Prospects on Low-Z Elements K Fluorescence and Actinide-Radionuclides L Fluorescence X-Ray Detection With Cooled CZT

Abstract

In the present study, we show that CZT detectors can be used in a wide X-ray energy range including low-energy X-rays down to 2.1 keV at $ - 17^{\circ} {\rm C}$ which may be extended down to 1.5 keV by additional cooling to $ - 26^{\circ} {\rm C}$ . CZT detector was operated in the low energy X-ray band ${ to detect the K fluorescence X-rays emitted by low-Z elements, such as Ca, K, Cl, S, and eventually even further P, Si, Al. Additionally, it was demonstrated the fine spectroscopic features of the CZT detector cooled to $ - 26^{\circ} {\rm C}$ , which make it suitable for the detection of L fluorescence X-rays emitted by high-Z elements in the $\sim 11 - 22~\hbox{keV}$ range, such as Th, Pa, U, Np and Pu, resulting from the decay of actinide radionuclides ${}^{234}{\rm U}{/^{235}}{\rm U}{/^{238}}{\rm U}$ , ${}^{237}{\rm Np}{,^{238}}{\rm Pu}{/^{239}}{\rm Pu}$ , ${}^{241}{\rm Am}$ and ${}^{244}{\rm Cm}$ , respectively. With this cooled CZT detector it was possible to resolve the main L X-ray lines as well as to measure its intensity. The relative intensity obtained for the Pu L X-ray lines ${{\rm L}_l}$ , ${{\rm L}_{\alpha 1,2}}$ , ${{\rm L}_{\beta 6,\eta }}$ , ${{\rm L}_{\beta 2,4}}$ , ${{\rm L}_{\beta 1,3,5}}$ , and ${{\rm L}_{\gamma 1,2,3,6}}$ was, respectively, $7.1 \pm 2.3$ , $100 \pm 2.5$ , $5.6 \pm 2.3$ , $31.9 \pm 2.5$ , $103.2 \pm 2.4$ and $29.8 \pm 2.2$ . The Np L X-ray most intense lines ${{\rm L}_{\alpha 1,2}}$ , ${{\rm L}_{\beta 2,4}}$ , ${{\rm L}_{\beta 1,3,5}}$ , and ${{\rm L}_{\gamma 1}}{,_{2,3,6}}$ yielded a relative intensity of $100 \pm 4.2$ , $36.4 \pm 3.3$ , $96.2 \pm 5.0$ and $34.3 \pm 3.7$ , respectively. The overall results are in good agreement with the values found in literature. The principal performance features of the CZT detector were, also studied experimentally or estimated from data tabulated in the literature. Notably, we found a $\sim 2.5$ -fold diminution of the electronic noise FWHM temperature sensitivity (from $\sim 41$ to $\sim 16~\hbox{eV}/^{\circ} {\rm C}$ ) and thus of the equivalent noise charge temperature sensitivity (from $\sim 3.8$ to $\sim 1.5{{\rm e}^ - }/^{\circ} {\rm C}$ ) when the temperature decreases from $ - 1$ to $ - 26^{\circ} {\rm C}$ . The influence of several properties, such as the charge mobility and lifetime, band gap energy, detector’s leakage current and capacitance, on CZT detector performance features was also addressed.