Numerical study of alpha particle loss with toroidal field ripple based on CFETR steady-state scenario

Effects of plasma equilibrium parameters on the alpha particle loss with the toroidal field ripple based on the CFETR steady-state scenario have been numerically investigated by the orbit-following code GYCAVA. It is found that alpha particle losses decrease and loss regions become narrower with the plasma current increasing or with the magnetic field decreasing. It is because the ripple stochastic transport and the ripple well loss of alpha particle are reduced with the safety factor decreasing. Decrease of the plasma density and temperature can reduce alpha particle losses due to enhancement of the slowing-down effect. The direction of the toroidal magnetic field can significantly affect heat loads induced by lost alpha particle. The vertical asymmetry of heat loads induced by the clockwise and counter-clockwise toroidal magnetic fields are due to the fact that the ripple distribution is asymmetric about the mid-plane, which can be explained by the typical orbits of alpha particle. The maximal heat load of alpha particle for the clockwise toroidal magnetic field is much smaller than that for the counter-clockwise one.

Effect of Au/Ni/4H–SiC Schottky junction thermal stability on performance of alpha particle detection

Au/Ni/n-type 4H-SiC Schottky alpha particle detectors are fabricated and annealed at temperatures between 400℃ and 700 ℃ to investigate the effects of thermal stability of the Schottky contact on the structural and electrical properties of the detectors. At the annealing temperature of 500 ℃, the two nickel silicides （i.e., Ni31Sil2 and Ni2Si） are formed at the interface and result in the formation of an inhomogeneous Schottky barrier. By increasing the annealing temperature, the Ni31Sil2 transforms into the more stable Ni2Si. The structural evolution of the Schottky contact directly affects the electrical properties and alpha particle energy resolutions of the detectors. A better energy resolution of 2.60% is obtained for 5.48-MeV alpha particles with the detector after being annealed at 600 ℃. As a result, the Au/Ni/n-type 4H-SiC Schottky detector shows a good performance after thermal treatment at temperatures up to 700℃.

Alpha particle detector with planar double Schottky contacts directly fabricated on semi-insulating GaN:Fe template

Alpha particle radiation detectors with planar double Schottky contacts(DSC)are directly fabricated on 5-μm-thick epitaxial semi-insulating(SI)GaN:Fe film with resistivity higher than 1×10^(8)Ω·cm.Under 10 V bias,the detector exhibits a low dark current of less than 5.0×10^(-11) A at room-temperature,which increases at higher temperatures.Linear behavior in the semi-log reverse current-voltage plot suggests that Poole-Frenkel emission is the dominant carrier leakage mechanism at high bias.Distinct double-peak characteristics are observed in the energy spectrum of alpha particles regardless of bias voltage.The energy resolution of the SI-GaN based detector is determined to be8.6%at the deposited energy of 1.209 MeV with a charge collection efficiency of81.7%.At a higher temperature of 90℃,the measured full width at half maximum(FWHM)rises to 235 keV with no shift of energy peak position,which proves that the GaN detector has potential to work stably in high temperature environment.This study provides a possible route to fabricate the low cost GaN-based alpha particle detector with reasonable performance.

Electromagnetic nature of nuclear forces and the toroid structure of the helion and the alpha particle

In the present paper, we consider the nucleons in the helium-3 and helium-4 nuclei as tori. These tori rotate with constant angular velocity around an axis, which is perpendicular to the rotation plane and passes through the centre of mass of the nuclei. Based on exact analytical expressions for the electrostatic interaction between two spheres with arbitrary radii and charges derived by us recently, we find that the well-known potential binding energy for the helion and for the alpha particle is of electromagnetic character. Using the above mentioned formulae, we find the interaction force in the nuclei under consideration. Our toroid model recovers the basic experimental results not only for the binding energy, but also for the stability, radii, spins and the magnetic moments of the helion and the alpha particle.

Simulations of energetic alpha particle loss in the presence of toroidal field ripple in the CFETR tokamak

Energetic alpha particle losses with the toroidal field ripple and the Coulomb collision in the CFETR tokamak have been simulated by using the orbit-following code GYCAVA for the steady-state and hybrid scenarios.The effects of the outer boundary and the ripple amplitude on alpha particle losses have been investigated.The loss fractions and heat loads of alpha particles in the hybrid scenario are much smaller than those in the steady-state scenario for a significant ripple amplitude.Some alpha particles in the plasma core are lost due to the ripple stochastic transport for a large ripple amplitude parameter.The heat loads with the last closed flux surface boundary are different from those with the wall boundary for the CFETR tokamak,which can be explained by typical alpha particle orbits.Discrete heat load spots have been observed in alpha particle loss simulations,which is due to the ripple well loss.The transition of the lost alpha particle behavior from the ripple stochastic diffusion to the ripple well trapping has been identified in our CFETR simulations.The Coulomb collision effect is responsible for this transition.

A New Method to Determine the Maximum Value of the Track Length of Alpha Particle in CR-39 Detector

The aim of this paper is to determine the maximum values of the track length (Lmax) of alpha particles in Nuclear Track Detector (type CR-39) using a new method by taking the relation between the etching time and the diameter square of alpha particle with different energies at constant bulk etch rate VB (1.45 μm/hr) by using TRACK_TEST program from Brun et al. function and Yu et al. function. Using the new equation, the maximum values of the track lengths of alpha particles measured in CR-39 detector have been found to be in a good agreement with the values measured by using Brun et al. function and Yu et al. function in TRACK_TEST program.

Measuring energy loss of alpha particles in different vacuum conditions

In this paper,energy loss of alpha particles in different vacuum levels is studied experimentally and via theoretical analysis.A better understanding of energy loss of a particle in vacuum will help detect more exact numbers of alpha particles.Two ^(239)Pu sources are used to measure the energy loss of a particle crossing different vacuum levels (different air pressures).The experimental data are obtained from an instrument-PAM-100 developed by authors. The experimental results have shown that increasing vacuum levels will lead to more alpha residual energy but less energy loss.When the vacuum level reaches 0.04 MPa,alpha particles(^(239)Pu,5.115 MeV)will lose the energy of about 0.175 MeV with traversing 5 mm distance.Theoretical calculations have shown a good agreement with experimental results.This implies that the instrument has a high accuracy and could be applied in field work.

Storage Stability of Alpha-Lipoic Acid-loaded Lipid Nanoparticles

Alpha-lipoic acid-loaded lipid nanoparticles(ALA-LNs) were prepared by high pressure homogenization method.The influences of storage conditions such as time and temperature on the physical and chemical storage stability of ALA-LNs were studied in details.The stability was evaluated by particle size and polydispersity index,morphology of ALA-LNs,and capacity of ALA loading.The dilution and pH stability of ALA-LNs suspensions were also studied.After three months storage,the mean size of ALA-LNs at 4 and 40 ℃ was increased by 2.68% and 3.62% compared with the original size,respectively.ALA-LNs stored at 40 ℃ had ellipsoid shape and the mean size was about 152 nm(SD=23.6).The loading capacity of ALA at 40 ℃ was much higher than those stored at other two temperatures.The good dilution and pH stability were also demonstrated.The sample had good fluidity even at 4 ℃.

自噬在α粒子辐射诱发人支气管上皮细胞恶性转化中的作用

目的:探讨自噬在α粒子辐射诱发永生化人支气管上皮细胞BEP2D恶性转化中的作用。方法:采用Western blot检测BEP2D细胞、α粒子作用BEP2D后的第24代细胞RH24以及α粒子作用BEP2D后的恶性转化细胞BERP35T-1(经鉴定为肺鳞癌细胞)内自噬相关蛋白LC3B-II、LC3B-I和P62的表达,透射电镜观察细胞内单位面积自噬小体的数量。分别用40和60μmol/L自噬抑制剂氯喹(CQ)及25 pmol/L自噬激活剂雷帕霉素(Rapa)作用BERP35T-1细胞,采用Western blot法检测细胞内LC3B和P62蛋白的表达情况,CCK-8法检测细胞的存活率,Transwell侵袭实验检测细胞的侵袭数,划痕愈合实验检测细胞划痕闭合率。结果:与BEP2D细胞相比,RH24和BERP35T-1细胞内LC3B-II/I蛋白比值增高(P<0.05或P<0.01),P62蛋白表达降低,自噬小体数量增多(P<0.01)。40和60μmol/L的CQ分别作用BERP35T-1细胞48 h后,细胞内LC3B-II/I蛋白比值和P62蛋白表达水平均升高,细胞的存活率、侵袭数和划痕闭合率均降低(均为P<0.01);25 pmol/L的Rapa作用BERP35T-1细胞48 h后,细胞内LC3B-II/I蛋白比值升高,P62蛋白表达减弱,细胞的存活率、侵袭数和划痕闭合率均升高(P<0.05或P<0.01)。结论:在α粒子辐射诱发BEP2D细胞恶性转化过程中,细胞自噬增强,可能由此提高细胞的增殖、侵袭和迁移能力,从而促进细胞恶性转化。

伴随粒子中子检测系统发展及应用

基于快中子技术的无损检测方法能够在不对检测物造成影响的情况下,发现其隐藏的危险品。利用D-T反应时伴随中子产生的反冲α粒子对有效中子进行标记,可大幅提高中子探测信噪比,同时通过空间分辨α粒子还可以获得被检测对象特征元素的空间信息,所以基于伴随α粒子的中子检测方法在安检领域具有重要的应用前景。本文简单介绍了基于伴随α粒子中子检测方法的原理和系统组成,并对系统的中子管、α粒子探测器和γ探测器等关键部件进行了介绍,接着介绍了目前世界上正在研究的伴随α粒子中子检测系统及其进展,最后对这种检测方法进行了展望。

基于动态分数阶和Alpha稳定分布的粒子群优化算法

针对传统粒子群优化算法(PSO)收敛速度慢及容易陷入局部极小化的问题,提出了一种改进的粒子群优化算法。新算法结合分数阶微分具有的记忆特性,使得粒子的更新融入了轨迹信息,提高了算法的收敛速度。使用Alpha稳定分布代替均匀分布使得粒子在一定概率条件下可以逃逸局部极小点,提高了粒子的全局搜索能力。仿真结果表明,算法不仅在单模态函数下具有更快的收敛速度和更有效的全局搜索能力,在复杂的具有欺骗性的多模态函数下也取得较理想的实验结果,证实了动态分数阶和Alpha稳定分布可以有效地提高粒子群优化算法的性能。

Single event effects evaluation on convolution neural network in Xilinx 28 nm system on chip

Convolutional neural networks(CNNs) exhibit excellent performance in the areas of image recognition and object detection, which can enhance the intelligence level of spacecraft. However, in aerospace, energetic particles, such as heavy ions, protons, and alpha particles, can induce single event effects(SEEs) that lead CNNs to malfunction and can significantly impact the reliability of a CNN system. In this paper, the MNIST CNN system was constructed based on a 28 nm systemon-chip(SoC), and then an alpha particle irradiation experiment and fault injection were applied to evaluate the SEE of the CNN system. Various types of soft errors in the CNN system have been detected, and the SEE cross sections have been calculated. Furthermore, the mechanisms behind some soft errors have been explained. This research will provide technical support for the design of radiation-resistant artificial intelligence chips.

对称Alpha稳定分布噪声下单天线干扰消除算法

蜂窝移动通信系统性能受限于码间干扰、同频干扰和脉冲噪声等因素。本文提出一种基于粒子滤波的单天线干扰消除算法。首先,对脉冲噪声采用Alpha稳定分布进行建模,并对该模型进行高斯近似,递推得到多个未知信道参数的联合后验概率。其次,提出基于延迟粒子滤波的同信道传输码元最大后验估计方法。理论推导和仿真实验结果表明本文算法能够消除码间干扰和同频干扰对码元检测的影响,与其他干扰消除算法相比,特别是在强脉冲噪声和未知信道参数情况下,具有一定的优势。

中国聚变工程试验堆上新经典撕裂模和纵场波纹扰动叠加效应对alpha粒子损失影响的数值模拟

托卡马克聚变堆中高能量alpha粒子的良好约束是获得稳态燃烧等离子体的前提,除了磁场波纹损失,不稳定性也会引起额外的损失.本文基于中国聚变工程试验堆(CFETR)参数, alpha粒子初始分布和新经典撕裂模(NTM)扰动分布,利用粒子导心跟踪方法分别对磁场波纹和NTM两种扰动及叠加下的粒子损失进行了详细的数值模拟.结果显示粒子损失份额不随NTM扰动幅度增大而增大,两种扰动的叠加效应不明显.通过扫描装置波纹度大小以及分析相空间粒子密度和波纹损失区分布,确认原因是CFETR波纹损失区较小,没有覆盖高能量粒子(EP)密度和NTM扰动主要分布区.此外, NTM没有引起直接粒子损失和俘获粒子剖面坍塌.显著的俘获粒子密度剖面展平,并扩展到波纹损失区是两种扰动叠加效应显著的前提.无碰撞波纹随机扩散是CFETR初始分布alpha粒子的主要损失通道,通行粒子约束不受磁场波纹影响.本文研究结果对CFETR概念设计中alpha粒子物理和低频不稳定性下的EP行为具有重要意义.

环境中子测量中的偶然符合alpha事例修正

在暗物质直接探测实验中,中子是十分重要的环境本底.利用快慢符合法,一个掺钆的液闪探测器被分别用于测量了世界最深的地下实验室-中国锦屏地下实验室的实验大厅及1m厚聚乙烯房间内的快中子本底通量及能谱.由于液闪无法通过信号波形区分中子与alpha事例,因此液闪中长寿命的U/Th核素衰变放出的alpha粒子是必须考虑的本底之一.在长期平衡假设条件下,实验测得液闪内部alpha粒子的总计数率为(0.548±0.002)s^-1,再通过偶然符合算法,可得到实验大厅356天总计2682个中子候选事例中,有6个偶然符合的alpha事例;聚乙烯房间173天总计44个中子候选事例中,有2个偶然符合的alpha事例.偶然符合的alpha粒子对大厅的快中子通量测量结果影响可以忽略,而对聚乙烯房间中的通量结果约有4%的影响.

Alpha粒子和柴油机尾气颗粒提取物共同处理哺乳动物细胞的协同毒性作用

为研究两种有害环境因子同时作用对人类健康的影响,以alpha粒子和柴油机尾气颗粒提取物(d iese lparticu late extract,DPE)共同处理皮肤成纤维细胞(AG1522)为实验模型,对细胞毒性、遗传毒性进行研究。实验发现和未处理的对照组相比,1 cGy alpha粒子和20μg/mL DPE处理24 h,共同作用于细胞能够导致细胞活力下降40%左右,微核形成率上升2倍多;而1 cGy alpha粒子单独辐照时细胞活力下降14.19%,微核形成率上升了36.84%,20μg/mL DPE单独处理24 h时细胞活力下降17.29%,微核形成率上升了73.68%。实验结果表明:这两种环境因子共同作用于哺乳动物细胞时,对于细胞的毒性不是简单的叠加,而是表现出一种协同效应。

基于Alpha-stable的粒子群算法变异策略研究及气动优化应用

提出了一种基于Alpha stable分布的新型变异方法。针对粒子群算法容易陷入局部最优的缺点,通过对比分析确定了一种调整Alpha stable分布的稳态系数动态变异策略,使粒子群算法能够在搜索初始阶段具有更强的种群多样性以及算法探索能力,减少陷入局部最优的可能;在算法末期增强粒子群优化算法的局部搜索能力,提高解的精度。将基于Alpha stable变异的粒子群优化算法(Alpha stable particle swarm optimization, ASPSO)与多种改进型粒子群优化算法以及差分进化算法(differential evolution algorithm, DE)进行了比较,基准测试函数结果表明新建立的ASPSO算法极大地提高了算法的收敛速度和精度。将其应用到RAE2822翼型的单点跨声速减阻优化中,在保持种群规模等参数相同的情形下,ASPSO算法的优化效果和效率都远高于传统PSO算法,最终得到的翼型也比PSO优化的翼型具有更高的升阻比,翼面波阻有明显降低。

Development of alpha surface contamination monitor based on THGEM for contamination distribution

In cases of high radiation emergencies,we propose a surface contamination monitor(SCM)that can quickly measure and pinpoint the contamination distribution in the affected population.Thick gaseous electron multiplier(THGEM)has several advantages,including fast response time and good spatial resolution.Based on new THGEMs,a two-dimensional imaging detector was developed for alpha detection,with a position resolution greater than 3 mm.The detector design and test results are described in this paper.Fast radiation imaging SCMs,with a 40mm×40 mm sensitive area,are currently under development.

流管几何对低速太阳风alpha粒子丰度的影响

建立了离子回旋共振机制驱动的一维三元（电子、质子、alpha粒子）低速太阳风流管模型,重点分析流管参数对alpha粒子丰度（定义为alpha粒子与质子数密度之比）的影响.流管几何形式与有关观测数据分析及二维太阳风模型的计算结果相一致.与以往研究相符,在太阳附近alpha粒子的丰度先增加（可超过冕底丰度的1～5倍）,尔后迅速降至行星际空间中的平均观测数值.alpha粒子丰度极大值αmax在大约1.5～1.7 Rs范围内获得,具体数值主要取决于流管的几何参数包括冕流尖点的高度与相应膨胀因子的极大值：尖点越靠近太阳、极大膨胀因子越大,则αmax越大.但是这两个参数对于行星际空间中alpha粒子的特征影响不大;而合理地改变流管在远处的膨胀因子,可定性解释低年低速太阳风中alpha粒子的平均丰度与太阳风速度正相关的观测现象.