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Spectroscopic Measurements of Temporal and Spatial Profiles of Electric Fields in a Discharge Plasma Fusion Neutron Source

放电等离子体聚变中子源电场时空分布的光谱测量

基本信息

批准号：
12480124
负责人：
YOSHIKAWA Kiyoshi
金额：
$ 8.06万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12480124/
关键词：
Discharge Plasma Fusion Neutron Source Inertial Electrostatic Confinement Fusion Laser-Induced Fluorescence Method Stark Effect Temporal and Spatial Profile Measurement ot Electric Field

项目摘要

For a highly accurate measurement of electric field with an improved spatial resolution by the laser-induced fluorescence (LIF) method, a CCD of 7 mm square with 256 x 256 pixels has introduced. Also, we have introduced a converter of transverse shape of optical beam from a circle to a line, i.e. a sheet beam. For the measurements with a high spatial resolution by making use of these equipments, it is also necessary to develop a method based on the laser-induced fluorescence method by use of Stark effect, to adapt the wide dynamic range of the electric field strength in the discharge plasma fusion neutron source.In 2000 in this study, for a higher sensitivity, we studied an LIF for n = 4 forbidden transition (4^1D →2^1P, 492.2nm), which is theoretically expected to have 10 times higher transition probability, and adaptable to a much lower electric field range of 0.05〜0.5 kV/cm, as well, than the n = 3 transition previously we used. For verification, the present method was applied to a … More U-shaped hollow cathode discharge plasma, within which the electric field profile is well known, and was found to show a excellent accuracy in detecting a weak field of around 0.1 kV/cm or less.In 2001, we applied the above highly sensitive LIF method to the discharge plasma fusion neutron source with both a photo-multiplier and, then, the CCD. Particularly with the CCD, however, the S/N ratio was found too small to identify the existence of electric field, exclusively due to its higher spatial and temporal resolution than the photo-multiplier. The poor S/N ratio is found to result, also, from a too small fraction of 2^1S state (approx. 20.6 eV above the ground level) helium atoms in the neutron source, especially at high-voltage mode operations. To overcome this problem, we, thus, started a study to develop an injector of 2^1S state helium atom beam into the LIF observation point.The CCD with an extremely high resolution, on the other hand, was found to be very efficient in measuring the spatial profile of the spontaneous emission intensity from the discharge plasma, and the energy distribution of the fast neutral helium atoms by use of Doppler shift spectroscopy, as well, with a high accuracy. Also, we achieved an enhanced neutron yield of 1.1 x 107 n/sec with an improved high-voltage holding capability with a design refinement of the neutron source. Less

为了提高激光诱导荧光(LIF)法测量电场的精度和空间分辨率，介绍了一种面积为7 mm、像素为256×256的电荷耦合器件。此外，我们还介绍了一种光束横向形状从圆到线的转换方法，即片状光束。为了利用这些设备进行高空间分辨率的测量，还需要发展一种基于斯塔克效应的激光诱导荧光法的方法，以适应放电等离子体聚变中子源电场强度的大动态范围。2000年，为了获得更高的灵敏度，我们研究了n=4禁戒跃迁(4^1D→2^1P，492.2 nm)的激光诱导荧光，理论上预计它有10倍的跃迁几率，也适用于0.05kV/cm~0.5kV/cm的低电场范围。而不是我们之前使用的n=3跃迁。为了验证该方法的有效性，将该方法应用于…更多的U形空心阴极放电等离子体，其中的电场分布是众所周知的，并且被发现在检测约0.1千伏/厘米或更小的弱场时具有良好的精度。2001年，我们将上述高灵敏的激光诱导荧光方法应用于带有光电倍增器的放电等离子体聚变中子源，然后是电荷耦合器件。然而，特别是对于电荷耦合器件，S/N比被发现太小而不能识别电场的存在，这完全是因为它比光电倍增器具有更高的空间和时间分辨率。研究发现，较差的S/N比也是由于2^1 s态(约.20.6 eV)氦原子在中子源中，特别是在高压模式运行时。为了克服这一问题，我们开始了一项研究，开发了一种2^1s态氦原子束注入激光诱导荧光观测点的装置，另一方面，利用高分辨率的CCD可以非常有效地测量放电等离子体的自发辐射强度的空间分布，以及利用多普勒频移光谱测量快中性氦原子的能量分布，而且精度很高。此外，我们还通过改进中子源的设计，提高了高压保持能力，提高了1.1 x 107n/s的中子产额。较少