Prospects for the use of the dosimeters with Geiger-Muller counters for the dosimetry of the pulse emission

Abstract

At the current time radiation therapy units based on the linear accelerators with the energy range of 1823 MeV are common in the Russian Federation. They generate pulsed bremsstrahlung radiation with the maximum energy of approximately 20 MeV. The State Register of measuring devices contains no dosimetry equipment for the measurement of the pulsed bremsstrahlung radiation for such energies. The most common dosimeter of X-ray and gamma radiation, DKS-1123AT, allows measuring the pulsed bremsstrahlung radiation up to 10 MeV, with the main uncertainty of measurement in the range of 3-10 MeV of 50%. No alternative solutions exist at the current time. Although the contribution of this part of the bremsstrahlung radiation spectra is not high, the situation requires actions. However, the State Register of measuring devices includes the DKG-RM1621 dosimeter for the measurement of X-ray and gamma radiation in the energy range of 15 KeV — 20 MeV, but it is now designedfor the measurement of the pulse emissions. The current study is focused on the evaluation of the use of the DKG-RM1621 dosimeterfor the measurement of the pulsed bremsstrahlung radiation and on the estimation of the dose rate range, where the results of the measurements would be valid. The study was performed using the inspection-security complex ST-2630M (JSC “Scantronix systems”) as the source of the pulsed bremsstrahlung radiation with the maximum energy of 3,5 and 6 MeV. This energy range is valid for the DKS-1123AT dosimeter, allowing using it for the comparison. The results indicate that, for the current source,the DKG-RM1621dosimter allows performing the measurements with the additional uncertainty up to 15%, with the mean dose rate of pulsed bremsstrahlung radiation up to 25 µ Sv/h. That is acceptable for the radiation control of the rooms adjacent to the location of a linear accelerator. The use of the additional coefficients to consider the impact of the idle time of the detector on the results of the measurements allows measuring dose rates up to 100 µ Sv/h.