The intensities of γ-rays from the decay of 196m2Au.

The intensities of γ-rays from the 196m2Au decay adopted in 1998 and 2007 ENSDF evaluations differ up to 20%. Gold samples were irradiated in intensive neutron fluxes with energies up to 35 MeV to produce the isotopes 196Au in all isomeric states. The intensities of gammas from the radioactive decay of the isomer 196m2Au were measured by means of the nuclear γ-ray spectrometry (HPGe detectors) and compared to the existing adopted data.

(83m)Kr radioactive source based on (83)Rb trapped in cation-exchange paper or in zeolite.

The mono-energetic conversion electrons from the decay of (83m)Kr represent a unique tool for energy calibration and systematic studies of the tritium beta spectrum measured in neutrino mass determination experiments. For this reason, the corresponding parent isotope was produced in reactions (nat)Kr(p,xn)(83)Rb. The behaviour of (83)Rb (T(1/2)=86.2d) and its daughter product (83m)Kr (T(1/2)=1.83h) was examined, when the (83)Rb was trapped in a cation-exchanger chromatographic paper or in zeolite. Using gamma spectroscopy measurements, recommendations for the production of a (83)Rb/(83m)Kr radionuclide generator based on these cation-exchangers and suitable for the neutrino mass determination experiment KATRIN were deduced.

Feasibility of photoelectron sources with sharp lines of stable energy between 20 and 80 keV.

Photo-absorption of γ-rays in thin Al, Co, Ti, and Mo convertors was examined with the aim to produce quasi monoenergetic photoelectrons having an energy spread of 0.5-4.7eV about mean kinetic energies at discrete values between 18632 and 80321eV. The photoelectron rates were estimated for commercial photon sources of (241)Am, (119m)Sn, (125m)Te and (109)Cd with activities of 0.55-3.7GBq. Photoelectrons ejected by (241)Am γ- and X-rays from Co convertors were measured with two different electron spectrometers and obtained energy spectra were compared with Monte Carlo predictions.

Spatially uniform calibration of a liquid xenon detector at low energies using (83m)Kr.

A difficult task with many particle detectors focusing on interactions below approximately 100 keV is to perform a calibration in the appropriate energy range that adequately probes all regions of the detector. Because detector response can vary greatly in various locations within the device, a spatially uniform calibration is important. We present a new method for calibration of liquid xenon (LXe) detectors, using the short-lived (83m)Kr. This source has transitions at 9.4 and 32.1 keV, and as a noble gas like Xe, it disperses uniformly in all regions of the detector. Even for low source activities, the existence of the two transitions provides a method of identifying the decays that is free of background. We find that at decreasing energies, the LXe light yield increases, while the amount of electric field quenching is diminished. Additionally, we show that if any long-lived radioactive backgrounds are introduced by this method, they will present less than 67x10(-6) events kg(-1) day(-1) keV(-1) in the next generation of LXe dark matter direct detection searches.

Improved methods of measurement and analysis of conversion electron and beta-particle spectra

A general statistical test of the stability of measurement conditions was demonstrated on the beta-spectra of 241Pu cumulated during four years. The alpha- and gamma-ray spectroscopy indicated stability of the 241Pu source. Monte Carlo modelling of individual collision events clarified the role of electron scattering and energy losses within a radioactive source down to energies of several hundreds of eV. The impact ionization by beta-particles of carbon and oxygen atoms in a surface contamination layer on the 241Pu and 63Ni sources was observed.