Improved designs for isocon cameras in HERTR systems

The HERTR imaging systems are experiencing Isocon tube failures at a rate which is not typical of more intensely used imaging systems containing Isocon tubes. Heat is the usual cause for early Isocon tube failures. A HERTR system was visited and it was decided that, indeed, heat was the probable cause for a failure. A mechanical design was prepared which was as similar as possible to the major confining structure surrounding the HERTR camera. In subsequent tests with the duplicate structure, the thermal failure mode was duplicated without continuing the tests to completion. A design change was initiated and tested with the duplicate system. Thermal characteristics of the altered system were measured. Additional deficiencies in the HERTR imaging system were noted during the course of the visit to the HERTR site. These deficiencies are also described in this report. Recommendations are made to alter the HERTR design to include the modifications made to the duplicate camera design. In the short term these modifications are simple and inexpensive to implement. Recommendations are also included for an extensive modification to high energy imaging systems, particularly those subject to pulsed operating conditions and to those operating in photon limited situations which is usual in X-ray imaging systems.