A detailed description of quantitative x-ray spectroscopy using single hit CCD cameras

Deep-depletion charge-coupled device (CCD) cameras can be used as x-ray spectrometers if the flux is limited to significantly less than one photon per pixel. The charge that is created by the absorbed photon is proportional to the x-ray energy, and consequently, the histogram of the CCD-sensor readout (in the limit of no noise and large pixel size) is a strictly linear spectrum. If the quantum efficiency of the detector, the attenuation of x-rays from the source to the detector, and the overall geometry of the setup are known, one can also calculate the absolute flux for a given photon energy from the source. We describe the efficient use of a commercial deep-depletion CCD camera as an absolutely calibrated x-ray spectrometer for the determination of laser-to-x-ray conversion efficiencies with the Z-Petawatt and Z-Beamlet lasers [P. Rambo et al., Proc. SPIE 10014, 100140Z (2016)] at Sandia National Laboratories. We explain procedures to reverse intrinsic degradations of x-ray induced pixel brightness and to mitigate external noise, and we identify spectral artifacts that are generated inside the detector.