Author Affiliations
Abstract
1 Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang, China
2 Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education, Beijing, China
All-fiber coherent beam combiners based on the self-imaging effect can achieve a near-perfect single laser beam, which can provide a promising way to overcome the power limitation of a single-fiber laser. One of the key points is combining efficiency, which is determined by various mismatches during fabrication. A theoretical model has been built, and the mismatch error is analyzed numerically for the first time. The mismatch errors have been numerically studied with the beam quality and combining efficiency being chosen as the evaluation criteria. The tolerance of each mismatch error for causing 1% loss is calculated to guide the design of the beam combiners. The simulation results are consistent with the experimental results, which show that the mismatch error of the square-core fiber is the main cause of the efficiency loss. The results can provide useful guidance for the fabrication of all-fiber coherent beam combiners.
all-fiber coherent beam combination mismatch analysis self-imaging High Power Laser Science and Engineering
2024, 12(2): 02000e13
强激光与粒子束
2023, 35(4): 041005
强激光与粒子束
2022, 34(10): 104010
Author Affiliations
Abstract
1 Key Laboratory of Particle & Radiation Imaging (Tsinghua University) Ministry of Education Beijing 100084 China
2 Science and Technology on High Power Microwave Laboratory Northwest Institute of Nuclear Technology Xi’an Shaanxi 710024 China
3 Department of Engineering Physics Tsinghua University Beijing 100084 China
Radio frequency (RF) breakdown can result in pulse shortening and seriously degrade the stability and reliability of relativistic backward wave oscillators (RBWOs). This paper discusses the energy range of electrons causing breakdown traces in slow-wave structures (SWSs) through particle-in-cell (PIC) simulation, numerical calculation, and experimental verification. The PIC simulation and numerical calculation results reveal that the energy of the majority of the field-induced electrons bombarding the SWS surfaces after being accelerated is less than 120 keV. Furthermore, the micro appearances of the breakdown traces in SWSs and the witness targets bombarded directly by electrons of various energy levels have been analyzed. Scanning electron microscope (SEM) shows that the breakdown traces are featured with corrugated morphologies with a wide range and a shallow depth. A mass of craters emerge in the vicinity of the corrugated morphologies. These appearances are quite similar to destructive traces impacted directly by low-energy electrons (around 160 keV). Thus, it is confirmed that the breakdown traces result from the bombardment of low-energy electrons. Therefore, the breakdown mechanism of field-emitted electrons impacting on the structure surfaces in RBWOs has been further improved.
Laser and Particle Beams
2022, 2022(1): 8327755
Author Affiliations
Abstract
1 Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900, China
2 Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education, Beijing 100084, China
The self-imaging effect in a square core fiber has been investigated, and an integrated all-fiber combiner has been proposed based on a large mode area double clad fiber, which can be employed to construct high power coherent beam combining sources in the all-fiber format. The influence of various parameters on beam quality () and efficiency of the all-fiber coherent beam combiner has been studied numerically, which reveals that the near diffraction-limited laser beam can be achieved. A principle demonstration of the self-imaging effect has been carried out experimentally in a square core fiber, which proves the feasibility of beam combining with the square fiber, and that it is a promising way to develop high power coherent beam combination sources.
Photonics Research
2022, 10(2): 02000444
1 中国科学院上海高等研究院, 上海 201204
2 中国科学院上海应用物理研究所, 上海 201800
3 清华大学工程物理系, 北京 100084
X射线自由电子激光试验装置(以下简称“SXFEL试验装置”)是中国第一台X射线相干光源,其输出波长小于9 nm。这台基于0.84 GeV 直线加速器、以掌握装置相关技术和实验演示种子型自由电子激光(FEL)级联与短波长回声型FEL为主要目标的自由电子激光装置,于2020年11月通过国家验收。本文将介绍SXFEL试验装置的基本情况和主要进展。
激光光学 X射线 自由电子激光 直线加速器
Author Affiliations
Abstract
1 Department of Engineering Physics, Tsinghua University, Beijing 100084, China
2 Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China
3 Xi’an Jiaotong University, Xi’an 710049, China
4 Institute of Applied Electronics, CAEP, Mianyang 621900, China
High-energy electron radiography (HEER) is a promising diagnostic tool for high-energy-density physics, as an alternative to tools such as X/γ-ray shadowgraphy and high-energy proton radiography. Impressive progress has been made in the development and application of HEER in the past few years, and its potential for high-resolution imaging of static opaque objects has been proved. In this study, by taking advantage of the short pulse duration and tunable time structure of high-energy electron probes, time-resolved imaging measurements of high-energy-density gold irradiated by ultrashort intense laser pulses are performed. Phenomena at different time scales from picoseconds to microseconds are observed, thus proving the feasibility of this technique for imaging of static and dynamic objects.
Matter and Radiation at Extremes
2019, 4(6): 065402
1 中国科学院上海应用物理研究所, 上海 201800
2 清华大学工程物理系, 北京 100084
3 上海科技大学物质科学与技术学院, 上海 201210
上海软X射线自由电子激光装置(SXFEL)是中国第一台X射线相干光源, 其最短波长可达到2 nm。这台基于1.5 GeV C波段高梯度电子直线加速器的激光装置包含1条种子型自由电子激光(FEL)束线、1条自放大自发辐射束线以及5个实验站。整个装置的研制分试验装置(SXFEL-TF)和用户装置(SXFEL-UF)两个阶段进行, 基于0.84 GeV直线加速器的SXFEL-TF以掌握种子型FEL级联技术和短波长回声型FEL为主要目标, 而SXFEL-UF的目标则是建成可提供5个实验站的用户装置并于2019年底开始首批实验。介绍了SXFEL的基本构成和目前装置研制的进展。
激光技术 自由电子激光 软X射线 相干光源
张琪 1,2,3郑曙昕 1,2,3李光锐 1,2,3姚红娟 1,2,3[ ... ]王学武 1,2,3
1 教育部粒子技术与辐射成像国家重点实验室(清华大学), 北京 100084
2 清华大学 先进辐射源及应用实验室, 北京 100084
3 清华大学 工程物理系, 北京 100084
从理论和模拟两方面研究了西安质子应用装置二极铁、四极铁电源电流纹波对引出束流的影响，并根据模拟结果确定出以下单种磁铁电源电流纹波标准：对于聚焦四极铁电源，电流纹波/设定值应小于1.2×10-4；对于散焦四极铁电源，电流纹波/设定值应小于2×10-3；对于二极铁电源，电流纹波/设定值应小于4×10-4。因西安质子应用装置同步环上所有磁铁电源采用同一纹波标准，综合考虑所有磁铁电源电流纹波后，最终确定电源电流纹波/设定值应小于1×10-4。
电流纹波 慢引出 RF-KO RF-KO power supply ripple slow extraction 强激光与粒子束
2018, 30(8): 085101
Author Affiliations
Abstract
1 Accelerator Technology and Applied Physics Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
2 Department of Engineering Physics, Tsinghua University, Beijing 100084, China
3 Key Laboratory of Particle and Radiation Imaging, Ministry of Education, Tsinghua University, Beijing 100084, China
Coherent pulse stacking (CPS) is a new time-domain coherent addition technique that stacks several optical pulses into a single output pulse, enabling high pulse energy and high average power. A Z-domain model targeting the pulsed laser is assembled to describe the optical interference process. An algorithm, extracting the cavity phase and pulse phases from limited data, where only the pulse intensity is available, is developed to diagnose optical cavity resonators. We also implement the algorithm on the cascaded system of multiple optical cavities, achieving phase errors less than 1.0° (root mean square), which could ensure the stability of CPS.
070.2025 Discrete optical signal processing 120.5050 Phase measurement 140.4780 Optical resonators Chinese Optics Letters
2018, 16(4): 040701
