[en] We present a tool to investigate neutron depolarisation effects with 10⁻⁴ precision. The test bench consists of two opaque ³He cells with in-situ adiabatic fast passage flipping of the helium spin. The cells polarise a neutron beam to more than 99.99 % and analyse its polarisation with high accuracy. For depolarisation studies, a sample can be inserted between the two cells and its effect on a primarily highly polarised beam is analysed. The test bench has been validated at the cold neutron beam PF1B at Institut Laue-Langevin, France. We present here preliminary results for the wavelength range from 5Å to 7Å. Polarisation with super mirrors is limited to about 99.7%. Direct evidence of depolarisation in the order of 10⁻³ in polarising super mirrors was found by the test bench.

No abstract available

No abstract available

No abstract available

No abstract available

[en] We propose a new arrangement of super mirror polarisers to polarise a white cold or thermal neutron beam. With this method, the dependence of the neutron polarisation on angle and wavelength is suppressed efficiently. For such a neutron beam, the average polarisation can be measured with a precision of better than 10^-3 using opaque spin filters. Average polarisation values of 0.997 for a cold neutron beam can be obtained. Furthermore, the method can be used for efficient polarisation analysis. Here, however, the precision is limited to a few times 10^-3 by depolarisation effects. We present the method and results of experimental tests

[en] Gravitationally bound quantum states of matter were observed recently due to unique properties of ultracold neutrons. We discuss here the actual status and possible improvements in this experiment. This phenomenon could be useful for various domains ranging from the physics of elementary particles and fields, to surface studies, or to foundations of quantum mechanics

[en] The Institut Laue Langevin operates a polarised ³He gas production facility based upon the Mainz system of metastable exchange optical pumping at low pressure. This device routinely fills target cells ∼ 0.25 litres in volume to pressures of the order of a few bar with ³He gas that is ≥ 55% polarised at a rate of ∼ 0.25 bar.litre.hr^-1. The current state of the development and usage of polarised ³He neutron spin filters at the ILL is discussed. Target cells with very long wall relaxation times have been produced and the method used to prepare them is presented. Two methods for producing homogeneous guide fields at the target position on the neutron beam-line have been pursued. Experiments are reviewed. These cover a range of physics including solid state magnetism, superconductivity and fundamental physics. These also include recent results of tests which demonstrate the feasibility of simultaneously analysing the polarisation of thermal neutrons scattered over a large solid angle using a banana shaped ³He cell and a multi-detector. (author)

[en] The proton asymmetry parameter C in neutron decay describes the angular correlation between neutron spin and proton momentum. In this Letter, the first measurement of this quantity is presented. The result C=-0.2377(26) agrees with the standard model expectation. The coefficient C provides an additional parameter for new and improved standard model tests

[en] We describe measurements of the parity-violating (P-odd) triton emission asymmetry coefficient a_P-odd in the ⁶Li(n,α)³H reaction with polarized cold neutrons. Experiments were carried out at the Petersburg Nuclear Physics Institute (Gatchina, Russia) and at the Institut Laue-Langevin (Grenoble, France). We employed an ionisation chamber in a configuration allowing us to suppress the left-right asymmetry well below 10^-8. An additional test for a false asymmetry due to eventual target impurities (''zero test'') resulted in a_0-test=(0.0±0.5)x10^-8. As final result of this series of experiments we obtained a_P-odd=(-8.8±2.1)x10^-8