Experiment investigation on pulsed gamma-ray fluence rate effect on Yb-doped yttrium aluminum garnet scintillator.

As an ultrafast inorganic scintillator, Yb-doped Y3Al5O12 [yttrium aluminum garnet (YAG)] crystals have potential applications in various fields, such as ultrafast radiation detection, solar neutrino detection, pulsed radiation imaging, and nuclear reaction kinetics diagnosis. In this work, the fluence rate effect of pulsed γ rays on the Yb:YAG scintillation crystal was investigated at the "QiangGuang-I" facility. The experiment results show that the fluence rate linear response upper limit of the Yb:YAG crystal is about 9.1 × 1018 MeV cm-2 s-1. The Yb:YAG crystal changed from colorless to yellow, and the relative light output decreased to 63% of its initial value after the irradiations, which were attributed to the radiation induced damage. It is deduced that oxygen vacancies and divalent Yb cations were generated after the irradiations.

Experimental study on the fluorescence spectrum in the near-ultraviolet and visible regions of a carbon dioxide gas Cerenkov medium.

We investigated the faint fluorescence spectrum of carbon dioxide in the near-ultraviolet and visible regions using an intense relativistic electron beam accelerator with an energy of 0.2-0.3 MeV. Monte Carlo simulations were carried out in advance to maximize the signal-to-noise ratio and a self-normalization pulse experimental layout was designed to overcome the shot-to-shot fluctuations in different pulses of the accelerator. Ultimately, the relative proportion sequences in the near-ultraviolet and visible regions of a carbon dioxide fluorescence spectrum were successfully obtained for the first time. The result shows that there exists distinct difference between fluorescence spectrum and Cerenkov spectrum, which can therefore provide basic support for selectively reducing the unwanted below-threshold fluorescence response of a carbon dioxide gas Cerenkov medium.

Development of a fast radiation detector based on barium fluoride scintillation crystal.

Barium fluoride (BaF2) is an inorganic scintillation material used for the detection of X∕gamma radiation due to its relatively high density, equivalent atomic number, radiation hardness, and high luminescence. BaF2 has a potential capacity to be used in gamma ray timing experiments due to the prompt decay emission components. It is known that the light output from BaF2 has three decay components: two prompt of those at approximately 195 nm and 220 nm with a decay constant around 600-800 ps and a more intense, slow component at approximately 310 nm with a decay constant around 630 ns which hinders fast timing experiments. We report here the development of a fast radiation detector based on a BaF2 scintillation crystal employing a special optical filter device, a multiple reflection multi-path ultraviolet region short-wavelength pass light guides (MRMP-short pass filter) by using selective reflection technique, for which the intensity of the slow component is reduced to less than 1%. The methods used for this study provide a novel way to design radiation detector by utilizing scintillation crystal with several emission bands.