Range-Finding Sensor Degradation in Gamma Radiation Environments

The effects of gamma radiation on common sensors used in robots intended for nuclear remediation scenarios are examined. Commercial rangefinders are chosen as an exemplar of the impact of gamma radiation on sensors and systems. This paper illustrates sensor radiation degradation not only in operational failure, but also in changes in the sensor transfer function. Three types of commercial range-finding sensors are considered [infrared (IR) triangulation using a position sensitive detector, sonar using time of flight, and laser rangefinder using triangulation and a CMOS camera]. Experimental results show significant changes in the IR sensor's static sensitivity with dose, abrupt failure of the laser range finder at low dose, and degradation and abrupt failure for the sonar detector. The input-output relationship of the IR sensor showed further variation after a period of room-temperature annealing. Significant part-to-part variation in radiation response is shown for both the sonar and IR sensor. System level impacts due to sensor input-output relationship degradation and a technique to diagnose the degradation extendable to more complex sensor assemblies are presented.