bluuebunny/crossref_metadata_2025_split huggingface dataset:
THz SASE FEL at PITZ: lasing at a wavelength of 100 μm
Authors: Krasilnikov M , Aboulbanine Z , Adhikari G , Aftab N , Asoyan A , Boonpornprasert P , Davtyan H , Georgiev G , Good J , Grebinyk A , Gross M , Hillert W , Hoffmann A , Kongmon E , Li X-K , Lueangaramwong A , Melkumyan D , Mohanty S , Niemczyk R , Oppelt A , Qian H , Richard C , Rossbach J , Schneidmiller E , Stephan F , Vashchenko G , Weilbach T , Yurkov M 
Published: January 2024

Abstract
Development of an accelerator-based tunable THz source prototype for pump-probe experiments at the European XFEL is ongoing at the Photo Injector Test facility at DESY in Zeuthen (PITZ). The proof-of-principle experiments on the THz SASE FEL are performed utilizing the LCLS-I undulator (on loan from SLAC) installed in the PITZ beamline. The first lasing at a center wavelength of 100 μm was observed in the summer of 2022. The lasing of the narrowband THz source was achieved using an electron beam with an energy of ∼17 MeV and a bunch charge up to several nC. Optimization of beam transport and matching resulted in the measurement of THz radiation with a pulse energy of tens of μJ, measured with pyroelectric detectors. The THz FEL gain curves were measured by means of specially designed short coils along the undulator. The results of the first characterization of the THz source at PITZ will be presented.
A force-neutral adjustable phase undulator for a compact x-ray FEL
Authors: Xu Joseph Z. , Qian Maofei , Zholents Alexander 
Published: January 2024

Abstract
The magnetic and mechanical designs of a force-neutral adjustable phase undulator (FNAPU) are presented. The FNAPU combines two magnetic assemblies with equal periods, one with an undulator magnetic structure and one with a force compensation magnet structure. The latter is used to neutralize the magnetic force affecting the undulator magnetic structure and vice versa in all undulator phases. Assembling in proximity a group of different FNAPUs is discussed.
Numerical Simulation of an Electron Beam for Magnetic Bunch Compressor Commissioning at PITZ
Authors: Kongmon E , Krasilnikov M , Li X-K , Boonpornprasert P , Vashchenko G , Aftab N , Richard C , Gross M , Oppelt A , Stephan F , Rimjaem S , Lueangaramwong A 
Published: January 2024

Abstract
A THz free electron laser (FEL) prototype has been developed at the Photo Injector Test Facility at DESY in Zeuthen (PITZ) for obtaining high intensity radiation for THz-pump and X-ray-probe experiments at the European XFEL. In this development, a magnetic chicane was recently installed to optimize the THz FEL performance. The aim of this study is to investigate the beam dynamics in the chicane for a trajectory commissioning by tracking the electron beam via ASTRA using a 3-dimensional (3-D) magnetic field of the chicane simulated with CST-EM Studio. The simulated results indicate the possibility to obtain a minimum-momentum dispersion of an electron beam after chicane with the high bunches charge of electron beam transportation.
Design, fabrication and cold-test of an X-band accelerating structure for linearizer
Authors: Huang X X , Tan J H , Wang C , Fang W C 
Published: January 2024

Abstract
X-band high gradient accelerating technology is a challenging and important technology in advanced electron linear accelerator facilities. The X-band accelerating structure can provide harmonic compensation to eliminate non-linear energy spread and realize linear compression of bunch in linac. In this paper, a special X-band traveling-wave accelerating structure is designed for linearizer, with accelerating gradient of 20 MV/m under the input power below 5 MW according to the requirement of Dalian Coherent Light Source. The fabrication and cold-test of the structure are successfully completed and the transmission efficiency of power is about 0.38.
A start-to-end optimisation of CLEAR for an inverse Compton scattering experiment, using RF-Track
Authors: Muşat V , Latina A , Malyzhenkov A , Aksoy A 
Published: January 2024

Abstract
The CERN Linear Electron Accelerator for Research (CLEAR) has been operating as a user facility since 2017, providing beams for various experiments. This paper describes a start-to-end optimisation of the CLEAR beamline as a driver for X-ray generation through inverse Compton scattering. The novel particle tracking code RF-Track was used to simulate the electron beam from the bunch generation at the cathode up to the interaction with a laser beam. Figures of merit of the scattered photon beam were computed in RF-Track, and optimised by tuning the beam parameters at injection and quadrupole strengths across the beamline. The aim of the optimisation was to maximise the scattered photon flux, and minimise the effects from static and dynamic imperfections. The start-to-end model of the CLEAR beamline was used to derive the impact of jitter on flux.
Radiation transport line for Terahertz Coherent Diffraction Radiation at ERL Test Accelerator in KEK
Authors: Honda Y. , Kato R. , Shimada M. , Takai R. 
Published: January 2024

Abstract
Coherent radiation from a short bunch of electron beams is expected to be utilized as a terahertz (THz) radiation source. We have conducted an investigation on a terahertz source based on coherent diffraction-radiation (CDR) that possesses a unique characteristic of radial polarization and is potentially useful for certain applications. Particularly, with the high repetition beam of an energy-recovery linac, it is possible to achieve a watt-class high power source. We have designed a CDR setup and THz transport line, and subsequently measured the THz beam profile at the end of the line. The results confirmed the preservation of the distinctive characteristics of CDR within the experimental area.
Commissioning of the ThomX Storage Ring
Authors: Kubytskyi V. , Chaikovska I. , Delerue N. , Mytrochenko V. , Loulergue A. 
Published: January 2024

Abstract
We will report on the ongoing ThomX ring commissioning, its status, its main challenges, our results and our planning. ThomX is a compact Compton-based X-ray source under commissioning at IJCLab in Orsay (France). This facility is composed of a 50-70 MeV linac, a transfer line and a storage ring whose circumference is 18 m. Compton scattering between the 50 MeV electron bunch of 1 nC and the 30 mJ laser pulses stacked in a Fabry-Perot cavity will result in the production of X-rays with energy ranging between 45 keV and 90 keV. We aim at a total flux of about 1013 X-rays per second. The injector commissioning started in the spring of 2021. The ongoing storage ring commissioning faces many challenges due to the rings low energy, its compactness, its non-linear beam dynamics, the time-limited beam storage and the need to achieve a very accurate and stable geometry of the collision region between the laser pulses and the electron bunch. The commissioning and operational experience is of great importance for the future Compton sources.
Copper Surface Treatment with deep UV Ultrafast Laser for Improved Photocathode Photoemissive Properties
Authors: Groussin B , Martinez Calderon M , Marsh B , Rossel R , Granados E 
Published: January 2024

Abstract
Cesium Telluride (Cs2Te) constitutes today the photoemissive semiconductor material of choice for electron accelerators due to its high quantum efficiency (QE) in the deep ultraviolet (DUV) spectral range, and capability to produce high charge over a long operation lifetime. Unfortunately, its chemical instability requires ultra-high vacuum (in the 10-10 mbar range). This inevitably complicates Cs2Te photocathode handling, and increases the overall cost compared to metallic counterparts. Copper photocathodes are alternative candidates, and although they are much more tolerant in terms of vacuum requirements, their use in high average current photo-injectors is limited due to their orders of magnitude lower QE (around 10-5 per unit). With the development of nanophotonics, plasmonic phenomena can now be exploited to tailor a new range of effects in the photoemission process. In this work, we focus on direct laser fabrication of nanostructures for plasmonic electric-field enhancement on copper, and study their potential for enhancing the quantum yield. We develop a methodology to fabricate the nanostructures by irradiating the Cu surface with 257 nm femtosecond pulses, well above copper’s work function. We directly obtained nanostructures 100-200 nm, matching the plasmonic resonance for photoinjector wavelengths. The study is accompanied by a parametric scan allowing to obtain the optimal laser machining parameters, and the analysis of the nanostructure morphologies obtained.
Simulation of Plasmonic Effects in Nanostructured Copper Surfaces for Field-assisted Photoemission
Authors: Groussin B , Martinez Calderon M , Marsh B , Granados E 
Published: January 2024

Abstract
Plasmonics in photoemission have recently gained interest due to their effect on important electron beam parameters such as emittance or quantum efficiency (QE), among others. For example, the presence of nanostructures at the surface of the photoemissive medium can increase the probability of electron emission if their morphological features match that of the plasmonic resonance when laser-irradiated in an electron gun. To determine the optimal size and geometry of these nanostructures and predict the resulting field enhancement, we conducted parametric electromagnetic simulations of nanostructured surfaces using COMSOL®. We investigated several types of geometries commonly found in laser processed copper substrates, optimized their performance under different irradiation wavelengths, and determined the expected maximal enhancement factor attainable.
Development of an X-band RF gun with four-feed coupler
Authors: Hu F , Zha H , Shi J , Gao J , Li Q , Gu W , Chen H 
Published: January 2024

Abstract
With the high accelerating gradient, radiofrequency (rf) gun has a significant feature of suppressing the growth of transverse emittance caused by space charge. Field emission cathodes were first used in vac-uum electronic devices, which do not require the high electron beam intensity, but the compact geometry size of the cathode. A new X-band (11.424 GHz) rf electron gun has been proposed with the highlight of four-feed coupler, which can eliminate the quadrupole field component observed and analysed from the imagine experiment carried on, which have affected the resolu-tion of the imaging system to some content.
Effect of SCU long range errors on the FEL performance
Authors: Grattoni V , Casalbuoni S , Geloni G , Lechner C , Schneidmiller E 
Published: January 2024

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.