bluuebunny/crossref_metadata_2025_split huggingface dataset:
Overview and prospects of plasma wakefield acceleration experiments at PITZ
Authors: Lishilin O , Chen Y , Good J , Gross M , Isaev I , Koschitzki C , Krasilnikov M , Loisch G , Melkumyan D , Niemczyk R , Oppelt A , Qian H , Stephan F , Brinkmann R , Martinez de la Ossa A , Osterhoff J , Grüner F J , Mehrling T , Schroeder C 
Published: December 2019

Abstract
The Photo Injector Test Facility at DESY in Zeuthen (PITZ) carries out studies of beam-driven plasma wakefield acceleration (PWFA). The facility possesses a flexible photocathode laser beam shaping system and a variety of diagnostics including a high-resolution dipole spectrometer and an rf deflector which enables the observation of the longitudinal phase space of electron beams after their passage through a plasma. Two plasma sources are available: a gas discharge plasma cell and a photoionized lithium vapor plasma cell. Studies at PITZ include investigations of the self-modulation instability of long electron beams and the high transformer ratio, i.e., the ratio between the maximum accelerating field behind the drive beam and the decelerating field within the beam. This overview includes the experimental results and plans for future experiments.
A simple way to introduce an adjustable femtosecond pre-pulse to enhance laser-driven proton acceleration
Authors: Wang P , Gao Y , Shou Y , Pan Z , Xu S , Wang D , Liu J , Cao Z , Mei Z , Kong D , Geng Y , Zhao Y , Lu H , Lin C , Yan X , Ma W 
Published: December 2019

Abstract
We demonstrate a simple way to introduce a femtosecond pre-pulse with adjustable intensity and delay without using an additional compressor to enhance laser-driven proton acceleration. Targets with different thicknesses were shoot at normal incidence by varying the pre-pulses. Experimental results show that significant enhancement of the proton energy can be achieved when the intensity of pre-pulse is optimized. Density profile of preplasma was obtained by hydrodynamic simulations. PIC simulations reveal that the preplasma generated by a femtosecond pre-pulse can increase the intensity of main pulse.
Cylindrical cavity design and particle-tracking simulation in cyclotron auto-resonance accelerator
Authors: Yuan Y T , Fan K J , Jiang Y 
Published: December 2019

Abstract
The Cyclotron Auto-Resonance Accelerator (CARA) is a novel concept of accelerating continuous-wave (CW) charged-particle beams. This type of accelerator has applications in environment improvement area and generation of high-power microwaves. In CARA, the CW electron beam follows a gyrating trajectory while undergoing the interaction with a rotating TE11-mode RF field and tapered static magnetic field. The cylindrical cavity operating at TE11p-mode is adapted to accelerate electron beam. The cavity size is optimized to obtain a beam with designed energy, then a design method of the TE11p-mode acceleration cavity is described here. Moreover, regardless of space charge effect, several particle-tracking simulations of CARAs are showed.
Collimation of heavy-ion beams in the HE-LHC
Authors: Abramov A , Bruce R , Crouch M , Fuster-Martinez N , Mereghetti A , Molson J , Nevay L J , Redaelli S 
Published: December 2019

Abstract
A design study for a future collider to be built in the LHC tunnel, the High-Energy Large Hadron Collider (HE-LHC), has been launched as part of the Future Circular Collider (FCC) study at CERN. It would provide proton collisions at a centre-of-mass energy of 27 TeV as well as collisions of heavy ions at the equivalent magnetic rigidity. HE-LHC is being designed under the stringent constraint of using the existing tunnel and therefore the resulting lattice and optics differ in layout and phase advance from the LHC. It is necessary to evaluate the performance of the collimation system for ion beams in HE-LHC in addition to proton beams. In the case of ion beams, the fragmentation and electromagnetic dissociation that relativistic heavy ions can undergo in collimators, as well as the unprecedented energy per nucleon of the HE-LHC, requires dedicated simulations. Results from a study of collimation efficiency for the nominal lead ion (208Pb82+) beams performed with the SixTrack-FLUKA coupling framework are presented. These include loss maps with comparison against an estimated quench limit as well as detailed considerations of loss spikes in the superconducting aperture for critical sections of the machine such as the dispersion suppressors.
RF measurements and tuning of the 325 MHz Ladder-RFQ
Authors: Schuett M. , Ratzinger U. , Syha M. , Wang H. 
Published: December 2019

Abstract
Based on the positive results of the 0.63 m unmodulated 325 MHz Ladder-RFQ prototype from 2013 to 2016 [1, 2], a modulated 3.3m Ladder-RFQ (s. Fig. 1) has been designed and built for the acceleration of up to 100 mA protons from 95 keV to 3.0 MeV at the FAIR p-Linac [3, 4]. In this paper, we will show the results of manufacturing as well as low level RF measurements of the Ladder-RFQ including flatness and frequency tuning.
VSWR Adjustment for ACS Cavity in J-PARC Linac
Authors: Tamura Jun , Kondo Yasuhiro , Morishita Takatoshi , Naito Fujio , Otani Masashi , Nemoto Yasuo 
Published: December 2019

Abstract
In the Japan Proton Accelerator Research Complex (J-PARC) linac, negative hydrogen beams are accelerated from 190 MeV to 400 MeV by Annular-ring Coupled Structure (ACS) cavities. The RF input coupler of the ACS21 cavity, which is the twenty-first (the last) accelerating cavity in the order of beam acceleration, had a comparatively larger Voltage Standing Wave Ratio (VSWR) value than the other ACS cavities. Therefore, we designed and manufactured a rectangular waveguide which have a capacitive iris to adjust the coupling factor of the ACS21 cavity. By making use of the summer maintenance period in 2018, we installed the newly manufactured waveguide to the cavity. Consequently, the VSWR of the ACS21 was successfully decreased to the target value which leads to the critical coupling under the nominal accelerating condition with 50-mA peak beam current.
Ultra-High Vacuum characterization of Molybdenum-Carbide Graphite for HL-LHC collimators
Authors: Accettura C , Beghi M , Bertarelli A , Bregliozzi G , Carra F , Cattenoz G , Guardia-Valenzuela J , Redaelli S , Taborelli M 
Published: December 2019

Abstract
In view of the High-Luminosity upgrade of the Large Hadron Collider (LHC) collimation system, a family of novel molybdenum-carbide graphite (MoGr) composites was developed to meet the challenging requirements of HL-LHC beam-halo collimation, in particular the electrical conductivity and thermo-mechanical performances. The Ultra-High Vacuum (UHV) behaviour of this material was extensively characterized to assess its compatibility with the accelerator’s specifications. The results presented in this paper correlate the outgassing behaviour with the microscopic features of MoGr compared to other graphite-based materials. Residual gas analysis (RGA) was exploited to optimize post-production treatments.
Transverse emittance measurement in the CERN Proton Synchrotron in view of beam production for the High-Luminosity LHC
Authors: Senes E , Emery J , Fraser M A , Guerrero Ollacarizqueta A , Huschauer A , Roncarolo F , Sirvent J L , Skowronski P , Tecker F , Forte V 
Published: December 2019

Abstract
In the framework of the LHC Injectors Upgrade project the improvements required to achieve the parameters of the future beams for the High-Luminosity LHC are being studied and implemented. In order to deliver high brightness beams, control over the beam intensity and emittance is fundamental. Therefore, a highly accurate and reliable transverse emittance measurement is essential. Presently at the CERN Proton Synchrotron, the only operationally available emittance monitors not impacting the facility beam production are the flying wire scanners used to measure the circulating beam profile. The wire scanners will be replaced with a new generation in the next two years and a prototype is already installed. The prototype has been commissioned with beams featuring a wide range of intensities and emittances. This paper evaluates the performance of the prototype with respect to the present system via beam-based measurements. The transverse emittance measurement is discussed, considering the different potential error contributions to the measurement, such as knowledge of the machine optics and the dispersive contribution to the beam size.
A central region upgrade of the k800 Superconducting Cyclotron at INFN-LNS
Authors: D’Agostino G , Calabretta L , Kleeven W , Rifuggiato D 
Published: December 2019

Abstract
The Superconducting Cyclotron (CS) at INFN-LNS in Catania is currently under an upgrade process. The plan is to deliver beams of ions with mass number A ⩽ 40 with power up to 10 kW by means of beam intensity increase. This ambitious goal can be achieved by increasing the efficiency of the injection and extraction processes. An extraction efficiency close to 100% is expected by extracting the specific ion beams from the CS by stripping and no longer by electrostatic deflectors. The beams are injected axially and bent onto the median plane with a spiral inflector. Currently, the injection efficiency is around 15% including the effect of a drift buncher placed in the axial injection line. In order to increase the injection efficiency, the study of an upgraded CS central region is ongoing at INFN-LNS. In this paper, the results of simulations of beam tracking through the cyclotron axial bore, the spiral inflector, the central region and further up to the extraction system are presented.
The New Eddy Current Type Septum Magnets for Upgrading of Fast Extraction in Main Ring of J-PARC
Authors: Shibata T , Ishii K , Sugimoto T , Matsumoto H , Fan K , Hamano K 
Published: December 2019

Abstract
The J-PARC Main Ring (MR) is currently working on upgrading the machine power reach to 750 kW by increasing the beam repetition rate from 0.4 Hz to 0.78 Hz. This new operation mode is referred as ”1 Hz” operation. The Fast eXtraction (FX) system in MR needs to upgrade to realize 1 Hz operation, and the improvement will be completed in 2021. The present FX Low-Field Septa (FX LF-Septa) which are conventional ones will be replaced with the new septa which is induced eddy current type (FX Eddy-Septa). The first FX Eddy-Septa system, which included the magnets and short pulse power supply (PS), was constructed in 2014. We have been studying the FX Eddy-Septa system to evaluate the stability of the output pulsed current and magnetic gap field since 2014. In winter of 2018, the 1 Hz operation test by using the two Main-chargers was conducted without any problem. The stability of the output pulsed current was 10 ppm. The leakage field was measured along the circulating beam line, and we found that the level of leakage field was still larger than our requirement. The PS has still several issues which must be solved. The switching time of the Main-charger to the Sub-charger must be reduced, the jitter of time lag between two discharge triggers must be eliminated, and the disagreement between the two current monitor systems must be solved.
J-PARC RCS: high-order field components inherent in the injection bump magnets and their effects on the circulating beam during multi-turn injection
Authors: Hotchi H , Harada H , Takayanagi T 
Published: December 2019

Abstract
We investigated the cause of the residual beam loss during multi-turn injection of the J-PARC 3-GeV rapid cycling synchrotron (RCS). In the RCS, four sets of injection bump magnets (pulsed dipole magnets) are employed for multi-turn injection. Numerical simulations considering the actual magnetic field profiles of the injection bump magnets well reproduced the empirical beam loss, and pointed that a 3rd-order random betatron resonance driven by a sextupole field component inherent in the injection bump magnets is the major source of the beam loss. In this paper, we describe the detailed mechanism of emittance growth and beam loss caused by such a high-order field component of the injection bump magnets including their correction scenario.
Current status of slow extraction from J-PARC Main Ring
Authors: Muto R. , Arakaki Y. , Kimura T. , Murasugi S. , Okada M. , Okamura K. , Shimogawa T. , Shirakabe Y. , Tomizawa M. , Toyama T. , Yanaoka E. , Matsumura A. 
Published: December 2019

Abstract
A 30 GeV proton beam accelerated in the J-PARC Main Ring (MR) is slowly extracted by the third integer resonant extraction and delivered to the hadron experimental facility. A dynamic bump scheme under achromatic condition drastically reduces beam hit rate on the septa devices, and we have attained 51 kW SX operation at 5.2 s cycle with high slow extraction efficiency of 99.5%. A spill duty factor indicating a uniformity of the time structure of the extracted beam is typically 50%. The current SX performance and future plans for improvements will be presented.
Frequency modulated capture of cooled coasting ion beams
Authors: Albright S , Angoletta M E 
Published: December 2019

Abstract
Transverse space charge effects in the Low Energy Ion Ring (LEIR) at CERN have been shown to be a major source of particle losses, which can be mitigated with a larger RMS longitudinal emittance. However, due to electron cooling during the injection plateau, the longitudinal density is very high prior to RF capture. In addition there is an uncontrolled cycle to cycle variation in the revolution frequency of the coasting beam on the flat bottom, which degrades the beam quality at capture. In this paper we show that applying an RF frequency modulation during the capture process allows both a controlled blow-up of the longitudinal emittance and a very good reproducibility in the longitudinal distribution, which in turn improves beam transmission through the machine.
New Analytical derivation of Group Velocity in TW accelerating structures
Authors: Behtouei M. , Faillace L. , Migliorati M. , Palumbo L. , Spataro B. 
Published: December 2019

Abstract
Ultra high-gradient accelerating structures are needed for the next generation of compact light sources. In the framework of the Compact Light XLS project, we are studying a high harmonic traveling-wave accelerating structure operating at a frequency of 35.982 GHz, in order to linearize the longitudinal space phase. In this paper, we propose a new analytical approach for the estimation of the group velocity in the structure and we compare it with numerical electromagnetic simulations that are carried out by using the code HFSS in the frequency domain.
Coupling Impedance of the Collimator Without RF-Shields at the RCS in J-PARC
Authors: Shobuda Y , Okabe K , Kamiya J , Moriya K 
Published: December 2019

Abstract
All holes on the chamber walls of synchrotrons should be filled with the radiofrequency (RF)-shields to suppress coupling impedances that excite beam instabilities. In a synchrotron, titanium nitride (TiN)-coated RF-shields are installed with collimators. If the holes, through which the collimator jaw enters and exits the chamber, are filled with such RF-shields, the shields may break down as the dynamic coefficient of TiN increases in vacuum. At the Rapid Cycling Synchrotron (RCS), the RF-shields are eliminated from the collimator after demonstrating that the effect due to the RF-shields is negligible on the impedance at low frequencies.
Studies on coherent multi-bunch tune shifts with different bunch spacing at the J-PARC Main Ring
Authors: Kobayashi A , Toyama T , Sato Y , Igarashi S , Shimogawa T , Sugiyama Y , Yoshii M 
Published: December 2019

Abstract
At a high-power proton synchrotron, betatron tune shifts induced by space charge effects cause beam loss which limits the beam intensity. To achieve further high beam intensity at the main ring of the Japan Proton Accelerator Research Complex, precise control of the tune shift is indispensable. When carrying out multi-bunch measurements, we observed that the dependence of the tune shift intensity on the number of bunches follow opposite slope trends for the horizontal and vertical directions. The dependence of the bunch spacing was also observed. We report on a simplified tune shift model reconstruction for understanding the origin of these phenomena and present a correction of the tune shifts for reducing beam loss up to 30 %.
Change of beam distribution due to decoherence in the presence of transverse feedback
Authors: Furuseth S V , Buffat X 
Published: December 2019

Abstract
The effect of Landau damping is often calculated based on a Gaussian beam distribution in all degrees of freedom. The stability of the beam is however strongly dependent on the details of the distribution. The present study focuses on the change of bunch distributions caused by the decoherence of the excitation driven by an external source of noise, in the presence of both amplitude detuning and a transverse feedback. Both multiparticle tracking simulations and theoretical models show a similar change of the distribution. The possible loss of Landau damping driven by this change is discussed.
The Cooling Effect of Beam Self-Fields on the Photocathode Surface in High Gradient RF Injectors
Authors: Chen Ye , Krasilnikov Mikhail , Stephan Frank 
Published: December 2019

Abstract
The intrinsic slice emittance of the emitted electrons on the photocathode surface at each moment during the transient photoemission process depends on the transverse size of the slice and the mean kinetic energy of the electrons within the slice. The latter relies on the surface barrier potentials of the cathode material at a fixed wavelength of the incident light, and is thus significantly influenced by the presence of strong rf and beam self-fields at /close to the cathode surface. This is, in particular, the case in high brightness injectors for modern free electron lasers. In this article, the beam self-fields are determined in a self-consistent approach, based on which improved transverse and temporal emission distributions are obtained. The nonlinear correlations of the intrinsic surface slice emittance within the bunch are shown for multiple bunch charges. A peak to peak variation of the intrinsic surface emittance is estimated as 30% for the highest charge-density case considered in this paper. An overall reduction of the average intrinsic emittance is computed as 10% accordingly. The cooling effect on the cathode surface is enhanced as the local space-charge density rises. The impacts of the cooling effect on downstream beam qualities are demonstrated through particle tracking simulations based on the injector setup at the Photo Injector Test Facility at DESY in Zeuthen (PITZ).
Length scales and alloys of iron
Authors: Bhadeshia H K D H 
Published: December 2019

Abstract
Many of the structures common within steels are not geometrically smooth, which means that their stereological parameters, such as the amount of interfacial area per unit volume, are resolution dependent. The tendency of brittle phases to crack is size dependent, as is the strength. The ability of steel to resist cleavage can be influenced by the size and distribution of coherent domains within the structure. A different diffusion theory applies when dealing with steep concentration gradients. All of these aspects are of importance in the design, characterisation and theory of steels, illustrated here with a few examples, where the neglect of length scales is improper.
Thermochemical surface engineering: a playground for science and innovation
Authors: Christiansen T L , Somers M A J 
Published: December 2019

Abstract
This article illustrates the plethora of different possibilities in thermochemical surface engineering (TSE) and the close interlink between science and innovation. Three widely different examples of gaseous TSE are presented: surface engineering of austenitic stainless steel by high- and low- temperature surface treatment, surface hardening of titanium by incorporation of nitrogen, oxygen and carbon, and direct synthesis of magnetic iron-nitride α”-Fe16N2. It is shown how 3D printed materials made of stainless steel and titanium can benefit from TSE.
Using synchrotron radiation to improve understanding of deformation of polycrystalline metals by measuring, modelling and publishing 4D information
Authors: Greeley D , Yaghoobi M , Pagan D , Sundararaghavan V , Allison J 
Published: December 2019

Abstract
The evolution of deformation in a Mg-Nd alloy has been investigated using 3D HEDM and crystal plasticity simulation using the PRISMS-Plasticity CPFE Code. Using a simplified representative volume element (RVE), the average stress-strain response is well predicted by the PRISMS-Plasticity simulation. The distribution of the resolved shear stresses corresponding to the basal mode for all grains is obtained using both HEDM and the CPFE. simulation. The results show that the CPFE predicted substantially narrower distributions, thus indicating the need for improved digital representation of the RVE. The results of these HEDM experiments and PRISMS-Plasticity simulations have been stored in the Materials Commons in a straight-forward manner and are being made available as a published dataset. Both PRISMS-Plasticity and the Materials Commons are open-source and available for use by the global materials community.
Comparison of the Elastic-Plastic Transition in Nanocrystalline Nickel Pillars Fabricated by Electron Beam Lithography and Focused Ion Beam Methods
Authors: Sedore Matthew , Diak Bradley J. , Murray Andrew , Riel Bruno 
Published: December 2019

Abstract
The elastic-plastic transition or yield behaviour was observed during compression of nanocrystalline nickel pillars fabricated by electroplating into electron beam lithography (EBL) forms or by focused ion beam (FIB) milling of the same electroplated structure. The experimental methodology allowed structures with different surface defect source/obstacles and similar bulk defects to be compared. Pillars with 1 to 2 um diameter cross-sections were made with height to diameter aspect ratios from 2:1 to 6:1, grain size of 91 ± 23 nm, and <110>, <111>, <100> textures in the growth direction. The pillars were compressed under a flat punch at constant loading rates from 1.5 to 30 μΝ/s using an instrumented indenter. EBL pillars generally showed a gradual elastic-plastic transition similar to yielding in bulk nickel followed by strain bursts. In contrast, FIB-milled pillars consistently showed stochastic yielding. The Young’s modulus was 55 to 350 GPa for all pillars, agreeing with values in the literature. The yield stress at 0.2% offset strain for EBL pillars ranged from 480 to 1800 MPa, and 320 to 700 MPa for FIB-milled pillars that was narrowed to 550 to 650 MPa after subsequent annealing, with initial deformation localized near the tops of FIB-milled pillars due to geometrical tapering. EBL pillar shear yield strengths exceed the literature reported for Ni and appear to lose their size dependence.
Load transfer and strain gradients in pearlite investigated by means of in-situ neutron diffraction
Authors: Tacq Jeroen , Verlinden Bert , Seefeldt Marc 
Published: December 2019

Abstract
In-situ neutron diffraction experiments have been performed during tensile testing of undeformed and cold rolled pearlite. The microstructure of the samples varied from spheroidised cementite to randomly oriented lamellae to lamellae aligned with the loading direction. Both the ferrite lattice strain and diffraction peak width have been analysed. Conclusions were drawn regarding the influence of cementite morphology on load transfer from ferrite to cementite. The ferrite lattice strain was found to decrease after yielding in a sample with aligned lamellae, whereas an increasing ferrite lattice strain would be expected. This might be explained based on the non-ideal nature of the lamellar microstructure. Upon unloading of the material, the diffraction peak width decreases, which may be attributed to strain gradients in the deformed pearlite.