Development of a hard X-ray polarimeter for solar flares and gamma-ray bursts

We describe recent work on the development of a Compton scatter polarimeter for measuring the polarization of hard X-rays (100-300 keV) from astrophysical sources. Results from measurements with a laboratory prototype are summarized, along with comparisons to Monte Carlo simulations. We also present our latest design concept, which envisions a complete polarimeter module on the front end of a 5-inch position-sensitive PMT. Although the emphasis of our development effort is towards measuring hard X-rays from solar flares, our latest design has the advantage that it is sensitive over a rather large field-of-view (> 1 steradian), a feature that makes the design especially attractive for gamma-ray burst studies.