Gamma-ray imaging with a large micro-TPC and a scintillation camera

Abstract

We report on the development of a large Compton camera with the full reconstruction of the Compton process based on a prototype. This camera consists of two kinds of detectors. One is a gaseous time projection chamber (micro-TPC) for measuring the energy and the track of a Compton recoil electron. The micro-TPC is based on a μ -PIC and a GEM, which are micro-pattern gas detectors (MPGDs). The size of the micro-TPC was 10 cm × 10 cm × 8 cm in the case of the prototype, and we enlarged it to 23 cm × 28 cm × 15 cm . The other detector part is a NaI (Tl) Anger camera for measuring the scattered gamma-ray. With these informations, we can completely reconstruct a Compton event, and determine the direction of the incident gamma-ray, event by event. We succeeded in reconstructing events of incident 662 keV gamma-rays. The measured angular resolutions of the “angular resolution measure” (ARM) and the “scatter plane deviation” (SPD) were 9 . 3 ∘ and 158 ∘ (FWHM), respectively.