We present a concept for an Advanced Compton Telescope (ACT) based on the use
of pixelized gas micro-well detectors to form a three-dimensional electron
track imager. A micro-well detector consists of an array of individual
micro-patterned proportional counters opposite a planar drift electrode. When
combined with thin film transistor array readouts, large gas volumes may be
imaged with very good spatial and energy resolution at reasonable cost. The
third dimension is determined from the drift time of the ionization electrons.
The primary advantage of this approach is the excellent tracking of the Compton
recoil electron that is possible in a gas volume. Such good electron tracking
allows us to reduce the point spread function of a single incident photon
dramatically, greatly improving the imaging capability and sensitivity. The
polarization sensitivity, which relies on events with large Compton scattering
angles, is particularly enhanced. We describe a possible ACT implementation of
this technique, in which the gas tracking volume is surrounded by a CsI
calorimeter, and present our plans to build and test a small prototype over the
next three years.
