Crystal Spectrometer Quantitative Preliminary Experimental Study

High power laser-matter interaction is a complex process in laser-plasma experiments which emits a large amount of x rays. Plasma parameters such as electron temperature, electron density and plasma expanding velocity can be obtained from the plasma-emitted x-ray spectra due to the reason that the x rays can easily escape from inside of the plasmas and almost not be affected by electronic and magnetic field in the plasmas. Therefore, precise diagnosis of the x-ray spectra from the plasmas is an important tool in the laser-plasma experiments. As we known, crystal spectrometer is one of the major instruments for x-ray spectral measurement, in which the diffraction crystal is a key component. In order to get the quantitative x-ray spectra from the laser-produced plasmas determinations of the x-ray line wavelengths and the crystal diffraction efficiencies are two vital aspects. The main purpose of this research work is to improve the wavelength-determining method and to establish calibration method of crystal diffraction efficiencies.In this paper the development of laser fusion and requirements of quantitative measurements of x-ray spectra using crystal spectrometers are introduced at first. Two theories describing crystal diffraction: kinetics and dynamics, are derived in detail, which are the basis of the crystal calibration datum-analyses.For the determination of x-ray wavelengths, an improving method based on the published auxiliary diaphragm method is proposed. In the improving method only one geometrical parameter of the crystal spectrometers is needed previously rather than two geometrical parameters in the published method.For determination of the crystal diffraction efficiencies, two series of experiments have been carried out. The first one was done on the 3B3 experimental station of Beijing Synchrotron Radiation Facility (BSRF) in Institute of High Energy Physics. The energy of the monochromic x-ray beam is in the range of 2.1 keV to 6 keV and can be changed continuously with spectral resolution of 0.1 eV. Two crystals (PET and T1AP) were used in this calibration experiment. The rocking curves for the two crystals at different x-ray energies have been obtained by scanning the x-ray energy at a series of specific Bragg diffraction angles which correspond to the responding x-ray energy points. As a result the integrated diffraction efficiencies (Rc) for the two crystals are easily determined from the rocking curves. It should be mentioned that not only the first order but also the second and third order diffraction efficiencies for the T1AP crystal have also been calibrated in this experiment. It...