High-purity Germanium Detector With A Shield, Collimator Emergency Early

There is an important practical value to employ an airborne HPGe detector to the monitoring in an early phase of a nuclear accident, or in the period of a nuclear terroristic event. Due to its excellent energy resolution of the HPGe detector, it can be used to distinguish radionuclide in a complex radiation field, and then judge the types and phase of a nuclear accident. The data measured by HPGe detector in an emergency situation can provide some guidance for decision-making and performing of emergency response action. So that it is necessary to study how to employ HPGe detector in airborne survey system. In this paper, it carried out some related researches on its static calibration and dynamic calibration of an airborne HPGe detector with a portable HPGe spectrometry.In order to improve its angular resolution, by use of MCNP4C Code it has been made the design of shielding of a detector and its two kinds of collimator aperture. In this paper, it has been simulated the energy response and angular response of the specially designed detector in each condition, and it was also carded out the energy resolution, energy response, and angular response of the specially designed detector under various conditions by experiment in laboratory. It was also calculated the minimum detectable activity by use of its efficiency and the detection limit in different conditions and distances.It is of a little changing with the energy resolution of the specially designed detector in various conditions. So that it is feasible for the distinguishing of radionuclide by use of the specially designed HPGe detector in airborne emergency monitoring. It is indicated that using of shielding and collimator aperture can improve its angular resolution. So it's useful to locate a radiation source or the plume by using the specially designed detectorIn this paper, it was discussed the dynamic calibration of the specially designed HPGe detector under the condition of a point radiation source. First, it was introduced the basic principle of the dynamic calibration. Second, it was introduced a simplified method to calculate the dynamic calibration factor. And last, it was calculated the dynamic calibration factor by using of the averaged value of the factor F(θ)·_A~Φ, or the averaged value of angular response function F(θ) and the averaged value of specific fluenceΦ/A, and so it would greatly simplify the calculation. According to the complexity of the simulated formula of F(0) andΦ/A, the F(θ) andΦ/A were calculated by using of an integral method or an numerical method. Here it was carried out the calculation of the dynamic calibration factors and the static calibration factors. By comparison of these values with the experiment results, they are tallied with by 30%. The causes of the deviations were analyzed and some improvement proposals are also put forward.In a word, it's feasible to distinguish radionuclide by applying a specially designed HPGe detector to airborne emergency survey, and the method of the calculation of the dynamic calibration factors is also feasible.