A Transmissive X-ray Polarimeter Design For Hard X-ray Focusing Telescopes

摘要

The X-ray Timing and Polarization (XTP) is a mission concept for a futurespace borne X-ray observatory and is currently selected for early phase study.We present a new design of X-ray polarimeter based on the time projection gaschamber. The polarimeter, placed above the focal plane, has an additional rearwindow that allows hard X-rays to penetrate (a transmission of nearly 80% at 6keV) through it and reach the detector on the focal plane. Such a design is tocompensate the low detection efficiency of gas detectors, at a low cost ofsensitivity, and can maximize the science return of multilayer hard X-raytelescopes without the risk of moving focal plane instruments. The sensitivityin terms of minimum detectable polarization, based on current instrumentconfiguration, is expected to be 3% for a 1mCrab source given an observing timeof 10^5 s. We present preliminary test results, including photoelectron tracksand modulation curves, using a test chamber and polarized X-ray sources in thelab.