Kelvinox^®MX : Dilution refrigerator with modular design

There are four models of KelvinoxMX.

Key:  ◊ = Included with system

System components:

The KelvinoxMX is made up from three main components:

• Primary insert : provide a 50 mm line-of-sight access into which a range of interchangeable experimental inserts can be fitted.  1.5 K cooling is provided by continuous flow of 4He through the innovative stretched 1 K condenser design which minimises microphonic noise generation.  Rapid experimental turnaround times are enabled by a sliding seal permitting safe removal and replacement of the dilution refrigerator, while minimising helium loss.
• Dilution unit: there are four choices of dilution unit.  MX100 - providing 100 µW, MX250 - providing 250 µW and MX400 - providing 400 µW.
• Experimental inserts: 
  Basic  - fitted with a 6 mm line-on-sight access to the inner vacuum can (IVC).
  High Frequency - equipped with semi-rigid and flexible co-axial lines.  Ideal for high frequency applications (<20GHz). It is also fitted with a 24-wire loom to the mixing chamber position.
  Rotator: this insert is fitted with similar services to the High Frequency model.  In addition, a rotating mechanism, Swedish rotator (manual or automated) is also supplied.
  Versatile: this is an ideal platform to customise your own experiment.  Experimental access is provided by a 15 mm diameter line of sight port to the mixing chamber and 3 x 8 mm diameter line of sight port to the IVC.  These are terminated at room temperature by NM25/16 flanges.
  Dipper: this adapts the versatile insert and allows it to be cooled independently of a KelvinoxMX by immersing it directly in liquid helium either in a transport dewar or in an Integra™ system dewar.

Automation and control of your dilution refrigerator using the KelvinoxIGH - Intelligent Gas Handling system :

All systems are delivered with a KelvinoxIGH which is a fully automated system which enables complete operation of a dilution refrigerator using sophisticated software and virtual instrument drivers for National Instruments'LabVIEWTM.

Options :

• EX100 : Basic experimental insert 
• EX200 : High frequency experimental insert
• EX300 : Manual rotator experimental insert
• EX310 : Automatic rotator experimental insert
• EX400 : Versatile experimental insert
• LE100 : LECSH low eddy current sample holder
• CS100 : ROTH1, 30 point calibrated RuO2 sensor to 50 mK
• CS200 : ROTH2, generic calibration RuO2 sensor
• RB100 : AVS47 resistance bridge with rf filtering, cables & IEEE interface
• TS530 : Temperature controller for use with AVS47 resistance bridge
• IPC : Isobus Picobus converter
• VB100 : Bucket IVC for EX400 insert
• VM100 : Magnet IVC for EX400 insert
• VS100 : Adapter bafle for EX400 insert
• VI100 : ISO-K adapter for EX400 insert
• HTC : Helium cold trap
• Transfer tubes
• HE3F : 3He flow meter
• BK100 : Bucket IVC
• VIN : Valves in pumping lines

Solutions to helium rising costs  :

The KelvinoxMX is compatible the IntegraAC, recondensing liquid helium cryostat.

This product has been developed to significantly reduce the consumption of liquid helium by recondensing helium gas evaporated within the system, which would other wise be vented from the cryostat. This decreases the frequency of helium refills. Cryogenic systems can be kept cold continuously, even when in stand by mode, leading to greater freedom to schedule experimental time.

The Dilution Process:

When a mixture of 3He and 4He is cooled below 870 mK, it separates into two phases. The lighter 'concentrated phase' is rich in 3He and the heavier 'dilute phase' is rich in 4He. The concentration of 3He in each phase depends upon the temperature. Since the enthalpy of the 3He in the two phases is different, it is possible to obtain cooling by evaporating the 3He from the concentrated phase into the dilute phase.

These concentrated and dilute phases separate and a phase boundary established in the mixing chamber, where the cooling process takes place.

To establish continuous cooling one must promote the flow of 3He across the phase boundary in a continuous process. This is achieved by raising the temperature of the dilute phase to ~700 mK outside of the mixing chamber in the still. The vapor pressure of 3He at this temperature is two orders of magnitude higher than that of 4He allowing 3He to be preferentially pumped using external room temperature mechanical pumps or charcoal sorption pumps. This exhausted 3He can be returned to the system, condensed on the 1K pot, pre-cooled at the still and then further cooled through heat exchange with the exiting stream using a continuous heat exchanger ~150 mK and a series of silver sinter step heat exchangers from 100 mK to 20 mK, before being reintroduced to the mixing chamber to continue the process.

To protect the cooling platform from heating the dilution unit and 1K pot are housed in a vacuum with a radiation shield from either the still or 100 mK cold plate that surrounds the heat exchangers and sample space below the mixing chamber.

With careful design temperatures below 5 mK are achievable with a dilution refrigerator.

The KelvinoxMX design allows the cryogenic cycle of the dilution refrigerator and the experimental wiring to be kept seperate.  The experimental insert is interchanged at room temperature using the large 50 mm line-of-sight port on the primary insert.  Once the experimental insert is aligned with the primary insert, thermal straps secure the two together.  These thermal straps are designed to be easy to use whilst also ensuring an optimised thermal link.  The sealing between the primary insert and the experimental insert is formed at the top place by an O-ring seal and a novel design of indium seal at the IVC flange.  The system is then ready to be cooled down as a standard dilution refrigerator.

KelvinoxIGH - Gas handling system