Cryogen free He-3 refrigerators

Cryogen free He-3 Refrigerators (Registered Trademark: Cryocloud^®), including one-shot He-3 refrigerator/insert and continuous He-3 refrigerator, are widely used in STM, AFM, Near-field optics, ARPES, SQUIDS, TES, Quantum Hall effect, X-ray, Neutron scattering, De Haas van Alphen testing, Superconducting detectors, Astronomy, Quantum computing, etc.

The top of the one-shot He-3 refrigerator is integrated with a He-3 storage tank, and the interior is equipped with a He-3 pot, a cryopump, and sealed He-3 gas loop. He-3 gas in the He-3 storage tank is condensed by a cold source and flows into the He-3 pot. The He-3 pot is cooled down to 300mK or even lower by the built-in cryopump, and can be maintained at the base temperature for dozens of hours or even longer. According to different cooling sources, single-shot He-3 refrigerators can be divided into two categories: integrated single-shot He-3 refrigerators and split single-shot He-3 refrigerators. Among them, the 4K cold head of the integrated single-shot He-3 refrigerator is integrated into the He-3 refrigerator cryostat. The cooling source of the split single-shot He-3 refrigerator comes from the helium recirculating cryogenic system (Qcryo). The superfluid helium is transferred from Qcryo to the single-shot He-3 refrigerator through a flexible super insulated pipeline to condense He-3 gas. This split design completely isolates the vibration of the 4K cold head and compressor from the He-3 refrigerator, making it particularly suitable for experiments such as STM and AFM that are highly sensitive to vibration.

The continuous He-3 refrigerator is equipped with an external high-speed vacuum pump station and a gas handling system, which allows condensed He-3 inside the pot to be pumped to obtain ultra-low temperature while the pumped He-3 gas is processed by the gas handling system before entering the He-3 refrigerator. After multi-stage pre-cooling, it is condensed and then injected into the He-3 pot, achieving long-term continuous operation at the base temperature. Continuous He-3 refrigerators include integrated continuous He-3 refrigerators and split continuous He-3 refrigerators. The 4K cold head of the integrated continuous He-3 refrigerator is integrated into the He-3 refrigerator cryostat, while the cooling source of the split continuous He-3 refrigerator comes from the Qcryo. This split design completely isolates the vibration of the 4K cold head and compressor from the He-3 refrigerator, which is particularly suitable for experiments that are sensitive to vibration. Various options including built-in superconducting magnets are provided. 

1.Integrated continuous He-3 refrigerator 

Model: Cryoloud-100

Using 4K pulse tube or GM cooler as the cold source, efficient pre-cooling and condensation of He-3 are achieved through multi-stage heat exchange and counterflow technology, as well as optimized flow resistance. The gas handling system with external liquid nitrogen cold trap and sealed circulation pump station ensures that the He-3 refrigerator runs continuously for a long time. The specially designed high-performance thermal switch greatly shortens the initial cooling down time.

The outstanding advantage of the integrated continuous He-3 refrigerator is its large cooling capacity and ability to operate continuously for a long time, making it particularly suitable for angular momentum resolved photoelectron spectroscopy (ARPES) experiments that require large cooling capacity, experiments that require cooling of large mass samples, or experiments that require long-term uninterrupted ultra-low temperature testing. The integrated continuous He-3 refrigerator also offers the option of top loading and unloading design, using a insert with a force generator in conjunction with a loading locking design, allowing the He-3 refrigerator to perform sample replacement while in operation. The integrated continuous He-3 refrigerator can be equipped with built-in single-axis, two-axis, and three-axis superconducting magnets.

Integrated continuous He-3 refrigerator

2.Split continuous He-3 refrigerator 

Model: Cryoloud-200

The cold source of the split continuous He-3 refrigerator comes from the helium recirculating cryogenic system(Qcryo). Thoroughly isolate the vibration of the 4K cold head and compressor from the He-3 refrigerator, Split continuous He-3 refrigerator is especially suitable for vibration sensitive experiments such as SPM, microscopic optics, quantum optics, and quantum precision measurement. The cryostat of the split continuous He-3 refrigerator can be designed to be ultra-high vacuum compatible according to requirements, and can be baked to 150℃, making it particularly suitable for applications that require low vibration, low temperature, and ultra-high vacuum (such as STM, NanoARPES).

Split continuous He-3 refrigerator

Typical cooling curve of split continuous He-3 refrigerator

The cooling power VS temperature of a typical split continuous He-3 refrigerator (Note: The cooling power is related to vacuum pump station)

3.Integrated single-shot He-3 refrigerator

Model: Cryoloud-300

The integrated single-shot He-3 refrigerator usually uses a pulse tube cooler as the cold source. The top of the He-3 refrigerator is integrated with a He-3 storage tank, and the cryostat of the refrigerator is integrated with a He-3 pot, a cryopump, and sealed He-3 gas loop. The He-3 gas in the He-3 storage tank is condensed and flows into the He-3 pot. The optimized condensation design combined with the high-efficiency thermal switch design makes the initial cooling time usually less than 10 hours. The built-in cryopump can pump the He-3 pot to below 270mK and maintain at the base temperature for more than 100 hours.

Compared with the continuous He-3 refrigerator, the single-shot He-3 refrigerator does not require an external gas handling system, has the characteristics of simple operation, high cost-effectiveness, and low maintenance costs.

The integrated single-shot He-3 refrigerator (Cryoloud-300) shown in below figure uses a split valve pulse tube cooler and the cold head suspension anti-vibration, integrates 16 RF semi-rigid cables and 72 low-temperature twisted pair cables, He-3 cold plate diameter of 20cm, initial cooling time:<8 hours, base temperature:<280mK,  holding time:>100 hours, temperature stability: ± 1mK.

Integrated single-shot He-3 refrigerator

Typical cooling down and holding curve of Cryoloud-300

4. Split single-shot He-3 refrigerator 

Model: Cryoloud-400

The cooling source of the split single-shot He-3 refrigerator comes from the Qcryo，Similar to the integrated single-shot He-3 refrigerator, the top of the split single-shot He-3 refrigerator integrates a He-3 storage tank, and the cryostat of the refrigerator integrates a He-3 pot, a cryopump and sealed He-3 gas loop. The He-3 gas in the He-3 storage tank condenses and flows into the He-3 pot, which can be lowered to 270mK by the built-in cryopump and maintains at the base temperature for dozens of hours or even longer.

Unlike the integrated single-shot He-3 refrigerator, the split single-shot He-3 refrigerator's cooling source comes from Qcryo. Addressing the common issue of big vibration in current cryogen free He-3 refrigerators, it is particularly suitable for experiments that are sensitive to vibration, such as STM, SEM, AFM, microscopic optics, single photon detection, quantum precision testing, and other fields. Compared with the continuous He-3 refrigerator, the split single-shot He-3 refrigerator does not require a complex external He-3 circulation gas path, has relatively simple operation, high cost-effectiveness, and low maintenance costs.

Split single-shot He-3 refrigerator 

Ultra high vacuum compatible with Cryoloud-400-UHV, integrated with shutters, capable of baking up to 150℃, with a vibration level of less than 10nm, a base temperature of less than 290mK, and a holding time of over 120 hours at the base temperature. It is particularly suitable for SPM applications that require low vibration and ultra-high vacuum.

UHV compatible split single-shot He-3 refrigerator & Typical holding curve of Cryoloud-400-UHV

5. He-3 insert

Model: Cryoloud-500

The He-3 insert can match with a top-loading 1.5K refrigerator (Acryo-1.5K) and cryogen free variable temperature superconducting magnet (CryoM), with a built-in cryopump and sealed He-3 gas loop. It operates in single-shot mode, with a base temperature of ≤ 270mK and holding time of ≥ 60 hours without extra heat load and a cooling capacity of ≥ 100uW at 350mK. The standard He-3 insert sample environment is vacuum, with the option of He-3 exchange gas and longer holding time. Typical applications include electromagnetic transport testing, quantum Hall effect, superconducting device testing, Squid testing, high voltage (DAC), thermal transport testing, etc.

He-3 insert

Typical cooling power of He-3 insert