双真空烘烤排气台的研制及应用

分析了放电管稳定试验前的烘烤排气对等离子体焦点装置试验结果的影响,介绍了双真空烘烤排气台的原理和结构设计,并利用试验数据说明了该排气台在等离子体焦点装置试验中的重要性,在实际应用中具有潜在的实用价值。     

双真空烘烤排气台的研制及应用

为了解决DPF实验中经常出现的首次中子产额不稳定、中子波形经常出现双峰以及每次充氘后稳定放电实验次数较少的问题，特地研制了双真空烘烤排气装置。     

等离子体焦点装置径向运动电流壳层的不稳定现象

在ＤＰＦ－４０等离子体焦点装置中，首次观测到径向运动电流壳层的一种不稳定现象，即不稳定模式。它属于ｍ＝０模的ＭＨＤ不稳定性，但仅具有半个波长并且发生在等离子体－电极边界上。在相继的一系列放电中，该不稳定模式五通常的稳定模式以随机方式发生。两种模式对壳层和箍缩等离子体的位形结构和运动方式及中子产额等具有显著的影响。     

影响DPF焦点装置中子稳定性的因素和改进措施

简要叙述了稠密等离子体聚焦装置作为中子发生器的工作原理，对影响稠密等离子体聚焦装置放电出中子产额及其稳定性的一些因素和改进措施进行了简单讨论．通过使用不同电极形状的场畸变开关很好地提高了焦点装置的运行，使装置输出中子的起伏得到明显的改善．通过对腔内电极的清洁，在不更换气体的条件下，聚焦装置放电出中子产额稳定.The principle of dense plasma focus(DPF) as neutron generator has been investigated in this paper. We have stated briefly some factors that mainly influnce the DPF s neutron yield and some methods improving the stability of neutron yields on the dense plasma focus. It is showed that the fluctuation of DPF output neutron becomes smaller by using different types of field-distortion elements. Over 100 consecutive shots without purging the test gas the neutron yields has no obvious change.     

HL-2M 真空烘烤系统工程设计与介质流量分析

从工艺、结构和设备几个方面对 HL-2M 真空烘烤系统进行设计。在定流量工况下进行仿真分析。 在总流量 2.5kg⋅s⁻¹,真空室流量 2.1kg⋅s⁻¹,偏滤器流量 0.21kg⋅s⁻¹ 下,验证了系统的烘烤效果。     

HL-2A装置主机真空性能的改善

HL-2A装置真空室内部件数目繁多，容器本体上的密封部位多达几百个，特别是真空室内多极场线圈真空套从真空室的预装阶段开始，经常会出现一些漏气问题，此问题在原ASDEX运行时就是一个棘手的问题，已进行了多次修补。大部分漏点均发生在厚度仅为约0．2mm的波纹管上，无法采用氩弧焊接，所有这些漏点的修补均采用无铅焊料通过钎焊工艺完成。     

HL-2M 装置真空烘烤控制系统概述

HL-2M 真空烘烤系统采用两台可编程逻辑控制器(PLC)构成一个自动控制系统,根据工艺要求编制 相应逻辑程序来控制各执行机构,实现对系统加热器电功率、换热器热负荷以及阀门开度的程序调节,达到±2℃ 温升梯度的烘烤目的。PLC 与阀岛建立工业以太网(Profinet)通信协议,通过地址映射的方式控制进出真空室和偏 滤器的开关阀,调整烘烤系统的负载投入。     

EAST铰链式机械臂真空存储舱 CASK系统研制

总体描述了EAST机械臂真空舱系统设计,介绍了实现进展情况。EAST铰链式机械臂是用于在不破坏EAST内部真空环境下对第一壁内部进行近距离观测、快速维修的一种检修工具。考虑到对EAST铰链式机械臂的存储、支撑以及工作条件,需要设计和制造出一个密封的真空舱系统。该系统可以在真空条件下通过一个直径为250mm的连接端口连接到EAST主体机构上。系统设计主要分为真空存储舱CASK腔体、真空系统以及烘烤系统三个部分。     

稠密等离子体聚焦装置的中子产额及其稳定性研究

叙述了稠密等离子体聚焦装置(DPF)作为中子发生器的工作原理,讨论了影响DPF中子产额及其稳定性的一些因素和改进措施。利用不同电极形状、不同绝缘气体的场崎变开关可以很好地提高聚焦装置的运行性能,使装置输出中子的起伏由过去的约两个量级降到目前的3倍左右。通过对腔内电极的清洁,在不更换气体的条件下。中子产额无明显下降。     

利用Si–PIN探测器测量DPF装置中子产额

介绍了Si-PIN中子探测器的结构和测量原理,分析了探测器对14MeV中子的灵敏度.利用该探测器测量了等离子焦点装置的D-T脉冲中子产额,实验结果与SDIN500探测器测量结果在5?%不确定度范围内一致     

用于DPF装置中子测量的闪烁体探测器

 介绍了一种用于等离子体焦点装置(DPF装置)中子波形测量的塑料闪烁体探测器,该探测器由ST401型塑料闪烁体、XP2262B型光电倍增管构成。利用银活化中子探测器和DPF装置对该塑料闪烁体探测器进行标定,确定其中子灵敏度为0.022 5 pC每中子,,中子产额测量范围达到10⁹～10¹¹每脉冲,可以满足DPF装置中子参数测量的需要。     

Multiple focus formation in a Mather gun device

Along with the normally produced pulses of dI/dt, x-ray, optical emission, neutrons and ions by a Mather type plasma focus gun, one more set of pulses were observed to be generated by a low energy device at Trombay, a few 100 ns after the first set of pulses, in majority of the discharges. In a small number of discharges even three or more sets of pulses were observed. Signals from pick-up probes placed in the run down region of the device suggest formation of more than one sheath which subsequently may form more than one focus which in turn is responsible for the second and subsequent sets of pulses.     

Nano-structured Fe thin film deposition using plasma focus device

This paper reports the deposition of nano-structured Fe thin films using 3.3 kJ Mather-type plasma focus. The conventional hollow copper anode was replaced by anode fitted with solid Fe top and the deposition was done using different numbers of deposition shots at two different angular positions. Scanning Electron Microscopy shows that the size of nano-phase agglomerate is smaller when the sample is deposited using either lesser number of deposition shots or at higher angular position with respect to anode axis. X-ray Diffraction shows that crystal structure characteristics change with increase in number of deposition shots. Measurements of magnetic properties using Vibrating Sample Magnetometer identify intermediate magnetization and coercivity in Fe thin films deposited at smaller angular position with respect to anode axis. It is concluded that the morphological, structural and magnetic characteristics of Fe thin films deposited using plasma focus device depend not only on the number of focus deposition shots but also on the angular position of the sample.     

Experimental study of the neutron emission mechanisms in a Filippov-type plasma focus device

The results of an experimental investigation of neutron emission characteristics in the Filippov-type plasma focus facility Dena (90 kJ, 25 kV, 288 µF) with D₂ + %1 Kr as working gas are presented. From the experimental results, one can conclude that both thermonuclear and nonthermonuclear mechanisms are always present in neutron production, but their contributions to the total neutron yield are strongly dependent on the initial pressure and discharge voltage. It has been found that at constant discharge voltages and low pressures the beam—target interaction mechanism plays an important role in the neutron production and with increasing the pressure, its role decreases and the importance of thermonuclear mechanism increases. Also at constant pressures, the contribution of beam—target interaction mechanism in neutron production decreases with increasing the discharge energy. The value of the index in the empirical neutron yield scaling law Y_n I E^/2 was found to be about 3.82.     

Discrimination of positive particles emitted in deuterium plasma focus device using SSNTD

The yields of different positive particles emitted in deutherium plasma focus device were measured. The particles, among the other particles, were detected. CR-39 and LR-115 (Kodak) SSNTD were used.     

Role of ion energy flux on the structural and morphological properties of silicon oxy-nitride composite films deposited by plasma focus device

ABSTRACT

Crystalline silicon oxy-nitride (SiON) composite films are deposited on Si substrate for multiple (5, 15, 25 and 50) focus shots (FS) by plasma focus device. The X-rays diffraction patterns reveal the development of various diffraction peaks related to Si, Si₃N₄, and SiO₂ phases which confirms the formation of SiON composite film. The intensity of Si₃N₄ (1 0 2) plane is linearly increased with the increase of FS. The Si₃N₄ (1 0 2) phase does not nucleate for 5 FS. Raman analysis confirms the formation of β–Si–N phase. Raman and Fourier transform infrared spectroscopy analysis reveals that the strength of chemical bonds like Si–N, Si–O formed during the deposition process of SiON composite films is associated with the bonds intensity which in turn depends on the number of FS. The field emission scanning electron microscopic analysis reveals that the surface morphology like size, shape and distribution of micro/nano-dimensional particles, film compactness and the formation of micro-rods, micro-teethes and micro-tubes of SiON composite films is entirely associated with the rise in substrate surface transient temperature which in turn depends on the increasing number of FS. The EDX spectrum confirms the presence of Si (22.5?±?4.7 at. %), N (13.4?±?4.5 at. %) and O (54.7?±?11.3 at. %) in the SiON composite film. The thickness of SiON composite film deposited for 50 FS is found to ～15.47?µm.     

On the frequency of oscillations in the pair plasma generated by a strong electric field

We study the frequency of the plasma oscillations of electron–positron pairs created by the vacuum polarization in a uniform electric field with strength E   in the range 0.2Ec<E<10Ec$0.2E_c<E<10E_c$. Following the approach adopted in Ruffini, et al. (2007) [1] we work out one second order ordinary differential equation for a variable related to the velocity from which we can recover the classical plasma oscillation equation when E→0$E\to 0$. Thereby, we focus our attention on its evolution in time studying how this oscillation frequency approaches the plasma frequency. The time-scale needed to approach to the plasma frequency and the power spectrum of these oscillations are computed. The characteristic frequency of the power spectrum is determined uniquely from the initial value of the electric field strength. The effects of plasma degeneracy and pair annihilation are discussed.     

Deposition of tungsten nitride thin films by plasma focus device at different axial and angular positions

Tungsten nitride thin films were deposited on stainless steel-304 substrates by using a low energy (2 kJ) Mather type plasma focus device. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and microhardness are used to study the surface of treated samples. The XRD analysis shows that the degree of crystallinity of deposited thin films strongly depends on axial and angular positions of samples. The SEM micrographs of the deposited films at different angular positions (0°, 10° and 30°) and axial position of 8 cm show that the content of WN sub-micro crystalline structures on the surface of deposited films decreased with increasing the angle with respect to anode axis. From AFM results we observe that for the sample deposited at 8 cm and 0° axial and angular positions, respectively, the most uniform surface and the most homogenous distribution of grains are obtained. Also the hardness results show that the highest mechanical hardness is obtained when the film is deposited at 8 cm and 0° axial and angular positions, respectively.     

Application of medium energy plasma focus device in study of radioisotopes

Pulsed neutrons generated in a plasma focus device are used for the thermal neutron activation analysis (TNAA) of selected three elements having widely different half-lives varying from a few seconds to a few days [Dysprosium (Dy), Manganese (Mn) and Gold (Au)]. Neutron pulse having strength of $(1.2\pm 0.3)\times {10}^9$ neutrons/pulse with a pulse width of $46\pm 5\text{ns}$ is produced by “MEPF-12” device operated at a filling gas (deuterium + 0.5% krypton) pressure of 3 mbar. The fast 2.45 MeV D–D neutrons are thermalized before irradiating the sample. The decay gammas from the radioisotopes ^165mDy ($T_{1/2}=1.26\text{min.}$), ⁵⁶Mn ($T_{1/2}=2.58\text{hrs.}$), and ¹⁹⁸Au ($T_{1/2}=2.69\text{days}$) produced via reactions, ¹⁶⁴Dy($n,\gamma$)^165mDy, ⁵⁵Mn($n,\gamma$) ⁵⁶Mn, and ¹⁹⁷Au($n,\gamma$) ¹⁹⁸Au respectively are counted off-line in a lead shielded well type $76\times 76{\text{mm}}^2$ NaI(Tl) detector coupled to a calibrated 2048 channel analyzer. The values of half-lives evaluated from the measured decay gammas, $1.43\pm 0.3\text{min.}$, $2.56\pm 0.5\text{hrs.}$ and $2.84\pm 0.6\text{days}$ respectively for the radioisotopes of Dy, Mn and Au, are seen to be close to the values reported in literature.