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Janis exchange gas systems offer two main advantages to the experimenter:
rapid sample exchange while the refrigerator is operating, and efficient
cooling for non-conductive or irregularly shaped samples not easily clamped to a
cold finger (e.g., powders, liquid solutions, etc.).
These advantages are made possible by using the refrigerator to cool a
column of helium exchange gas surrounding the sample.
The sample is inserted, via a long rod, into a nearly isothermal region
of the gas column for cooling. Sample
exchange by simply removing the sample rod, switching samples on the
rod, and reinserting the rod into the cryostat.
The entire sequence takes only a matter of minutes and is performed while
the refrigerator is operating. Thus
the time to cool successive samples is greatly reduced as compared with
sample in vacuum cryostats.
The cooler is mounted above
the sample chamber in these cryostats. This
design permits the sample region to be inserted into the sample chamber of a
spectrometer or the room temperature bore of a superconducting magnet.
Optimized for experiments
requiring optical access to the sample, the SHI-950 and
SHI-950-5 systems include the following components:
- Isothermal static helium gas
sample chamber, with exchange gas introduction valve
- Optical vacuum shroud and
radiation shield
- Gold-plated OFHC copper
sample holder
- Adjustable sample positioner
with 8-pin and 10-pin electrical feedthroughs for thermometry and customer
wiring into the sample area
- Two spare electrical access
ports
- Evacuation valve and safety
pressure relief
- Four-way optical access into
the sample chamber
- Silicon diode thermometer
and control heater
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Pulse Tube Cooled version
is also available. |
