X-RAY SPECTROSCOPY AND CALIBRATIONS IN THE 50 EV TO 60 KEV RANGE

摘要

Spectrometers have been developed to record x-ray spectra in the energy range 50 eV to 60 keV. The dispersion elements are transmission crystals for energies higher than approximately 11 keV, reflection crystals for 1 keV to 20 keV, and transmission gratings for energies less than 1 keV. The spectra are recorded on CCD or CMOS detectors with phosphor conversion screens. Silicon photodiodes are positioned in front of the detectors to provide absolute x-ray flux calibrations. The diodes have 1 mm~2 area and subnanosecond time response. The diodes, transmission gratings, and attenuation filters were absolutely calibrated using synchrotron radiation. In addition, the diodes were calibrated in pulsed mode using the soft x-ray (70 eV to 250 eV) pulses from individual electron bunches circulating in the storage ring, and a self-calibration model extends the calibration to higher energy. X-ray spectra in the energy range >12 keV were recorded at the OMEGA laser using a transmission crystal. Spectra in the energy range <1 keV were recorded at the NIKE laser using a transmission grating and fast silicon photodiodes. A NIF core diagnostic is being built that covers the 1-20 keV range with one transmission crystal and four reflection crystals.