Assembly and Test of the Gas Pixel Detector for X-ray Polarimetry

Abstract

The gas pixel detector (GPD) dedicated for photoelectric X-ray polarimetry is selected as the focal plane detector for the ESA medium-class mission concept X-ray Imaging and Polarimetry Explorer (XIPE). Here we show the design, assembly, and preliminary test results of a small GPD for the purpose of gas mixture optimization needed for the phase A study of XIPE. The detector is assembled in house at Tsinghua University following a design by the INFN-Pisa group. The improved detector design results in a good uniformity for the electric field. Filled with pure dimethyl ether (DME) at 0.8 atm, the measured energy resolution is 18% at 6 keV and inversely scales with the square root of the X-ray energy. The measured modulation factor is well consistent with that from simulation, up to ~0.6 above 6 keV. The residual modulation is found to be 0.30% +/- 0.15% at 6 keV for the whole sensitive area, which can be translated into a systematic error of less than 1% for polarization measurement at a confidence level of 99%. The position resolution of the detector is about 80 um in FWHM, consistent with previous studies and sufficient for XIPE requirements.

accepted for publication in Nuclear Instruments and Methods in Physics Research Section A (NIMA)

References in corpus (4)

• A Sealed Gas Pixel Detector for X-ray Astronomy
• Direct reading of charge multipliers with a self-triggering CMOS analog chip with 105k pixels at 50 micron pitch
• X-ray Polarimetry: a new window on the high energy sky
• A versatile facility for the calibration of X-ray polarimeters with polarized and unpolarized controlled beams

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