bluuebunny/crossref_metadata_2025 huggingface dataset:
NCAM regulates temporal specification of neural progenitor cells via profilin2 during corticogenesis
Authors: Huang Rui , Yuan De-Juan , Li Shao , Liang Xue-Song , Gao Yue , Lan Xiao-Yan , Qin Hua-Min , Ma Yu-Fang , Xu Guang-Yin , Schachner Melitta , Sytnyk Vladimir , Boltze Johannes , Ma Quan-Hong , Li Shen
Published: December 2019

The development of cerebral cortex requires spatially and temporally orchestrated proliferation, migration, and differentiation of neural progenitor cells (NPCs). The molecular mechanisms underlying cortical development are, however, not fully understood. The neural cell adhesion molecule (NCAM) has been suggested to play a role in corticogenesis. Here we show that NCAM is dynamically expressed in the developing cortex. NCAM expression in NPCs is highest in the neurogenic period and declines during the gliogenic period. In mice bearing an NPC-specific NCAM deletion, proliferation of NPCs is reduced, and production of cortical neurons is delayed, while formation of cortical glia is advanced. Mechanistically, NCAM enhances actin polymerization in NPCs by interacting with actin-associated protein profilin2. NCAM-dependent regulation of NPCs is blocked by mutations in the profilin2 binding site. Thus, NCAM plays an essential role in NPC proliferation and fate decision during cortical development by regulating profilin2-dependent actin polymerization.
Modulation of the immune microenvironment by tumor-intrinsic oncogenic signaling
Authors: Nguyen Kim Bich , Spranger Stefani
Published: December 2019

The development of cancer immunotherapies has been guided by advances in our understanding of the dynamics between tumor cells and immune populations. An emerging consensus is that immune control of tumors is mediated by cytotoxic CD8+ T cells, which directly recognize and kill tumor cells. The critical role of T cells in tumor control has been underscored by preclinical and clinical studies that observed that T cell presence is positively correlated with patient response to checkpoint blockade therapy. However, the vast majority of patients do not respond or develop resistance, frequently associated with exclusion of T cells from the tumor microenvironment. This review focuses on tumor cell–intrinsic alterations that blunt productive anti-tumor immune responses by directly or indirectly excluding effector CD8+ T cells from the tumor microenvironment. A comprehensive understanding of the interplay between tumors and the immune response holds the promise for increasing the response to current immunotherapies via the development of rational novel combination treatments.
Single-cell analysis of RORα tracer mouse lung reveals ILC progenitors and effector ILC2 subsets
Authors: Ghaedi Maryam , Orangi Mona , Martinez-Gonzalez Itziar , Wei Lisa , Lu Xiaoxiao , Das Arundhoti , Heravi-Moussavi Alireza , Marra Marco A. , Takei Fumio
Published: December 2019

Lung group 2 innate lymphoid cells (ILC2s) drive allergic inflammation and promote tissue repair. ILC2 development is dependent on the transcription factor retinoic acid receptor–related orphan receptor (RORα), which is also expressed in common ILC progenitors. To elucidate the developmental pathways of lung ILC2s, we generated RORα lineage tracer mice and performed single-cell RNA sequencing, flow cytometry, and functional analyses. In adult mouse lungs, we found an IL-18Rα+ST2− population different from conventional IL-18Rα−ST2+ ILC2s. The former was GATA-3intTcf7EGFP+Kit+, produced few cytokines, and differentiated into multiple ILC lineages in vivo and in vitro. In neonatal mouse lungs, three ILC populations were identified, namely an ILC progenitor population similar to that in adult lungs and two distinct effector ILC2 subsets that differentially produced type 2 cytokines and amphiregulin. Lung ILC progenitors might actively contribute to ILC-poiesis in neonatal and inflamed adult lungs. In addition, neonatal lung ILC2s include distinct proinflammatory and tissue-repairing subsets.
Single-cell analysis of RORα tracer mouse lung reveals ILC progenitors and effector ILC2 subsets
Authors: Ghaedi Maryam , Shen Zi Yi , Orangi Mona , Martinez-Gonzalez Itziar , Wei Lisa , Lu Xiaoxiao , Das Arundhoti , Heravi-Moussavi Alireza , Marra Marco A. , Bhandoola Avinash , Takei Fumio
Published: December 2019

Lung group 2 innate lymphoid cells (ILC2s) drive allergic inflammation and promote tissue repair. ILC2 development is dependent on the transcription factor retinoic acid receptor–related orphan receptor (RORα), which is also expressed in common ILC progenitors. To elucidate the developmental pathways of lung ILC2s, we generated RORα lineage tracer mice and performed single-cell RNA sequencing, flow cytometry, and functional analyses. In adult mouse lungs, we found an IL-18Rα+ST2− population different from conventional IL-18Rα−ST2+ ILC2s. The former was GATA-3intTcf7EGFP+Kit+, produced few cytokines, and differentiated into multiple ILC lineages in vivo and in vitro. In neonatal mouse lungs, three ILC populations were identified, namely an ILC progenitor population similar to that in adult lungs and two distinct effector ILC2 subsets that differentially produced type 2 cytokines and amphiregulin. Lung ILC progenitors might actively contribute to ILC-poiesis in neonatal and inflamed adult lungs. In addition, neonatal lung ILC2s include distinct proinflammatory and tissue-repairing subsets.
Low temperature photoluminescence study of GaAs defect states*
Authors: Huang Jia-Yao , Shang Lin , Ma Shu-Fang , Han Bin , Wei Guo-Dong , Liu Qing-Ming , Hao Xiao-Dong , Shan Heng-Sheng , Xu Bing-She
Published: December 2019

Low temperature (77 K) photoluminescence measurements have been performed on different GaAs substrates to evaluate the GaAs crystal quality. Several defect-related luminescence peaks have been observed, including 1.452 eV, 1.476 eV, 1.326 eV peaks deriving from 78 meV GaAs antisite defects, and 1.372 eV, 1.289 eV peaks resulting from As vacancy related defects. Changes in photoluminescence emission intensity and emission energy as a function of temperature and excitation power lead to the identification of the defect states. The luminescence mechanisms of the defect states were studied by photoluminescence spectroscopy and the growth quality of GaAs crystal was evaluated.
Oxide-aperture-dependent output characteristics of circularly symmetric VCSEL structure
Authors: Liao Wen-Yuan , Li Jian , Li Chuan-Chuan , Guo Xiao-Feng , Guo Wen-Tao , Liu Wei-Hua , Zhang Yang-Jie , Wei Xin , Tan Man-Qing
Published: December 2019

The influence of oxidation aperture on the output characteristics of the circularly symmetric vertical-cavity-surface-emitting laser (VCSEL) structure is investigated. To do so, VCSELs with different oxide aperture sizes are simulated by the finite-difference time-domain (FDTD) method. The relationships among the field distribution of mode superposition, mode wavelength, output spectra, and far-field divergence with different oxide apertures are obtained. Further, VCSELs respectively with oxide aperture sizes of 2.7 μm, 4.4 μm, 5.9 μm, 7 μm, 8 μm, 9 μm, and 18.7 μm are fabricated and characterized. The maximum output power increases from 2.4 mW to 5.7 mW with oxide aperture increasing from 5.9 μm to 9 μm. Meanwhile, the wavelength tuning rate decreases from 0.93 nm/mA to 0.375 nm/mA when the oxide aperture increases from 2.7 μm to 9 μm. The thermal resistance decreases from 2.815 °C/mW to 1.015 °C/mW when the oxide aperture increases from 4.4 μm to 18.7 μm. It is demonstrated theoretically and experimentally that the wavelength spacing between adjacent modes increases with the augment of the injection current and the spacing becomes smaller with the oxide aperture increasing. Thus it can be reported that the aperture size can effectively reduce the mode overlaying but at the cost of the power decreasing and the wavelength tuning rate and thermal resistance increasing.
Doppler radial velocity detection based on Doppler asymmetric spatial heterodyne spectroscopy technique for absorption lines*
Authors: Kuang Yin-Li , Fang Liang , Peng Xiang , Cheng Xin , Zhang Hui , Liu En-Hai
Published: December 2019

Doppler asymmetric spatial heterodyne spectroscopy (DASH) technique has developed rapidly in passive Doppler-shift measurements of atmospheric emission lines over the last decade. With the advantages of high phase shift sensitivity, compact, and rugged structure, DASH is proposed to be used for celestial autonomous navigation based on Doppler radial velocity measurement in this work. Unlike atmospheric emission lines, almost all targeted lines in the research field of deep-space exploration are the absorption lines of stars, so a mathematical model for the Doppler-shift measurements of absorption lines with a DASH interferometer is established. According to the analysis of the components of the interferogram received by the detector array, we find that the interferogram generated only by absorption lines in a passband can be extracted and processed by a method similar to the approach to studying the emission lines. In the end, numerical simulation experiments of Doppler-shift measurements of absorption lines are carried out. The simulation results show that the relative errors of the retrieved speeds are less than 0.7% under ideal conditions, proving the feasibility of measuring Doppler shifts of absorption lines by DASH instruments.
Enhanced optical molasses cooling for Cs atoms with largely detuned cooling lasers*
Authors: Zhang Di , Li Yu-Qing , Wang Yun-Fei , Fu Yong-Ming , Li Peng , Liu Wen-Liang , Wu Ji-Zhou , Ma Jie , Xiao Lian-Tuan , Jia Suo-Tang
Published: December 2019

We report a detailed study of the enhanced optical molasses cooling of Cs atoms, whose large hyperfine structure allows to use the largely red-detuned cooling lasers. We find that the combination of a large frequency detuning of about −110 MHz for the cooling laser and a suitable control for the powers of the cooling and repumping lasers allows to reach a cold temperature of ∼ 5.5 μK. We obtain 5.1× 107 atoms with the number density around 1× 1012 cm−3. Our result gains a lower temperature than that got in other experiments, in which the cold Cs atoms with the temperature of ∼ 10 μK have been achieved by the optical molasses cooling.
High Luminosity LHC Optics and Layout HLLHCV1.4
Authors: Maria R De , Bruce R , Gamba D , Giovannozzi M , Plassard F
Published: December 2019

The goal of the High Luminosity Project is the upgrade of the LHC to deliver an integrated luminosity of at least 250 fb-1 per year in each of the two high-luminosity, general-purpose detectors ATLAS and CMS. This article presents the latest layout design and the corresponding optics features, which comprise optimisation of the orbit corrector and crab cavity systems, and new estimates of the performance reach thanks to the new concept of fully remote alignment. In addition, the new optics version incorporates improvements required by beam instrumentation, dump system, and collimation system, as well as low-beta solutions for the LHCb experiment.
Collimation system studies for the FCC-hh
Authors: Bruce R , Abramov A , Bertarelli A , Besana M I , Carra F , Cerutti F , Faus-Golfe A , Fiascaris M , Gobbi G , Krainer A , Lechner A , Mereghetti A , Mirarchi D , Molson J , Pasquali M , Redaelli S , Schulte D , Serluca M , Skordis E , Varasteh M
Published: December 2019

The Future Circular Collider (FCC-hh) is being designed as a 100 km ring that should collide 50 TeV proton beams. At 8.3 GJ, its stored beam energy will be a factor 28 higher than what has been achieved in the Large Hadron Collider, which has the highest stored beam energy among the colliders built so far. This puts unprecedented demands on the control of beam losses and collimation, since even a tiny beam loss risks quenching superconducting magnets. We present in this article the design of the FCC-hh collimation system and study the beam cleaning through simulations of tracking, energy deposition, and thermo-mechanical response. We investigate the collimation performance for design beam loss scenarios and potential bottlenecks are highlighted.
Monitoring and Modelling of the LHC Emittance and Luminosity Evolution in 2018
Authors: Papadopoulou S. , Antoniou F. , Efthymiopoulos I. , Hostettler M. , Iadarola G. , Karastathis N. , Kostoglou S. , Papaphilippou Y. , Trad G.
Published: December 2019

Operating at 6.5 TeV, the LHC surpassed the expectations and delivered an average of 66 fb–1 integrated luminosity to the two high luminosity experiments ATLAS and CMS by the end of 2018. In order to provide a continuous feedback to the machine coordination for further optimizing the performance, an automated tool for monitoring the main beam parameters and machine configurations, has been devised and extensively used. New features like the coupling between the two planes and effects of noise, were added to the numerical model used since 2016 to calculate the machine luminosity. Estimates, based both on simulations and on observed beam parameters, were reported fill-by-fill as well as in overall trends during the year. Highlights of the observations including the observed additional emittance blow up (on top of IBS, SR and elastic scattering) as well as additional losses (on top of the expected proton burn off) are presented for the 2018 data. Finally, cumulated integrated luminosity projections from the model for the entire 2018 data based on different degradation mechanisms are compared also with respect to the achieved luminosity.
Design study of an electron storage ring for the future plan of Hiroshima Synchrotron Radiation Center
Authors: Matsuba S. , Shimada K. , Katoh M. , Kawase K. , Harada K.
Published: December 2019

We present the latest result from the design study for the future plan of Hiroshima synchrotron radiation center (HSRC). The design goal is the energy of around 500 MeV, the circumference shorter than 50 m and the emittance smaller than 10 nm with straight sections for undulators more than 4. We have selected the lattice structure similar to ASTRID 2 compact light source in Aarhus University, Denmark.
Design Status of DESY IV – Booster Upgrade for PETRA IV
Authors: Chao Hung-Chun
Published: December 2019

In PETRA IV project the on-axis injection scheme is preferred since there is no sufficient dynamic aperture for off-axis injection in ultra low emittance storage rings. The challenge is the frequent preparation the injected bunches with the smaller emittance and larger intensity. The current injector complex including the accumulator and booster does not fulfill the requirements and thus will need refurbishments. The injector upgrade option chosen will be composed of an upgraded electron gun, a higher energy LINAC, and the new booster synchrotron DESY IV which has smaller emittance. DESY IV will be located in the existing tunnel of the current booster DESY II. The design of the lattice and some simulation results are addressed in this article.
Radiation damage to undulator electronics at an electron accelerator
Authors: Chung Ting-Yi , Chang Cheng-Hsing , Chen Yi-Wei , Chen Ang-Yu , Huang Jui-Che , Jan Jyh-Chyuan
Published: December 2019

Experience gained from commissioning and operation of three elliptical polarization undulators (EPU) at the TPS taught us that undulator driving systems can behave erratically following a beam dump or loss. In this work, we discuss possible harmful radiation sources in a storage ring and analyse the effect of lack of electronic component radiation resistance in the system. According to measurements of spatial radiation distribution at the TPS, we propose solutions and an improved design for Phase-II EPUs.
Preparation of the EBS beam commissioning
Authors: Liuzzo S M , Carmignani N , Franchi A , Perron T , Scheidt K B , Taurel E , Torino L , White S M
Published: December 2019

In 2020 the ESRF storage ring will be upgraded to a Hybrid Multi Bend Achromat (HMBA) lattice. The commissioning of the new ring will require dedicated tools, either updated from the existing ones or newly developed. Most of the software and procedures were tested on the existing storage ring before its decommissioning. In particular we present experiments on first-turn steering and beam accumulation, check of magnet polarity and calibration, and injection tuning. The use of a control-system simulator proved to be crucial for the debugging of the software and the development of the new control system, as far as beam measurements and manipulations are concerned.
Measurements of the momentum compaction factor of the ESRF storage ring
Authors: Carmignani N , De Nolf W , Franchi A , Nash B , Sahle Ch J , Torino L
Published: December 2019

In a storage ring, the momentum compaction factor can be obtained by measuring the variation of the beam energy as a function of the RF frequency. In this paper we present the measurement of the momentum compaction factor from two different methods. With the first, we measure the variation of the undulator spectra for different RF frequencies. With the second, we measure the variation of the hard x-rays flux produced by a dipole for different RF frequencies.
Superconducting undulator coils with period length doubling
Authors: Casalbuoni S , Glamann N , Grau A W , Holubek T , Saez de Jauregui D
Published: December 2019

Only since few years it has been demonstrated experimentally that NbTi based superconducting undulators (SCUs) have a higher peak field on axis for the same gap and period length in operation with electron beam with respect to permanent magnet undulators (even the ones in vacuum and cooled to cryogenic temperatures). Another advantage of NbTi based SCUs with respect to permanent magnet devices is radiation hardness, widely demonstrated for NbTi magnets, which is and will become an increasingly important issue with the small gaps in the newest machines as round beam storage rings and FELs. Moreover, SCU technology allows switching of the period length by changing the current direction in one of separately powered subset of winding packages of the superconducting coils. This feature further broadens the energy range of the emitted photons, required by the different beamlines. To this end a 0.41 m long superconducting undulator coil with switchable period length between 17 mm and 34 mm has been developed. In this contribution we describe the design and report on the quench tests, as well as on the magnetic field measurementsThe first section in your paper.
Incorporation of a MESA linac module into bERLinPro
Authors: Kuske B , Anders W , Jankowiak A , Neumann A , Aulenbacher K , Hug F , Stengler T , Stoll C P
Published: December 2019

bERLinPro is an Energy Recovery Linac (ERL) project, currently being set up at the Helmholtz-Zentrum Berlin fur Materialien und Energie, Berlin, Germany. bERLinPro is designed as - and for - experiments in accelerator physics and as a test bed for novel ERL components. MESA is an ERL project under construction at the Johannes Gutenberg- Universitt, Mainz, Germany. MESA is designed as a user facility to perform experiments in dark matter physics and precision measurements of natural constants. Despite the diverse goals, the main linac, providing the larger part of the particles energy, is fairly compatible. It is planned to test and run the MESA linac module in bERLinPro, prior to its usage in MESA. The goals and benefits of this unique cooperation for both projects are outlined in this paper. The necessary adaptions in bERLinPro, including hardware aspects, the new optics, and the scope of performance are described.
Mode-locked pulse oscillation of a self-resonating enhancement optical cavity
Authors: Hosaka Y , Honda Y , Omori T , Urakawa J , Kosuge A , Sakaue K , Takahashi T , Uesugi Y , Washio M
Published: December 2019

A power enhancement optical cavity is a compelling means of realizing a pulsed laser with a high peak power and high repetition frequency, which is not feasible using a simple amplifier scheme. However, a precise feedback system is necessary for maintaining the narrow resonance condition of the optical cavity; this has become a major technical issue in developing such cavities. We have developed a new approach that does not require any active feedback system, by placing the cavity in the outer loop of a laser amplifier. We report on the first demonstration of a mode-locked pulse oscillation using the new system.
Error study and correction of Hefei Advanced Light Source
Authors: Xu Derong , Bai Zhenghe , Li Wei
Published: December 2019

Hefei Advanced Light Source (HALS) is a future diffraction limited storage ring. The machine performance under all kinds of magnet errors is a vital component in physical design. In this paper, we present our work on the closed orbit correction, the linear beam optics compensation and the coupling control in HALS. After correction, the dynamical aperture can suffice the injection scheme.
Comparison of optimization methods for hybrid seven-bend-achromat lattice design
Authors: Yang P H , Bai Z H , Xu J H , Tan J J , Wang L
Published: December 2019

Generally, for a hybrid multi-bend-achromat (MBA) lattice with fixed linear optics, there is little potential to further optimize the nonlinear dynamics due to limited free knobs. To obtain a hybrid MBA lattice with better nonlinear dynamics performance, it is better to consider some indicators of nonlinear dynamics as objective functions in designing the linear optics using an optimization algorithm. In this paper, integral strengths of sextupoles and natural chromaticities are used as the nonlinear dynamics indicators, and different optimization methods with both or either of the two indicators are carried out and compared. As an example, a hybrid 7BA lattice with an energy of 2.4 GeV is designed towards an emittance of less than 70 pm-rad.
Multi-Bend Achromat Lattice Design for the Future of TPS Upgrade
Authors: Chiu M S , Huang J C , Chou P J , Lee S Y
Published: December 2019

We present a TPS upgrade option with the hybrid 7BA (H7BA) lattice. We also derive a simple formula on optimal dipole angle distribution among H7BA dipoles. The agreement is satisfactory. We also report preliminary results on the dynamic aperture (DA) optimization. Possible improvement on H7BA lattice is outlined.
Optimization and Measurements on the Double Mini-Betay Lattice in the TPS Storage Ring
Authors: Chiu M S , Chen C H , Liu Y C , Tseng F H , Kuo C C , Tsai H J , Chen J Y , Hu K H , Chiu P C , Liao C Y , Cheng Y S , Lee T Y , Lin W Y , Chen B Y , Hsu T W , Huang B Y , Huang J C , Chou P J
Published: December 2019

The Taiwan Photon Source (TPS) is capable of operating in multi-bunch and single-bunch mode. To operate in a hybrid mode as requested by users, we developed a lattice with chromaticities of 0.8/2 (ξx/ξy) to provide higher single bunch currents. Beam dynamics simulations and lattice characterizations including dynamic aperture, frequency map analysis, tune shift with energy, tune shift with amplitude, and betatron coupling will be discussed in this report.
Undulator Radiation Dose Caused by Synchrotron Radiation at the European XFEL
Authors: Liu S , Li Y , Wolff-Fabris F
Published: December 2019

Radiation damage of the undulators is a big concern for the light sources. At the European XFEL (EuXFEL), dosimeters based on on-line Radfets are used for the undulator radiation dose measurements. However, since the Radfets are not only sensitive to the electrons and neutrons but also to the photons, it can capture the synchrotron radiation (SR) generated in the undulators, which is not considered to be the main source for undulator radiation damage. Therefore, it is important to estimate the contribution of synchrotron radiation to the radiation doses measured by the Radfets. For this purpose, we have first calculated the synchrotron radiation profile using SPECTRA, and then put the profile into the tracking code BDSIM to track it through the whole undulator beam line. The radiation doses from SR have been simulated and compared with the measured values. The differences in the radiation doses measured by the Radfets before and after Pb shielding will also be presented.
Simulation of Short-Pulse Generation from A Dynamically Detuned IR-FEL Oscillator and Pulse Stacking at An External Cavity
Authors: Sumitomo Yoske , Hajima Ryoichi , Hayakawa Yasushi , Sakai Takeshi
Published: December 2019

At the LEBRA facility of Nihon U., we have an IR-FEL oscillator to generate radiations in the range of wavelengths 1 – 6 um for various experiments. A research program has been established to explore the application of the IR-FEL to generate attosecond UV and X-ray pulses through the high harmonic generation (HHG), where the IR-FEL pulses must have a high-peak power and a short-pulse duration. For the suitable FEL pulse generation within a limited macro-pulse length at the LEBRA LINAC, we apply a dynamical modulation to the electron bunch repetition, that is equivalent to a dynamical detuning of the FEL cavity length. We illustrate the potential performance of the IR-FEL with the dynamical detuning by time-dependent 3D FEL simulations. We also evaluate the enhancement of the FEL pulses by an external cavity stacking for the sake of the HHG application.
Stimulated Excitation by Seeding with Cherenkov Radiation in an Optical Cavity
Authors: Jiang S. , Li W. , He Z. , Wang L. , Jia Q. , He D.
Published: December 2019

By seeding with narrow-band Cherenkov radiation from a dielectric loaded waveguide(DLW), stimulated excitation in an optical cavity is presented. The evolution and energy loss of the field oscillating in the optical cavity is analyzed by theoretical and numerical calculation. The results show that the high order TM modes of the Cherenkov radiation can be better preserved after a large number of roundtrips in the optical cavity and this scheme offers a potential method of realizing high power Terahertz radiation source in a compact facility.
Realizing low-emittance lattice solutions with Complex Bends
Authors: Smaluk Victor , Shaftan Timur
Published: December 2019

A concept of new lattice element called “Complex Bend” is recently proposed at NSLS-II. Replacing the regular dipoles in the Double-Bend Achromat lattice by Complex Bends significantly reduces the beam emittance. The first attempt of lattice design for potential NSLS- II upgrade based on Complex Bend, is described. Compared with the current NSLS-II lattice, the new solution modifies only three of the six girders per cell. The linear optics has been matched keeping unchanged the lattice parameters at the straight sections, where the light-generating insertion devices are located. The Complex Bend gradient is limited by 250 T/m assuming possible use of permanent magnets. The lattice provides 65 pm emittance without damping wigglers, use of which results in further decrease of the emittance.
Negative Electron affinity GaAs Cathode Activation with CsKTe Thin Film
Authors: Kuriki Masao , Masaki Kazunari
Published: December 2019

Negative Electron Affinity (NEA) GaAs cathode is an unique device which can generate a highly polarized electron beam with circularly polarized light. The NEA surface is conventionally made by Cs and O/NF3 adsorption on the cleaned p-doped GaAs crystal, but the robustness of the cathode is very limited, so that the electron emission is easily lost by residual gas adsorption, ion back-bombardment, etc. To improve the cathode robustness, NEA activation with a stable thin-film on GaAs surface according to Hetero junction hypothesis has been proposed by the author. An experiment of the NEA activation with CsKTe thin film was carried out at Hiroshima University and a significant electron emission with 1.43 eV photon was observed which strongly suggested NEA activation. The cathode showed 16 to 20 times improvement of lifetime comparing to GaAs activated with Cs and O.
Microwave thermionic electron gun for synchrotron light sources
Authors: Kutsaev S V , Agustsson R , Berry R , Borland M , Chao D , Chimalpopoca O , Nassiri A , Smirnov A Yu , Sun Y , Taletski K , Verma A , Waldschmidt G , Zholents A
Published: December 2019

Thermionic RF guns are the source of electrons used in many practical applications, such as drivers for synchrotron light sources, preferred for their compactness and efficiency. RadiaBeam Systems has developed a new thermionic RF gun for the Advanced Photon Source at Argonne National Laboratory, which would offer substantial improvements in reliable operations with robust interface between the thermionic cathode and the cavity, as well as better RF performance, compared to existing models. This improvement became possible by incorporating new pi-mode electromagnetic design, robust cavity back plate design, and a cooling system that will allow stable operation for up to 1 A of beam current and 100 Hz rep rate at 3.0 μs RF pulse length, and 70 MV/m peak on axis field in the cavity. In this paper we discuss the electromagnetic and engineering design of the cavity and provide the test results of the new gun.
The design and preliminary test of a stripline kicker for HALS
Authors: Liu W , Shang L , Shang F L , Song W B , Sun Z B
Published: December 2019

Stripline kicker is an important component of both on-axis longitudinal accumulation [1] and on-axis swap out injection schemes in HALS (Hefei Advanced Light Source). After more than one year of R&D, construction of the first prototype is completed. The kicker performance is simulated. The results show that in the range of 0 ~ 1 GHz, on differential mode, S11 is less than - 20 dB. In order to facilitate installation, the extension part and PTEF bracket were designed. The assembly of kicker and commercial feedthrough has been tested with pulse generator and network analyzer.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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).