The minimum measured temperature is 6 or 7 K. Safe minimum, assuming all the shielding is in
place, is usually ~10K. In this
case "Shielding" means a small (12mm ID) Be cap, an Al/Kapton
intermediate shield and the outer Be vacuum window.
The sample holder should (1) support the sample (2) provide
thermal contact (3) not create background.
For small samples, we typically use a "Type 1"
holder - where the sample is glued to a thin glass or pointed sapphire rod and
this is glued into the holder. (With wax samples have fallen off at low T.) Note that
for cases where precise low-T control is required, glass is not reccomended
For large samples, a "Type 2" holder is OK and
usually the sample is attached directly to the copper using varnish. Of course, this is NOT appropriate for a transparent sample!
In both cases, the sample should be about 30 to 31 mm from a
tapped hole in the cryostat (M4) as shown.
Other alternatives are also shown.
For Bragg geometries (the usual case, as most samples
absorb) the surface of the sample should be on the axis of the holder.
Sample Size Guidelines (approximate only!)
Small Sample = Dimension transverse to the incident beam < 0.4 mm in one direction.
Large Sample = Dimensions transverse to the incident beam > 1 mm in each direction.
Sample Holder Drawings