Desktop cryogen free NMR
Systems
Cryogenic have built a miniature
cryogen free magnet with 5 ppm uniformity at fields of
2.5 Tesla and 10-7 in
persistent mode.
The magnet is cooled by a small
refrigerator to 3K without the use of liquid helium. The
overall dimensions of the cryostat are 260mm x 240mm x
540mm. The workspace is a bore of 51mm but other sizes
are practical in the same geometry.
For the lower field the system is
designed to run with a 1 killowatt air-cooled
single-phase compressor making the magnet easy to use by
non-specialists and to transport between locations. The
magnet is intended for use in ESR as well as low field
NMR experiments. It is thought to be the smallest high
field superconducting NMR magnet yet
built.
The magnet operates in vacuum and there is no
requirement for any liquid cryogens. The current for the
magnet is set at 30 amps. A resistive lead extends from
room temperature to the 1st stage of the cooler. The
heat load from the current leads is about 1.5 watts. The
1st stage operates close to 50K, which is well below the
transition temperature of BISCO high temperature
superconductors, which are used to carry the current
from the 50K stage to the 4K stage. These impose a heat
load of 25 milliwatt on the 4K stage to which the magnet
is attached.
Nominal
Specifications and Dimensions
| Field |
2.5 Tesla |
| Working Bore |
51mm |
| Operating Current |
30 Amp |
| Persistent Mode |
10-7 per hour |
| Homogeneity |
5ppm in 10mm
DSV |
| Cryostat Dimension |
260 x 240 x
540mm |
| Weight |
40kg |
| Input power |
1 Kw |
| Operating Performance |
Stage 1: 55K
Stage 2: 2.6K
Magnet: 2.6K
Cooldown: 15
hours |
|
