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应用电子与多光子集团非线性Compton散射模型,将入射和散射光作为离子的传输机制,研究了Compton散射下多束相干强耦合激光等离子体中离子的运动,给出了相对论离子动力学方程,并进行了数值模拟。研究发现,散射使光的传播速度减小,系统的矢势和标势增大,由入射和散射光形成的多束相干强耦合激光能使质子加速到5.40GeV的能量,而耦合轴向电场在其中起着关键作用。     

Compton散射下等离子体中的离子加速

应用电子与多光子集团非线性Compton散射模型,将入射和散射光作为离子的传输机制,研究了Compton散射下多束相干强耦合激光等离子体中离子的运动,给出了相对论离子动力学方程,并进行了数值模拟。研究发现,散射使光的传播速度减小,系统的矢势和标势增大,由入射和散射光形成的多束相干强耦合激光能使质子加速到5.40GeV的能量,而耦合轴向电场在其中起着关键作用。     

质子束在等离子体中传输的粒子模拟

用粒子模拟程序研究了长脉冲质子束在等离子体中的传输特性,模拟结果表明,等离子体可以明显改善质子束的空间传输特性,大尺度的等离子体相对于等离子体层可以实现较长距离的稳定传输。研究发现,在实现长距离传输时,等离子体波会对质子束密度有较大的调制作用,严重影响质子束的传输性质,同时通过优化束密度分布可以有效减弱等离子体波的激发,实现束较稳定的传输。     

热电子等离子体低频不稳定性的非线性理论

本文分析了热电子等离子体中低频漂移不稳定性和交换不稳定性的非线性性质,导出了扰动幅度随时间变化的非线性耦合方程,得到了等离子体密度扰动的饱和幅度,讨论了热电子成分对饱和幅度的影响。漂移波引起的等离子体密度扰动相对幅度约20％,交换模引起的等离子体密度相对扰动幅度约5％。当热电子成分达到线性稳定条件所要求的阈值时,漂移波和交换模的饱和幅度降为零。 关键词：     

散裂靶中质子束窗的散射效应

 质子束窗是在高功率靶区中的一个分界窗,它将质子输运线上高真空区域和氦容器中的氦环境分开。在其他散裂中子源中质子束窗的热效应以及机械问题都已经被研究过了,但质子束在该窗中散射效应的研究却很少被报导,然而在靶设计中如果没有处理好质子束窗的散射效应会有很大的问题。报导了质子束窗散射效应的模拟计算结果,包括不同质子束窗的材料和结构选择,并以中国散裂中子源（CSNS）为例,介绍了在CSNS一期和二期中质子束窗采用周边水冷的铝合金单层结构,CSNS三期采用中间水冷的铝合金夹层结构。文中给出了不同结构的质子束窗和不同的与靶距离散射效应对靶上经非线性磁铁均匀化的束流分布的影响的模拟计算结果。模拟结果显示质子窗的散射效应对束流损失和靶上的束流分布有重要的影响。     

等离子体二维密度重建的影响因素

利用超强超短激光脉冲产生的高能质子束的库仑能量损失可以重建稠密等离子体的二维密度分布，使用同时迭代重建算法（SIRT算法）研究等离子体二维密度重建的影响因素.研究等离子体密度梯度、密度量级和质子束入射能量对重建误差的影响，分析质子束成像探测等离子体密度之前获得等离子体大概方位的重要性，通过数据拟合确定了能量噪声和重建误差之间的解析关系式.     

中性束注入加热下旋转和Zeff对EAST中子出射影响的研究

为了判断中性束注入加热效果和研究等离子体宏观旋转和有效电荷数(Z_eff)对中子出射的影响,结合实验数据,利用TRANSP模拟程序研究了EAST中性束注入加热时,等离子体旋转速度、有效电荷数Z_eff以及等离子体储能与中子出射率的关系。模拟结果表明,在能量为65keV、功率为2.89MW的中性束注入加热时,等离子体产生较大的旋转,旋转减少快离子热化时间,降低中子产额;有效电荷数Zeff增加时,快离子投掷角散射增强,束靶反应减少,中子产额缩减。中子出射率随等离子体储能的增加而增加。     

强激光与亚临界密度等离子体相互作用中的近前向散射驱动光子加速机制

通过二维粒子模拟(particle-in-cell)方法研究了强激光与亚临界密度等离子体相互作用中的近前向光子加速机制.该机制利用强激光在亚临界密度气体传输过程中的电离效应产生在纵向和横向上密度分布不均匀的电子等离子体.在纵向上,入射激光电离氦气产生一个陡峭的电子密度前沿分布.在密度前沿处,入射激光与电子等离子体波作用发生近前向散射.散射光频率较激光频率增大,在频谱中产生了第一个特征峰.在横向上,密度不均匀造成电子等离子体波具有不同的相速度并与入射激光相互作用,使入射激光发生近前向散射,在频谱中产生了第2个特征峰.由于密度分布的不均匀性较电子等离子体波的密度扰动大得多,因此基于微扰理论的散射模型和色散关系,如受激拉曼散射,无法解释频谱中两个特征峰的出现.进一步研究发现:在密度不均匀的情况下,入射激光、电子等离子体波和散射光三者之间仍满足动量和能量守恒的三波耦合关系.这能够解释两个特征峰对应的频率和强度增长过程.该研究对于强激光在亚临界密度气体传输过程中的频谱演化具有重要参考意义.     

1．053μm激光在腔靶中产生的非线性过程

波长１．０５３μｍ、脉宽约１ｎｓ、能量３００～６００Ｊ激光在亚毫米的腔靶中可以产生十分丰富的非线性过程。我们直接测量了受激Ｂｒｉｌｌｏｕｉｎ散射、受激Ｒａｍａｎ散射：通过谐波间接测量了共振吸收、离子声衰变和双等离子体衰变。其中受激Ｂｒｉｌｌｏｕｉｎ散射和受激Ｒａｍａｎ散射是腔靶中的主要非线性过程，它散射掉约４０％的入射光能量。激光激发的电子等离子体波是产生超热电子的根源，产生电子等离子体波的非线性过程是受激Ｒａｍａｎ散射、双等离子体衰变、共振吸收和离子声衰变。其中受激Ｒａｍａｎ散射是激发电子等离子体波的主要过程，它产生约占入射激光能量１０％的超热电子。各非线性过程发射的光谱与激光参数和等离子体状态有密切关系，仔细测量和研究这些谱的特性可以获得等离子体温度、密度的信息。     

超强激光功率密度对等离子体中自生磁场和电子热传导的影响

应用多光子非线性康普顿散射模型、3维粒子模拟模型和数值计算方法,研究了超强激光与等离子体作用中自生磁场产生和电子热传导过程,提出了将非线性康普顿散射光作为改变等离子体自生磁场和电子热传导的新机制,给出了自生磁场最大饱和值和超热电子热传导的修正方程和数值计算结果。研究发现在时间为100~160范围内,自生磁场能量随入射激光功率密度增大而迅速增大,之后处于较高饱和阶段。增大的初始时刻较散射前提前了20,增大阶段的时间延长了30,饱和阶段增幅为40。入射激光功率密度为1019~1020W/cm2时,自生磁场强度最大模拟值为1.47104~3.75104T,单电子能谱峰值出现在3.3MeV和6.6MeV附近,能谱曲线在4~15 MeV和11~14.3MeV范围迅速衰减,在6.7MeV和13.2MeV以上时,超热电子有效温度为2.6MeV和4.5MeV,比无散射的理论值和拟合值均有一定增大。随入射激光强度增大,热流随激光脉冲一起向等离子体内流动的时间缩短,自生磁场限制热流的时间延长。并对所得结果给出了初步物理解释。     

Mechanism of proton anisotropic velocity distribution in the solar wind

Although it has been long that spacecraft observed the anisotropy of velocity protons in the solar wind, there is still not a reasonable explanation. In this paper we try to give an explanation from the diffusion plateau of protoncyclotron resonance predicted by the quasi-linear theory for the resonance between the protons and the parallel propagating waves. We consider the effect of dispersion relation on diffusion plateau and notice that the diffusion plateau we have got by using cold plasma dispersion relation accords with the density contours in the velocity phase space detected at 0.3 AU in fast solar wind. For explaining proton distributions obtained in the fast solar wind from 0.7 AU to 1 AU hot plasma dispersion relation should be considered. We also give a theoretical relation of proton thermal anisotropy A and plasma parameter β.     

Splitting Scheme Integration of the Two-and-One-Half-Dimensional Vlasov Equation

A numerical splitting scheme technique is applied to the integration of the Vlasov equation in two-space and three velocity dimensions. Calculations are performed for a cold, stationary ion, mobile electron plasma in the presence of a constant external magnetic field. Results for Landau damping and the two-stream instability are presented in both one and two velocity dimensions. The Landau damping results show a plateau structure in the electron velocity distribution function in both the parallel and perpendicular directions formed as a result of the damping of a high initial electric field propagating at 45° to the parallel velocity axis. The two-stream velocity distribution function shows pitch angle scattering and velocity diffusion for an electron beam initially propagating at 45° to the magnetic field direction through a low-temperature equal density background. The two-stream distribution function evolves to a stable quasi-isotropic plateau structure similar to that found in auroral sounding rocket data.     

Second-Order Resonant Interaction of Ring Current Protons with Whistler-Mode Waves

We present a study on the second-order resonant interaction between the ring current protons with Whistler-mode waves propagating near the quasi electrostatic limit following the previous second-order resonant theory. The diffusion coefficients are proportional to the electric field amplitude E, much greater than those for the regular first-order resonance, which are proportional to the electric field amplitudes square E^2. Numerical calculations for the pitch angle scattering are performed for typical energies of protons Ek = 50 keV and 100 keV at locations L = 2 and L = 3.5. The timescale for the loss process of protons by the Whistler waves is found to approach one hour, comparable to that by the EMIC waves, suggesting that Whistler waves may also contribute significantly to the ring current decay under appropriate conditions.     

Distorted wave theory of scattering of nucleons with intermediate energies on nuclei

In the context of nonrelativistic theory in the distorted wave approximation, a three-dimensional form of analytical expression for the differential cross section of scattering of nucleons with intermediate energies on atomic nuclei is derived. In the context of this theory, the main parameters of elastic scattering of protons with incident energy of 1 GeV on the ²⁰⁸Pb nucleus are determined. For inelastic scattering of protons with nuclear surface vibrations, giant multipole resonances in the excited nucleus are investigated for the collective nucleus model. The energy losses of the scattered proton are calculated together with the energies of giant dipole and quadrupole resonances and nuclear surface vibration energy. This allows the deformation parameter of the excited nucleus to be calculated.     

一种二进制降能器设计方法

为提升在中国原子能科学研究院的100 MeV质子回旋加速器上进行多能点质子单粒子效应实验的效率,针对该加速器提供的100 MeV质子设计了一种二进制降能器.降能器包括6片铝降能片,厚度分别为0.5,1,2,4,8,16,32 mm,即后一片厚度均为前一片的2倍.提出相对厚度的概念,此概念也可用来表示产生的质子能点的次序以及降能器的状态或操作.降能器产生的9.69 MeV以上的61个质子能点间隔在0.84—4.09 MeV之间,且能量岐离均在10%以下,散射角半高宽均在45 mrad以下,基本可满足质子单粒子效应实验的要求.对加速器直接提供的质子的能量精度对降能器产生的质子能点的影响进行分析,发现经降能器产生的质子能量越低,其影响也就越大.此外,降能器对加速器直接能够提供的70—100 MeV能区的质子也是适用的,且可通过增加降能片数量的方式来获得更加连续化的质子能点.本文提出的降能器设计方法简单有效,具有较强的借鉴价值.     

Sun-Earth connection: Boundary layer waves and auroras

Boundary layers are the sites where energy and momentum are exchanged between two distinct plasmas. Boundary layers occurring in space plasmas can support a wide spectrum of plasma waves spanning a frequency range of a few mHz to 100 kHz and beyond. The main characteristics of the broadband plasma waves (with frequencies >1 Hz) observed in the magnetopause, polar cap, and plasma sheet boundary layers are described. The rapid pitch angle scattering of energetic particles via cyclotron resonant interactions with the waves can provide sufficient precipitated energy flux to the ionosphere to create the diffused auroral oval. The broadband plasma waves may also play an important role in the processes of local heating/acceleration of the boundary layer plasma.     

Spectral enhancement in the double pulse regime of laser proton acceleration

The use of two separate ultraintense laser pulses in laser-proton acceleration was compared to the single pulse case employing the same total laser energy. A double pulse profile, with the temporal separation of the pulses varied between 0.75-2.5?ps, was shown to result in an increased maximum proton energy and an increase in conversion efficiency to fast protons by up to a factor of 3.3. Particle-in-cell simulations indicate the existence of a two stage acceleration process. The second phase, induced by the main pulse preferentially accelerates slower protons located deeper in the plasma, in contrast to conventional target normal sheath acceleration.     

Dependence of single event upsets sensitivity of low energy proton on test factors in 65 nm SRAM

In order to accurately predict the single event upsets(SEU) rate of on-orbit proton, the influence of the proton energy distribution, incident angle, supply voltage, and test pattern on the height, width, and position of SEU peak of low energy protons(LEP) in 65 nm static random access memory(SRAM) are quantitatively evaluated and analyzed based on LEP testing data and Monte Carlo simulation. The results show that different initial proton energies used to degrade the beam energy will bring about the difference in the energy distribution of average proton energy at the surface and sensitive region of the device under test(DUT), which further leads to significant differences including the height of SEU peak and the threshold energy of SEU. Using the lowest initial proton energy is extremely important for SEU testing with low energy protons. The proton energy corresponding to the SEU peak shifts to higher average proton energies with the increase of the tilt angle, and the SEU peaks also increase significantly. The reduction of supply voltage lowers the critical charge of SEU, leading to the increase of LEP SEU cross section. For standard 6-transitor SRAM with bit-interleaving technology,SEU peak does not show clear dependence on three test patterns of logical checkerboard 55 H, all "1", and all "0". It should be noted that all the SEUs in 65 nm SRAM are single cell upset in LEP testing due to proton's low linear energy transfer(LET) value.