In a collaborative R&D project organized by Japan's Science and Technology Agency, Professor Jun Kataoka of Waseda University's Research Institute for Science and Engineering and Hamamatsu Photonics have been developing a compact Compton camera employing the company's Multi Pixel Photon Counter (MPPC). The first achievement, a 1.9kg Compton camera, was announced last September and several local governments are already using it in decontamination operations to deal with radioactive material scattered from the stricken Fukushima Daiichi Nuclear Power Plant.

The first version of the Compton camera announced last September detects radiation 2-dimensionally, horizontally and vertically. In the second version, the Waseda team added a 3D location measurement capability by segmenting the scintillator into approximately 2mm blocks with reflector film to detect depth.

The new camera, therefore, can detect the depth, too. The size is about the same though the camera is somewhat heavier at 2.5 kg, but the resolution is almost double the first version's, having been improved from 14 degrees to 8 degrees—if two hot spots exist in a angle of 14 degrees, the first camera detects them as one spot, but the new camera detects them as two spots—and sensitivity is 70% better, according to Kataoka.

The development team believes that the first-version camera has sufficient performance for decontamination work, and emphasizes the new camera's potential for wider applications in such fields as medicine and space.

They intend to elaborate the new version of the camera, fine-tuning it for particular applications. With the Fukushima cleanup in mind, the two versions of the camera are designed on the basis of about 10microSv/h detection. But for applications involving stronger radiation, a smaller camera could be designed, according to Kataoka.

Press releases:
Compton camera with higher sensitivity developed (Japanese only)
Hamamatsu releases a compact Compton camera to facilitate the work of radiation decontamination (Set. 10, 2013)