Research On Technology And Experiments Of Double-channel Elliptically-curved Crystal Spectrograph

In the experimental investigations of inertial confinement fusion (ICF), the laser focuses on a target and producs high-temperature plasmas.For understanding inner status and evolution, all parameters of status must be measured by experiment including electronic temperature density distribution of ionization temporal and dimensional distribution of electricity and electromagnetic wave transmission and fluctuation, which is called plasmas diagnosis.It is necessary to develop key technology with space and time-resolved ability for x-ray diagnosis in order to diagnose spatial distribution and temporal evolution of laser-produced plasmas. The domestic first double-channel elliptically-curved crystal spectrograph has been successfully developed and it is supported by the High-Technology Research and Development Program under Contract No.863-804-3.Then,the experiments have been carried out at the SG-2 and XG-2 laser facilities.Factors of influencing diffractive intensity and direction are detaily analyzed using x-ray diffractive theory.The basal principle of double-channel elliptically-curved crystal spectrograph is that x-ray emitted from the front focus is concentrated to the back focus by elliptically-curved crystal analyzer.And set a exit slit on the back focus,then spectrum can be recorded by detector behind the slit. For the purpose of detecting the laser-plasmas in 0.2—2nm region,four kinds of dispersive crystals including LiF PET Mica and KAP are utilized considering the selective requests and principle of crystal.The Bragg angles are in range of 30-67.5 degrees.Two results in experimental progresses are taken as research emphases.The one is that spectrum can not be recorded by 1mm LiF elliptically-curved crystal analyzer which was be abraded and polished.The other is that spectrogram was distorted and overlapped using Danba Mica elliptically-curved crystal analyzer.The success of getting spectrum depends on manufacture of analyzer , but until now there is no method of examining. So a new method is put forward to check analyzer by using XRD-6000 diffractometer produced by SHIMADZU corporation,and at the same time the experimental conditions for checking are presented.The diffractive characteristic of the flat crystal must be examined first before manufacturing the elliptically-curved crystal analyzer.A conclusion is drawn from examination that lmm flat crystal is not fit as dispersive element which was abraded and polished before. The reason is that the highest diffraction intensity is just 7000CPS. For the sake of increasing diffractive intensity, a series of experiments was conducted such as abrading,heating and cleaning. The result indicates that abrading can increase diffractive intensity of dispersive crystal, especially by using 600#SiC abrading agent. But consistency of abraded surface has great influence on intensity, so it is difficult for whole block of crystal. At last, carborundum was choiced as abrading agent, it ensures not only the increase of intensity but also consistency of enhancive intensity for big crystal.Through experiment of X-ray diffractive characteristic of natural Danba Mica, the reson that the spectrogram was distorted and overlapped is multilevel diffraction,disfigurement and adsorption of Danba Mica crystal. The experiment also reveales that diffrative intensity is relative to directions and it decreases rapidly if direction changes. In addition, some crystal must be cleft before using. Two elliptically-curved crystal analyzers were manufactured using Indian Mica,Yaan Mica and new LiF crystals respectively and examined successfully on XRD-6000 diffractometer.In the end, aiming experiment is presented and influence of spectral precision is analyzed if elliptically-curved crystal analyzer has location error on x or y axes. Experiments of getting laser-plasmas spectrum are described which were executed at the SG-2 and XG-2 high-power laser facilities.The double-channel elliptically-curved crystal spectrograph has been successfully developed, it has very important national-defence meaning for ICF experimental researches, which has own intellectual property. It has filled up the bank in the diagnostic instrument field and achieves international advanced level.