Sample cans are generally made of either vanadium or Ti.Zr null alloy since both of these materials give an almost featureless background. For most experiments cylindrical sample cans are used and the following are available:

A selection of fittings for sealing and mounting are available for the standard drawn vanadium cans. For room temperature and low temperatures a screw top fitting with a PTFE vacuum seal is normally used, whereas for high temperature there is a compresson fitting small enough to fit into the Leicester furnace. The Ti.Zr cans are normally sealed by use of a stopper with a rubber O-ring. The thin vanadium foil cans are made from 25 micron foil and hence they give a very small background and have a very small attenuating effect on the sample data, which can be very advantageous in extracting a reliable absolutely normalised result. However, these cans are not at all leak-proof. Furthermore the number of these cans available is at present small and you are advised to contact your local contact in advance if you wish to use them.

The size of sample can should be chosen so that the sample is large enough to give an adequate amount of scattering, but is sufficiently small that self attenuation and multiple scattering are not too severe. A commonly used rule-of-thumb is that the sample should not scatter more than 10% of the beam that is incident on it. The data analysis programs are designed for the well-conditioned setup where the sample extends both below the bottom of the beam and above the top of the beam (see also sections 3.4 and 3.5).

For plate geometry, there is a set of TiZr cans with O-ring vacuum seals. They have sample thicknesses of 1 mm, 2 mm or 4mm.

For special needs, cans with other geometries may be made by spot-welding thin vanadium sheet. For example, vanadium sachets have proved useful for thin small plate samples.

Last Updated 09 Nov 1998