共查询到20条相似文献，搜索用时 15 毫秒
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Wangwen XU 《等离子体科学和技术》2022,24(5):55001
The study of the interaction between ion beam and plasma is very important to the areas of inertial fusion energy and high energy density physics. With detailed one-dimensional electromagnetic particle-in-cell simulations, we investigate here the interaction of a laser-accelerated proton beam assuming an ideal monoenergetic beam with a gas-discharge plasma. After the saturation stage of the two-stream instability excited by the proton beam, significant high energy electrons are observed, with maximum energy approaching 2 MeV, and a new two-stream instability occurs between the high energy electrons and background electrons. The trajectories of plasma electrons are studied, showing the process of electron trapping and de-trapping from the wakefield. 相似文献
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ZHANG Ya 《等离子体科学和技术》2016,18(7):720-726
A one dimensional quantum-hydrodynamic/particle-in-cell(QHD/PIC) model is used to study the interaction process of an intense proton beam(injection density of 1017cm~(-3))with a dense plasma(initial density of ~ 1021cm~(-3)), with the PIC method for simulating the beam particle dynamics and the QHD model for considering the quantum effects including the quantum statistical and quantum diffraction effects. By means of the QHD theory, the wake electron density and wakefields are calculated, while the proton beam density is calculated by the PIC method and compared to hydrodynamic results to justify that the PIC method is a more suitable way to simulate the beam particle dynamics. The calculation results show that the incident continuous proton beam when propagating in the plasma generates electron perturbations as well as wakefields oscillations with negative valleys and positive peaks where the proton beams are repelled by the positive wakefields and accelerated by the negative wakefields. Moreover, the quantum correction obviously hinders the electron perturbations as well as the wakefields. Therefore, it is necessary to consider the quantum effects in the interaction of a proton beam with cold dense plasmas, such as in the metal films. 相似文献
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We put forward a new design of a compact beam transport system for intense laser-driven proton therapy, where instead of using conventional pulsed solenoids, our design relies on a helical coil irradiated by a nanosecond laser pulse to generate strong magnetic fields for focusing protons. A pair of dipole magnets and apertures are employed to further filter protons with large divergences and low energies. Our numerical studies combine particle-in-cell simulations for laser-plasma interaction to generate high-energy monoenergetic proton beams, finite element analysis for evaluating the magnetic field distribution inside the coil, and Monte-Carlo simulations for beam transport and energy deposition. Our results show that with this design, a spread-out Bragg peak in a range of several centimeters to a deep-seated tumor with a dose of approximately 16.5 cGy and fluctuation around 2% can be achieved. The instantaneous dose rate reaches up to 109 Gy/s, holding the potential for future FLASH radiotherapy research. 相似文献
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We conducted 2-D particle-in-cell simulations to investigate the impact of boundary conditions on the evolution of magnetic reconnection. The results demonstrate that the boundary conditions are crucial to this evolution. Specifically, in the cases of traditional periodic boundary (PB) and fully-opened boundary (OB) conditions, the evolutions are quite similar before the system achieves the fastest reconnection rate. However, differences emerge between the two cases afterward. In the PB case, the reconnection electric field experiences a rapid decline and even becomes negative, indicating a reversal of the reconnection process. In contrast, the system maintains a fast reconnection stage in the OB case. Suprathermal electrons are generated near the separatrix and in the exhaust region of both simulation cases. In the electron density depletion layer and the dipolarization front region, a larger proportion of suprathermal electrons are produced in the OB case. Medium-energy electrons are mainly located in the vicinity of the X-line and downstream of the reconnection site in both cases. However, in the OB case, they can also be generated in the electron holes along the separatrix. Before the reverse reconnection stage, no high-energy electrons are present in the PB case. In contrast, about 20% of the electrons in the thin and elongated electron current layer are high-energy in the OB case. 相似文献
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A special method is proposed of a laser-induced cavity pressure acceleration scheme for collimating, accelerating and guiding protons, using a single-cone target with a beam collimator through a target normal sheath acceleration mechanism. In addition, the problems involved are studied by using two-dimensional particle-in-cell simulations. The results show that the proton beam can be collimated, accelerated and guided effectively through this type of target. Theoretically, a formula is derived for the combined electric field of accelerating protons. Compared with a proton beam without a beam collimator, the proton beam density and cut-off energy of protons in the type II are increased by 3.3 times and 10% respectively. Detailed analysis shows that the enhancement is mainly due to the compact and strong sheath electrostatic field, and that the beam collimator plays a role in focusing energy. In addition, the simulation results show that the divergence angle of the proton beam in type II is less than 1.67 times that of type I. The more prominent point is that the proton number of type II is 2.2 times higher than that of type I. This kind of target has important applications in many fields, such as fast ion ignition in inertial fusion, high energy physics and proton therapy. 相似文献
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为调试100 MeV回旋加速器高功率束流及放射性同位素研制,设计了一条高功率质子束流线及可插拔式高功率束流调试靶。研究了100 MeV回旋加速器引出区色散效应及剥离膜的散射效应,从而优化了光学模拟的初始参数,使得模拟结果更加精确。高功率束流调试靶设计为可插拔式以代替常用固定式调试靶,该靶插入束流管道中时可进行高功率质子束流调试,在拔出时,质子束流可直接轰击束流线终端的靶站以生产放射性同位素。优化了高功率束流调试靶的水冷结构,确保调试靶可承受500μA以上的质子束流。经调试,该束流线可传输最高流强520μA的质子束流。 相似文献
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Huaxiang ZHANG 《等离子体科学和技术》2020,22(10):105102-105102
The property of scrape-off layer (SOL) currents induced by a biased electrode is investigated by fully kinetic collisionless two-dimensional particle-in-cell (PIC) simulations. A reduced Vlasov–Darwin model is employed, which is capable of describing the low-frequency kinetic behavior without electromagnetic vacuum modes A linear decay distribution of electron currents parallel to the background magnetic field is exhibited. Simulation analyses indicate that the cross field ion current is a key factor in sheath formation and global current balance. The influences of electrode area, biasing voltage and plasma source on the SOL current profile are studied, respectively. Characteristic plasma parameters in the far SOL region of the EAST tokamak are used in simulations to assess the current driving ability of the electrode biasing method. Due to the limitations of computational power, the geometrical size of the simulation domain is significantly smaller than the realistic SOL, which may lead to an absence of the quasi-neutral region in the upstream plasma. At last, a heuristic method is proposed to calculate the upper bound of the total current strength. 相似文献
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陈龙;高维富;崔作君;段萍;许雪松;阚子晨;檀聪琦;陈俊宇 《等离子体科学和技术》2024,26(6):064007-1-064007-10
The configuration of electrode voltage and zero magnetic point position has a significant impact on the performance of the double-stage Hall effect thruster. A 2D-3V model is established based on the two-magnetic peak type double-stage Hall thruster configuration, and a particle-in-cell simulation is carried out to investigate the influences of both acceleration electrode voltage value and zero magnetic point position on the thruster discharge characteristics and performances. The results indicate that increasing the acceleration voltage leads to a larger potential drop in the acceleration stage, allowing ions to gain higher energy, while electrons are easily absorbed by the intermediate electrode, resulting in a decrease in the anode current and ionization rate. When the acceleration voltage reaches 500 V, the thrust and efficiency are maximized, resulting in a 15% increase in efficiency. After the acceleration voltage exceeds 500 V, a potential barrier forms within the channel, leading to a decrease in thruster efficiency. Further study shows that as the second zero magnetic point moves towards the outlet of the channel, more electrons easily traverse the zero magnetic field region, participating in the ionization. The increase in the ionization rate leads to a gradual enhancement in both thrust and efficiency. 相似文献
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依据现有的实验室驱动源能力建立杆箍缩二极管（RPD）粒子模拟计算模型,获得了工作电压为1 MV的RPD电参数特性及电子、离子时空分布特性,并设计了RPD实验装置。在1 MV驱动源平台上开展了实验研究,实验中采用B dot、D dot、热释光剂量片和SiPin二极管测试了RPD电流、电压、辐射剂量和光脉冲信号,分析了RPD电参数及X射线辐射特性。结果表明,阳极采用1.5 mm钨时,1 MV电压下1 m处辐射剂量约1 R,并得出剂量与电压Ud、电流Id的关系式D(R=1 m)=120U1.55d∫Iddt;二极管阻抗范围为26.4~36.7 Ω,空间电荷限制阶段平均阻抗下降率大于2 Ω/ns,磁绝缘阶段平均阻抗下降率小于0.5 Ω/ns;光脉冲宽度较电压脉冲宽度约缩短20%~30%,与电压、电流的关系为∝IdU1.55 d。实验测试的剂量和光脉冲信号结果与拟合计算式计算结果符合较好。 相似文献
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静态随机存取存储器质子单粒子效应实验研究 总被引：6，自引：3，他引：6
描述了测量静态随机存取存储器质子单粒子翻转截面的实验方法。采用金箔散射法可以降低加速器质子束流五六个量级,从而满足半导体器件质子单粒子效应的要求。研制的弱流质子束流测量系统和建立的注量均匀性测量方法解决了质子注量的准确测量问题。提高了存储器单粒子效应长线测量系统的性能,保证了翻转数的准确测量。实验测得静态随机存取存储器质子单粒子翻转截面为１０＾－１４ｃｍ＾２／ｂｉｔ量级,随质子能量的增大略有增大。 相似文献
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Two-stage γ ray emission via ultrahigh intensity laser pulse interaction with a laser wakefield accelerated electron beam 
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下载免费PDF全文 In this study, we investigate the generation of twin γ ray beams in the collision of an ultrahigh intensity laser pulse with a laser wakefield accelerated electron beam using a particle-in-cell simulation. We consider the composed target of a homogeneous underdense preplasma in front of an ultrathin solid foil. The electrons in the preplasma are trapped and accelerated by the wakefield. When the laser pulse is reflected by the thin solid foil, the wakefield accelerated electrons continue to move forward and pass through the foil almost without influence from the reflected laser pulse or foil. Consequently, two groups of γ ray flashes, with tunable time delay and energy, are generated by the wakefield accelerated electron beam interacting with the reflected laser pulse from the foil as well as another counter-propagating petawatt laser pulse behind the foil. Additionally, we study the dependence of the γ photon emission on the preplasma densities, driving laser polarization, and solid foil. 相似文献
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It is shown that a steepening of the radial plasma pressure profile leads to a decrease in the critical value of beta, above which, small-scale balloon-type perturbations in a mirror trap become unstable. This may mean that small-scale ballooning instability leads to a smoothing of the radial plasma profile. The critical beta values for the real magnetic field of the gas-dynamic trap and various plasma pressure radial profiles was also calculated. For a plasma with a parabolic profile critical beta is evaluated at the level of 0.72. A previous theoretical prediction for this trap was almost two times lower than maximal beta 0.6 achieved experimentally. 相似文献
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For an MHD stable system, we investigate the interplay between drift wave (ETG and gyro-Bohm) radial transport and axial losses
in the GAMMA-10 experimental facility and the proposed kinetically stabilized tandem mirror (KSTM) fusion reactor. Numerical
coefficients in the models are taken to be consistent with tokamak and stellarator databases. The trade off between radial
losses and the Pastukhov end losses is examined. We propose the use of a genetic algorithm to optimize the fusion power amplification
Q = P
fusion/P
injected as a function of the key system parameters. 相似文献
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pA量级质子束流测量系统 总被引：2，自引：0，他引：2
研制的质子束流测量系统,本底电流仅为１０＾－１４Ａ量级,可测最大电流达ｍＡ量级。在质子单粒子效应实验中,测得了ｐＡ量级的质子束及其随时间变化的关系,为半导体体器件粒子翻转截面的计算提供了必需的数据。 相似文献