Measurement of Atomic Number by MV X-Ray Scattering Spectra Analysis

In order to measure atomic number (Z) of materials, we present a Z identification method based on MV X-ray scattering spectra analysis in this paper. Scattering photons, which include positron annihilation photons, bremsstrahlung photons and Compton scattered photons, are generated by interactions of X-rays with matters and carry their Z information. A LaBr₃(Ce) detector is used for its short resolving time (<; 100 ns) to measure scattered photons to alleviate pulse pileup problem in the 5 μs X-ray pulse duration. ADC with high sampling rate of 120 MHz and high resolution of 14-bit is used to digitize signal waveform from the preamplifier of the LaBr₃(Ce) detector. An offline algorithm is designed to reconstruct scattering spectra. Appropriate shielding structure is set up to reduce the number of transmission photons from accelerator target and scattering photons in environment that enter the detector. These designs ensure effective acquisition of scattering photons in the intense pulsed radiation field. We investigated 10 materials with Z from 13 to 82. Preliminary experimental results show that Z of different materials can be determined successfully.