bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic aperture studies for vertical fixed field accelerators
Authors: Vanwelde M , Hernalsteens C , Gnacadja E , Ramoisiaux E , Tesse R , Pauly N 
Published: January 2024

Abstract
Vertical orbit excursion Fixed Field Accelerators (vFFAs) feature highly nonlinear magnetic fields and strong transverse motion coupling. The detailed study of their Dynamic Aperture (DA) requires computation codes allowing long-term tracking and advanced analysis tools to take the transverse motion linear and nonlinear coupling into account. This coupling completely transforms the beam dynamics compared to a linear uncoupled motion, and an explicit definition of the DA is needed to characterize the performance and limitations of these lattices. A complete study of the DA in the 4D phase space in highly nonlinear and strongly coupled machines must give a measure of the stability domain but also means to assess the operating performance in the physical coupled space. This work presents a complete set of methods to perform such detailed analysis. These methods were explored and compared to compute and characterize the DA of an example vFFA lattice. The whole procedure can be further applied to evaluate DA using realistic models of the magnetic fields, including fringe fields and errors.
Study for Space Charge Effect in tune Space at CSNS-II/RCS
Authors: Li Y. , Xu S.Y. , Yuan Y.S. , Huang L.S. , Wang S. 
Published: January 2024

Abstract
CSNS-II is an upgrade project of China Spallation Neutron Source (CSNS), requiring an increase in beam power from 100 kW to 500 kW. In order to find a suitable working points area in advance and evaluate the influence of the space charge effect on the Rapid Cycling Synchrotron (RCS) of CSNS-II, the measurements of beam loss with various tunes on CSNS/RCS was carried out and the beam loss simulation in the transverse tune space at CSNS-II/RCS has been performed. Finally, four candidate working points are compared.
RF conditioning towards continuous wave of the RFQ of the Linear IFMIF Prototype Accelerator
Authors: De Franco A. , Comunian M. , Fagotti E. , Grespan F. , Hayashi K. , Hirosawa K. , Kondo K. , Kubo N. , Marchena A. , Masuda K. , Moya I. , Palmieri A. , Pisent A. , Scantamburlo F. , Sugimoto M. 
Published: January 2024

Abstract
The Linear IFMIF Prototype Accelerator (LIPAc) is designed to accelerate 125mA of deuteron beam to 9MeV in continuous wave (CW). The superconductive RF Linac has not yet been installed and the final accelerating stage now under commissioning is the RFQ. This system has been designed and developed by INFN (Italy) before installation in QST (Japan). The RFQ is the longest in the World with its 9.8m and requires RF power injection from 8 independent and synchronized coupler ports. LIPAc demonstrated the acceleration of 125mA deuteron beam at 5MeV for 1ms with a 1s repetition period in 2019. A fundamental milestone to extend beam operations to CW is the completion of the RFQ cavity RF conditioning up to CW. This work presents the strategy followed to successfully reach CW RF injection at 80% of the nominal 132kV vane voltage. The field distribution correction scheme (acting on cooling system at various power levels) was successfully verified. We discuss as well the main challenges encountered on the way, which include updates of the RF system, failure of a circulator (by arcs) and the damages occurred on some of the RF couplers. Finally, the recent status and outlook will be provided.
Measurement and Analysis of the Intensity-dependent Effects on the CSNS Medium Energy Beam Transport line
Authors: Chen Hai , Luo Xibao , Peng Jun , Liu Xingguang 
Published: January 2024

Abstract
A power upgrade project (CSNS-II) has been approved in 2021 to increase the beam power to 500 kW for the China Spallation Neutron Source (CSNS), for which the Linac energy will reach 300 MeV and the beam intensity is expected to be 50 mA. In this study, the beam measurement results given by the wire scanners at various current intensities, and the numerical modeling and fitting methods to obtain the evolution of the beam envelope and emittance along the CSNS medium energy beam transfer (MEBT) are given and discussed. Finally, new matching results have been given to control the emittance blowup.
Studies of the spin coherence time of protons at COSY
Authors: Melnikov A , Aksentyev A , Senichev Y , Kolokolchikov S 
Published: January 2024

Abstract
The search for the Electric Dipole Moments (EDM) of charged particles in storage rings necessitates polarized beams with long Spin Coherence Time (SCT) of the circulating beam. The SCT is the time during which the RMS spread of the orientation of spins of all particles in the bunch reaches one radian. A long SCT is needed to observe the coherent effect of a polarization build-up induced by the EDM. For deuterons the SCT of 1000 s has been achieved at the COoler SYnchrotron COSY (Jülich, Germany). Accomplishing such long SCT for protons is far more challenging due to their higher anomalous magnetic moment, but essential for the planned EDM experiments. It has been shown that for protons the SCT is strongly influenced by nearby intrinsic and integer spin resonances. The strengths of the latter have been calculated for a typical optics setting of COSY and the overall influence on the SCT was predicted. In addition, the efficiency of proton spin flipping with an RF solenoid from initially vertical direction into the ring plane is also investigated.
Investigation of micro spill in RF KO extraction using tailored excitation signals
Authors: Niedermayer P. J. , Singh R. , Franchetti G. , Cortés García E. C. , Feldmeier E. , Haberer T. 
Published: January 2024

Abstract
Radio Frequency Knock Out (RF KO) extraction is used to extract stored particle beams from synchrotrons through transverse excitation, delivering spills of particles for experiments and medical therapy. Minimizing the fluctuations of spill intensity is vital to prevent detector pile-up and interlocks while making most efficient use of the extracted beam. To improve the spill quality, different excitation signals with characteristic frequency spectra are explored. Results of experimental studies at the Heidelberg Ion Beam Therapy Center (HIT) are presented. These demonstrate the possible improvements by tuning multi-band spectra at different harmonics. Particle tracking simulations of the slow extraction process at HIT are used to understand how different excitation signals influence the spill quality.
The Leakage Field of the New High-Field Septum Magnets for Fast Extraction in Main Ring of J-PARC
Authors: Shibata T , Ishii K , Iwata S , Matsumoto N , Igarashi S , Yasui T , Asami T , Sato Y , Sugimoto T , Matsumoto H 
Published: January 2024

Abstract
As part of the effort to increase the beam power of the Main Ring (MR) for fast extraction (FX) in J-PARC to 750 kW, five new septum magnets for FX (FX-septa) were installed in the MR in 2022. The most significant goal for the magnets was to achieve an extremely low leakage field in the circulating line. To realize the low leakage field, new pure iron duct-type magnetic shields were mounted in the circulating ducts of the two high-field FX-septa in 2022. In July 2022, we verified that the impact of the leakage field of all of the FX-septa on the 3-GeV circulating beam was below 10% of that of the previous FX-septa. We also measured the leakage field in the circulating ducts of the two high-field FX-septa with new shields in October 2022, and confirmed that the quadrupole field component was reduced to ≈1% of that of the previous high-field FX-septa.
Differential equation model of the tune ripple effect on beam spill ripple in RFKO slow extraction
Authors: Wang Z J , Yao H J , Ye W B , Liu X Y , Li Y , Xiong Y , Zheng S X , Wang X W 
Published: January 2024

Abstract
Beam uniformity is an important factor that must be considered in slow extraction optimization, and the tune ripple caused by the power supply ripple is an important factor that causes beam uniformity to deteriorate. In this study, based on the beam excitation concept for two regions (extraction and diffusion regions), a differential equation of beam spill under the influence of a mono frequency tune ripple was established. By solving and analysing the differential equation, several conclusions were obtained and verified by simulation.
Linear optics compensation for the HEX superconducting wiggler at NSLS-II
Authors: Li Yongjun , Ha Kiman , Hidaka Yoshiteru , Rainer Robert , Shaftan Timur , Smaluk Victor , Tanabe Toshiya , Tian Yuke , Wang Guimei , Yang Xi 
Published: January 2024

Abstract
At the NSLS-II ring, a 1.2 m long superconducting wiggler with the maximum 4.34T magnetic field has been installed at a low-β straight section (cell 27) to drive the high energy engineering X-ray scattering (HEX) beamline. To mitigate the potential performance degradation due to the linear optics distortion, a local compensation scheme was adopted and confirmed with the online beam measurement. A feedforward control to enable a dynamic compensation of the linear optics distortion was deployed. It can maintain the storage ring lattice performance when the device main coil current ramps.
Exploration of beamline configuration space for identifying robust quadrupole configurations
Authors: Vilsmeier D , Sapinski M 
Published: January 2024

Abstract
Experimental beamlines often are regularly reconfigured to meet changing requirements of the experiments and to minimize beam losses. The configuration is usually done with the help of beam optics tools like MADX. These tools offer matching capabilities which allow to find solutions in terms of quadrupole strengths. However, such solutions are found by satisfying the given constraints only and do not take into account limited precision of actual quadrupole devices. Under the influence of quadrupole errors due to magnetic hysteresis, power converter trips etc, the original beamline optics often degrades. This results in beam losses or loss of focus at the experimental target. Readjustment of the optics costs valuable experiment time. Hence, it is desirable to operate a beamline configuration which not only meets the requirements but is also robust against quadrupole errors. Such a configuration will deviate from its nominal properties only by a small margin even when the quadrupole strengths deviate within specified intervals. We present the systematic exploration of beamline configuration space to identify robust configurations. The results are discussed for the BIGKARL beamline at Forschungszentrum Jülich and the findings are supported by experimental data.
Strongly curved super-conducting magnets: beam optics modeling and field quality
Authors: Benedetto E , Barna D , D’Addazio M , Maria R De , Felcini E , Frisella G , Garolfi L , Latina A , Norman H , Oponowicz E , Pullia M , Vaszary T , Veres D 
Published: January 2024

Abstract
Superconducting (SC) dipoles with a strong curvature (radius smaller than 2 meters, for an aperture of about 100 mm and a length of 1-3 meters) are required for applications where compactness is key, such as the synchrotron and gantry for Carbon-ion therapy developed within the European program HITRIplus. Such magnets challenge several assumptions in the field description and put to the test the range of validity of beam optics codes. In particular, the equivalence that holds for the straight magnets between the transverse multipoles description obtained from the Fourier analysis (used for magnet design and measurements) and the Taylor expansion of the vertical field component along the horizontal axis (used in beam optics) is not valid any longer. Proper fringe field modelling also becomes important due to the curved geometry and the aperture being large compared to the magnetic length. We explore the feasibility and the limits of modelling such magnets with optics elements (such as sector bends and multipoles), which allows parametric optics studies for optimization, field quality definition and fast long-term multi-pass tracking.
Space Charge Forces analytical model for emittance compensation
Authors: Carillo M. , Bosco F. , Chiadroni E. , Faillace L. , Giuliano L. , Mostacci A. , Migliorati M. , Spataro B. , Rosenzweig J. , Palumbo L. 
Published: January 2024

Abstract
Space charge forces represent main induced effects in an RF-injector that degrade the beam quality. In this scenario the laser distribution sent on the photocathode acquires an important role in the emittance compensation process, as the slice analysis shows. Starting from the preliminary studies performed on [1], a novel semi-analytical model of space charge forces is proposed in detail for bunch with arbitrary charge distribution to derive expressions of self-induced forces. The performance of the fields at low energy regime (as the field has not expired RF forces) is under present analysis, we can investigate use of this model in low charge regime. Further, the model has been bench-marked with the behavior of the distributions present in the literature and studied for new ones. It has also been applied for the study of the optimization of a C-band hybrid photoinjector now being commissioned, thus explaining the factor two reduction of the emittance observed at the exit of the gun by changing the initial distribution at the cathode.
Characterization of the longitudinal beam coupling impedance and mitigation strategy for the fast extraction kicker KFA79 in the CERN PS
Authors: Neroni M , Barnes M , Ducimetiere L , Lasheen A , Mostacci A , Popovic B , Trubacova P , Vollinger C 
Published: January 2024

Abstract
In the framework of the High Luminosity Upgrade of the LHC (HL-LHC) the beam intensity from the injectors must be doubled while keeping longitudinal beam parameters unchanged. As such, high-quality beams with high intensities are required also from the Proton Synchrotron (PS). The beam coupling impedance plays a crucial role and mitigation measures must be taken to remain within a stringent impedance budget. Kicker magnets are important contributors to the overall broadband impedance of the PS. Moreover, the detailed study of kicker impedances revealed additional resonant modes which may be critical for the beam stability. The longitudinal beam coupling impedance for the fast extraction kicker KFA79 is presented in this study, and a solution to reduce the impedance of the critical resonant modes is introduced. Electromagnetic (EM) simulations have been performed to determine the impedance behaviour. Finally, the insertion of transition pieces between magnet modules is presented as a measure for mitigating the low frequency resonant impedance contributions.
Upgrade the impedance model in RCS of CSNS
Authors: Huang L. , Liu H. , Rao L. , Xu S. 
Published: January 2024

Abstract
The Rapid Cycling Synchrotron (RCS) in the China Spallation Neutron Source (CSNS) is a high-intensity proton accelerator that is susceptible to collective instabilities and performance limitations due to its impedance. With impedance study of key components and new component installations, the impedance model should be updated. This article presents a comprehensive estimate of the coupling impedance and outlines the impedance model of the RCS.
Evaluation of the impact of REBCO-coated conductors on the resistive wall impedance of the FCC-hh
Authors: Tagdulang N. , Günzel T. , Krkotić P. , O’Callaghan J. M. , Pont M. 
Published: January 2024

Abstract
The beam screen for the Future Circular hadron-hadron Collider (FCC-hh) has a baseline design based on a copper (Cu) coating. Calculations have indicated that the resistive wall impedance will be the major contributor to the beam impedance for the FCC-hh at both injection and collision and that Cu loss might be on the limit to ensure beam stability. To increase the safety margin, it is desirable to reduce the resistive wall impedance. In this contribution, we present an approach to reduce the beam impedance based on the reduction of the surface resistance of the beam screen coating by using High-Temperature Superconductors based on REBaCu3O7−x
coated conductors (REBCO-CCs). These HTS-CCs have transition temperatures around 90 K, and critical current densities which are high enough even in the presence of a strong magnetic field, being therefore, good candidates to substitute Cu in the FCC-hh beam screen, which will be operating at around 50 K and under a magnetic field of 16 T. Using measured data of the surface impedance of REBCO-CCs, the beam impedance has been estimated for an elliptical beam screen with the same vertical dimension as that of the baseline design. A REBCO-CCs contribution dependence study to determine the optimum beam screen will be shown. Resistive wall impedance studies using an ellipse are a step forward towards determining the performance of the REBCO-CCs on the FCC-hh beam screen.
Resistive-wall instability evaluation along the ramp in the SOLEIL II booster
Authors: Foosang W , Gamelin A , Tordeux M-A , Alexandre P 
Published: January 2024

Abstract
The ultra-low emittance specification of the SOLEIL II storage ring requires a challenging lattice design of the booster that will inject the beam into it. The dimension of the vacuum chamber in the new booster must be reduced compared to that in the present machine. The resistive-wall (RW) instability is then expected to become more important than in the current booster. However, the Amplitude-Dependent Tune Shift (ADTS) is also expected to be stronger due to the strong sextupole magnets necessary for chromatic error correction in the new lattice. It could then be an important effect to fight against this instability. Therefore, evaluating this instability is important to ensure the machine’s feasibility. This work studies the beam dynamics along the ramp in the RW instability regime using the code mbtrack2. The turn-by-turn tracking allows us to see the evolution of the beam thoroughly and understand how RW, synchrotron radiation, and ADTS impact the beam stability.
Advanced Studies for the Dynamics of High Brightness Electron Beams with the Code MILES
Authors: Bosco F. , Behtouei M. , Camacho O. , Carillo M. , Chiadroni E. , Faillace L. , Ficcadenti L. , Francescone D. , Giannessi L. , Giribono A. , Giuliano L. , Nguyen F. , Palumbo L. , Rosenzweig J. , Silvi G. J. , Spataro B. , Vaccarezza C. , Migliorati M. 
Published: January 2024

Abstract
High brightness electron beams enable a wide spectrum of applications ranging from short wavelength radiation sources to high gradient wakefield acceleration. The rich dynamics that are intrinsic in charged particles accelerated in complex systems require a careful description in the analysis and design of a given machine, particularly regarding its stability. Numerous computer codes are in use by the accelerator community for such purposes. In particular, MILES is a simple tracking code we have developed that allows fast evaluations of collective effects in RF linacs. In this paper we extend the simple models previously developed to describe specific, diverse applications that can benefit from the fast simulation tools developed in MILES. Examples of this kind include particle driven acceleration schemes in a plasma where driver and witness beams propagate in the “comb” pulse-train configuration. Specifically, we investigate the self-induced fields excited within the X-band rf-linac stage of EuPRAXIA@SPARC_LAB. Further, we discuss additional advanced topics such as resistive wall wakefield effects in planar FEL undulators and their impact on the radiation emitted.
Measurements of longitudinal Loss of Landau damping in the CERN Proton Synchrotron
Authors: Intelisano L , Damerau H , Karpov I 
Published: January 2024

Abstract
Landau damping represents the most efficient stabilization mechanism in hadron synchrotron accelerators to mitigate coherent beam instabilities. Recent studies allowed expanding the novel analytical criteria of loss of Landau damping (LLD) to the double harmonic RF system case above transition energy, providing an analytical estimate of the longitudinal stability. The threshold has a strong dependence on the voltage ratio between the harmonic and the main RF systems. Based on that, measurements of single bunch oscillations after a rigid-dipole perturbation have been performed in the CERN Proton Synchrotron (PS). Several configurations have been tested thanks to the multi-harmonic RF systems available in the PS. Higher-harmonic RF systems at 20 MHz and 40 MHz, both in phase (bunch shortening mode) and in counter-phase (bunch lengthening mode) with respect to the principal one at 10 MHz, have been measured.
A modified round to flat beam transformation lattice for angular dispersion induced microbunching technique
Authors: Chen W. , Kang Y. , Sun H. , Li C. L. , Wang Z. , Zhang Q. L. , Wang K. , Feng C. , Jiang B. C. 
Published: January 2024

Abstract
The angular dispersion induced microbunching (ADM) technique has been proposed to generate high brightness coherent radiation in storage rings by taking advantage of it’s very low vertical emittance. To apply a similar scheme in the linac, it is necessary to reduce the vertical emittance of the electron beam. Generally, angular-momentum-dominated round beams can be generated by immersing the cathode into the axial solenoid magnetic field. The angular momentum can be then removed by skew quadrupoles downstream of the solenoid, resulting in a flat beam with low vertical emittance. In this paper, we propose a possible scheme that holds the possibility to improve the performance of round to flat beam transformation technique by chromatic correction. In this scheme, a chicane is used to introduce the transverse dispersion and sextupoles are employed to correct the chromatic effect. Three-dimensional numerical simulations have been carried out and the results show that a flat beam with transverse emittance ratio of ∼840 can be generated for a bunch charge of 0.5 nC.
Beam dynamics optimization for high gradient beam driven plasma wakefield acceleration at SPARC-LAB
Authors: Carillo M. , Alesini D. , Anania M. P. , Behtouei M. , Bellaveglia M. , Biagioni A. , Chiadroni E. , Cianchi A. , Costa G. , Crincoli L. , Dotto A. Del , Giorno M. Del , Pirro G. Di , Faillace L. , Francescone D. , Galletti M. , Giannessi L. , Giribono A. , Giuliano L. , Iovine P. , Mostacci A. , Petrillo V. , Pompili R. , Parise G. , Romeo S. , Rossi A. R. , Silvi G. J. , Shpakov V. , Vaccarezza C. , Villa F. , Ferrario M. 
Published: January 2024

Abstract
The SPARC_LAB test facility at the LNF (Laboratori Nazionali di Frascati, Rome) holds a high brightness photo-injector used to investigate advanced beam manipulation techniques. High brightness electron bunch trains (so-called comb beams) can be generated striking on the photo-cathode of a Radio Frequency (RF) photo-injector with a ultra-short UV laser pulse train in tandem with the velocity bunching technique. Beam dynamics studies have been performed with the aim of optimizing the dynamics of the double beam (driver and witness) used to perform particle driven plasma wake field acceleration (PWFA). In this scenario different scans on beam parameters were carried on adopting the ASTRA simulation code, in order to optimize the witness beam quality and improve the plasma booster stage performances. A benchmark of the simulations has been then performed, reproducing the experimental data obtained from the optimization of machine performances, and a good agreement was found.