MEASUREMENT OF GAMMA-RAY DOSE RATE USING SMARTPHONES

The CMOS (Complementary Metal Oxide Semiconductor) image sensor of a smartphone has been known for its sensitivity to gamma-rays. In this research, the four models of smartphones (Samsung Galaxy GT-S5570 mini, Samsung Galaxy SII, Samsung Galaxy SIII and Huawei Ascend P7) were selected and tested for measurement of gamma-rays emitted from Iridium-192, Cobalt-60 and Cesium-137 sources. During measurements, the phones were set in video mode while the camera lenses were covered with black adhesive tape to prevent light exposure. Interaction of gamma-rays with the CMOS clearly appeared as flashing bright spots on the dark background image. The bright spots were then counted by the freely available ImageJ software. Preliminary results indicated that the number of bright spots increased linearly with increasing gamma-ray dose rate from these three sources. Among these four models of smartphone, Huawei Ascend P7 gave the highest sensitivity and the second was Samsung Galaxy SIII. Then Huawei Ascend P7 and Samsung Galaxy SIII were calibrated and tested in measurement of gamma-ray dose rate in comparison with the known values and with the dose rate survey meter. The results were very satisfactory. Application software for Android smartphones was finally developed so that the number of bright spots could be simultaneously counted and converted to gamma-ray dose rate to display on the smartphones.