bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of SCU long range errors on the FEL performance
Authors: Grattoni V , Casalbuoni S , Geloni G , Lechner C , Schneidmiller E
Published: January 2024

The FEL performance strongly correlates with the undulator field quality. The definition of mechanical tolerances for the undulator magnets allows us to achieve the wished field quality. These mechanical tolerances should be defined both on short and long-range errors. With long-range errors, we address problems like deformations of the yoke caused by the support structures or unwanted tapering, which can arise in the positioning procedure of the ideally parallel undulator coils. In this contribution, we quantify the effect and set tolerances of a few types of long-range errors on the FEL radiation generated specifically from superconducting undulator coils.
An in-vacuum measurement system for CPMUs at Diamond Light Source
Authors: Patel Z , Cheng W , George A , Hale S , Marziani M , Ramezani Moghaddam A , Reeves M , Sharma G , Tripathi S
Published: January 2024

An in-vacuum Hall probe measurement system was designed, built, and used to measure four Cryogenic Permanent Magnet Undulators (CPMUs) at Diamond Light Source. The devices were tuned to correct the phase error at cold temperatures based on the measurements from the in-vacuum system. The in-vacuum system consists of a stretched wire system supplied by Danfysik and an in-house built Hall probe system. The Hall probe system has gone through two iterations: the first beam was prone to deforming with temperature changes; the second was made thicker following design changes to the magnet holders and girders of the CPMUs which allowed more space for the beam inside the vacuum vessel. The design and commissioning of the measurement system will be presented, along with some measurements of the CPMUs at room temperature and at 77 K. Details such as triggering of the Hall probe measurements, height compensation, and temperature compensation will be covered.
CPMU Development at Diamond Light Source
Authors: Sharma G , George A , Hale S , Marziani M , Mercado R , Patel Z , Ramezani-Moghaddam A , Reeves M , Tripathi S
Published: January 2024

Over the last three years (2020-2022) Diamond Light Source has installed four in-house designed, built, and measured Cryogenic Permanent Magnet Undulators (CPMUs). All four are 2 m long with a 17.6 mm period and have a minimum operating gap of 4 mm. These have replaced existing 2 m long in-vacuum Pure Permanent Magnet (PPM) devices to improve the flux to several of Diamond’s MX (Macromolecular Crystallography) beamlines by a factor of 2-4. In this paper we present the mechanical and cryogenic design considerations, and the shimming procedures and tools developed to produce these devices. The performance of the CPMUs compared to their PPM counterparts will also be reviewed.
Permanent Helical Undulators with Strong Fields
Authors: Bamberg E. , Magory E. , Balal N. , Bratman V.L.
Published: January 2024

Undulators containing magnetized rare-earth helices can provide a significantly higher oscillatory electron velocity than the widely used planar Halbach undulators. Using Wire Electrical Discharge Machining (WEDM), it is possible to manufacture NdFeB helices with a period of 1 mm or less with high accuracy. In this work, we describe the results of manufacturing and studying prototypes of undulators in the form of one or two axially and radially magnetized helices. More efficient hybrid systems of two axially oppositely magnetized and two steel non-premagnetized helices with a field on the axis of the order of 1 T are also shown. Micro-undulators of this type can significantly increase the efficiency of XFELs and Inverse FELs.
Characterization of plasma-discharge Capillaries for Plasma-based Particle Acceleration
Authors: Crincoli L , Anania M P , Biagioni A , Carillo M , Costa G , Del Giorno M , Galletti M , Iovine P , Lollo V , Mariani C , Pellegrini D , Pompili R , Romeo S , Ferrario M
Published: January 2024

Novel particle accelerators based on plasma technology allow a drastic reduction in size, due to the high accelerating field established inside plasmas, which are created and confined by specific devices. Plasma Wakefield Acceleration experiments are performed at the SPARC_LAB test facility (Laboratori Nazionali di Frascati - INFN) by using gas-filled capillaries, in which the plasma formation is achieved by ionizing hydrogen gas through high voltage pulses. In this work, the characterization of gas-filled plasma-discharge capillaries is presented. Several geometrical configurations are tested, including capillaries with different channel shapes and arrangement of inlets positions for the gas injection. Such configurations are designed in order to enhance the uniformity of the plasma density distribution along the plasma channel, which is necessary to improve particle beam acceleration. Plasma sources are characterized by means of the spectroscopic technique based on the Stark broadening method, which allows to measure the evolution of the plasma density profile along the channel. In addition, the CFD software OpenFoam is used to simulate the dynamics of the neutral gas during the filling of the capillary.
EARLI: design of a laser wakefield accelerator for AWAKE
Authors: Minenna D. F. G. , Ballage C. , Bencini V. , Bethuys S. , Cros B. , Dickson L. , Doebert S. , Farmer J. , Gschwendtner E. , Jeandet A. , Marini S. , Massimo F. , Moulanier I. , Muggli P. , Nghiem P. A. P. , Ricaud S. , Simon-Boisson C. , Vasilovici O.
Published: January 2024

Following the successful Run 1 experiment, the Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) Run2 experiment requires the design and implementation of a compact electron source. The “high-quality Electron Accelerator driven by a Reliable Laser wakefield for Industrial uses” (EARLI) project aims to design a stand-alone high-quality electron injector based on a laser wakefield accelerator (LWFA) as an alternative proposal to AWAKE’s baseline design of an X-band electron gun. This project is currently in the design phase, including simulations and experimental tests. Exhaustive beam physics studies for conventional accelerators are applied to LWFA physics.
Numerical studies for EuPRAXIA@SPARC_LAB plasma beam driven working point
Authors: Romeo S. , Del Dotto A. , Ferrario M. , Giribono A. , Rossi A.R. , Silvi G.J. , Vaccarezza C.
Published: January 2024

The realization of a plasma based user facility on the model of EuPRAXIA@SPARC_LAB requires to design a working point for the operation that allows to get an high accelerating gradient preserving a low emittance and low energy spread of the accelerated beam. Such beam is supposed to pilot a soft x-ray free electron laser with a wavelength of 2-4 nm. In this work several simulation scans are presented, varying at the same time the plasma density and driver-witness separation in order to show that, in a realistic working point for EuPRAXIA@SPARC_LAB, it is possible to find an ideal compromise for a witness with a peak current ¿1kA that allows to preserve the energy spread of the core (80% of the charge) below 0.1%, while maintaining an accelerating gradient inside the plasma module around of 1 GV/m. The study is completed with a parametric analysis with the aim of establishing the stability requirements of the RF working point and the plasma channel in order to preserve the energy jitter at the same level of the energy spread.
Research on longitudinal dynamics and design of RF parameters of synchrotron for XiPAF-upgrading project
Authors: Li Yan , Liu Wolong , Yang Ye , Liu Xiaoyu , Zhao Mingtong , Wang Zejiang , Xiong Yang , Yao Hongjuan , Zheng Shuxin , Xing Qingzi , Guan Xialing , Wang Xuewu , Wang Zhongming , Qiu Mengtong
Published: January 2024

Xi ’an 200 MeV Proton Application Facility (XiPAF) will be upgraded to proton and heavy ion synchrotron recently. In order to ensure the enough life of heavy ion beam, the synchrotron requires ultra-high vacuum, and the designed static vacuum is better than 5×10-10 Pa. In order to place enough vacuum pumps in the synchrotron, the circumference of the synchrotron was increased from 30.9 m to 39.96 m. The revolution frequency range of heavy ions is 0.49∼1.03 MHz. In order to reduce the engineering difficulty and improve the lower limit of frequency bandwidth requirement of the RF system, the harmonic of h=2 is used to capture and accelerate the heavy ions, and the frequency bandwidth range of the RF system is adjusted from 1∼6 MHz to 0.8∼5.0 MHz. In this paper, the longitudinal dynamics parameters of the upgraded synchrotron are designed, and the simulation calculation is carried out. Finally, the parameter requirements of the RF system are proposed.
Novel multi-beam front end for LANSCE accelerator facility
Authors: Batygin Y. K. , Barraza J. , Bishofberger K. A. , Dale G. E. , Dimitrov D. A. , Draganic I. N. , Gorelov D. V. , Henestroza E. , Kurennoy S. S. , Lyles J. T. M.
Published: January 2024

The LANSCE accelerator facility has been in operation for 50 years performing important scientific support for national security. The unique feature of the LANSCE accelerator facility is multi-beam operation, delivering beams to five experimental areas. To reduce long-term operational risks and to realize future beam performance goals in support of the laboratory missions, we are developing a novel high-brightness Front End injector. The proposed injector includes two independent low-energy transports for H+ and H- beams merging beams at the entrance of a single RFQ. These beamlines also perform preliminary beam bunching before RFQ. The challenge of the present project is associated with the simultaneous acceleration of protons and H- ions with multiple beam flavors in a single RFQ, which has never been done before. The proposed injector must provide better than existing beam parameters while beam intensity is supposed to be increased by a factor of two and injection energy is reduced from 750 keV to 100 keV. The paper discusses the details of the design and presents injector parameters.
Implementation Status of Myrrha Phase 1 (Minerva)
Authors: Dorda U , Fabich A
Published: January 2024

The MYRRHA design for an accelerator driven system (ADS) is based on a 4 mA, 600 MeV CW superconducting proton linac. The construction of the first stage (called MINERVA) by the Belgium Nuclear Research Centre SCK CEN was approved in 2018. It consists of a 100 MeV superconducting RF linac as well as two independent target stations, one for radio-isotope research and production of radio-isotopes for medical purposes, the other one for fusion materials research. This contribution presents the main design choices and current status of the overall project parts (civil engineering, particle accelerator and target facilities)
Alvarez Drift Tube Linac for Medical Applications in the Framework of Hitriplus Project
Authors: Mamaras A. , Sampsonidis D. , Bellan L. , Bisoffi G. , Comunian M. , Thonet P. A. , Vretenar M.
Published: January 2024

A first beam dynamics and RF design of an Alvarez-type drift tube linac (DTL) has been defined in the framework of the EU project, HITRIplus. It is meant primarily as a carbon (12C4+) and helium (4He2+) ion injector of a compact synchrotron for patient treatment. As a second implementation, helium particle acceleration with a higher duty cycle (10%) enables radioisotope production. The 352.2 MHz structure efficiently accelerates ion species with A/q=3 and 2, in the energy range from 1 to 5 MeV/u and for a beam current up to ∼0.5 mA. The design extends to a full length of ∼6.4 meters. Permanent magnet quadrupoles are utilized all along the DTL for focusing both ion beams. This paper presents a first-phase analysis towards a realistic DTL design capable of providing full beam transmission and minimum overall emittance increase for both A/q values.
Comparison of 352 MHz linac structures for injection into an ion therapy accelerator
Authors: Nikitovic L. , Torims T. , Vretenar M.
Published: January 2024

In the frame of ongoing initiatives for the design of a new generation of synchrotron-based accelerators for cancer therapy with ion beams, an analysis of linac designs has been started, to address a critical element with a strong impact on the performance and cost of the accelerator. The goal is to identify alternatives at lower cost and a similar or possibly smaller footprint than the standard 217 MHz injector presently used in all carbon therapy facilities in Europe. As an additional feature, a new linac design can be tailored to produce radioisotopes for treatment and diagnostics in parallel with operation as a synchrotron injector. In this paper, the attractive option of moving to 352 MHz frequency is analyzed, to a profit of reliable mechanical designs already developed for protons and of the cost savings that can be obtained using Radiofrequency (RF) power sources klystrons with a much lower cost per Watt than tubes or solid-state units. The paper is presenting a Quasi-Alvarez Drift Tube Linac (QA-DTL) version of an injector linac for carbon ions at q/A=1/3 and compare it with Inter-Digital H-Mode DTL (IH-DTL) designs. The option of a Separated-tank IH-DTL structure (S-IH-DTL) is also discussed, along with a standard IH-DTL, both at 352 MHz. Finally, a DTL design at 352 MHz for the injection of fully stripped helium ions into the synchrotron is presented.
Dynamic aperture studies for vertical fixed field accelerators
Authors: Vanwelde M , Hernalsteens C , Gnacadja E , Ramoisiaux E , Tesse R , Pauly N
Published: January 2024

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Symplectic neural surrogate models for beam dynamics
Authors: Huang C-K , Tang Q , Batygin Y K , Beznosov O , Burby J , Kim A , Kurennoy S , Kwan T , Rakotoarivelo H N
Published: January 2024

Development of robust machine-learning (ML) based surrogates for particle accelerators can significantly benefit the modeling, design, optimization, monitoring and control of such accelerators. It is desirable that the surrogate models embed fundamental physical constraints to the interaction and dynamics of the beams, for which an accelerator must be designed to operate upon. We implement and train a class of phase space structure-preserving neural networks — Henon Neural Networks (HenonNets) [1], for nonlinear beam dynamics problems. It is demonstrated that the trained HenonNet model predicts the beam transfer matrix to a reasonably good accuracy while strongly maintaining the symplecticity. To explore such model’s applicability and flexibility for high brightness or intensity beams, we further test it with beam dynamics in the presence of electrostatic and radiative collective effects. Our results indicate that HenonNet may be used as a base ML model for the surrogate of complex beam dynamics, thus opening up a wide range of applications.
A machine learning approach to shaping magnetic fringe fields for beam dynamics control
Authors: Gallagher T , Wolski A , Muratori B D
Published: January 2024

Fringe fields at the entrances and exits of multipole magnets can adversely affect the dynamics of particles in an accelerator, but there is also the possibility that fringe fields could be used to enhance accelerator performance. Design work could benefit from computational tools for constructing realistic models of multipole fringe fields at an early stage in the design process; and methods for relating the magnet geometry to the field shape and to the beam dynamics would also be of significant value. We explore novel techniques to produce magnet designs that satisfy specific requirements for the beam dynamics. Machine learning tools are used to link properties of the beam dynamics in the fringe fields to the magnet geometry in an efficient way.
Improvement of the longitudinal phase space tomography at the J-PARC synchrotrons
Authors: Okita H. , Tamura F. , Yamamoto M. , Nomura M. , Shimada T. , Saha P. K. , Yoshii M. , Ohmori C. , Sugiyama Y. , Hasegawa K. , Hara K. , Albright S. , Kelliher D. J.
Published: January 2024

The longitudinal phase space tomography, which reconstructs the phase space distribution from the one-dimensional bunch profiles, is used in various accelerators to measure longitudinal beam parameters. At the J-PARC, an implementation of the phase space tomography based on the Convolution Back Projection method (CBP) has been used to measure the momentum spread of the injected beam. The method assumes that the beam distribution rotates without significant deformation during the synchrotron oscillation. Because of the nonlinearity of synchrotron motion with sinusoidal RF voltage, the method can be used only in limited situations such as small amplitude synchrotron oscillation. Algebraic Reconstruction Techniques (ART) in conjunction with particle tracking, which is implemented in the CERN’s tomography code, allows accurate reconstructions even for nonlinear large amplitude synchrotron oscillations. We present the overview of the application of the CERN’s tomography code to the J-PARC synchrotrons. The results of benchmarking are also reported.
Cherenkov diffraction radiation dielectric button characterization via a slab-line
Authors: Pakuza C , Wendt M
Published: January 2024

Cherenkov diffraction radiation is generated when a charged particle beam passes in close proximity to a dielectric target, and is currently being studied and developed for various non-invasive beam instrumentation applications at CERN. One such instrument is a beam position monitor (BPM) composed of four cylindrical dielectric inserts. A challenge of using the conventional stretched wire technique to characterize the BPM up to high frequencies is the coupling of unwanted higher order modes (HOM) into the inserts that are dielectric-loaded circular waveguides. To minimize the generation of HOMs and excite mainly the transverse electromagnetic (TEM) mode as a model of the beam field, a set-up comprising a dielectric insert mounted on a slab line with 50 Ω characteristic impedance was tested. The results and comparison with numerical simulations in CST are be presented.
New digital low-level RF controls based on the Red Pitaya STEMlab for the TLS Linac system
Authors: Cheng Y S , Lee S H , Wu C Y , Liao C Y , Liao J K , Chen J , Hu K H , Hsu K T
Published: January 2024

The Linac system at Taiwan Light Source (TLS) has been in operation for almost a quarter of a century and requires upgrades to improve its reliability. To achieve this, some components of the control system have been replaced with new digital low-level RF control units that use emerging technologies. A new unit is based on the open-source hardware platform which is named “Red Pitaya STEMlab” and offers a compact size and low power consumption. The unit features DAC (Digital-to-Analog Converter) blocks for downloading arbitrary waveforms with external trigger play and ADC (Analog-to-Digital Converter) blocks for waveform acquisition, enabling the development of real-time diagnostic toolkits. The new low-level RF control interface has been fully integrated into the existing EPICS software framework for system integration. The new digital low-level RF control system supports I/Q (in-phase/quadra-ture-phase) data with online amplitude and phase set-tings, and a waveform digitizer for inspecting low-level RF signals from the klystron modulator. Specific graphical applications have been designed and integrated into the existing operation interfaces. The system has been successfully achieved during routine operations. This paper describes the details of these efforts.
Superconducting multipole triplet field measurements
Authors: Esper A , Stodel M H , Savajols H , Authier M , Aburas M , Carville F , Drouart A , Jacquot B , Lefevre A , Esnault F
Published: January 2024

This paper presents magnetic field measurements for the Superconducting Multipole Triplets (SMT) prototypes of the Super Separator Spectrometer (S3). These advanced magnets, based on innovative concept design, generate magnetic fields of quadrupole, sextupole, octupole, and dipole. Magnetic field measurements have been conducted with a prototype mapping system to align the magnets and assess their performance. Moreover, detailed information on the experimental setup will be presented along with magnetic field analysis on the SMT’s multipoles.
Handling the Functional Features of Accelerator Components Using ISO GPS Situation Features
Authors: Nicquevert B , Rey F
Published: January 2024

The building blocks of a scientific facility based on particle beams comprise magnets and electro-magnetic devices. The optical design usually imposes a demanding accuracy with respect to their theoretically exact position and orientation. It happens that the functional features are either not clearly defined – what is the « axis » of a magnet –, or not explicitly used along their lifecycle. Improving how to handle these functional features would contribute to meeting demanding challenges. The European Spallation Source (ESS) is aiming at providing a powerful proton linear accelerator and a target system to produce pulsed neutrons. The challenging complex design and integration yielded to introducing a tool shared in common by all stakeholders along the lifecycle: the “situation features”, as defined in ISO GPS (Geometrical Product Specifications) standards. They are here developed, and extended to beyond-mechanics use cases. Two examples of fiducialization and installation phases are presented for neutron beam guides and quadrupole magnets. Perspectives of generic use are also highlighted.
SuperKEKB personnel protection system
Authors: Mimashi T , Ono M , Kudo K , Tanaka M , Tanaka N , Ogawa E
Published: January 2024

The Super-KEKB[1] personnel protection system (PPS) takes care of not only Super-KEKB accelerator, but also Photon Factory - Advanced Ring (PF-AR), Positron Damping Ring (PDR)[2] and their beam transport lines (BT)[3]. The logic of the PPS has been changed to adapt the new accelerator operation scheme. The Experimental Physics and Industrial Control System (EPICS) was introduced into the PPS. Many tools developed under EPICS environment are used.
A two harmonics circuit for the powering of the very fast RCS (Rapid Cycling Synchrotron) of the muon collider accelerator
Authors: Boattini F. , Aguglia D. , Brauchli G. , Bottura L.
Published: January 2024

This paper analyses the application of a two harmonics circuit with additional active filter for the powering of the four RCS stages of the muon acceleration to the ultimate 10 TeV energy level.
LHC low-beta quadrupole magnets: cryogenic refrigeration capacity and improved controls for luminosity optimization
Authors: Bradu B. , Brodzinski K. , Gahier V. , Ferlin G. , Younes-Cronnier M.
Published: January 2024

The LHC low-β quadrupole magnets, also known as “Inner Triplets”, are the final focusing magnets located on each side of LHC interaction points. The current LHC Inner triplets are NbTi superconducting magnets operated in superfluid helium at 1.9 K and use a bayonet heat exchanger to extract the heat deposited by the secondary particles coming from the proton collisions. The dynamic heat loads in Inner Triplet are consequently proportional to the LHC luminosity and due to the recent upgrades of LHC and its injectors, the cryogenic capacity limit can be reached around ATLAS and CMS experiments where the luminosity can go slightly beyond the LHC ultimate luminosity. First, this paper summarizes the history of the Inner Triplet cryogenics with the different tests performed in the past to assess their cooling capacity. Then, the different techniques implemented in the cryogenic control system to handle the luminosity transients are detailed and finally, a new control interaction between the cryogenic system and the LHC luminosity server is detailed to optimize online the LHC luminosity.
Study on the vacuum properties of laser-etched oxygen-free copper
Authors: Zhang W L , Ma W J , Wang S H , Fan L , Ge X Q , Bian B Y , Fang J W , Wang Y
Published: January 2024

The performance of operating particle accelerators has been seriously affected by the electron cloud (e-cloud) effect. The secondary electron emission (SEE) and the e-cloud can be effectively suppressed through laser-etching the inner surface of the vacuum chamber. Oxygen-free copper (OFC) has become the first choice for the vacuum chambers of modern accelerators due to its high electric and thermal conductivity and effective radiation shielding property. It is necessary to study the vacuum properties of the laser-etched OFC for the application in the particle accelerators. In this paper, the photon stimulated desorption (PSD) yield and the outgassing rate of the laser-etched OFC were measured. The results show that the laser-etched OFC presents lower PSD yield compared to the untreated OFC, while the outgassing rates of the laser-etched and unetched samples are similar.