Development of α-ray visualization survey meter in high gamma and neutron background environment.

Abstract

A survey meter was developed to reliably detect and visualize surface contamination of suits and objects by α-nuclides in high γ/n-rays background radiation environment. The survey meter features a semi-opaque ZnS:Ag scintillator mounted directly onto a multi-anode photomultiplier tube (MA-PMT) and amplification circuits, ensuring output gain equalization for all channels. α-ray events induce localized light emission in thin-film scintillators. By directly mounting the scintillator, diffusion of light before reaching the MA-PMT is suppressed, concentrating it in just a few channels, thereby facilitating discrimination from background radiation. This design also enables clear visualization of the shape of surface contamination. The prototyped survey meter is capable of responding up to 2.1 × 107 cpm, with no γ-ray response even in high-radiation environments exceeding 1 Sv/h. In actual environments with high background radiation, contamination of ~1/100th of the surface contamination density limit of 4 Bq/cm2 could be reliably detected.