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This paper discusses the latest progress in the development of GRAPE(Gamma-Ray Polarimeter Experiment), a hard X-ray Compton Polarimeter. Thepurpose of GRAPE is to measure the polarization of hard X-rays in the 50-300keV energy range. We are particularly interested in X-rays that are emittedfrom solar flares and gamma-ray bursts (GRBs). Accurately measuring thepolarization of the emitted radiation from these sources will lead, to a betterunderstating of both the emission mechanisms and source geometries. The GRAPEdesign consists of an array of plastic scintillators surrounding a centralhigh-Z crystal scintillator. We can monitor individual Compton scatters thatoccur in the plastics and determine whether the photon is photo absorbed by thehigh-Z crystal or not. A Compton scattered photon that is immediately photoabsorbed by the high-Z crystal constitutes a valid event. These valid eventsprovide us with the interaction locations of each incident photon andultimately produces a modulation pattern for the Compton scattering of thepolarized radiation. Comparing with Monte Carlo simulations of a 100% polarizedbeam, the level of polarization of the measured beam can then be determined.The complete array is mounted on a flat-panel multi-anode photomultiplier tube(MAPMT) that can measure the deposited energies resulting from the photoninteractions. The design of the detector allows for a large field-of-view (>pisteradian), at the same time offering the ability to be close-packed withmultiple modules in order to reduce deadspace. We plan to present in this paperthe latest laboratory results obtained from GRAPE using partially polarizedradiation sources.Comment: 10 pages; conference paper presented at the SPIE conference "UV,  X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XIV." To be  published in SPIE Conference Proceedings, vol. 589

Developing a Compton polarimeter to measure polarization of hard x-rays in the 50-300 keV energy range