Gas Microchannel Plate–Pixel Detector for X-ray Polarimetry

Abstract: POLAR-2 is a gamma-ray burst (GRB) polarimeter that is designed to study the polarization in GRB radiation emissions, aiming to improve our knowledge of related mechanisms. POLAR-2 is expected to utilize an on#2;board polarimeter that is sensitive to soft X-rays (2–10 keV), called low-energy polarization detector (LPD). We have developed a new soft X-ray polarization detector prototype based on gas microchannel plates (GMCPs) and pixel chips (Topmetal). The GMCPs have bulk resistance, which prevents charging-up effects and ensures gain stability during operation. The detector is composed of low-outgassing materials and is gas-sealed using a laser welding technique, ensuring long-term stability. A modulation factor of 41.28% ± 0.64% is obtained for a 4.5 keV polarized X-ray beam. A residual modulation of 1.96% ± 0.58% at 5.9 keV is observed for the entire sensitive area.