We demonstrate a stationary helium gas density gradient which is needed for a proposed novel low-energy mu super(+) beam line. In a closed system with constant pressure the corresponding density ...gradient is only a function of the temperature. In a neutron radiography experiment two gas cells with different geometries were filled with super(3)He gas at constant pressures of about 10 mbar. Temperatures in the range from to were applied and density distributions with a maximum to minimum density ratio of larger than 3 were realized. The distribution was investigated employing the strongly neutron absorbing isotope super(3)He. A simple one-dimensional approach derived from Fourier's law describes the obtained gas density with a deviation .
We present the new spectrometer for the neutron electric dipole moment (nEDM) search at the Paul Scherrer Institute (PSI), called n2EDM. The setup is at room temperature in vacuum using ultracold ...neutrons. n2EDM features a large UCN double storage chamber design with neutron transport adapted to the PSI UCN source. The design builds on experience gained from the previous apparatus operated at PSI until 2017. An order of magnitude increase in sensitivity is calculated for the new baseline setup based on scalable results from the previous apparatus, and the UCN source performance achieved in 2016.
Physics at the Planck scale could be revealed by looking for tiny violations of fundamental symmetries in low energy experiments. In 2008, a sensitive test of the isotropy of the universe has been ...performed with stored ultracold neutrons (UCN), this is the first clock-comparison experiment performed with free neutrons. During several days we monitored the Larmor frequency of neutron spins in a weak magnetic field using the Ramsey resonance technique. A nonzero cosmic axial field, violating rotational symmetry, would induce a daily variation of the precession frequency. Our null result constitutes one of the most stringent tests of Lorentz invariance to date.
.
We report on the design and first tests of a device allowing for measurement of ultracold neutrons polarisation by means of the simultaneous analysis of the two spin components. The device was ...developed in the framework of the neutron electric dipole moment experiment at the Paul Scherrer Institute. Individual parts and the entire newly built system have been characterised with ultracold neutrons. The gain in statistical sensitivity obtained with the simultaneous spin analyser is
% relative to the former sequential analyser under nominal running conditions.
A compact apparatus to perform polarised neutron radiography on macroscopic objects is presented. Its working principle, based on Ramsey's resonance technique, allows to observe interactions between ...neutron spins and magnetic fields. Despite its shortness of only 480
mm, the magnetic field homogeneity allows for large beam cross-sections of up to 20×20
mm
2. The applied magnetic field at the sample position is variable and can be tuned from about 4 to almost 32
mT without violating the Ramsey resonance condition. The performance of the apparatus is demonstrated in systematic tests, which show a phase stability of 1 degree and a sensitivity of about 7.5×10
−8
Tm.
We report on the measurement of a Larmor frequency shift proportional to the electric-field strength for $^{199}{\rm Hg}$ atoms contained in a volume permeated with aligned magnetic and electric ...fields. This shift arises from the interplay between the inevitable magnetic field gradients and the motional magnetic field. The proportionality to electric-field strength makes it apparently similar to an electric dipole moment (EDM) signal, although unlike an EDM this effect is P- and T-conserving. We have used a neutron magnetic resonance EDM spectrometer, featuring a mercury co-magnetometer and an array of external cesium magnetometers, to measure the shift as a function of the applied magnetic field gradient. Our results are in good agreement with theoretical expectations.
A transmission neutron polariser (Fe/Si supermirror) has been successfully implemented in the small angle neutron scattering instrument SANS-I at the SINQ neutron source. The polariser is needed for ...investigations of magnetic nanostructures as well as for spin contrast variation techniques relying on the spin-dependent neutron scattering length of polarised nuclei. The V-shaped polariser is installed in the first section of the collimator system of the SANS instrument and its performance is optimised for neutrons with a wavelength between 0.5 and 1.0
nm. For a precise polarisation analysis of a beam with selectable incident divergence, such as in SANS experiments, an opaque spin filter is ideal. We used a solid polarised proton target exploiting the strong spin-dependent neutron scattering cross-section of hydrogen and determined the neutron beam polarisation to a precision of
δ
p
/
p
∼
0.5
%
for different collimations in a broad wavelength band.
.
This paper summarizes the results from measurements aiming to characterize ultracold neutron detection with
6
Li-doped glass scintillators. Single GS10 or GS20 scintillators, with a thickness of ...100-200μm, fulfill the ultracold neutron detection requirements with an acceptable neutron-gamma discrimination. This discrimination is clearly improved with a stack of two scintillators: a
6
Li-depleted glass bonded to a
6
Li-enriched glass. The technique of optical contact bonding is used between the two glasses in order to eliminate the need for optical glue or grease between them. Relative to a
3
He Strelkov gas detector, the scintillator’s detection efficiency is lower for UCN energies close to the scintillator’s Fermi potential (85-100 neV), but becomes larger at higher UCN energies. Coupled to a digital data acquisition system, counting rates up to a few 10
5
counts/s can be handled. A detector based on such a scintillator stack arrangement was built and has been used in the neutron electric dipole moment experiment at the Paul Scherrer Institute since 2010. Its response for routine runs of the neutron electric dipole moment experiment is presented.
The measurement of the neutron electric dipole moment (nEDM) constrains the contribution of CP-violating terms within both the Standard Model and its extensions. The experiment uses ultracold ...neutrons (UCN) stored in vacuum at room temperature. This technique provided the last (and best) limit by the RAL/Sussex/ILL collaboration in 2006: dn<2:9×10-26 e cm (90% C.L.). We aim to improve the experimental sensitivity by a factor of 5 within 2-3 years, using an upgrade of the same apparatus. We will take advantage of the increased ultracold neutron density at the Paul Scherrer Institute (PSI) and of a new concept including both, external magnetometers and a cohabiting magnetometer. In parallel, a next generation apparatus with two UCN storage chambers and an elaborate magnetic field control is being designed aiming to achieve another order of magnitude increase in sensitivity, allowing us to put a limit as tight as dn<5×10-28 e cm (95% C.L.), if not establishing a finite value.
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