Heat Shield Ablation Sensor Utilizing CdTe Gamma Detectors

A miniaturized, flight proven gamma sensor embodying a CdTe device has been developed for applications of gamma backscatter to measurement of heat shield recession and nosetip shape change. A 10 mm diameter by 2 mm thick chlorine doped CdTe gamma detector operated at circa 50 volts bias was combined with an unusual preamplifier employing tripolar pulse shaping. The package, which incorporates mechanical isolation, damping, and component rigidization, has operated satisfactorily under test at a random vibration level of 2 gc2/Hz and peak sinusoidal acceleration of 10,000 ge at a frequency of 24 kHz. Several of these gamma sensors have been flown in a single vehicle to obtain measurements of changes in nosetip shape.