CMD

Cool to the max by using the latent heat of enthalpy produced as liquid Helium 3 dissolves in liquid Helium 4. Once again, our Continuous Miniature Dilution (CMD) coolers are compact, sealed units that need no external gas supply and will never need to be refilled with expensive Helium 3. The CMD incorporates our 300mK continuous cooler (CC7) to pre-cool and buffer the dilution module. If you are interested in the potential applications for this unique cooling technology, get in touch with us to discuss your needs and how we might help.

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CMD performance notes

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Overview

The CMD is a small dilution system designed to interface to a low-power 4K precooler, such as a Gifford-McMahon (GM) cryocooler. It consists of a sealed dilution module, pre-cooled by CRC’s continuous CC7 system. The CC7 has two sets of 3He and 4He modules, cycled alternately to keep the central 300mK split condenser permanently cold. This in turn cools the condenser of the dilution module. The dilution module Mixing Chamber is the cold head of the CMD system.

Unlike a conventional dilution cooler, the CMD has no external gas handling or pumped gas circulation. The sorption cooler only requires electrical connections to the outside of the cryostat. This makes it very small and compact.

RDK-101 Performance Notes

RDK-408 Performance Notes

Sumitomo Heavy Industries’ RDK-408D2 4K GM Cryocooler, run with an FA-40 compressor, provides a second stage cooling capacity of approximately 0.9W at 4.2K (1).

Mixing Chamber Average Temperature on RDK-408

Seen above is the load response of the dilutor (on an RDK-408) utilising the still’s pre-wired precision heater to increase circulation rate of the helium. From experimental results, the CMD can operate 450µW applied to the still, the dilution module can provide approximately 3.5µW of cooling power at 100mK. This may vary between CMD systems. In CRC’s system, this takes approximately 43 hours to cool to dilution temperatures.

CMD, Operated from RDK-408/FA-40

CMD Pin-Out

Precooler Modules — 21 Pin (Female)
Function	Type	PIN #	Drive current or voltage	Resistance
3He HEAD THERMOMETER V+ 3He HEAD THERMOMETER V-	Resistance thermometer	1 12	100nA Constant Current	1kΩ
4He HEAD THERMOMETER V+ 4He HEAD THERMOMETER V-	Resistance thermometer	2 13	100nA Constant Current	1kΩ
DIODE 4He PUMP I+ DIODE 4He PUMP I-	Diode thermometer	4 14	10 µA
DIODE 3He PUMP I+ DIODE 3He PUMP I-	Diode thermometer	5 15	10 µA
DIODE 4He SWITCH I+ DIODE 4He SWITCH I-	Diode thermometer	6 16	10 µA
DIODE 3He SWITCH I+ DIODE 3He SWITCH I-	Diode thermometer	7 17	10 µA
HEATER 4He SWITCH I+ HEATER 4He SWITCH I-	Low power heater (a few mW)	8 18	4 to 5 Volts	10kΩ
HEATER 3He SWITCH I+ HEATER 3He SWITCH I-	Low power heater (a few mW)	9 19	4 to 5 Volts	10kΩ
HEATER 4He PUMP I+ HEATER 4He PUMP I-	High power heater (up to about 2W)	10 20	50 to 100 mA 15 to 30 V	300Ω
HEATER 3He PUMP I+ HEATER 3He PUMP I-	High power heater (up to about 2W)	11 21	50 to 100 mA 15 to 30 V	300Ω

Dilution Module — 15 Pin (Female)
Function	Type	PIN #
Mixing Chamber V+ Mixing Chamber V- Mixing Chamber I+ Mixing Chamber I-	Resistance thermometer	1 9 2 10
Still V+ Still V- Still I+ Still I-	Resistance thermometer	3 11 4 12
Condenser Plate V+ Condenser Plate V- Condenser Plate I+ Condenser Plate I-	Resistance thermometer	5 13 6 14
Still Heater I+ 100kΩ Still Heater I- 100kΩ	Low power heater (a few mW)	8 15

Connector diagrams

Assembly diagram

References

1. Sumitomo Heavy Industries. RDK-408D2 4K Cryocooler Series. [Online] [Cited: 09 16 2026.] https://shicryogenics.com/product/rdk-408d2-4k-cryocooler-series/.

2. —. RDK-101D 4K Cryocooler Series. [Online] [Cited: 16 09 2026.] https://shicryogenics.com/product/rdk-101d-4k-cryocooler-series/.

3. —. RDK-101D 4K Cryocooler Series. [Online] 16 09 2026. https://shicryogenics.com/product/rdk-101d-4k-cryocooler-series/.

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