injection system was commissioned in winter 2020/21 and is now used operationally to tailor the transverse characteristics for the various beam types at CERN, such as high-intensity fixed target beams, LHC single bunch beams, and high-brightness beams for LHC. This contribution outlines the different injection strategies for producing the various beam types and discusses the application of numerical optimization algorithms to adjust injection settings in operation efficiently.
Optimization of low-energy slow extraction efficiency of XiPAF
Authors: Wang Z J , Yao H J , Yang Y , Liu X Y , Li Y , Xiong Y , Zheng S X , Wang X W
Published: January 2024

Xi’an Proton Application Facility (XiPAF) synchrotron provides 10∼200MeV proton beam for the experimental simulation of the space radiation environment. Due to the space charge effect, the slow extraction of 10 MeV proton beam is a work full of challenges. In a past experiment, the total extraction efficiency was over 65% with 4.5 ∽ 6.5×1010 protons stored before extraction but decreased to 52% with 9×1010 protons stored. In order to study the beam loss caused by a strong space charge effect, based on experimental parameters, the beam loss fractions at different positions of XiPAF synchrotron are obtained through the simulation. According to the beam loss analysis, optimized parameters are found for reference in subsequent experiments. It is also noted that negative beam average momentum spread before extraction is beneficial to the improvement of extraction efficiency.
OffSet measurements at Rapid Cycling Synchrotron in China Spallation Neutron Source
Authors: An Yuwen , Li Yong , Lu Xiaohan , Xu Shouyan
Published: January 2024

The Rapid Cycling Synchrotron(RCS) is the key part of the China Spallation Neutron Source(CSNS) with a repetition rate of 25 Hz. The lattice of the RCS is based on triplet cells with a superperiod of four. Due to the utilization of the trim quadrupoles in June 2021, the Beam Position Monitor(BPM) offsets have been carefully measured, and the beam operation is more stable. In this paper, we will review the preparation of BPM offsets measurements with the virtual accelerator and the experimental results in beam commissioning.
Design of the gradient dipole magnet for LLICTF
Authors: Chu Yimeng , Wang Zhijun , Huang Junren , Chen Weilong , Xu Zhenyu , Liang Zehua , Sun Kunxiang
Published: January 2024

The Lanzhou Light Ion Cancer Therapy Facility (LLICTF) is a compact medical accelerator currently under construction. It is designed to treat cancer using a 230 MeV, 30 mA H+ beam and a 85 MeV/u, 1 mA 3He2+ beam. The facility comprises two ion sources, a low-energy beam-transport (LEBT), a Radio Frequency Quadrupole (RFQ), a medium-energy beam-transport (MEBT), and the main ring accelerating structure. Due to the presence of two ion sources, it is necessary to introduce a dipole magnet which is symmetrically focused as much as possible to meet the focusing requirements of the LEBT beam. Therefore, a gradient dipole magnet has been designed to achieve this symmetrical focusing. This paper discusses the theoretical and simulated symmetric focusing of the gradient dipole magnet. It also analyzes the effect of fringe fields and space charge. Additionally, this paper presents the results of the model design with CST and the multi-particle simulation results with TraceWin.
Beam dynamics optimization of EuPRAXIA@SPARC_LAB RF injector
Authors: Silvi G J , Bacci A L , Carillo M , Chiadroni E , Faillace L , Francescone D , Giribono A , Iovine P , Mostacci A , Ferrario M , Pompili R , Vaccarezza C
Published: January 2024

At EuPRAXIA@SPARC_LAB an X-ray FEL user facility is driven by a plasma accelerator in the particle-driven configuration where an ultra-relativistic beam, the driver, through a plasma generates a wake of charge density useful for accelerating a witness beam. The electron bunches are generated through the so-called comb technique in an RF injector that consists of a 1.6-cell S-band gun followed by four S-band TW accelerating structures. The main working point foresees a 30pC witness and a 200pC driver longitudinally compressed in the first accelerating structure operated in the velocity-bunching regime, which allows to accelerate and manipulate the beam to reach proper transverse and longitudinal parameters. The optimization of the witness emittance is performed with additional magnetic field around the gun and the velocity bunching S-band structures and by shaping the laser pulse at the cathode. The paper reports on beam dynamics studies performed also with the insertion of an X-band RF cavity after the gun that is proposed to shape the beam current distribution and stabilize it with respect to RF jitters.
Electron cloud build-up studies for FCC-ee
Authors: Sabato L , Pieloni T , Iadarola G , Mether L
Published: January 2024

The Future Circular Collider (FCC) study is developing designs for a new research infrastructure to host the next generation of higher performance particle colliders to extend the research currently being conducted at the LHC. In particular, FCC-ee is an electron-positron collider, which is the first stage towards a 100 TeV proton-proton collider FCC-hh. FCC-ee may be affected by electron cloud (e-cloud) and the strongest effects are foreseen for the Z configuration, due to the highest number of bunches, which corresponds to the smallest bunch spacing. The presence of a large electron density in the beam pipe can limit the achievable performance of the accelerator through different effects like transverse instabilities, transverse emittance growth, particle losses, vacuum degradation and additional heat loads of the inner surface of the vacuum chambers. In the design phase, the goal is to suppress the e-cloud effects in FCC-ee and, therefore, a preliminary study to identify the parameters, which play a significant role in the e-cloud formation has been performed. In this paper, an extensive e-cloud simulation study is presented. In particular, the impact of the e-cloud is studied for different configurations, for example: for the electron and the positron beam; in the different elements of the particle accelerator; changing the beam chamber geometry; for different values of the Secondary Emission Yield (SEY); and for different beam parameters.
A novel fiber-optic beam monitor
Authors: Usherovich S. , Casolaro P. , Gottstein A. , Mateu I. , Dehnel M. , Braccini S. , Hoehr C.
Published: January 2024

A novel beam monitor based on Ce-doped silica optical fibers is being presented. Four fibers are mounted on the outside of a beam transport pipe, at the location of a beam stop at a proton cyclotron. The secondary radiation caused by the proton beam interaction with the beam stop is measured by the optical fibers via Radiation-Induced Emission (RIE). The light signal in the individual fibers is correlated to the proton flux closest to the fiber and can therefore be used as a detector to monitor the position of the proton beam in the beam stop. Initial testing shows that monitoring of a 150 nA beam of 18 MeV protons into a beam dump is possible. The monitor can measure relative beam current and beam displacement in X and Y as a function of magnetic steering.
Capacitive BPM electromagnetic design optimisation
Authors: Bilanishvili S. , Zobov M.
Published: January 2024

Capacitive beam position monitors (BPM) are widely used as diagnostics tools in particle accelerators. Typically due to a large number of BPM in an accelerator, their contribution to the beam coupling impedance cannot be neglected. In addition to the broadband part at low frequencies, the impedance exhibits resonant peaks at higher frequencies due to electromagnetic fields trapped around the BPM button and in the feedthrough assembly. Coupling of these peaks with beam spectrum lines can result in the BPM overheating. In this paper, we discuss the BPM design optimization aimed at the beam coupling impedance minimization while keeping the BPM signal transfer impedance.
Bunch-by-bunch transverse position measurement during injection
Authors: Huang Chih-Hsien , Hsu Kuo-Tung , Liao Chih-Yu , Chiu Pei-Chen , Cheng Yung-Sen , Liao Jin-Kun , Hu Kuo-Hwa
Published: January 2024

Bunch-by-bunch systems have been developed at the Taiwan Light Source and the Taiwan Photon Source to monitor transverse position and filling patterns. The system comprises four channels with a 500 MHz sampling rate synchronized with the accelerator’s radio frequency. It is utilized to diagnose injection transients due to kick mismatch, beam oscillations resulting from damped betatron oscillations and wakefield, and monitor the injection current of each bunch.
About the damage mechanisms of thin targets exposed to high-power particle beams
Authors: Sapinski Mariusz
Published: January 2024

Thin targets, in the forms of wires, stripes, or foils, are often used in accelerators to measure the properties of particle beams. Motivations for a small thickness, typically between several and hundred micrometers, are diverse. The minuscule diameter of a wire allows for precision measurement because it is probing a small fraction of the beam’s transverse profile. In case of high-power beams, the important rationale is also a small energy which beam deposits in the target and a good cooling because of a large surface-to-volume ratio. In certain beam conditions, the temperature of the target is still very high and leads to wire damage. This paper presents detailed analysis of ductile breakage of a molybdenum wire and gives a short overview of other damage mechanisms for various materials.
Improvements in longitudinal phase space tomography at PITZ
Authors: Aftab N , Boonpornprasert P , Georgiev G , Good J , Gross M , Hillert W , Hoffmann A , Krasilnikov M , Li X-K , Niemczyk R , Oppelt A , Qian H , Reader A J , Richard C , Stephan F , Vashchenko G
Published: January 2024

Methodical studies to improve the existing e-beam Longitudinal Phase Space (LPS) tomography were performed at the Photo Injector Test facility at DESY in Zeuthen. Proof-of-principle simulations were done to address some core concerns e.g. booster phase range, space charge effects and noisy artefacts in results. Phase advance analysis was done with the help of an analytical model that determined the booster phase range and step size. A slit was introduced before the booster to truncate the beam and reduce space charge forces. The reconstruction method adopted was image space reconstruction algorithm owing to its assurance of non-negative solution. An initial scientific presumption of LPS from low energy momentum measurements was established to reduce artefacts in the phase space. This paper will explain the proof-of-principle simulations highlighting the key aspects to obtain accurate results. Reconstructed LPS for different experimental cases will be presented to demonstrate the diagnostic capability.
Observation of Beam Emittance Reduction due to Gas Sheet Injection for Beam Profile Measurement
Authors: Yamada I , Chimura M , Kamiya J , Kinsho M
Published: January 2024

In a high intensity ion accelerator, a non-destructive beam monitor is required to realize a continuous measurement of the beam for improving the beam quality in operation for users. We have developed a non-destructive 2-D beam profile monitor detecting photons produced by interaction between a beam and a sheet-shaped gas. Though the developed monitor is a non-destructive type, the injected gas sheet should induce scattering of the beam particles which makes the beam emittance large. We have measured a beam current and a phase space distribution of the J-PARC 3 MeV, 60 mA H− beam with change of the gas sheet flux. It was found that the beam current reduction was in linear relation and the root mean square emittance was constant or decreased by up to 4.5% in y-y′ plane and did not change in x-x′ plane against a rise in the gas sheet flux. These result indicate that the developed monitor can be utilized as a non-destructive one depending on the gas sheet flux condition.
Implementation and performance estimation of new archive system for the TLS control system
Authors: Liao J K , Cheng Y S , Hsu L P , Chen J , Hu K H , Hsu K T
Published: January 2024

The TLS (Taiwan Light Source) is a third generation of synchrotron light source that has been operated for more than 25 years, and its control system is a proprietary designed system. The TLS control system maintenance is difficult because of component outage problems. Some parts of the control system are being rejuvenated with the help of the EPICS framework used in the TPS (Taiwan Photon Source) control system to ensure that TLS continues to operate normally, saving both manpower and money. A new EPICS archive system was needed to efficiently record various machine parameters and status information during routine operations. As a result, the EPICS Archiver Appliance has been evaluated as suitable for deploying to archive TLS machine data which encapsulated the PV (Process Variable) channel access. Specific graphical user interfaces and API packages have been supported for quickly retrieving archived data, as well as a plotting function for easy diagnosis. Furthermore, the performance of this new TLS archive system has been estimated, and related system resources will be manually adjusted for better service. The efforts will be summarized in this paper.
New Injection Controls Environment for the Taiwan Light Source
Authors: Chen J , Liao C Y , Wu C Y , Cheng Y S , Liao J K , Hsu K T , Hu K H
Published: January 2024

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.
Development of EPICS-Based Data Acquisition system for Beam Loss Monitor and sX-map
Authors: Kuriyama Y. , Iwashita Y. , Fuwa Y. , Hayano H.
Published: January 2024

Beam commissioning is underway at KEK’s Superconducting RF Test Facility (STF). Since beam diagnostics are important to realize stable operation, we have developed a time-resolved beam loss distribution monitor as one of the beam diagnostics. This monitor uses up to 16 PIN photodiodes as X-ray sensors to observe X-rays generated due to beam loss of a pulsed beam with a width of approximately 800 μs, which is divided into 100 μs intervals. Thus, 128 data can be acquired per bunch. The data is read out by an EPICS-based data acquisition system. On the other hand, we are also developing an EPICS-based data acquisition system for an inspection method for the superconducting cavities(sX-map) for the vertical test of bare cavities. sX-map strips are inserted inside the stiffener ring at the iris of superconducting cavities. In this presentation, an overview of these EPICS-based data acquisition systems and their integration with the existing control system will be presented.
Studies of radiation background at the synchrotron light source DELTA
Authors: Khan Shaukat , Mai Carsten , Kebekus Marcel , Schmidt Gerald
Published: January 2024

The 1.5-GeV electron storage ring of the synchrotron radiation source DELTA at TU Dortmund University is surrounded by a 1 m thick concrete radiation shielding wall with a height varying between 3.0 and 4.3 m and with open top. The installation of a new 7-T superconducting wiggler and tentative plans for a new building in the vicinity motivated recent studies of background radiation either directly escaping the open-topped radiation shield or being scattered by air or the roof of the hall (the so-called radiation skyshine). Spectra of gamma radiation were recorded under different conditions using a high-purity germanium detector. Long-term measurements were made with photoluminescence dosimeters. The paper presents the results together with calculations of the spectral distribution of wiggler radiation as well as a model for the spatial distribution of radiation emitted by the whole storage ring.
Upgrades and developments related to stable ion beams injectors at INFN-LNL
Authors: Galatà A , Fagotti E , Francescon P , Gallo C S , Giora D , Martini D , Minarello A , Miglioranza M , Pasquato F , Roetta M , Rossignoli M
Published: January 2024

The LNL accelerator complex is equipped with two stable ion beams injectors, employing respectively negative and positive ion sources. In particular, a sputtering-type negative ion source and an Electron Cyclotron Resonance Ion Source (ECRIS) are installed on high voltage platforms, to provide the optimum injection energy in the downstream accelerators. Recently, the two injectors have been object of upgrades and developments, in order to improve the overall safety and reliability of the two systems, as well as the beams available for the users. This contribution describes the work related to the above-mentioned activities, the technical choices employed and the latest results on ion beams production.
New event based timing system for the Taiwan Light Source
Authors: Wu C Y , Liao C Y , Chen J , Lee D , Cheng Y S , Hu K H , Hsu K T
Published: January 2024

The Taiwan Light Source (TLS) is a third generation synchrotron light source that has been in operation since 1993. However, the legacy timing system is obsolete and needs to be upgraded to an event based timing system. This upgrade is intended to replace obsolete components and improve functionality. The new timing system must coordinate the operation of the linac, the White circuit based booster synchrotron, and the storage ring for beam generation, injection, extraction, and accumulation, while also supporting top up operation of the storage ring. To achieve this, a cPCI (CompactPCI) based EPICS IOC (Input Output Controller) and expandable fanless embedded computers have been adopted for the new TLS timing system, replacing the existing VME-based ILC (Intelligent Local Controller) to provide an easy to maintain control environment. However, the resonant excitation of the booster magnets with the event system requires special attention in the design and implementation phases. This paper summarizes the design ideas and implementation process for addressing this issue.
Preparations of QWR superconducting cavities for beam commissioning
Authors: Kim H , Jung Y , Kim J , Jang H , Kim Y , Gil D , Jeon S , Son K , Lee M , Ki T
Published: January 2024

Quarter-wave resonator (QWR) cavities are prepared for beam commissioning. RF conditioning is performed for each QWR cavity. The total heat load, including static and dynamic heat loads, is measured for each cavity. The helium pressure fluctuation is reduced by changing the flow rate, supply pressure, return pressure, cryogenic valve control, etc. The cavity pressure is monitored during RF preparation. The amplitude and phase of the QWR cavity are stably controlled for beam commissioning.
High-Efficiency Industrial 130 kW cw Solid-State RF Amplifier for 1.3 GHz
Authors: Nedos M , Pupeter N , Wied V , Keune B , Quitmann C , Blokesch G
Published: January 2024

A new 1.3 GHz solid-state high-power RF amplifier (SSA) has been built for the Lighthouse project in close cooperation between Cryoelectra and RI Research Instruments. The amplifier was developed by Cryoelectra as a scalable compact system with an RF-power density of 40kW/m2. Its industrial design is very reliable and easy to maintain. The SSA delivers a continuous RF output power of more than 130 kW with a wall-plug efficiency of 63% and with very low phase noise. The power is generated by 40 patented RF amplifier modules each containing 8 GaN transistor units. Their outputs are combined by a coaxial 8-way combiner in the center of the module. Each module is connected to the 4x9-way cable-free waveguide combiner network and can be exchanged in the event of fault within minutes thanks to quick connectors. A sophisticated control system continuously monitors the state of all components for reliable machine and personnel protection.

Despite all the challenges encountered during development and production, the SSA was built and handed over to the client in the shortest possible time. It passed the acceptance test on site exceptionally well.
New SiC Kicker Power Supply for J-PARC
Authors: Takayanagi T. , Ono A. , Sugita M. , Yamamoto K. , Oguri H. , Kinsho M. , Horino K. , Ueno T. , Oda K. , Tokuchi A. , Ikoma N.
Published: January 2024

A new kicker power supply using silicon carbide metal–oxide semiconductor field-effect transistors (SiC-MOSFETs) is under development at the Japan Proton Accelerator Research Complex (J-PARC). SiC-MOSFETs fabricate compact high-speed pulse power supplies to replace the thyratron switch power supply. The base circuit of the new power supply uses the linear transformer driver (LTD) system, and the semi-conductor module circuit comprises a radial symmetry type that achieves low noise. The three main components of the current kicker power supply, i.e., the thyratron, pulse-forming network (PFN) circuit, and end clipper, can be assembled on a single board as the new module circuit board. The new power supply contains a 1.25 kV/2 kA main board that forms a trapezoidal pulse and a 0.1 kV/2 kA correction board, compensating for the flat section droop. The 32 main boards and 20 correction boards are hierarchically connected in series to achieve the waveform specifications required for the J-PARC rapid cycling synchrotron (RCS) kicker power supply: output voltage of 40 kV, output current of 2 kA, and pulse width of 1.2 μs. Furthermore, a 25 % power saving has been confirmed and an insulating cylinder for the conductor has been developed to suppress corona discharge and withstand continuous operation for a long time.
Finite Element Analysis for NEG coated vacuum chamber based on ANSYS Workbench
Authors: Ma Wenjing , Zhang Wenli , Xu Xiaopeng , Wei Jianya , Wang Sihui , Ge Xiaoqin , Bian Baoyuan
Published: January 2024

The Hefei Advanced Light Facility (HALF) is a diffraction limited storage ring (DLSR) being constructed. As the main component of the storage ring vacuum system, the vacuum chamber transports the beam and withstands the thermal effect of synchrotron radiation simultaneously. The thermal and mechanical condition of the vacuum chamber of HALF were quantitatively analysed by means of ANSYS Workbench in this work. Combining the Computational Fluid Mechanics (CFD) and Finite Elements Analysis (FEA), the temperature and thermal stress maps of the vacuum chamber were calculated. The CFD calculation displays that the heat transfer coefficient between the water and the chamber is 7966-13093 W/(m2·°C). The thermal-mechanical simulation shows that the maximum temperature and thermal stress are 53.5 °C and 42.1 MPa, respectively. The static structural analysis was performed on vacuum chamber under the ultra-high vacuum condition, with the maximum stress of 1.7 MPa and the maximum deformation of 0.0003 mm. These results show that the vacuum chamber meets the design requirements and provide a critical theoretical basis for the design of the vacuum system of HALF.