bluuebunny/crossref_metadata_2025_split huggingface dataset:
Status report of the SINBAD-ARES RF photoinjector and linac commissioning
Authors: Panofski E , Assmann R W , Burkart F , Dorda U , Floettmann K , Huening M , Marchetti B , Marx D , Mayet F , Walker P A , Yamin S 
Published: December 2019

Abstract
The accelerator R&D facility SINBAD (Short innovative bunches and accelerators at DESY) will drive multiple independent experiments, including the acceleration of ultrashort electron bunches and the testing of advanced high-gradient acceleration concepts. The SINBAD-ARES (Accelerator Research Experiment at SINBAD) setup hosts a normal conducting RF photoinjector generating a low-charge electron beam, which is afterwards accelerated by an S-band linac section. The linac as well as a magnetic chicane will allow the production of ultrashort bunches with excellent arrival-time stability. The high brightness beam has then the potential to serve as a test beam for next-generation compact acceleration schemes. The setup of the SINBAD-ARES facility will proceed in stages. We report on the current status of the ARES RF gun commissioning and linac setup.
Simulation studies for a EEHG seeded FEL in the XUV
Authors: Grattoni V. , Faatz B. , Paraskaki G. , Ackermann S. , Assmann R. W. , Lechner C. , Zemella J. , Kazemi M. M. , Lang T. , Hillert W. , Reiche S. 
Published: December 2019

Abstract
Echo-enabled harmonic generation (EEHG) is a promising technique for seeded free electron lasers (FELs) not only to go down to wavelengths of 4 nm but also to simplify the schemes that are currently used to achieve a similar wavelength range (double cascade HGHG). Thus a study optimizing the EEHG performance in the wavelength range from 60 to 4nm has been performed. The more critical working point, at 4 nm, is here analyzed in terms of seed laser stability for two different seed laser frequencies: visible and UV.
Wake-T: a fast particle tracking code for plasma-based accelerators
Authors: Ferran Pousa A , Assmann R , Martinez de la Ossa A 
Published: December 2019

Abstract
The design and study of plasma-based accelerators relies typically on costly 3D Particle-In-Cell (PIC) simulations due to the complexity of the laser-plasma and beam-plasma interactions. However, under certain assumptions, more efficient and simple models can be implemented to describe the dynamics of the accelerated beams. Wake-T (Wakefield particle Tracker) is a new code for analytical and numerical particle tracking in plasma-based accelerators which is orders of magnitude faster than conventional PIC codes. This allows for fast parameter scans and is well suited for the initial design and optimization of these novel accelerators.
Numerical Study of Photonic-Crystal-Based Dielectric Accelerators
Authors: Torrisi G. , Mauro G. S. , Celona L. , Mascali D. , Gammino S. , Sorbello G. , De Angelis C. , Locatelli A. 
Published: December 2019

Abstract
All-dielectric electromagnetic band gap (EBG) waveguides structures promise significant improvement of accelerating gradient of laser-driven acceleration with the potential to miniaturize the accelerator itself. In this work we study photonic crystal structures designed for acceleration of relativistic electrons. We explore the performance of the all-dielectric EBG accelerating structures thanks to full wave electromagnetic simulations of couplers and accelerating waveguides. The characteristic interaction impedance, accelerating gradient and all the key parameters that are typically used to characterize linear accelerators are evaluated and used to compare the properties of the accelerating mode field distribution in different geometries.
Moderation of positive muons by helium gas
Authors: Li Yang , Bao Yu , Fan Ruirui , Li Xiao , Ning Changjun , Tong Xin , Wang Pengcheng 
Published: December 2019

Abstract
Efficiently creating beams of spin-polarized positive muons with energies between eV and keV (so-called slow muon beams) is important for further development and application of muon spin rotation, relaxation, and resonance techniques. One existing moderation method involves the use of wide-band-gap materials as moderators such as rare gas solids and solid nitrogen thin films (band-gap energy between 11 eV and 22eV). Based on this moderation method, we have studied the use of helium gas as a moderator, with the goal of producing the slow muon beam more efficiently. Because of helium’s high (24.6 eV) ionization energy and because the cross section for muonium formation is suppressed in helium gas, we expect the production of slow muons using helium gas to be highly efficient.
Negative Muonium Ion Production With a C12A7 Electride Film
Authors: Otani M. , Fukao Y. , Futatsukawa K. , Kawamura N. , Matoba S. , Mibe T. , Miyake Y. , Shimomura K. , Yamazaki T. , Hasegawa K. , Kitamura R. , Kondo Y. , Morishita T. , Iijima T. , Inami K. , Sue Y. , Yotsuzuka M. , Iinuma H. , Nakazawa Y. , Ishida K. , Saito N. , Yasuda H. 
Published: December 2019

Abstract
Negative muonium atom (μ
+
e
–
e
–, Mu–) has unique features stimulating potential interesting for several scientific fields. Since its discovery in late 1980’s in vacuum, it has been discussed that the production efficiency would be improved using a low-work function material. C12A7 was a well-known insulator as a constituent of alumina cement, but was recently confirmed to exhibit electric conductivity by electron doping. The C12A7 electride has relatively low-work function (2.9 eV). In this paper, the negative muonium production measurement with several materials including a C12A7 electride film will be presented.
Advanced Beam Dynamics Design for the Superconducting Heavy Ion Accelerator HELIAC
Authors: Schwarz Malte , Aulenbacher Kurt , Barth Winfried , Basten Markus , Burandt Christoph , Busch Marco , Conrad Thorsten , Dziuba Florian , Gettmann Viktor , Heilmann Manuel , Kürzeder Thorsten , Lauber Simon , List Julian , Miski-Oglu Maksym , Podlech Holger , Rubin Anna , Yaramyshev Stepan 
Published: December 2019

Abstract
The standalone superconducting (SC) continuous wave (CW) heavy ion linac HELIAC (HElmholtz LInear ACcelerator) is a common project of GSI and HIM under key support of IAP Frankfurt and in collaboration with Moscow Engineering Physics Institute (MEPhI) and Moscow Institute for Theoretical and Experimental Physics (KI-ITEP). It is intended for future experiments with heavy ions near the Coulomb barrier within super-heavy element (SHE) research and aims at developing a linac with multiple CH cavities as key components downstream the High Charge State Injector (HLI) at GSI. The design is challenging due to the requirement of intense beams in CW mode up to a mass-to-charge ratio of 6, while covering a broad output energy range from 3.5 to 7.3MeV/u with minimum energy spread. In 2017 the first superconducting section of the linac has been successfully commissioned and extensively tested with beam at GSI. In the light of experience gained in this research so far, the beam dynamics layout for the entire linac has recently been updated and optimized with particular emphasis on realistic assumptions of cavity gap and drift lengths as well as gap voltage distributions for CH3-CH11.
Upgrade of the 3-MeV Linac for testing of Accelerator Components at J-PARC
Authors: Kondo Y. , Morishita T. , Hirano K. , Ito T. , Kikuzawa N. , Kitamura R. , Oguri H. , Ohkoshi K. , Shinozaki S. , Shinto K. , Fang Z. , Fukui Y. , Futatsukawa K. , Ikegami K. , Miyao T. , Nanmo K. , Otani M. , Shibata T. , Hori T. , Nemoto Y. , Sato Y. , Kobayashi F. , Takahashi D. , Tasaki R. , Ito Y. , Kato Y. , Ishiyama T. , Sawabe Y. 
Published: December 2019

Abstract
We have upgraded a 3-MeV linac at J-PARC. The ion source is same as the J-PARC linac’s, and the old 30-mA RFQ is replaced by a spare 50-mA RFQ, therefore, the beam energy is 3 MeV and the nominal beam current is 50 mA. The main purpose of this system is to test the spare RFQ, but also used for testing of various components required in order to keep the stable operation of the J-PARC accelerator. The accelerator has been already commissioned, and measurement programs have been started. In this paper, present status of this 3-MeV linac is presented.
Longitudinal Measurements and Beam Tuning in the J-PARC Linac MEBT1
Authors: Otani M. , Futatsukawa K. , Miyao T. , Liu Y. , Hirano K. , Kondo Y. , Miura A. , Oguri H. 
Published: December 2019

Abstract
The Japan Proton Accelerator Research Complex (J-PARC) linac is operated with design peak current of 50 mA from 2018. For operation with such a high beam current, it is important to understand transverse and longitudinal beam properties especially in low-velocity region. A medium energy beam transport (MEBT1) line between the 3-MeV radio-frequency quadrupole linac (RFQ) and the 50-MeV drift-tube linac (DTL) is a 3-m-long transport line to match the beam to the DTL and produces a macro pulse configuration for a 3-GeV rapid-cycling synchrotron (RCS). In this paper, recent measurements and beam tuning results in MEBT1 will be presented.
Charge stripping at high energy heavy ion Linacs
Authors: Barth W , Fomichev A , Grigorenko L , Kulevoy T. , Polozov S , Yaramyshev S 
Published: December 2019

Abstract
For each heavy-ion accelerator facility charge stripping is a key technology – the stripping charge state, its efficiency to produce ions in the selected charge state, and the beam quality after stripping substantially determine the entire accelerator performance. Modern heavy ion accelerator facilities such as the future Facility for Antiproton and Ion Research (FAIR) at GSI, Darmstadt, Germany provide for high-intensity heavy-ion beams beyond 200 MeV/u. Heavy ions generated in an ion source at comparatively low charge states are pre-accelerated in a Linac to a few MeV/u, after charge stripping the average charge state is increased and one (or several) ion charge states are selected for further acceleration. This enables more efficient acceleration up to the final beam energy, compared to acceleration of ions with a low charge state. C-foil stripping allows for highest mean charge state and best stripping efficiency into the desired charge state. Therefore minimum acceleration voltage could be expected utilizing C-foil stripping. Due to the high power deposited by the ions in the stripping media and radiation damages if solids are used, self-recovering stripper media must be used in any case. First layout scenarios for a 200 MeV/u heavy ion Linac considering efficient heavy ion stripping will be presented.
Beam breakup simulations for the Mainz Energy recovering Superconducting Accelerator MESA
Authors: Stoll C P , Hug F 
Published: December 2019

Abstract
MESA is a two pass energy recovery linac (ERL) currently under construction at the Johannes Gutenberg-University in Mainz. MESA uses four 1.3 GHz TESLA type cavities with 12.5 MVm-1 of accelerating gradient in two modified ELBE type cryomodule with improved thermal connection of the HOM antennas and cw operation. In the first stage of MESA operation 1mA of beam current is foreseen, which will later be upgraded to 10 mA. One potential limit to maximum beam current in ERLs is the transverse beam breakup (BBU) instability induced by dipole Higher Order Modes (HOMs). These modes can be excited by bunches passing through the cavities off axis. Following bunches are then deflected by the HOMs, which results in even larger offsets for recirculated bunches. This feedback can even lead to beam loss. Simulation results for HOM spectra of a single TESLA cavity are available for example in [1]. It was possible to measure the HOM spectra in the cold, not tuned cavities at DESY and in the cold string tuned to the 1.3 GHz fundamental mode at Mainz. Results for the maximum beam current for MESA, limited by BBU, for the various HOM spectra are presented.
Experimental determination of proton hardness factors at several irradiation facilities
Authors: Allport P. , Bögelspacher F. , Bruce K. , Canavan R. , Dierlamm A. , Gonella L. , Knights P. , Mateu I. , Moll M. , Nikolopoulos K. , Phoenix B. , Price T. , Ram L. , Ravotti F. , Simpson-Allsop C. , Wood C. 
Published: December 2019

The scheduled High Luminosity upgrade of the CERN Large Hadron Collider presents new challenges in terms of radiation hardness. As a consequence, campaigns to qualify the radiation hardness of detector sensors and components are undertaken worldwide. The effects of irradiation with beams of different particle species and energy, aiming to assess displacement damage in semiconductor devices, are communicated in terms of the equivalent 1 MeV neutron fluence, using the hardness factor for the conversion. In this work, the hardness factors for protons at three different kinetic energies have been measured by analysing the I–V and C–V characteristics of reverse biased diodes, pre- and post-irradiation. The sensors were irradiated at the MC40 Cyclotron of the University of Birmingham, the cyclotron at the Karlsruhe Institute of Technology, and the IRRAD proton facility at CERN, with the respective measured proton hardness factors being: 2.1± 0.5 for 24 MeV, 2.2 ± 0.4 for 23 MeV, and 0.62± 0.04 for 23 GeV. The hardness factors currently used in these three facilities are in agreement with the presented measurements.
Braiding properties of paired spin-singlet and non-Abelian hierarchy states
Authors: Tournois Yoran , Ardonne Eddy 
Published: December 2019

Abstract
We study explicit model wave functions describing the fundamental quasiholes in a class of non-Abelian fractional quantum Hall states. This class is a family of paired spin-singlet states with

internal degrees of freedom. We determine the braid statistics of the quasiholes by determining the monodromy of the explicit quasihole wave functions, that is how they transform under exchanges of quasihole coordinates. The statistics is shown to be the same as that of the quasiholes in the Read–Rezayi states, up to a phase. We also discuss the application of this result to a class of non-Abelian hierarchy wave functions.
Additive manufacturing of metal components – process-material interaction in different process chains
Authors: Hansen H N , Hattel J H , Pedersen D B , Mohanty S , Andersen S A , Nadimpalli V K , Klingaa C G , Dahmen T , Zhang Y 
Published: December 2019

Abstract
In this paper we describe metal additive manufacturing (AM) processes in general, and laser bed fusion processes in particular. The process characteristics are described, and the various modelling approaches demonstrated. The open AM architecture developed at DTU Mechanical Engineering is introduced, as well as an alternative process chain based on AM and subsequent injection moulding.
The ESRF dark-field x-ray microscope at ID06
Authors: Kutsal M , Bernard P , Berruyer G , Cook P K , Hino R , Jakobsen A C , Ludwig W , Ormstrup J , Roth T , Simons H , Smets K , Sierra J X , Wade J , Wattecamps P , Yildirim C , Poulsen H F , Detlefs C 
Published: December 2019

Abstract
We present an instrument for dark-field x-ray microscopy installed on beamline ID06 of the ESRF — the first of its kind. Dark-field x-ray microscopy uses full field illumination of the sample and provides three-dimensional (3D) mapping of micro-structure and lattice strain in crystalline matter. It is analogous to dark-field electron microscopy in that an objective lens magnifies diffracting features of the sample. The use of high-energy synchrotron x-rays, however, means that these features can be large and deeply embedded. 3D movies can be acquired with a time resolution of seconds to minutes. The field of view and spatial resolution can be adapted by simple reconfiguration of the x-ray objective lens, reaching spatial and angular resolution of 30-100 nm and 0.001°, respectively. The instrument furthermore allows pre-characterization of samples at larger length scales using 3DXRD or DCT, such that a region of interest (e.g. a single grain) can be selected for high-resolution studies without the need to dismount the sample. As examples of applications we show work on mapping the subgrains in plastically deformed iron and aluminum alloys, mapping domains and strain fields in ferroelectric crystals, and studies of biominerals. This ability to directly characterize complex, multi-scale phenomena in-situ is a key step towards formulating and validating multi-scale models that account for the entire heterogeneity of materials. As an outlook, we discuss future prospects for such multi-scale characterization by combining DFXM with 3DXRD/DCT, and coherent x-ray methods for coarser and finer length-scales, respectively.
Cold rolling behaviour of Cu with highly oriented nanotwins: the importance of local shear strain
Authors: Lu Q H , Bai J S , Cheng Z , Lu L 
Published: December 2019

Abstract
To clarify the deformation mechanism of nanotwinned materials under a complex stress state and large strain level, the microstructure evolution of pure Cu samples with high density of preferentially oriented nanotwins cold rolled to a strain up to 65% was systematically characterized by means of electron backscatter diffraction and transmission electron microscopy in this study. Heterogeneous deformation behavior was observed in nanotwinned Cu at different rolling strains. At a rolling strain of 15%, uniform deformation carried by the interactions between dislocations and twin boundaries dominate. At the same time, a small amount of strain localization in the direction ±45° respective to the rolling direction takes place, carried by detwinning and shear bands. As the rolling strain increased to 50%, detwinning becomes a dominant deformation mechanism and produces a large amount of coarse twin/matrix lamellae. A unique laminated structure with high angle lamellar boundaries (larger than 50° misorientation angle) and an average lamellar thickness of about 150 nm evolves from the coarse twin/matrix lamellae. As the rolling strain is increased up to 65%, an extensive laminated structures embedded with a few preserved twin blocks are prevalently formed. It is found that the local shear strain plays a critical role in the microstructure evolution of the nanotwinned Cu under cold rolling. When the local shear strains are so small as to be negligible, uniform deformation is sustained by interactions of dislocation/twin boundaries and the nanoscale twins survive. As the local shear strain increases up to 1, detwinning prevails and results in coarse twin/matrix lamellae. When the local shear strain is larger than 1, formation of shear bands composed of dislocation cells, sub-grains and fragments of twin lamellae instead of the detwinning process takes place, finally evolving into a laminated structure.
Quantification of local boundary migration in 2D/3D
Authors: Zhang Yubin 
Published: December 2019

Abstract
With the development of advanced electron and X-ray microscopy techniques, the local boundary migration during recrystallization and grain growth can be followed in 2D at a sample surface and/or in 3D inside bulk samples during in/ex situ annealing. The results show that locally boundaries migrate in a much more complex way than commonly imagined, for example by the development of local protrusions and retrusions and by migrating in a stop-go type of fashion. A quantitative analysis of the local boundary migration is essential for understanding this heterogeneous process. In this paper, methods for quantifying local boundary migration are summarized, including methods for quantification of local boundary migration velocities, misorientation (angle/axis pair) and plane normal of migrating/non-migrating boundaries, driving force (from both the energy stored in the deformation matrix and local boundary curvature), boundary mobility and activation energy. Through a quantitative analysis of both experimental and simulation data, local boundary migration is rationalized in several material systems during recrystallization and grain growth.
Integral mean curvature analysis of 3D grain growth: Linearity of dV/dt and grain volume
Authors: Patterson BR , DeHoff RT , Sahi CA , Sun J , Oddershede J , Bachmann F , Lauridsen E , Jensen D Juul 
Published: December 2019

Abstract
The volumetric growth rate of individual grains has been found to be directly proportional to the individual grain volume V as dV/dt = β(Vo
-V). This simple result is explained through the DeHoff relationship dV/dt = −kMs
between growth rate and the integral mean curvature of individual grains, M

s
, combined with the experimentally observed relationship between M

s
and grain volume, M

s
= α(Vo
-V). These relationships have now been observed consistently in both 3D grain growth simulations and experiments. This paper describes the relationships among these kinetic and geometric grain characteristics that provide this simple description of 3D grain growth.
Study of potential recrystallization nuclei in the cold-rolled microstructure of an electrical steel by electron backscatter diffraction
Authors: Hsu WC , Chang L , Kao PW 
Published: December 2019

Abstract
Strain induced boundary migration (SIBM) is widely recognized to be the main mechanism corresponding to recrystallization in metals of low or medium amount of deformation. The nucleation process in recrystallization of heavily deformed metals is, however, less understood for key issues such as how the nuclei are formed and where they are located. The evolution of texture from deformation to recrystallization cannot thus be explained well. In this study, an attempt was conducted to identify the potential recrystallization nuclei (PRN) in the cold-rolled microstructure of an electrical steel by electron backscatter diffraction (EBSD). This work demonstrates that the SIBM mechanism can be the main mechanism corresponding to recrystallization nucleation in a heavily deformed steel. The same area in both the cold-rolled and partially recrystallized states was analysed using EBSD to obtain the correlation between the recrystallized grains and the cold-rolled substructures. The deformed grains having high stored energy were first selected, followed by identifying substructures surrounded entirely or partly by high angle boundaries in these heavily deformed grains. The deformation induced grains having low intra-granular misorientation of 2° or less exhibit a very similar orientation distribution to that of the recrystallized grains and are proposed to be the PRN in subsequent recrystallization.
Microstructure and strength of weldment in Pt20Rh alloys dispersion-strengthened by ZrO2particles
Authors: Hu Faping , Wang Ziyang , Yu Tianbo , Yang Zonglun , Wei Guobing , Luo Xuan , Hansen Niels , Huang Xiaoxu , Xie Weidong 
Published: December 2019

AbstractA series of Pt20Rh alloys dispersion-strengthened by different volume fractions of ZrO2particles have been prepared by internal oxidation of Pt20Rh powder followed by consolidation and hot forging. The alloys were cold rolled to sheets, followed by annealing. The effects of welding on the microstructure and mechanical properties were also investigated. The microstructure of the rolled sheets showed a lamellar structure and the yield stress was significantly increased with increasing volume fraction of dispersion particles. After welding, the yield stress at room temperature was almost unchanged, although a small decrease was observed at 1000 °C. However, the work hardening capacity and ultimate tensile stress were significantly reduced in the welded sample due to grain coarsening and to increased pore density in the fusion zone.