Crystal Alignment

In-situ Crystal Alignment at Low Temperature

J. Allibon, E. Bourgeat-Lami, L. Chapon, Ph. Decarpentrie, J.-P. Gonzales, J. Halbwachs, E. Lelièvre-Berna, J. Ollivier, B. Ouladdiaf, G. Pastrello
Institut Laue Langevin, 71 Avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France

To carry out elastic Spherical Neutron Polarimetry experiments, 3D access to Bragg peaks in different scattering planes is required to elucidate complex magnetic structures from a few specifically chosen Bragg reflections [1] and to determine magnetisation distributions from many reflections [2]. We present the performances obtained during the commissioning phase on the polarized neutron diffractometer D3 with the non-magnetic Eulerian cradle called Cryocradle [3].

Very compact three-axis spectrometers are proposed to measure smaller samples. They will integrate focusing optics from the monochromator to the sample, a compact wide-angle analyser and motorized collimators located very near the sample position. Because these optical components will be installed inside and outside the cryostat, the only way to align the crystal on the instrument will be to manipulate it from inside the cryostat. We present the performance of a new eucentric system based on the idea developed by Berneron et al. in the 80s [4].

[1] P.J. Brown, Physica B 297 (2001) 198
[2] P.J. Brown, J.B. Forsyth, E. Lelièvre-Berna and F. Tasset, J. Phys. Cond. Matter 14 (2002) 1957
[3] E. Lelièvre-Berna, E. Bourgeat-Lami, Y. Gibert et al., Physica B 356 (2005) 131
[4] M. Berneron, A. Filhol, J.-J. Vernier et al.,
Revue Phys. Appl. 19 (1984) 795