Gradiometric investigation of a cesium-vapor quantum magnetometer

Experiments aimed to determine the sensitivity and the optical shift of the output frequency of a magnetometer based on optical pumping of cesium atoms and intended for a neutron magnetic resonance stabilization system are described. A gradiometric arrangement used in these experiments makes it possible to reduce the effect of magnetic field variations on measurements.     

Supersource of ultracold neutrons at the WWR-M reactor and the program of fundamental research in physics

A high-intensity source of ultracold neutrons (UCNs) and very cold neutrons is being developed based on the WWR-M operating research reactor at the St. Petersburg Nuclear Physics Institute for research in the field of fundamental physics and nanostructures. Superfluid helium will be used in this source, which should yield a UCN density of 10₄ cm⁻³, which exceeds the density of the currently existing UCN sources (throughout the world) by three orders of magnitude. Having possessed the most intense UCN source, the WWR-M reactor will become an international center of UCN-based fundamental research.     

Simulation of Experiment on Measurement of Neutron Lifetime Using the Big Gravitational Trap of Ultracold Neutrons with the Absorber

Technical Physics - At present, the experiment on measuring neutron lifetime using a big gravitational trap is being performed at Petersburg Nuclear Physics Institute. It is planned to achieve a...     

Observation of the penetration of subbarrier ultracold neutrons through beryllium foils and coatings

The subbarrier passage of ultracold neutrons through beryllium foils and coatings with a probability much higher than that of tunneling is observed. This effect may be responsible for the so-called anomalous loss of ultracold neutrons. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 5, 317–322 (10 September 1997)     

A liquid hydrogen source of ultra-cold neutrons

A liquid hydrogen source of ultra-cold neutrons (UCN) developed for an experimental search for the electric dipole moment of the neutron is described. The results of an investigation of the yield of UCN from gaseous, liquid, and solid hydrogen as a function of temperature are presented. The UCN counting rate obtained at the output of the 6 × 7 cm² neutron guide tube is 5 × 10⁴ n/s. This counting rate corresponds to a flux of neutrons whose velocity along the axis of the neutron guide tube is below 7 m/s. Preliminary measurements of the UCN yield from liquid and solid deuterium have been carried out.     

High-density ultracold neutron sources for the WWR-M and PIK reactors

It is proposed to equip the PIK and WWR-M research reactors at the Petersburg Nuclear Physics Institute (PNPI) with high-density ultracold neutron (UCN) sources, where UCNs will be obtained based on the effect of their accumulation in superfluid helium (due to the specific features of this quantum fluid). The maximum UCN storage time in superfluid helium is obtained at temperatures on the order of 1 K. These sources are expected to yield UCN densities of 10³–10⁴ cm^–3, i.e., approximately three orders of magnitude higher than the density from existing UCN sources throughout the world. The development of highest intensity UCN sources will make PNPI an international center of fundamental UCN research.     

Neutron lifetime measurement on setups with gravitational trap

Currently, the best accuracy of neutron lifetime measurements has been attained in the experiment with a gravitational trap for ultracold neutrons (UCNs), performed at the Petersburg Nuclear Physics Institute (PNPI); the measured lifetime was 878.5 ± 0.8 s. A new setup with a big gravitational trap has been designed to continue the methods and approaches used in the previous experiment. It is planned to reduce the measurement error to 0.2 s, i.e., improve the existing accuracy by a factor of 4. The spectrometer was designed at PNPI and installed on the PF2/MAM beam at the Institute Laue–Langevin. Test experiments have been performed.     

New measurement of the neutron lifetime with a large gravitational trap

The lifetime of the neutron is one of the key physical quantities used to determine the weak interaction parameters and to test predictions of the theory of primary nucleosynthesis. The lifetime of the neutron has been measured in the reported experiment by the method of storing neutrons in a material trap with a gravitational valve. Fomblin grease UT-18 hydrogen-free fluorine polymer has been used as coating. The resistance of the coating to repeated cooling down to 80 K combined with heating up to 300 K has been studied. The probability of losses in the trap is as small as 1.5% of the neutron decay probability. The lifetime of the neutron τ_n = (881.5 ± 0.7_stat ± 0.6_syst)s obtained at the new step is in good agreement with a commonly accepted value of (880.2 ± 1.0) s presented by the Particle Data Group.     

Experimental value of G A/GV from a measurement of both P-odd correlations in free-neutron decay

A new experimental value of the fundamental weak-interaction parameter λ=G _A/G_V (?1.2686±0.0046) is obtained for the first time by an original method that consists in measuring both P-odd correlations in free-neutron decay.     

Estimation of the ultracold neutron production by a source designed for the WWR-M reactor

The results of calculations related to designing an ultracold neutron source with superfluid helium for the WWR-M reactor have been presented. The ultracold neutron production rate has been estimated for different types of premoderator chamber filling. The dependence of this rate on the temperature of helium has been determined. If the premoderator chamber is filled with liquid orthodeuterium, the ultracold neutron production rate remains almost constant in the range of helium temperatures of 1.0–1.5 K and is as high as 3.1 × 10³ cm^–3 s^–1.