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Experiments and instruments

A series of short movies showing how neutron experiments are prepared or performed. Some of these movies have an historical interest since they captured important moments in the life of the ILL.

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Films and animations

D3

D3 is a spin polarized hot neutron diffractometer. It offers a unique way of accurately measuring the magnetization distribution within crystals at the atomic level. When equiped with CRYOPAD, very precise spherical polarimetric scattering measurements can be performed.

The performances of the instrument depends strongly on its ability of producing an intense and well-polarized neutron beam, and then of analyzing the diffracted beams. This is why the ILL has made great efforts to develop new highly efficient polarization techniques. One of the best successes is the development, in a close collaboration with the University of Mainz (Germany), of a neutron spin filter based on polarized helium-3 gas (3He).

First experiment at the ILL with a 3He neutron spin filter for 100 meV energy neutrons (nov. 1996)

The movies below shows the historic experiment when the first spin filter was produced and then tested on D3 in 1996.

The nuclei of a helium-3 gas (3He) can be polarised. The neutron absorption properties are strongly dependant on the spin polarisation. Hence passing a neutron beam through a bottle filled up with this polarised gas leads to a final beam which is of one polarisation, even for a wide range of neutron wavelengths (white beam polarisation).

Click here to download the 320x240 MPEG-4 movie (file size: 24 Mb)

©1996, E. Lelièvre-Berna, Institut Laue-Langevin

Sequences of this first movie:

- W. Heil (left) and H.Humblot (middle) working on the 3He polariser.
- The 3He filling station uses laser light to polarise metastable 3He atoms. The gas atoms at low pressure (0.7 mbar) are optically pumped. The resulting electronic polarisation is partially transferred to the nuclei through a hyperfine interaction. When enough nuclear-spins have been polarised, the 3He gas is then compressed in a two-stage non-magnetic titanium compressor. We see H.Humblot adjusting the assembly.
- The neutron-spin filter cell is filled with the polarised gas at several atmospheres pressure and then is removed from the compressor by W. Heil. The polarisation remains for a long duration inside the bottle. With the help of T. Roberts, he puts the cell in a special container to transport it to D3 without loss of polarisation.
- W.Heil and H. Humblot carry the filter to the ILL reactor hall where A. Leadbetter (ILL director) is anxiously waiting for them at D3.
- F. Tasset, H. Humblot and W. Heil install the 3He spin-filter on D3.
- F. Tasset is looking at the ratemeter to get a first estimate of the neutron-beam polarisation.

First experiment with the 3He neutron spin filter (nov 1996)

This second movie shows F. Tasset, assisted by H. Humblot and W. Heil installing the spin filter on the D3 diffractometer at the ILL. After several years to develop the technique and the special bottle, this is now the moment of success in actually polarising a neutron beam.

During this experiment, the neutron-beam polarisation achieved by the filter was determined with high accuracy from spin dichroism measurements. It was verified that no significant relaxation was induced by neutron capture, and the wavelength variation of the polarisation down to 0.33Å was in good agreement with the 1/v dependency of the absorption cross-section.

Click here to download the 320x240 MPEG-4 movie (file size: 5 Mb)

©1996, E. Lelièvre-Berna, Institut Laue-Langevin

Sequences of this second movie:

- The cell filled with polarised 3He arrives on D3. The transport container includes two magnetic coils which maintain the polarisation. H. Humblot, F. Tasset, W. Heil and E. Bourgeat-Lami prepare for the measurements.
- F. Tasset transfers the cell into CRYOPAD which provides a homogeneous magnetic field and also acts as a spin flipper.
- The movie ends with a brief view of the zero-field polarimeter developed at PNPI (Gatchina, Russia). This polarimeter is capable of measuring very small rotations of the neutron polarisation.

References

- H. Humblot, W. Heil, E. Lelièvre-Berna and F. Tasset, "The 3He neutron spin filter at ILL", Neutron News 8, 4 (1997) 27-32.
- W. Heil, K.H. Andersen, D. Hofmann, H. Humblot, J. Kulda, E. Lelièvre-Berna, O. Schärpf and F. Tasset, "3He neutron spin filter at ILL'', Physica B 241-243 (1998) 56-63.
- W. Heil, J. Dreyer, D. Hofmann, H. Humblot, E. Lelièvre-Berna and F. Tasset, 3He neutron spin filter'', Physica B 267-268 (1999) 328-335.
- K.H. Andersen, E. Bourgeat-Lami, J. Dreyer, W. Heil, D. Hofmann, H. Humblot, S. Ivanov, J. Kulda, E. Lelièvre-Berna, A. Petoukhov, L.-P. Regnault, T. W. Roberts, J.R. Stewart, F. Tasset, M. Thomas and A.R. Wildes, "Recent news on ILL polarised 3He developments", Physica B 276-278 (2000) 65-66.
- T.W. Roberts, H. Humblot, F. Tasset, E. Lelièvre-Berna, A.R. Wildes, A. Ivanov, A.K. Petoukhov, L.-P. Regnault, A.D. Hillier, J. Kulda, J.R. Stewart, M. Thomas, P. Malbert, D. Jullien, Y. Gibert, R. Gay, E. Bourgeat-Lami and R. Chung, "The current status of the 3He neutron spin filter (NSF) project at the ILL", Physica B 297 (2001) 282-287
- E. Lelièvre-Berna, "Novel polarized neutron tools", Advances in Neutron Scattering Instrumentation, Ian Anderson and Bruno Guérard, Editors, Proceedings of SPIE 4785 (2002) 112-125, ISBN 0-8194-4552-5
- A. S. Wills, E. Lelièvre-Berna, A. Sella, F.G. Cloke, P.L. Arnold, F. Tasset, J. Schweizer, R. Ballou, "Magnetisation distribution measurements from powders using a 3He spin filter: a test experiment", Physica B 356 (2005) 254-258
- A.K. Petoukhov, V. Guillard, K.H. Andersen, E. Bourgeat-Lami, R. Chung, H. Humblot, D. Jullien, E. Lelièvre-Berna, T. Soldner, F. Tasset and M. Thomas, "Compact magnetostatic cavity for polarised 3He neutron spin filter cells", Nuclear Instruments and Methods in Physics Research B 560 (2006) 480-484
- E. Lelièvre-Berna, "Mid-term report of the NMI3 neutron spin filter project", Physica B 397 (2007) 162-167
- E. Babcock, A. Petoukhov, J. Chastagnier, D. Jullien, E. Lelièvre-Berna, K.H. Andersen, R. Georgii, S. Masalovich, S. Boag, C.D. Frost and S.R. Parnell, "AFP flipper devices: Polarized 3He spin flipper and shorter wavelength neutron flipper", Physica B 397 (2007) 172-175.

English checked by: Ronen Ghosh, April 2007.
Updates: A.Filhol, 1 Nov 2008, 9 Sept 2009.

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