V. I. Fominykh

Coincidence summing in γ-ray spectra and determination of the intensity of weak crossover γ transitions

The intensities of peaks formed in γ-ray spectra by summing the pulses due to coincident cascade γ transitions in radioactive nuclides are used to determine the intensities of weak crossover γ-radiative transitions. A procedure for measuring γ-ray spectra and calculating the intensities of crossover γ transitions is proposed. The dead time of the measuring facility and a decrease in the intensity of cascade γ-ray peaks, caused by their coincidence with the photopeak and the Compton distribution due to the γ-transition-partner in the cascade, are taken into account. This procedure has been tested by measuring γ spectra of 209Tl, 208Tl, 207Bi, and 44Sc decays. It is shown that the proposed technique can be used to observe crossover γ transitions with an intensity as high as ∼5×10−5 per decay. The upper limits on the intensities of crossover γ transitions in decays of 208Tl and 207Bi nuclei have been determined for the first time.

Negative-muon capture in 150Sm

The energy and time spectra of γ rays emitted during negative-muon capture in 150Sm were studied. The total muon lifetime in 150Sm was measured. The yields of several radioactive isotopes in this reaction were determined. The partial γ-ray yield upon muon capture by a 150Sm nucleus were measured.

Muon capture rates in Se and Cd isotopes

Energy and time spectra of γ rays following nuclear capture of negative muons in natural Se and Cd and isotopically enriched 76Se and 106Cd targets have been measured with HPGe detectors. Total muon lifetimes in Se and Cd isotopes and partial μ capture rates to excited levels of 76As and 106Ag are obtained. These results are necessary for calculation of nuclear matrix elements of the 2β decay of 76Ge and 106Cd respectively.

Background structure in the Heidelberg-Moscow experiment on the search and investigation of double beta decay of 76Ge1

Independent analysis of the spectra from the Heidelberg-Moscow experiment has been carried out. A direct comparison of the peak intensities in the spectra allows for the conclusion that in the energy range up to 3200 keV the background is due to the detection of γ rays from the decay of trace impurities of anthropogenic and cosmogenic nuclides occurring in the apparatus between the HPGe detectors and the main (Pb and Cu) shielding. The 226Ra, 214Pb, and 214Bi γ rays observed in the spectra are shown to arise in the 226Ra rather than 238U decay chain. The estimates of the expected intensities of the weak 214Bi γ rays in the spectrum region around Qββ(76Ge) = 2039 keV do not contradict the observation of the peak at 2039 keV as claimed by Klapdor-Kleingrothaus and coauthors.

A compact separator of monoenergetic electrons

A separator of monoenergetic electrons is described, in which two kinds of assemblies of “miniorange”-type magnetic filters (six magnets in each) are used. The 207Bi isotope with an activity of 240 kBq (7 μCi) that emits K1063 and K1770 conversion electrons serves as the electron source. For different kinds of assemblies, the intensity of electrons with energies of ∼970 and ∼1680 keV is accompanied by an increase in the radiation intensity by factors of 3 and 4, respectively, as compared to the intensities measured without magnetic filters, the energy resolution being ∼30 keV. A single cycle of chamber evacuation guarantees constancy of the instrument’s parameters for one month.

Stabilization of nuclear radiation spectra by the hardware and software correction

Two types of stabilization of nuclear radiation spectra are described. In the first case, the instability is corrected by changing parameters of the linear discharge device of the analog-to-digital converter by applying correcting voltages. In the second case, the amplitude of analog signals coming from the output of the linear amplifier is changed by the thermoresistor supplied with a heating winding. It is shown that, using mathematical transformations, it is possible to correct spectrum distortions caused by instability of the equipment.