Micromachined Si-Well Scintillator Pixel Sensors for Thermal Neutron Detection

Abstract

With the introduction of new high-intensity neutron sources new sensors have to be developed for thermal neutrons combining high spatial resolution, fast response and high detection efficiency. The sensors are intended for energy selective imaging with pulsed neutron sources. This requires time resolved detection on a microsecond scale, ruling out CCD’s for scintillation light readout. In order to achieve these characteristics we have proposed a new type of position sensitive sensor for thermal neutrons, which consists of a matrix of well-type silicon sensors filled with 6Li6 158Gd(BO3)3 (Ce3+) scintillation powder [1], [2]. The neutron detection is based on the 6Li (n,α) reaction, which produces in the scintillation material ∼35000 photons. The emitted light is confined by the vertical silicon sidewalls, is reflected at the top by several layers of Teflon tape and observed by means of silicon photodiodes in the bottom of the wells. In this paper we present a matrix of 700 µm wide well sensors at pitches of 0.9 and 1 mm, which allows millimeter spatial resolution.