Novel spectrometers for environmental dose rate monitoring

Abstract

A new generation of dosemeters, based on the scintillators LaBr, CeBr and SrI, read out with conventional photomultipliers, to be used in the field of environmental gamma-radiation monitoring, was investigated. The main features of these new instruments and especially their outdoor performance, studied by long-term investigations under real weather conditions, are presented. The systems were tested at the reference sites for environmental radiation of the Physikalisch-Technische Bundesanstalt. The measurements are compared with that of well characterized classical dose rate reference instruments to demonstrate the suitability of new spectrometers for environmental dose rate monitoring even in adverse weather conditions. Their potential to replace the (mainly Geiger Müller based) dose rate meters operated in about 5000 European early waning network stations as well as in environmental radiation monitoring in general is shown.

Monte Carlo Simulations of scintillation detectors for the use as dosemeters

“…To determine the conversion function from counts of the pulse height spectra to ambient dose equivalent (𝐻 * (10)), or any other dose quantity, a set of different mono-energetic photon energies is considered. The procedure is as follows (detailed explanations can be found in [17] and the references therein): from the simulation of 𝑖 pulse height spectra for 𝑖 monoenergetic photon fields with the energy 𝐸 𝑖 , respectively, a matrix n with entries 𝑛 𝑖 𝑗 from each spectrum 𝑖 and its counts in the 𝑗 th energy bin is generated. Using this matrix n, and the energy dependent conversion coefficients 𝑣 𝑖 , the dose 𝑑 𝑖 (generated by the photon field with energy 𝐸 𝑖 ) can be expressed by the following equation: This equation can be numerically solved and for each energy 𝐸 𝑖 a conversion coefficient 𝑣 𝑖 can be calculated.…”

“…To improve the results, the 𝑣 𝑖 can be fitted with a spline function (and additional 𝑣 𝑖 at each energy bin can be generated by "interpolation") or with a derived function in order to reduce statistical fluctuations and to avoid "dose steps" at the borders of the selected energy bins. Details on this procedure and the achievable accuracies are given in [17]. With a conversion function derived from spline-interpolations for each of the energy bins of the spectrum (in this case 2048) the dose contribution of each bin was calculated and added up.…”

“…In [17], the dose rates of this calibration facility were also calculated according to the CeBr 3 pulse height spectra, but with an experimentally determined conversion function. 8) 207 ( 8) 201 ( 8) 297 (3) 300 ( 14) 310 ( 14) 301 ( 14) 346 (3) 355 ( 10) 366 (10) 356 (10) These results are much better for each system compared to the ones of the low background underground laboratory UDO II.…”

Cadmium Zinc Telluride Solid-State Detector Characterisation for Its Use as a Spectro-Dosemeter

“…where i w are the energy-dependent pulse-height spectra to ambient dose equivalent rate conversion coefficients, i E are the photon energies, and i n are the number of counts (intensity) assigned to i different energy regions (bins) of the spectra [8], [9]. For all the conversion coefficient estimation measurements, the detector was placed at a 2 m distance from the radiation source, at the gamma radionuclide reference irradiation facility available at the Underground Dosimetry Laboratory (UDO II) which is maintained by PTB.…”

Detection of rain events in radiological early warning networks with spectro-dosimetric systems

“…The ratio of the peak centre of any measured spectrum and a reference 2017 JINST 12 P10005 spectrum is used to correct the slope of the linear energy calibration function of the spectrum. Details of this method are explained in [7].…”