A New Method for Remote Detection of Ionizing Radiation Using Transient Optical Absorption

Increasing demand for the detection of high-intensity ionizing radiation, especially the neutron radiation, puts forward the challenge to substantially enhance the radiation hardness of radiation detectors. We suggest an approach to meet this challenge by introducing an all-optical method to gauge the irradiation flux by radiation-induced modulation of the optical absorption coefficient in radiation-hard single crystals. We demonstrate the feasibility of this approach by using the transient absorption modulation caused by nonequilibrium charge carriers created in Gd2Al2Ga3O12:Ce (GAGG:Ce) crystal by the radiation to be detected. To optimize the detection unit, we mimicked the effect of ionizing radiation by using laser pulses to generate the nonequilibrium electron–hole pairs. The best sensitivity was obtained by exploiting multi-pass transitions of the probing laser beam in the GAGG:Ce single crystal with inclined opposite sides. The optimized system was then applied for the detection of X-ray pulses, and sufficient sensitivity and good linearity of its response was demonstrated. In the presented detection scheme, the radiation-hard detecting crystal is the only part of the system exposed to irradiation, enabling the system to be used for monitoring high-intensity neutron sources.