Alpha spectroscopy instrumentation
For the analysis of alpha radioactive isotopes, NED-NTUA employs a PIPS detector , with 450 mm2 active area, installed in a 7401-VR vacuum chamber by Canberra. The chamber is equipped with a sample reverse bias system to prevent recoil contamination of the detector. The chamber is evacuated by a rotary oil pump, while pressure is controlled by an electronic controller.
The spectrum is collected by an Amptec Pocket MCA-8000A multichannel analyzer, in the energy range 1-10 MeV with a resolution of 2048 channels. When analysing good quality electrodeposited sources, a FWHM of 18-20 keV is acheived.
Radiochemical source preparation
Preparation of alpha spectroscopy sources from environmental samples is preformed at the NED-NTUA Radiochemical Laboratory Radioisotope separations are performed by ion exchange. Analytical quality is controlled by using certified tracer radionuclide soultions. Sources are preared by electrodeposition on stainless steel, using an electrodeposition apparatus supplied by ITN Portugal.
NED-NTUA has so far developed and applied techniques for the analysis of Uranium isotopes in water and air samples, achieving LLDs in the order of 10 mBq, depending on sample type and quality. The procedures for Uranium isotope analysis by alpha spectrometry have been succesfully tested by participating in Intercomparison Excercise IAEA-CU-2008-04r.