Calibration of spectrometric detectors for air kerma rates in environmental monitoring

Abstract

The spectrometric systems, especially based on NaI(Tl) and HPGe detectors, are used for nuclide identification and calculation of their activities from the ground measurements and air-borne monitoring. The determination of the air kerma (dose) rates is also very important for environmental measurements. In such cases, the detectors should be calibrated for air kerma (dose) rates in nGyh–1 or µGyh–1. A simple calibration of NaI(Tl), HPGe as well as plastic detectors for the low-level air kerma rates is presented in this contribution. This calibration is based on comparing the relative absorbed energy rate in detectors (MeVs–1) calculated from spectra with the air kerma rates calculated by the Monte Carlo simulation and supplementary to the data from the RSS Reuter&Stokes high pressure ion chamber. This method also eliminates the conversion from the non-air kerma rates in crystals to the air kerma rates. Three different types of small cylindrical detectors were calibrated for the air kerma rates from the background of 26 nGyh–1 to some tens of µGyh–1 in the energy range to the maximum of 3 MeV. The results of calibrations of the 3" x 3" NaI(Tl), HPGe detector and a small plastic detector (made of polystyrene) including soxme examples of environmental measurements are presented.

Keywords

• air kerma rate calibration
• nai(tl)
• hpge and plastic detector
• monte carlo simulation