Optical Screen Processed Using Laser Beam for Pixel Array of High- Z Plastic Scintillator

When a high-Z (atomic number) metal-oxide nanoparticle-loaded plastic scintillator (High-Z PLS) is mounted onto a fast pixelated photodetector, such as a silicon avalanche-photodiode array, high detection efficiency for high energy X-rays can be added to nanosecond response. To provide a spatial resolution of
$\lt 100~\mu $
m, an optical screen between the pixels of the High-Z PLS is required to prevent light leakage from neighboring pixels. In this study, we attempted to form such an optical screen on a sample of 20 wt% hafnium-oxide nanoparticle-loaded PLS (Hf-PLS) using a focused laser beam. Optical transmittance of the laser-irradiated tracks was investigated. A significant decrease of 38.5% in the transmittance at 380–420 nm, which corresponds to the scintillation-light wavelength, was observed on the track. Three laser tracks with 3.2-mm pitch were formed in a 1-mm-thick sample of 20 wt% Hf-PLS with dimensions of
$^{V}2.4$
mm
$\times ^{H}12.3$
mm
$\times ^{t}1$
mm. An SiPM array coupled with the sample was used to obtain the X-ray count distribution over the tracks using a 60-keV X-ray beam. The screen width of reducing scintillation light was measured to be 120–
$250~\mu $
m [full-width at half-maximum (FWHM)] with a 30-
$\mu $
m-diameter pinhole X-ray beam.