Dose mapping of hard X-ray radiation due to runaway electrons in Alvand tokamak using combination of high-dose and low-dose level dosimeters

Tokamaks are one of the strongest types of hard x-ray (HXR) sources that always generate energetic hard x-rays because of the bremsstrahlung radiation, when energetic runaway electrons are accelerated in the presence of the toroidal electric field. In addition, the characteristics of small-sized tokamaks make them capable of having a considerable population of runaway electrons during discharge time. In this research, the hard x-ray dose distribution of Alvand tokamak is measured and calculated using EBT3 radiochromic film and GR-200 TLD as a high-dose and low-dose dosimeters, respectively. The purpose of this measurement is to obtain a dose distribution map in the Alvand tokamak laboratory (35 m x 13 m) and its environment. It has been determined that the maximum absorbed dose on the equatorial plane of the vacuum chamber is approximately 73 mSv/shot for a 3 ms discharge. According to the observations, the occurrence of Z instability in the vertical position of the plasma leads to the concentration of a substantial amount of radiation in an upward conical shell, which reaches up to 250 mSv/shot at a 60-degree angle above the horizontal line. Calculating the amount of radiation attenuation of the concrete shield installed in the vicinity of Alvand tokamak Laboratory, which is about 99.3 % +/- 0.35, is an important result from the radiation protection point of view. This result indicates that the dose limit in public area is about background level and this area is effectively protected from the intense radiation of Alvand tokamak by the concrete shield.