Imaging of hard x-ray radiations using Gafchromic™ dosimetry film in Damavand tokamak

Abstract

In the present study, a series of experiments were performed to study collisions of runaway electrons in the Damavand tokamak by imaging hard x-ray radiations, as one of the secondary effects of these electrons, using radiochromic films. For these experiments, GAFCHROMIC™EBT2 dosimetry films were selected due to their high resolution imaging capability. These instruments were installed in two strip and screen structures for one- and two-dimensional imaging in high-dose areas of the Damavand tokamak, and after irradiation on the device, the recorded data were extracted using a flatbed scanner. The results showed that in runaway discharges of the Damavand tokamak, if active plasma position control system is off, predominant collision of the runaway electrons column occurs with outer wall of the vacuum chamber. Also, the recorded images indicated that dimensions of temporary sources of hard x-rays in the Damavand tokamak are about 10 cm × 10 cm. Two-dimensional imaging in these experiments showed that toroidal field coils are exposed to significant hard x-ray radiations, making the use of radiation-sensitive diagnostic systems in this area questionable. The results obtained from measurements also indicated that the highest radiation dose in the Damavand tokamak is in the limiter region and reaches up to 300 mSv shot−1.