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Register a new userInvestigating solid $alpha-^{15}$N$_{2}$ as a new source of ultra-cold neutrons
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The dynamical structure factor of solid $^{15}$N$_{2}$ in the $alpha$ phase ($T<35$K) is measured at the IN4 time-of-flight spectrometer at the Institut Laue Langevin, and the potential performance of this substance as a UCN converter is assessed. The cross-section to down-scatter neutrons to ultra-cold neutron energies is determined as a function of incident energy, as well as the up-scattering mean free path. The UCN production cross-section is found to be approximately 20% of that of deuterium. However, UCN with energy 181 neV have an up-scattering mean free path of 46 cm at $T=5.9$ K, which is $sim20$ times larger than deuterium. Therefore, a large volume $alpha-^{15}$N$_{2}$ source may produce an improved UCN density if sufficient isotopic purity can be achieved.
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Ultra-cold neutrons (UCN), neutrons with energies low enough to be confined by the Fermi potential in material bottles, are playing an increasing role in measurements of fundamental properties of the neutron. The ability to manipulate UCN with material guides and bottles, magnetic fields, and gravity can lead to experiments with lower systematic errors than have been obtained in experiments with cold neutron beams. The UCN densities provided by existing reactor sources limit these experiments. The promise of much higher densities from solid deuterium sources has led to proposed facilities coupled to both reactor and spallation neutron sources. In this paper we report on the performance of a prototype spallation neutron-driven solid deuterium source. This source produced bottled UCN densities of 145 +/-7 UCN/cm3, about three times greater than the largest bottled UCN densities previously reported. These results indicate that a production UCN source with substantially higher densities should be possible.
We present the status of the development of a dedicated high density ultra-cold neutron (UCN) source dedicated to the gravitational spectrometer GRANIT. The source employs superthermal conversion of cold neutrons to UCN in superfluid helium. Tests have shown that UCN produced inside the liquid can be extracted into vacuum. Furthermore a dedicated neutron selection channel was tested to maintain high initial density and extract only neutrons with a vertical velocity component 20 cm/s for the spectrometer. This new source would have a phase-space density of 0.18 cm-3(m/s)-3 for the spectrometer.
We present two new types of spectroscopy methods for cold and ultra-cold neutrons. The first method, which uses the RB drift effect to disperse charged particles in a uniformly curved magnetic field, allows to study neutron $beta$-decay. We aim for a precision on the 10$^{-4}$ level. The second method that we refer to as gravity resonance spectroscopy (GRS) allows to test Newtons gravity law at short distances. At the level of precision we are able to provide constraints on any possible gravity-like interaction. In particular, limits on dark energy chameleon fields are improved by several orders of magnitude.
A pixel detector with high spatial resolution and temporal information for ultra-cold neutrons is developed based on a commercial CCD on which a neutron converter is attached. 10B and 6Li are tested for the neutron converter and 10B is found to be more suitable based on efficiency and spatial resolution. The pixel detector has an efficiency of 44.1 +- 1.1% and a spatial resolution of 2.9 +- 0.1 um (1 sigma).
This work presents selected results from the first round of the DFG Priority Programme SPP 1491 precision experiments in particle and astroparticle physics with cold and ultra-cold neutrons.
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