Cryogen Free Integrated Variable Temperature Insert (CFiVTI)

The cryomagnet system incorporates a Variable temperature sample space of 25mm or 30mm cooled by gas flow. A single cryocooler is used to cool both the VTI and the magnet using our patented design. Helium gas is circulated using a room temperature dry pump and cooled by the first and second stages of the cryocooler to 4K at which point it condenses into liquid helium. The liquid is collected in a small buffer tank just below the second stage. From here it is drawn off and expanded through a Joule Thompson needle valve to achieve a temperature of 1.6K. The gas then passes through a heat exchanger controlled to achieve the set temperature and from there to VTI sample space. The exchange gas in the sample chamber ensures rapid temperature change and good thermal contact to the sample.

The temperature of the sample chamber is varied by using a heater and Cernox thermometer on the heat exchanger which is controlled by a temperature controller (Lakeshore 340).

Samples are top loaded into the sample access column via an airlock and gate valve located at the top of the VTI to allow access to the centre of the temperature-controlled region.

A helium gas reservoir (50 litre NTP capacity) is supplied filled with helium gas at one atmosphere. The gas used is 99.995% purity and in the event of accidental contamination, when changing samples for instance, the gas can be replaced at low cost.

All the measurement probes are designed to top load into the variable temperature sample space.

Experienced operators can typically change samples in a few minutes.

Researchers can choose the Experiment Measurement Options that meet their immediate requirements and add-on or upgrade measurement options in the future

High Temperature Option

To perform measurements at above room temperature, two separate heated sample mounts are offered for electrical or magnetic measurement systems, which increase the standard temperature range. In normal operation, the system has a continuous temperature range of 1.6 to 300K. With these inserts the range can be extended to a temperature range of up to 750K.

Cryogen Free Variable Temperature Insert Specifications

Temperature range:
1.6 to 350K VTI with sample in continuous gas flow.
1.6 to 350K VTI with sample in exchange gas.
Up to 750K with heated sample platform.
Under 300mK with He3 insert.
Dilution Refrigerator insert to 30mK.

Temperature control accuracy
(with Lakeshore series unit)
5mK @ 10K   10mK @100K   50mK @ 300K

Typical sample cool down time from 300K to 1.6K: 30 minutes