Joule-Thomson miniature coolers [ Return towards Cryogenic coolers for optronics ]

Technology tailored to very rapid cool-down operations

This range of coolers is used for the cryogenic refrigeration by Joule-Thomson cycle, in a temperature range of 80-100 K, of infrared detectors or electronic components, on the ground or on-board, in conditions of harsh environmental stress such as defense systems.

For this type of application, the technological simplicity and sturdiness of miniature coolers based on a compressed gas unit are evidence of reliability and ease of integration.

The range comprises coolers that differ according to refrigerant capacity, cool-down time and autonomy specific to the application. These levels of performance are obtained as a function of the type of gas used, pure gas like nitrogen or argon, or gas mixture, and the inlet pressure of this gas.
These coolers comprise:
- A heat exchanger in which the high pressure gas is pre-cooled in counterflow by the expanded low pressure cold gas
- An expansion outlet of fixed cross-section (single flow devices), or dual cross-section (dual flow devices), or variable cross-section (metered devices)
- A valve with actuator and obturator to vary the cross-section of the expansion outlet (dual flow and metered devices)
- Differential contraction valve for rapid cool-down of a significant thermal mass
JT coolers are mounted in cryostats with thermal insulation vacuum. The gas is liquefied at the well bottom on which the infrared detector for cooling is assembled.

Range

	Single flow JT	Dual flow JT	Metered JT
Cool-down time at 20°C	< 2 s	< 10 s	< 60 s
Cryogenic temperature	100 K	95 K	80 K
Gas used	Argon	Argon or mixtures	Nitrogen
Typical autonomies	> 10 s	> 1 mn	> 1 h
Main applications	Missile homing devices	Missile homing devices	Missile homing devices, radar, thermal cameras

Do not hesitate to get in touch with us in relation to specific products.

Key benefits

Very fast cool-down time (up to 1s)
Access to a wide variety of technologies
Significant autonomy after launch and good temperature stability
Long operating lifetime

Main technical characteristics

Cooling operations based on different types of gas: argon, nitrogen, freon, air, nitrogen argon mixtures,
Dewar diameter: 3.3 mm, 5.18 mm, 7.23 or on request
Thermal mass to be cooled: from 15 J to 300 J (or on request)
Heat loss: from 130 mW to 200 mW (or on request)
Very low induced vibration level

Standards

Gas purity: DEF STAN 58-96 issue 2
Environment: MIL STD 810D

References

Missile guidance systems, main programs in terms of volume: 15,000 Mistral ground-to-air Missile coolers (SAGEM Défense Sécurité), 7,000 Magic 1 and 2 air-to-air Missile coolers (SAGEM Défense Sécurité)