TRACKING, IMAGING AND POLARIMETER PROPERTIES OF THE TIGRE INSTRUMENT

The Tracking and Imaging Gamma-Ray Experiment (TIGRE) was designed to observe cosmic gamma ray sources at energies of 0.3 to 100 MeV. It use s multi- layer silicon strip detectors to track Compton recoil electro ns and positron- electron pairs and small CsI(Tl) crystals to measure the position and energy of the scattered photon. The energy and moment um of the scattered electron and the scattered photon allows the deter mination of the incident direction uniquely. Traditional Compton teles copes all use a time-of-flight between two detectors, whereas TIGRE us es the electron track in the silicon strips to distinguish between upw ard and downward moving photons. This allows one to decrease the dista nce between the two detection arrays thereby increasing the instrument efficiency significantly. TIGRE is also a gamma-ray polarimeter, maki ng use of the sensitivity of the Klein-Nishina cross section for large Compton scatter events. We discuss the results of the up/down trackin g discrimination, CLAD imaging and the polarimetry properties of TIGRE .