激光等离子体X射线极化光谱研究

为了诊断激光等离子体X射线的极化光谱，研制了一种新型的基于空间分辨的极化谱仪。将平面晶体和球面弯晶色散元件在极化谱仪内正交布置，即在水平通道用PET平面晶体作为色散元件，而在垂直通道用Mica球面弯晶作为色散元件，球面半径为380mm。信号采用成像板进行接收，有效接收面积为30×80mm，从等离子体光源经晶体到成像板的光路约为980mm。物理实验首次在中国工程物理研究院激光聚变研究中心“2×10J激光装置”上进行，成像板获得了铝激光等离子体X射线的光谱空间分辨信号。实验结果表明该谱仪具有较高谱分辨率，适合激光等离子体x射线极化光谱的诊断。

X-ray Polarization Spectroscopy in Laser-produced Plasmas

To diagnose the presence of electron beams in high-temperature plasmas, polarization spectroscopy of x-ray lines is a useful diagnostic method to measure directly the presence of hot electron velocity distribution function inside a strong intense laser fusion produced plasmas. A novel polaried spectroscopy is designed and manufactured based on spatial resolution in laser-product plasmas experiments. This measurement relies on the sensitivity of two crystal spectrometers to the linear polarization of x-ray lines which depends on the value of the Bragg angle. The differential transmission spectrum representing the difference between the values of transmission for linearly polarized radiation with the orthogonal polarizations that are parallel and perpendicular to the optical axis is obtained with crystals at two different Bragg angles. One of dispersive elements is PET flat crystal set parallel channel, and another is Mica spherically bent crystal installed perpendicular channel, whose radius is 380 mm.The image plate ,the effective area of 30×80mm, is employed to record the spatial-resolved spectrum of polarization spectroscopy of x-ray lines. The designed long optical path of the X-ray spectrometer beam is about 980mm from the source to the crystal and the detector. The first experiment was carried out at the 2×10J laser facility of Research Center of Laser Fusion, China Academy of Engineering Physics (CAEP); the X-ray spectrum emitted from the aluminum plasmas was recorded by the image plate. These experimental results show that x-ray polarization spectroscopy is a good tool for diagnosing high-density plasmas created by lasers and that this diagnostic technique could also be applied to other areas of high-temperature plasma research.