M.L. McConnell, J.R. Macri, and J.M. Ryan

Space Science Center, Morse Hall, University of New Hampshire, Durham, NH 03824

We have developed a modular design for a Compton scatter polarimeter that can be used for studying the polarization of hard X-rays (50-300 keV) from solar flares. A complete polarimeter module is designed to fit on the front end of a 5-inch position-sensitive photomultiplier tube (PSPMT). The PSPMT is used to determine the Compton interaction location within an annular array of small plastic scintillator elements. Some of the photons that scatter within the plastic scintillator are subsequently absorbed by a small centrally-located array of CsI crystals that is read out by an independent multi-anode PMT. The independence of the two PMT readout schemes provides appropriate timing information. For a detector depth of 10 cm, the performance is optimized at about 200 keV, where the effective area for polarization measurements is 3cm² and the polarization modulation factor is 55%. We have recently been conducting laboratory tests using a science model based on this design concept. These tests are designed to evaluate the performance characteristics of the design and to more fully validate our Monte Carlo simulation code. Here we shall review the characteristics of this modular design, discuss possible implementation strategies, report on the results from the laboratory tests, and compare those results with simulations. We will also outline our plans for future development, including the possibility of incorporating such detectors into an imaging polarimeter.