This paper reviews the development status of GRAPE (the Gamma-Ray Polarimeter
Experiment), a hard X-ray Compton Polarimeter. The purpose of GRAPE is to
measure the polarization of hard X-rays in the 50-300 keV energy range. We are
particularly interested in X-rays that are emitted from solar flares and
gamma-ray bursts (GRBs), although GRAPE could also be employed in the study of
other astrophysical sources. Accurately measuring the polarization of the
emitted radiation will lead to a better understating of both emission
mechanisms and source geometries. The GRAPE design consists of an array of
plastic scintillators surrounding a central high-Z crystal scintillator. The
azimuthal distribution of photon scatters from the plastic array into the
central calorimeter provides a measure of the polarization fraction and
polarization angle of the incident radiation. The design of the detector
provides sensitivity over a large field-of-view (>pi steradian). The design
facilitates the fabrication of large area arrays with minimal deadspace. This
paper presents the latest design concept and the most recent results from
laboratory tests of a GRAPE science model.
