J. Stanicek

Internal pair production in alpha-decaying nuclei and gamma-ray intensities of 241Am

Abstract The measurement of internal pair production accompanying the alpha-decay of 210Po, 239Pu and 241Am has confirmed that this process occurs with probability of about 10−9. The investigation of gamma-rays of 241Am has shown that the contribution of excited levels with energy above 2 mec2 to internal pair production is negligible because intensities of only about 10−7% have been found. Several non-identified gamma-rays with energies above 900 keV have been observed which might be due to new high excited levels of 237Np.

Recent results from the AMS/IBA laboratory at the Comenius University in Bratislava: preparation of targets and optimization of ion sources

Developments of solid targets and optimizations of ion sources were carried out with the aim to produce high ion yields for applications of tandem accelerators as mass spectrometers. A comparison of Al− yields from different aluminum targets showed that the best results were obtained with AlN targets. Transmission studies of 9Be and 12C ions through the Pelletron accelerator showed highest efficiencies for 9Be2+ and 12C2+. First results obtained with a simplified version of the AMS line are presented as well.

Reference material for natural radionuclides in glass designed for underground experiments

A reference material designed for the determination of natural radionuclides in solid samples (glass pellets) is described and the results of certification are presented. The material has been certified for 7 natural radionuclides (40K, 226Ra, 228Ra, 228Th, 232Th, 235U and 238U). An information value is given for 210Pb. Radon (222Rn) emanation experiments showed results comparable within participating laboratories, however, the number of data and precision was too low to carry out a certification process. The reference material may be used for quality management of analytical laboratories engaged in the high-sensitive analysis of radionuclides in the construction materials of detectors placed in ultra low background underground laboratories.

Higher-order processes accompanying nuclear decays

Higher-order processes such as internal pair production, internal bremsstrahlung, and internal ionization have been studied. The internal electron-positron pair production during beta decay of 32P was found to be (6.8+or-1.3)*10-9, an order of magnitude larger than the theoretical estimation. A good agreement between the theoretical and experimental shape of internal bremsstrahlung spectrum of 32P was found. The internal ionization probability of (21.9+or-3.9)*10-4 for the beta + decay of 65Zn was obtained.

TPC for investigation of double beta decaying nuclei in solid samples

A design of a large volume time projection chamber (TPC) for double beta decay measurements with solid samples is presented. The total surface of measured samples can be up to 2.5 m2. The chamber will operate in a magnetic field up to 0.07 T. The expected spatial resolution is better than 1 mm in electron drift direction and about 2 mm along the sense wires. The momentum resolution of about 10% should be reached. The background of the TPC will be very effectively suppressed by the visualization of each event. The TPC operating in an underground laboratory should reach a limit on the half-life of neutrinoless double beta decay of 1024 years.