SuperVariTemp Cryostat Systems - Sample in Flowing Vapor
The Janis Research SuperVariTemp (SVT) system is the basis for a variety of variable temperature cryostats. Offering quick sample exchange, an operational range of 1.5-300 K and highly efficient operation, this versatile system is often incorporated into Janis' CNDT series dewars or, for maximum flexibility, this concept is applicable with virtually any dewar.
By controlling the temperature of the flowing helium vapor in which samples are immersed, both the sample and holder are simultaneously cooled to the same temperature, thereby eliminating the need for thermal anchoring and sample mount heating. The helium flow rate and heater current are balanced to provide flowing vapor/sample temperatures over the range of 1.5-300 K; automatic temperature controllers together with application specific thermometry provide accurate and precise temperature control.
The SVT cryostat makes full use of the cooling power of escaping helium vapor as it exits the sample chamber, resulting in improved efficiency over exchange gas systems. Operation of the SVT typically adds about 0.1 L/hr to the total liquid helium evaporation rate of the dewar. The sample chamber is thermally isolated from the helium reservoir by the dewar vacuum, thereby eliminating heat conduction into the reservoir. This provides for low helium consumption rate even at higher sample temperatures.
The SVT's unique design allows for operation below 4.2 K without wasteful pumping on the main helium reservoir. Operation below lamda is readily achieved with the sample immersed, either in liquid or vapor, by simply throttling the rate of helium introduced to the sample chamber while evacuating the sample tube.
All SVT Models Include:
- Janis Research SuperVariTemp system
- Top-loading sample positioner
- One (1) 10-pin and two (2) 8-pin electrical feedthroughs
- Safety pressure relief valve
- System test
- Isothermal zone sample tube (provides uniform sample temperature and enhanced operation with LN2)
- Bottom looking optical access
- Indium sealed, strain-relieved, cold windows
- Cooled radiation shield windows
- Liquid helium level indicator
- Liquid nitrogen autofill system
- Multi-pin and coaxial electrical connectors
- Alternative window materials
Optical cryostat for experiments requiring long hold times or a larger sample space, featuring a 6 liter liquid helium capacity.
Non-optical cryostat for experiments requiring long hold times or a larger sample space, featuring a 6 liter liquid helium capacity.
Similar to the standard SVT-200T, but custom designed for NMR Spectroscopy.
Designed with long-running experiments in mind, this optical cryostat features an increased liquid helium efficiency and a 5 liter helium capacity.
This cryostat incorporates an increased liquid helium efficiency in a tubular tail design for long-running non-optical experiments.
The system's ultra-low cryogen consumption, remarkable temperature homogeneity and stability make it ideal for long or short term experiments.
Janis offers special sample positioners with the ability to rotate the sample about the optical axis of the cryostat.