DEVELOPMENT AND TESTING OF A NOVEL GAMMA RAY CAMERA FOR RADIATION SURVEYING, CONTAMINATION MEASUREMENT AND RADIATION DETECTION

This paper records the design and operation of a novel gamma-ray camera device. The instrument combines in one detector head a sensitive and highly collimated LaBr3 scintillation detector with an optical (video) camera with controllable zoom and focus and a laser range finder. The LaBr3 detector resolution is nearly three times that of NaI. The detector is housed in an effective tungsten shield, which provides a shielding ratio of 50:1 in the forward direction and 10:1 on the sides and to the rear for incident 1,500 keV gamma-rays. The detector head is mounted on a pan/tile mechanism with a range of motion of 360 degrees (pan) and +/- 90 degrees (tilt). The detector head with pan/tilt is normally mounted on a tripod but can also be mounted on vehicles or a mobile robot for access to high dose-rate areas. A single combined power and communication cable of up to 100 metres connects the detector head to a distant operator station. This consists of a small power supply box connected to 110 or 230 VAC and a notebook computer. Operation of the detector head with all of its measuring functions is controlled from the notebook computer over Ethernet. The unit can be powered from a 24 volt battery and be controlled using wireless Ethernet for remote operation. The device is portable and can be deployed readily indoors or in the field by an operator. Software allows both automatic and manual operation and an operator can specify coordinates to search a specific position or area or a search can be conducted automatically in 4p steradians, using the full capabilities of the pan/tilt mechanism. Each gamma-ray measurement captures an entire spectrum for each incremental measurement position. From each spectrum a number of pre-set gamma-ray regions of interest corresponding to radionuclide peaks can be obtained. The unit reports the intensity (dose-rate) and activity for a variety of pre-selected radionuclides at different positions in relation to a video image. The results of Monte Carlo MCNP modelling are compared with measurements of radioactive sources.