Development of Si-CMOS hybrid detectors towards electron tracking based Compton imaging in semiconductor detectors

TL;DR

This paper introduces Si-CMOS hybrid detectors for electron tracking in Compton imaging, demonstrating successful electron trajectory imaging and energy resolution improvements in prototype tests.

Contribution

It proposes a novel Si-CMOS hybrid detector concept and demonstrates its capability for electron tracking in semiconductor Compton cameras.

Findings

Successful imaging of recoiled electron trajectories

Energy resolutions of 4.1 keV (CMOS) and 1.4 keV (N-side) at 59.5 keV

Initial electron direction determined using graph theory algorithm

Abstract

Electron tracking based Compton imaging is a key technique to improve the sensitivity of Compton cameras by measuring the initial direction of recoiled electrons. To realize this technique in semiconductor Compton cameras, we propose a new detector concept, Si-CMOS hybrid detector. It is a Si detector bump-bonded to a CMOS readout integrated circuit to obtain electron trajectory images. To acquire the energy and the event timing, signals from N-side are also read out in this concept. By using an ASIC for the N-side readout, the timing resolution of few us is achieved. In this paper, we present the results of two prototypes with 20 um pitch pixels. The images of the recoiled electron trajectories are obtained with them successfully. The energy resolutions (FWHM) are 4.1 keV (CMOS) and 1.4 keV (N-side) at 59.5 keV. In addition, we confirmed that the initial direction of the electron is determined using the reconstruction algorithm based on the graph theory approach. These results show that Si-CMOS hybrid detectors can be used for electron tracking based Compton imaging.