| This thesis begins with a current review of the state of high energy {dollar}gamma{dollar}-ray astronomy. Thereafter, the operating principles of the EGRET {dollar}gamma{dollar}-ray telescope are stated, together with the performance originally expected. The mechanical design and assembly of the large total absorption, or TASC, detector for EGRET is then described, followed by a review of the measurements made and actions taken to assure the integrity of the TASC detector in the five-year period between assembly and launch. A description of the electronic system associated with TASC is then provided, together with its operation in coordination with the rest of the EGRET telescope. The results of an initial exploration and calibration of the TASC detector alone in a positron beam at SLAC are then discussed. Thereafter, the design of an experiment to calibrate the fully assembled EGRET detector in a calibration {dollar}gamma{dollar}-ray beam at SLAC is described. The results of this calibration relating particularly to the performance of the TASC detector are then outlined. Finally, a recalibration experiment conducted two years later at the MIT Bates Accelerator Center is discussed. |
