7 Conclusions

Event reconstruction in future high resolution Compton telescopes will present a number of complications compared to historical configurations. The initial complication of multiple-scattering of photons in GCTs, however, turns out to be an advantage: the application of CKD to 3+ site events, combined with the high spectral and spatial resolution of GeDs, allows extremely efficient background suppression, crucial for Compton telescope performance. This paper has outlined a set of tests and restrictions, accounting for realistic instrument/detector performance, to reconstruct photopeak events in GCTs while rejecting a large fraction of the background events. Table 2 presents the fraction of events, photon and background, that remain after each rejection technique is subsequently applied. (The numbers in Table 2 assume only W₁ is tested for $\beta ^{-}$ decay energies.) Development of these event reconstruction techniques allows realistic evaluation of the performace and sensitivity of GCT designs. Our next goal is to simulate the efficiency, resolution, background and sensitivity of several Compton telescope configurations, utilizing the event reconstruction techniques developed here to realistically determine the performace of these instruments. CKD rejection has been shown to be the most efficient background rejection technique; however, the addition of effective TOF, backscatter, nonlocalized $\beta ^{-}$ decay, and positron signature tests dramatically improve background rejection capabilities. We anticipate that use of these techniques will achieve overall sensitivity improvements in GCTs by factors of $\sim 5-10$.

Acknowledgements

S.E. Boggs would like to thank the Millikan Postdoctoral Fellowship Program, CIT Deparment of Physics, for support.