Valery Petukhov

A multicathode counter is designed to search for cold, dark matter, presumably composed of dark photons, by detecting single electrons emitted from the surface of the metal cathode of the counter during the conversion of dark photons on its surface. The counter design allows for the efficient discrimination of the background from an ambient radioactivity and the electron thermal emission by subtracting the count rate measured in the blocking potential configuration. The paper provides a detailed description of the design of a multicathode counter.

In this paper we report the results obtained in experiment PHELEX during 208 days of measurements on the search for dark photons with a multi-cathode counter with an iron cathode that revealed in 4 runs with a confidence level better than 5 σ a systematic excess of single electron events in the time interval from 8-00 till 12-00 sidereal time. The fact that we see this effect in stellar frame and do not in solar frame can be considered as evidence that the observed effect is due to dark photons.

This paper reports the PHELEX experiment, i.e., PHoton–ELectron EXperiment, to search for the dark photons (DPs) of cold dark matter using a multicathode counter technique specifically developed for this purpose by the authors. The paper presents new data, a novel upper limit for the constant of kinetic mixing, and the first results of measurements of the diurnal variations in solar and stellar frames. The perspectives of this method are outlined in terms of the search for DPs.

We propose a method of search for cold dark matter, which presumably consists of hidden photons, by detecting single electrons emitted from the surface of the metal cathode of a counter as a result of the conversion of hidden photons. To detect single electrons, a special multi-cathode counter has been designed. The counter allows one to discriminate the background by subtracting from the effect the dark count rate measured in a configuration with a blocking potential that prevents the drift of the cathode-emitted electrons to the central counter. The measurement results are presented and significant progress in the development of the methodology is demonstrated. Further steps to improve the method are discussed.

Here we present measurements of the rates of emission of single electrons from the cathode of a proportional counter filled with a mixture of Ar + CH4 (10%) at 1 bar. We interpret the results as a possible photoelectric effect associated with hidden photons (HPs). Our results set upper limits for HPs from cold dark matter (CDM). We also discuss future options for searches for HPs from CDM using a multi-cathode counter technique.

A method for registration of the coherent scattering reactor antineutrino on nuclei using a three-section low-background proportional counter was proposed. It is planned to use argon and xenon as the working substance. As has been shown on a test bench, pulse shape discrimination can effectively suppress the background from electromagnetic interference and microphonic effects in the energy range from 20 to 100 eV where the effect of coherent scattering of neutrinos on nuclei is expected with a factor of about 10³. Problems of the neutron background generated by cosmic-ray muons are analyzed. The scheme of the experimental setup is presented.

Gaseous detector with a sub-keV electron equivalent threshold is a very perspective tool for the precision measurement of the neutrino magnetic moment and for observing coherent scattering of neutrinos on nuclei. The progress in the development of low noise electronics makes it possible to register the rare events at the threshold less than 100 eV. The construction of the gaseous detector is given and the typical pulses with amplitudes of a few eV observed on a bench scale installation are presented. The possible implications for future experiments are discussed.

Data obtained by the radiotracer method on a specially designed test bench show that a lithium oxide film serves as a trap for beryllium extracted from lithium. No tangible chemisorption of beryllium on the titanium surface is observed. These finding are used to design and fabricate a lithium detector for solar neutrinos. They will also find application in designing power nuclear facilities with liquid-metal heat carriers.