Prof. Jerzy-Wojciech Mietelski (The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences (IFJ PAN))
The use of digital coincidence opens new perspectives for low background gamma rays measurements. The basic idea is that two detectors are collecting independently gamma spectra, but spectrum is not stored as one dimensioned array of counts but two-dimensional array where data on each registered photon energy is registered together with information on its arrival with several nanoseconds precision. During off-line analyses of such spectrum different numeric filters can be applied to search for coincidences between different parts of each spectra, for example annihilation line at one spectrometer with certain gamma line of a beta plus emitter registered on another detector. The coincidences between any gamma ray line of certain radionuclide and X-ray line of daughter are also possible. The constructed by us system uses two HPGe detectors: coaxial in vertical cryostat and planar in L shape cryostat. They are shielded by one 5 cm thick standard lead shield. Spectra are collected using CAEN digitizerand they are registered using build-in software. The off-line analyses are made by means of purposely written our own code. At moment of writing abstract the system is not operating yet. First it will be applied for attempt of 85Kr determination on environmental levels (collected in a cryogenic charcoal trap) using gamma-X ray coincidences and 22Na in air using 511 keV/1275 keV coincidences. The first results will be presented during Conference. Work was carried out under the strategic research project “Technologies supporting the development of safe nuclear power” financed by the National Centre for Research and Development (NCBiR). Research Task “Development of methods to assure nuclear safety and radiation protection for current and future needs of nuclear power plants”, contract No. SP/J/6/143339/11.
Dr Renata Kierepko (The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences (IFJ PAN))