A chamber (422) for a cryostat (420) includes: first and second annular sections (4221, 4222) separated and spaced apart from each other along a first direction, and a third annular section (4223) extending in the first direction between the first and second annular sections and connecting the first and second annular sections to each other. The first and second annular sections define corresponding first and second internal volumes, the third annular section defines a third internal volume, and the third internal volume is substantially less than the first internal volume and substantially less than the second internal volume.