We compare the expected effects of so-called gravitationally enhanced depolarization of ultracold neutrons to measurements carried out in a spin-precession chamber exposed to a variety of vertical ...magnetic-field gradients. In particular, we have investigated the dependence upon these field gradients of spin depolarization rates and also of shifts in the measured neutron Larmor precession frequency. We find excellent qualitative agreement, with gravitationally enhanced depolarization accounting for several previously unexplained features in the data.
If a new light boson existed, it would mediate a new force between ordinary fermions, like neutrons. In general such a new force is described by the Compton wavelength λc of the associated boson and ...a set of dimensionless coupling constants. For light boson masses of about 10−4 eV/c2, λc is of the order millimeters. Here, we propose a table-top particle physics experiment which provides the possibility to set limits on the strength of the coupling constants of light bosons with spin-velocity coupling. It utilises Ramsey's technique of separated oscillating fields to measure the pseudo-magnetic effect on neutron spins passing by a massive sample.
We report on a novel neutron radiography technique that uses the Ramsey principle, a method similar to neutron spin echo. For the first time quantitative imaging measurements of magnetic objects and ...fields could be performed. The strength of the spin-dependent magnetic interaction is detected by a change in the Larmor precession frequency of the neutron spins. Hence, one obtains in addition to the normal attenuation radiography image a so-called neutron spin phase image, which provides a two-dimensional projection of the magnetic field integrated over the neutron flight path.
We report on a search for ultralow-mass axionlike dark matter by analyzing the ratio of the spin-precession frequencies of stored ultracold neutrons and Hg199 atoms for an axion-induced oscillating ...electric dipole moment of the neutron and an axion-wind spin-precession effect. No signal consistent with dark matter is observed for the axion mass range 10−24≤ma≤10−17eV . Our null result sets the first laboratory constraints on the coupling of axion dark matter to gluons, which improve on astrophysical limits by up to 3 orders of magnitude, and also improves on previous laboratory constraints on the axion coupling to nucleons by up to a factor of 40.
We report on muonium (Mu) emission into vacuum following μ(+) implantation in mesoporous thin SiO(2) films. We obtain a yield of Mu into vacuum of (38±4)% at 250 K and (20±4)% at 100 K for 5 keV μ(+) ...implantation energy. From the implantation energy dependence of the Mu vacuum yield we determine the Mu diffusion constants in these films: D(Mu)(250 K)=(1.6±0.1)×10(-4) cm(2)/s and D(Mu)(100 K)=(4.2±0.5)×10(-5) cm(2)/s. Describing the diffusion process as quantum mechanical tunneling from pore to pore, we reproduce the measured temperature dependence ∼T(3/2) of the diffusion constant. We extract a potential barrier of (-0.3±0.1) eV which is consistent with our computed Mu work function in SiO(2) of -0.3,-0.9 eV. The high Mu vacuum yield, even at low temperatures, represents an important step toward next generation Mu spectroscopy experiments.
We report on a novel application of the Neutron Spin Phase Imaging technique, by performing polarised neutron radiography on dia- and paramagnetic samples. In order to achieve the necessary ...sensitivity we employed a 2.5T Ramsey apparatus which was used in a previous experiment to measure the spin-dependent neutron scattering length of the deuteron. First successful results on aluminium, lead, titanium and heavy water (D2O) samples are presented. They are in good quantitative agreement with expected values deduced from susceptibility measurements.
►Neutron Spin Phase Imaging is a neutron radiography technique sensitive to magnetic fields and samples. ►We studied the possibility to image weakly magnetic samples from dia- and paramagnetic material. ►A neutron Ramsey apparatus with a field of 2.5 Tesla was used. ►The method delivers quantitatively correct results.
Highly collimating neutron optical devices Piegsa, F.M.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2009, Letnik:
603, Številka:
3
Journal Article
Recenzirano
Two Soller type highly collimating neutron optical devices with a length of 200
mm are presented. They provide a triangular shaped beam divergence distribution with a FWHM of about
0
.
11
∘
(2
mrad) ...and a peak transmission of up to 80% for neutrons with a wavelength
λ
0
of 5
Å. This corresponds to an improvement of more than a factor three compared to state of the art collimators. Measurements are presented which demonstrate the usefulness of these devices also for neutron radiography.
The leak rate of helium gas through thin Kapton HN foils was measured for various temperatures between 310 and 150K and gas pressures ranging from 10 to 300mbar. From these measurements the ...permeability constant P(T) and its temperature dependence were determined. At room temperature the permeability constant for Kapton HN is P(T=296K)=(2.56±0.31) barrer. The temperature dependence of P(T) was verified to drop exponentially with decreasing temperature, causing a change in the permeability by more than two orders of magnitude in the range between 310 and 150K.
We report on a laser based 199Hg co-magnetometer deployed in an experiment searching for a permanent electric dipole moment of the neutron. We demonstrate a more than five times increased signal ...to-noise-ratio in a direct comparison measurement with its 204Hg discharge bulb-based predecessor. An improved data model for the extraction of important system parameters such as the degrees of absorption and polarization is derived. Laser- and lamp-based data-sets can be consistently described by the improved model which permits to compare measurements using the two different light sources and to explain the increase in magnetometer performance. The laser-based magnetometer satisfies the magnetic field sensitivity requirements for the next generation nEDM experiments.
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