Field test around Fukushima Daiichi Nuclear Power Plant site using improved Ce:Gd(Al,Ga)O scintillator Compton camera mounted on an unmanned helicopter

Shikaze, Yoshiaki ; Nishizawa, Yukiyasu; Sanada, Yukihisa   ; Torii, Tatsuo  ; Jiang, J.*; Shimazoe, Kenji*; Takahashi, Hiroyuki*; Yoshino, Masao*; Ito, Shigeki*; Endo, Takanori*; Tsutsumi, Kosuke*; Kato, Sho*; Sato, Hiroki*; Usuki, Yoshiyuki*; Kurosawa, Shunsuke*; Kamada, Kei*; Yoshikawa, Akira*

The Compton camera was improved for use with the unmanned helicopter. Increase of the scintillator array from 44 to 88 and expanse of the distance between the two layers contributed to the improvements of detection efficiency and angular resolution, respectively. Measurements were performed over the riverbed of the Ukedo river of Namie town in Fukushima Prefecture. By programming of flight path and speed, the areas of 65 m 60 m and 65 m 180 m were measured during about 20 and 30 minutes, respectively. By the analysis the air dose rate maps at 1 m height were obtained precisely with the angular resolution corresponding to the position resolution of about 10 m from 10 m height. Hovering flights were executed over the hot spot areas for 10-20 minutes at 5-20 m height. By using the reconstruction software the -ray images including the hot spots were obtained with the angular resolution same as that evaluated in the laboratory (about 10).