Author Affiliations
1 State Key Laboratory of Nuclear Physics and Technology, and Key Laboratory of HEDP of the Ministry of Education, CAPT, Peking University, Beijing, China
2 Beijing Laser Acceleration Innovation Center, Beijing, China
3 Institute of Guangdong Laser Plasma Technology, Guangzhou, China
Post-acceleration of protons in helical coil targets driven by intense, ultrashort laser pulses can enhance ion energy by utilizing the transient current from the targets’ self-discharge. The acceleration length of protons can exceed a few millimeters, and the acceleration gradient is of the order of GeV/m. How to ensure the synchronization between the accelerating electric field and the protons is a crucial problem for efficient post-acceleration. In this paper, we study how the electric field mismatch induced by current dispersion affects the synchronous acceleration of protons. We propose a scheme using a two-stage helical coil to control the current dispersion. With optimized parameters, the energy gain of protons is increased by four times. Proton energy is expected to reach 45 MeV using a hundreds-of-terawatts laser, or more than 100 MeV using a petawatt laser, by controlling the current dispersion.
current dispersion helical targets laser-driven ions synchronous post-acceleration 
High Power Laser Science and Engineering
2023, 11(4): 04000e51
Author Affiliations
1 State Key Laboratory of Nuclear Physics and Technology, and Key Laboratory of HEDP of the Ministry of Education, CAPT, School of Physics, Peking University, Beijing 100871, China
2 Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
3 Key Laboratory of Nuclear Physics and Ion-Beam Application (MOE), Institute of Modern Physics, Fudan University, Shanghai 200433, China
4 School of Nuclear Science and Technology, University of South China, Hengyang 421001, China
5 INPAC and School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
6 Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
7 Institute of Experimental and Applied Physics, Czech Technical University in Prague, Husova 240/5, 11000 Prague 1, Czech Republic
8 ELI Beamlines Center, Institute of Physics of the Czech Academy of Sciences, 252 41 Dolní Břežany, Czechia
9 Cyclotron Institute, Texas A&M University, College Station, Texas 77843, USA
In this work, the high-energy-density plasmas (HEDP) evolved from joule-class-femtosecond-laser-irradiated nanowire-array (NWA) targets were numerically and experimentally studied. The results of particle-in-cell simulations indicate that ions accelerated in the sheath field around the surfaces of the nanowires are eventually confined in a plasma, contributing most to the high energy densities. The protons emitted from the front surfaces of the NWA targets provide rich information about the interactions that occur. We give the electron and ion energy densities for broad target parameter ranges. The ion energy densities from NWA targets were found to be an order of magnitude higher than those from planar targets, and the volume of the HEDP was several-fold greater. At optimal target parameters, 8% of the laser energy can be converted to confined protons, and this results in ion energy densities at the GJ/cm3 level. In the experiments, the measured energy of the emitted protons reached 4 MeV, and the changes in energy with the NWA’s parameters were found to fit the simulation results well. Experimental measurements of neutrons from 2H(d,n)3He fusion with a yield of (24 ± 18) × 106/J from deuterated polyethylene NWA targets also confirmed these results.
Matter and Radiation at Extremes
2022, 7(6): 064403
Author Affiliations
1 State Key Laboratory of Nuclear Physics and Technology, and Key Laboratory of HEDP of the Ministry of Education CAPT Peking University Beijing 100871 China
2 Hebei Key Laboratory of Compact Fusion Langfang 065001 China
3 ENN Science and Technology Development Co., Ltd. Langfang 065001 China
4 Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800 China
5 School of Nuclear Science and Technology University of South China Hengyang 421001 China
6 Beijing Laser Acceleration Innovation Center Huairou Beijing 101400 China
7 Institute of Guangdong Laser Plasma Technology Baiyun Guangzhou 510540 China
Here, we report the generation of MeV alpha-particles from H-11B fusion initiated by laser-accelerated boron ions. Boron ions with maximum energy of 6 MeV and fluence of 109/MeV/sr@5 MeV were generated from 60 nm-thick self-supporting boron nanofoils irradiated by 1 J femtosecond pulses at an intensity of 1019 W/cm2. By bombarding secondary hydrogenous targets with the boron ions, 3 × 105/sr alpha-particles from H-11B fusion were registered, which is consistent with the theoretical yield calculated from the measured boron energy spectra. Our results demonstrated an alternative way toward ultrashort MeV alpha-particle sources employing compact femtosecond lasers. The ion acceleration and product measurement scheme are referential for the studies on the ion stopping power and cross section of the H-11B reaction in solid or plasma.
Laser and Particle Beams
2022, 2022(3): 5733475
1 北京大学核物理与核技术国家重点实验室, 北京 100871
2 西北核技术研究所激光与物质相互作用国家重点实验室, 陕西 西安 710024
3 北京激光加速创新中心, 北京 101407
4 北京大学应用物理与技术研究中心, 北京 100871

飞秒激光作用于等离子体可以产生短脉宽、高亮度的极紫外(EUV)辐射,在高分辨率成像、时间分辨谱学等方面都有潜在的应用。为进一步提高辐射亮度,利用相对论飞秒激光与碳纳米管泡沫(CNF)靶相互作用实现了高转换效率的EUV辐射。实验结果表明,当激光能量为1.2 J,CNF密度为4 mg/cm 3时,单发产生的EUV辐射光谱强度在0.1 mJ·nm -1·sr -1量级。相比高密度固体靶,采用低密度CNF靶可以有效地提高激光吸收率,进而实现两个量级的EUV辐射效率增益。同时发现,基于CNF的EUV辐射在15~30 nm波长范围内具有准连续的宽谱特征,适合于超快吸收光谱等应用。

X射线光学 极紫外辐射 飞秒激光 碳纳米管泡沫 宽谱辐射 X-ray optics extreme-ultraviolet radiation femtosecond laser carbon nanotube foams continuum radiation 
2022, 42(11): 1134021
Author Affiliations
1 State Key Laboratory of Nuclear Physics and Technology, Center for Applied Physics and Technology, School of Physics, Peking University, Beijing100871, China
2 Beijing Laser Acceleration Innovation Center, Beijing101400, China
3 Institute of Guangdong Laser Plasma Technology, Guangzhou510540, China
Carbon nanotube foams (CNFs) have been successfully used as near-critical-density targets in the laser-driven acceleration of high-energy ions and electrons. Here we report the recent advances in the fabrication technique of such targets. With the further developed floating catalyst chemical vapor deposition (FCCVD) method, large-area ($>25\kern0.5em {\mathrm{cm}}^2$) and highly uniform CNFs are successfully deposited on nanometer-thin metal or plastic foils as double-layer targets. The density and thickness of the CNF can be controlled in the range of $1{-}13\kern0.5em \mathrm{mg}/{\mathrm{cm}}^3$ and $10{-}200\kern0.5em \mu \mathrm{m}$, respectively, by varying the synthesis parameters. The dependence of the target properties on the synthesis parameters and the details of the target characterization methods are presented for the first time.
carbon nanotube foams laser-driven acceleration near-critical density targets ultraintense laser 
High Power Laser Science and Engineering
2021, 9(2): 02000e29
Author Affiliations
1 State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing100871, China
2 State Key Laborartory of Laser Interaction with Matter, Northwest Institute of Nuclear Technology, Xi’an710024, China
3 Fakultät für Physik, Ludwig-Maximilians-University, D-85748Garching, Germany
Single-shot laser-induced damage threshold (LIDT) measurements of multi-type free-standing ultrathin foils were performed in a vacuum environment for 800 nm laser pulses with durations τ ranging from 50 fs to 200 ps. The results show that the laser damage threshold fluences (DTFs) of the ultrathin foils are significantly lower than those of corresponding bulk materials. Wide band gap dielectric targets such as SiN and formvar have larger DTFs than semiconductive and conductive targets by 1–3 orders of magnitude depending on the pulse duration. The damage mechanisms for different types of targets are studied. Based on the measurement, the constrain of the LIDTs on the laser contrast is discussed.
laser-induced damage threshold ultrathin targets laser-driven ion acceleration 
High Power Laser Science and Engineering
2020, 8(4): 04000e41

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