Design study on the merger for BXERL-FEL

In North China, there is a preliminary proposal for ERL-FEL light source （BXERL-FEL） with its aim at ＂one machine, two purposes＂ （the XFEL and ERL work simultaneously）. One of the key technologies is the merger section. In this paper, we give the physical design of the merger section for BXERL-FEL which merges three kinds of electron beam.     

Towards one machine, two purposes: using a common SC linac for XFEL and ERL simultaneously

The linac based XFEL and ERL are advanced (or, say, 4th generation) light sources, with different electron beam parameters and different advantages. However, the linac used for XFEL and ERL should provide very advanced beams with high energy, high peak and/or average current, very low emittance and low energy spread, thus making the linac very complicated and expensive. To share the XFEL and ERL advantages and save the construction-operation budget, a proposal of using a common superconducting electron linac for hard X-ray XFEL and ERL is described in this paper. The interactions between the XFEL and ERL beams via the accelerating structure are studied and the result is positive.     

Towards one machine, two purposes: using a common SC linac for XFEL and ERL simultaneously

The linac based XFEL and ERL are advanced （or, say, 4th generation） light sources, with different electron beam parameters and different advantages. However, the linac used for XFEL and ERL should provide very advanced beams with high energy, high peak and/or average current, very low emittance and low energy spread, thus making the linac very complicated and expensive. To share the XFEL and ERL advantages and save the construction-operation budget, a proposal of using a common superconducting electron linac for hard X-ray XFEL and ERL is described in this paper. The interactions between the XFEL and ERL beams via the accelerating structure are studied and the result is positive.     

Design study of a L-band DC photocathode gun

In this paper, we the design study of a L-band DC photocathode gun injector for the ERL (Energy Recovery Linac) test facility. The main parameters of the injector are energy of 2.3 MeV, a bunch length of 2 ps, and a normalized emittance of 2.1 mm.mrad.     

Design study of a L-band DC photocathode gun

In this paper, we the design study of a L-band DC photocathode gun injector for the ERL （Energy Recovery Linac） test facility. The main parameters of the injector are energy of 2.3 MeV, a bunch length of 2 ps, and a normalized emittance of 2.1 mm.mrad.     

Design study of a L-band photocathode RF injector

In the proposal of the Beijing Advanced Light Source, a compact combination of XERL and XFEL using a common SC linac is being considered. In the meantime, an ERL-FEL test facility is being proposed and will be used for THz radiation. In this test facility, a L-band photocathode RF injector is needed. In this paper, we give the physical design of the L-band photocathode RF injector for the test facility.     

Design study of a L-band photocathode RF injector

In the proposal of the Beijing Advanced Light Source, a compact combination of XERL and XFEL using a common SC linac is being considered. In the meantime, an ERL-FEL test facility is being proposed and will be used for THz radiation. In this test facility, a L-band photocathode RF injector is needed. In this paper, we give the physical design of the L-band photocathode RF injector for the test facility.     

Design studies on a 500 kV DC gun photo-injector for the BXERL test facility

BXERL is a proposal for a test facility(Beijing X-ray Energy Recovery Linac),which requires its injector to provide an electron beam of 5 MeV,77 pC/ bunch at a repetition rate of 130 MHz(average current of 10 mA).In this paper,we present the design of the injector,which consists of a 500 kV photocathodeDC gun equipped with a GaAs cathode preparation device,a 1.3 GHz normal conducting RF buncher,two solenoids,and one cryomodule containing two 1.3 GHz 2-cell superconducting RF cavities as the energy booster.The detailed beam dynamics show that the injector can generate electron bunches with a RMS normalized emittance of 1.49 7rmm-mrad,a bunch length of 0.67 mm,a beam energy of 5 MeV and an energy spread of 0.72%.     

Design studies on a 500 kV DC gun photo-injector for the BXERL test facility

BXERL is a proposal for a test facility (Beijing X-ray Energy Recovery Linac), which requires its injector to provide an electron beam of 5 MeV, 77 pC/ bunch at a repetition rate of 130 MHz (average current of 10 mA). In this paper, we present the design of the injector, which consists of a 500 kV photocathode DC gun equipped with a GaAs cathode preparation device, a 1.3 GHz normal conducting RF buncher, two solenoids, and one cryomodule containing two 1.3 GHz 2-cell superconducting RF cavities as the energy booster. The detailed beam dynamics show that the injector can generate electron bunches with a RMS normalized emittance of 1.49 πmm·mrad, a bunch length of 0.67 mm, a beam energy of 5 MeV and an energy spread of 0.72%.     

Beam dynamics studies of the photo-injector in low-charge operation mode for the ERL test facility at IHEP

The energy recovery linac test facility(ERL-TF), which is a compact ERL-FEL(free electron laser)two-purpose machine, was proposed at the Institute of High Energy Physics, Beijing. As one important component of the ERL-TF, the photo-injector that started with a photocathode direct-current gun has been designed. In this paper, optimization of the injector beam dynamics in low-charge operation mode is performed with iterative scans using Impact-T. In addition, the dependencies between the optimized beam quality and the initial offset at cathode and element parameters are investigated. The tolerance of alignment and rotation errors is also analyzed.     

Beam dynamics studies of the photo-injector in low-charge operation mode for the ERL test facility at IHEP

The energy recovery linac test facility （ERL-TF）, which is a compact ERL-FEL （free electron laser） two-purpose machine, was proposed at the Institute of High Energy Physics, Beijing. As one important component of the ERL-TF, the photo-injector that started with a photocathode direct-current gun has been designed. In this paper, optimization of the injector beam dynamics in low-charge operation mode is performed with iterative scans using Impact-T. In addition, the dependencies between the optimized beam quality and the initial offset at cathode and element parameters are, investigated. The tolerance of alignment and rotation errors is also analyzed.     

CTF磁压缩器的误差研究

磁压缩器广泛应用在自由电子激光装置中. 电子束团的归一化发射度增长由二极磁铁的高阶分量误差及准直误差引起. 本文描述了CTF (CXFEL Test Facility)的第一个磁压缩器的误差研究.     

Design studies on the ERL-FEL test facility at IHEP, Beijing

A proposed compact ERL test facility at IHEP, Beijing, is presented in this paper, and includes the design parameters, the essential lattice, and the key components features, such as the photocathode DC gun and the CW superconducting accelerating structures. Some important beam physics issues such as the space charge effect, the coherent synchrotron radiation (CSR) effect and the beam break-up (BBU) effect are briefly described with the simulation results.     

射频超导技术与ERL技术新进展

射频超导谐振腔可以工作在连续波或长宏脉冲模式. 射频超导技术已发展为加速各种带电粒子束的重要手段. 射频超导技术发展的前期受材料性能、腔的处理以及加工安装水平等的限制. 经过几十年的不断改进, 射频超导技术获得了重大突破. 射频超导腔应用到超导加速器上并成功运行, 积累了腔的质量控制工艺和工业化制备的大量经验. 近期国际上面对未来大科学装置项目, 在射频超导技术方面进行了大量的研发工作, 主要包括提高超导腔加速梯度的新腔型研究和采用新型材料(大晶粒铌材)超导腔的研究. 能量回收直线加速器(ERL)技术是近年来获得发展的重要加速器技术. ERL具有高效、节能、稳定性好、低辐射水平等优势, 被越来越多地应用到先进光源和自由电子激光装置中.     

An intense terahertz radiation source at the Compact ERL

The Compact ERL is an energy recovery LINAC (ERL) test facility that is planned for KEK. The circumference of the recirculation path will be 70 m. Initially, the beam energy will be about 65 MeV and the current about 10 mA. Although the primary purpose of the machine is to aid the development of the key technologies that are essential for building an ultra-brilliant new synchrotron light source based on an ERL, the Compact ERL itself has great potential as an intense source of terahertz radiation. To generate the intense terahertz radiation, an electron bunch of a very short bunch length is required and bunch compression is inevitable. We discuss the parameters of the Compact ERL, present the results of a simulation of bunch compression, and make an estimate of the generated coherent synchrotron radiation.     

Evolutionary genetic optimization of the injector beam dynamics for the ERL test facility at IHEP

The energy recovery linac test facility （ERL-TF）, a compact ERL-FEL （free electron laser） two-purpose machine, has been proposed at the Institute of High Energy Physics, Beijing. As one important component of the ERL-TF, the photo-injector was designed and preliminarily optimized. In this paper an evolutionary genetic method, non-dominated sorting genetic algorithm II, is applied to optimize the injector beam dynamics, especially in the high-charge operation mode. Study shows that using an incident laser with rms transverse size of 1-1.2 ram, the normalized emittance of the electron beam can be kept below 1 mm.mrad at the end of the injector. This work, together with the previous optimization of the low-charge operation mode by using the iterative scan method, provides guidance and confidence for future construction and commissioning of the ERL-TF injector.     

北京大学ERL装置交汇段的研究与设计

 在交汇段设计理论的基础上,针对北京大学ERL的具体情况,对交汇段的束流传输结构进行了优化设计,通过模拟得到了满足要求的一组设计参数;研究了空间电荷效应以及相干同步辐射对束流发射度、能散及包络的影响。结果表明：空间电荷效应对发射度影响不大,但对束流包络影响较明显;相干同步辐射引起的发射度增长及能散较小,且不影响束流包络。     

Multifarious injection chamber for molecular structure study (MICOSS) system: development and application for serial femtosecond crystallography at Pohang Accelerator Laboratory X‐ray Free‐Electron Laser

The multifarious injection chamber for molecular structure study (MICOSS) experimental system has been developed at the Pohang Accelerator Laboratory X‐ray Free‐Electron Laser for conducting serial femtosecond crystallography. This system comprises several instruments such as a dedicated sample chamber, sample injectors, sample environment diagnostic system and detector stage for convenient distance manipulation. Serial femtosecond crystallography experiments of lysozyme crystals have been conducted successfully. The diffraction peaks have reached to ～1.8 Å resolution at the photon energy of 9.785 keV.     

BXERL photo-injector based on a 217 MHz normal conducting RF gun

The Beijing X-ray Energy Recovery Linac (BXERL) test facility is proposed in Institute of High Physics (IHEP). In this proposal, the main linac requires the injector to provide an electron beam with 5 MeV energy and 10 mA average current. An injector based on DC gun technology is the first candidate electron source for BXERL. However, the field emission in the DC gun cavity makes it much more difficult to increase the high voltage to more than 500 kV. Another technology based on a 217 MHz normal conducting RF gun is proposed as the backup injector for this test facility. We have designed this RF gun with 2D SUPERFISH code and 3D MICROWAVE STUDIO code. In this paper, we present the optimized design of the gun cavity, the gun RF parameters and the set-up of the whole injector system. The detailed beam dynamics have been done and the simulation results show that the injector can generate electron bunches with RMS normalized emittance 1.0 uppi mmcdotmrad, bunch length 0.77 mm, beam energy 5.0 MeV and energy spread 0.60%.     

LAMOST's view on the Gaia-Sausage-Enceladus merger event

正A combination of massive spectroscopic surveys and Gaia DR2 has brought light into the chemical and kinematical properties of a large number of stars,thus building up a mature picture of the Gaia-Sausage-Enceladus (GSE) galaxy and unraveling its impact on the reconstruction of the history of our Galaxy.Based on the largest spectroscopic data set established in the LAMOST survey [1,2],Profs.Gang Zhao and Yuqin Chen (National Astronomical Observatories,Chinese Academy of Sciences)[3] recently explored the chemical and orbital properties of metal-rich Sausage-kinematic(MRSK) stars,