Analyses of silicon dioxide, magnesium oxide, lead fluoride, bismuth as low-pass velocity filters for neutrons

Transmission measurement of neutrons by filter materials for low energy neutrons is important for the study of structure and dynamics of condensed matter. Since only thermal neutrons are useful for such experiments, filter materials that transmit thermal neutrons while attenuating fast neutrons and gamma rays are of considerable interest

Imaging solar neutrons below 10 MeV in the inner heliosphere

Inner heliosphere measurements of the Sun can be conducted with the proposed Solar Sentinel spacecraft and mission. One of the key measurements that can be made inside the orbit of the Earth is that of lower energy neutrons that arise in flares from nuclear reactions. Solar flare neutrons below 10 MeV suffer heavy weak-decay losses before reaching 1 AU. For heliocentric radii as close as 0.3 AU, the number of surviving neutrons from a solar event is dramatically greater. Neutrons from 1-10 MeV provide a new measure of heavy ion interactions at low energies, where the vast majority of energetic ions reside. Such measurements are difficult because of locally generated background neutrons. An instrument to make these measurements must be compact, lightweight and efficient. We describe our progress in developing a low-energy neutron telescope that can operate and measure neutrons in the inner heliosphere and take a brief look at other possible applications for this detector

Magnetic trapping of ultracold neutrons

Three-dimensional magnetic confinement of neutrons is reported. Neutrons are loaded into an Ioffe-type superconducting magnetic trap through inelastic scattering of cold neutrons with 4He. Scattered neutrons with sufficiently low energy and in the appropriate spin state are confined by the magnetic field until they decay. The electron resulting from neutron decay produces scintillations in the liquid helium bath that results in a pulse of extreme ultraviolet light. This light is frequency downconverted to the visible and detected. Results are presented in which 500 +/- 155 neutrons are magnetically trapped in each loading cycle, consistent with theoretical predictions. The lifetime of the observed signal, 660 s +290/-170 s, is consistent with the neutron beta-decay lifetime.Comment: 17 pages, 18 figures, accepted for publication in Physical Review

Correlation Time-of-flight Spectrometry of Ultracold Neutrons

The fearures of the correlation method used in time-of-flight spectrometry of ultracold neutrons are analyzed. The time-of-flight spectrometer for the energy range of ultracold neutrons is described, and results of its testing by measuring spectra of neutrons passing through interference filters are presented.Comment: 16 pages, 5 figure

Probing Strongly Coupled Chameleons with Slow Neutrons

We consider different methods to probe chameleons with slow neutrons. Chameleon modify the potential of bouncing neutrons over a flat mirror in the terrestrial gravitational field. This induces a shift in the energy levels of the neutrons which could be detected in current experiments like GRANIT. Chameleons between parallel plates have a field profile which is bubble-like and which would modify the phase of neutrons in interferometric experiments. We show that this new method of detection is competitive with the bouncing neutron one, hopefully providing an efficient probe of chameleons when strongly coupled to matter

Time-of-flight discrimination between gamma-rays and neutrons by neural networks

In gamma-ray spectroscopy, a number of neutrons are emitted from the nuclei together with the gamma-rays and these neutrons influence gamma-ray spectra. An obvious method of separating between neutrons and gamma-rays is based on the time-of-flight (tof) technique. This work aims obtaining tof distributions of gamma-rays and neutrons by using feed-forward artificial neural network (ANN). It was shown that, ANN can correctly classify gamma-ray and neutron events. Testing of trained networks on experimental data clearly shows up tof discrimination of gamma-rays and neutrons.Comment: 10 pages, 8 figure

Observation of Scalar Aharonov-Bohm Effect with Longitudinally Polarized Neutrons

We have carried out a neutron interferometry experiment using longitudinally polarized neutrons to observe the scalar Aharonov-Bohm effect. The neutrons inside the interferometer are polarized parallel to an applied pulsed magnetic field B(t). The pulsed B field is spatially uniform so it exerts no force on the neutrons. Its direction also precludes the presence of any classical torque to change the neutron polarization