SHI’s Two-Stage 4 K GM Cryocoolers: Enriching

Emerging Technologies through Leading-Edge

Advancements

T. Lei1, S. Dunn1, B. Gronemeyer1, M. Xu2, T. Morie2, and Y. Hiratsuka2

1
Sumitomo (SHI) Cryogenics of America, Inc., Allentown, PA 18103, USA
2
Sumitom Heavy Industries, Ltd., Tokyo 188-8585, Japan

ABSTRACT
The SHI Cryogenics Group, along with its parent company Sumitomo Heavy Industries, Ltd.,
is a global leader in cryogenic technology. During its 60-year history it has grown to design and
manufacture the broadest array of cryocoolers and related cryogenic systems worldwide, serving
magnetic resonance imaging (MRI), semiconductor, flat panel display, laboratory, aerospace, and
other research applications. Aligning with our goal to create a better tomorrow through innovative
solutions, we enable emerging technologies through advancements in cryocooler development and
provide exceptional performance and service through our global network.
With our customers facing helium supply shortages and higher costs, we developed the leading-
edge RDE Two-Stage 4 K Gifford-McMahon (GM) Cryocooler Series, enabling the MRI industry
to transition from helium bath designs to low cryogen designs. Specifically, we present the RDE-
418D4 cryocooler, which increases cooling performance by 20% over our previous models and
provides 2.0 W at 4.2 K and 50 W at 50 K with a power consumption as low as 7.5 kW at 60 Hz.
For the fast growth of quantum technologies, our RDK-101D(L) cryocooler, which has been
the world’s smallest two-stage 4 K GM cryocooler, continues to evolve and enables applications
like desktop quantum systems, single photon detectors, and optical quantum systems. This
innovative, low-vibration cryocooler features a guaranteed minimum temperature of <2.3K and
provides 0.16/0.2 W at 4.2 K (50/60 Hz) with about 1 kW input power. Our pulse tube refrigerator
product line is expanding rapidly to meet the growing needs of dilution refrigerators and quantum
computing systems. Our newest model, RP-222B3S, provides 2.0 W at 4.2 K.

INTRODUCTION
With roots in both Sumitomo Heavy Industries (Japan) and Air Products and Chemicals (United
States), SHI Cryogenics Group has been providing solutions for cryogenic refrigeration to
government, industry, and academia for well over 60 years. We reach around the globe with
manufacturing in Japan, the Philippines, and the United States; research and development in Japan
and the United States; and sales and service support in Germany, the United Kingdom, Japan,
China, South Korea, Taiwan, and the United States.
A strong research and development program has enabled our group to provide reliable prod-
ucts for the ever-changing applications around us. This R&D effort has enabled our current com-

Cryocoolers 22, edited by R.G. Ross, Jr., J.R. Raab and S.D. Miller
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Figure 1. Specified and typical performance of the RDE-418D4 cold head

mercial cryogenic product line to include single- and two-stage GM cryocoolers, single- and two-
stage GM-type pulse tube cryocoolers, cryopumps, cold traps, and helium compressors.
Recent improvements in our two-stage 4 K products have helped lead the way for emerging
applications in magnetic resonance imaging (MRI) and quantum technologies.

4 K GM ADVANCEMENTS FOR LOW-CRYOGEN MRI

Clinical MRI has revolutionized medicine, but it has also become the largest single consumer
of helium, representing approximately 20% of the global helium demand [1]. Each new traditional
MRI system ships with 1,000 liters or more of liquid helium. A cryocooler typically prevents
helium loss after a system’s final installation. However, shipping, maintenance, and service events
consume significant additional quantities of liquid helium, as cryocooler operation is generally
unavailable during these times. To confront the increasingly tight helium supply, MRI manufacturers
have begun to introduce systems with little helium content. In 2019, Philips introduced the first
commercial low-cryogen MRI system, their BlueSeal product, containing only seven liters of liquid
helium and is sealed against helium loss. In 2021, Siemens released their Magnetom Free.Max
system containing less than one liter of liquid helium and also sealed against loss. These systems
no longer have the temperature stability and heat capacity of the liquid helium bath and no longer
can be cooled down with liquid helium. Therefore, they require 4 K cryocoolers with high quality
and reliability, increased capacity with higher efficiency, faster cool-down, and backward
compatibility. Working on these goals in advance of the need, SHI’s development program allowed
us to have our fourth generation RDE-412D4 and RDE-418D4 cold heads available when needed.
Following our typical development process, the RDE-418D4 program was built around
application experience, theoretical analysis, numerical modeling, comprehensive testing, and
manufacturing process development. This program yielded over 20% improvement in 4 K capacity
for the same system size, weight, and input power, Figure 1.
A close working relationship with our customers provided an early understanding of the need.
Our theoretical analysis and numerical modeling identified the regenerator as an opportunity to
improve our existing RDK product. We then evaluated possible configurations and changed the
regenerator composition relative to its length to achieve an optimized temperature profile. This
work has been more extensively reported, Xu, et al. [2]. In summary, Figure 2 shows a schematic
representing our in-house numerical model and how a multi-composition regenerator can be included
in the analysis. Figure 3 shows the analysis output for various regenerator compositions. Figure 4
is an example output showing P-V changes due to regenerator changes. Based on the modeling,
we built successful prototypes and the eventual product.
In addition to the performance increase discussed above, we made several system operating
improvements for low-cryogen MRI applications. The RDE series variable-speed capability is
available for further cool down time reduction. It is based on our first-to-market and industry-
changing energy-efficient SICERA® cryopump technology. This technology, featuring EtherCAT
communication protocol, utilizes inverters in both cryopumps and compressors to manage cooling
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Figure 2. In-house numerical model schematic Figure 3. Numerical model temperature

profiles for various regenerator configurations

Figure 4. Numerical model cold end P-V diagrams for alternate regenerator configurations

loads and maximize power savings in cutting-edge semiconductor chip manufacturing processes.
Other compressor improvements have increased operating up time and cryo system reliability—
all-important to systems having no liquid bath to provide hold time. Specifically, increased oil
separator efficiency and increased fouling resistance have decreased compressor maintenance
requirements. Also, increased process monitoring, on-the-fly diagnostic algorithms, and increased
customer integration via networks such as CANBUS have enabled the implementation of redundancy
and allowed more efficient and remote troubleshooting and service planning.
For the RDE-418D4, as with our new designs generally, we completed extensive product
validation testing to ensure performance, reliability, and manufacturability. We have testing labs in
both Japan and the United States to support our entire product line. As an example of validation
testing, results of the effect of magnetic field on second stage temperature are presented here,
Morie, et al. [3]. Figure 5 gives test chamber field profile, and Figure 6 shows the effect of field
strength on second stage temperature with different regenerators.

Figure 5. SHI test chamber magnetic field profile with picture of test chamber
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Table 1. RDK-101D Specified Performance

Figure 6. 2nd stage temperature variation with

axial field strength and type of regenerator

4 K GM ADVANCEMENTS FOR QUANTUM APPLICATIONS

SHI 4 K advancements meet the needs of quantum applications in various ways. Several
emerging technologies rely on the small footprint and low input power of our RDK-101 GM cold
head. We offer the RDK-101D with standard performance, Table 1, and the more recent RDK-
101DL, with a guaranteed minimum temperature below 2.3 K.
One application, desktop quantum computing, especially benefits from the RDK-101D’s minimal
size and power. The company Equal1 is exploring a concept, Figure 7, based on their Disruptive
Quantum on Silicon technology that incorporates an RDK-101D cold head with a CNA-11 air-
cooled compressor. In addition to small size, this cryocooler system’s ready availability and
reliability eliminated refrigeration setbacks and enabled Equal1’s fast development pace. Montana
Instruments CryoCore® platform, Figure 8, is another example of a system enabled by the small size of
the RDK-101 series cold head. This system, capable of sample temperatures from 4.9 K to 350 K,

Figure 7. Equal1’s desktop quantum computing concept with RDK-101D and CNA-11 compressor

Figure 8. Montana Instruments CryoCore® platform

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Figure 9. Photon Spot systems using the RDK-101D cryocooler

Figure 10. RDK-101D performance with (a) CNA-11 compressor and (b) linear compressor

mounts on optic benches in a user-friendly, compact manner and allows the user to pay minimal
attention to the cryocooler. In yet a third example, Photon Spot, a maker of cryogenic systems and
superconducting photon detectors, also relies on the small size of the RDK-101D for their smaller
systems, Figure 9. They benefit from cold head temperatures reliably below 3 K. For some
configurations, they use a sorption refrigerator in conjunction with an SHI cryocooler to reach
0.8 K.
We have also tested the RDK-101D with a linear compressor prototype. This work, previously
reported in more detail, Hiratsuka [4], has demonstrated the ability to extend the low-temperature
capability using the same input power, Figure 10. It is a further example of the breadth of our development
programs and shows a potential way to achieve the low temperatures used in quantum systems.
Until recently, the RDK-101 series cold heads were the smallest commercially available, but
our new RDC-02 GM cold head now holds that distinction. Figure 11 shows the 20% smaller size
of the RDC-02 compared to the RDK-101D. Our previously reported work on this cold head, Xu,

Figure 11. CNA-11 cold head (left) and RDC-02 cold head (right) with cold end lengths
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Table 2. RDC-02 specified performance

Table 3. Customer RDC-02 temperature data

Table 4. Customer RDC-02 vibration data

et al.[5], covered results for the R&D prototypes. Through further refinement, we reduced the
length to the current 218.7 mm. Table 2 shows the specified performance of this cutting-edge
product.
Testing of this cold head at S2 Corporation has demonstrated very good second stage temperature
below our guaranteed minimum of 2.2 K, Table 3, and 9 to 11% z-axis vibration reduction compared
to the RDK-101D, Table 4. S2 Corporation’s low vibration cryogen-free cryostats feature rapid
sample change and turn-around time. They benefit from the RDC-02’s robustness for variable
speed operation, which permits a 38% reduction in cool down time, Figure 12.

Figure 12. RDC-02 test set-up and cool down time versus frequency
SHI’S TWO-STAGE 4K GM CRYOCOOLERS 225

Figure 13. ColdEdge Technologies Figure 14. ColdEdge Technologies

Stinger® system with SHI cold head ULV system with SHI cold head

For high cooling capacity quantum applications, both our GM cryocooler and GM-type pulse
tube advancements support emerging technologies such as larger dilution refrigerators for quantum
computing. Our new RP-222B3S pulse tube provides 2.0 W/4.2 K and 60 W/50 K cooling and low
vibration when operating at either 50 or 60 Hz. Compared to our RP-182B2S pulse tube, it has a
simplified layout, equivalent or lower vibration, and greater than 20% efficiency improvement. As
for our larger 4K GM cryocoolers, these are also used in vibration-sensitive applications through
products such as ColdEdge Technologies’ Stinger® and Ultra-Low Vibration (ULV) systems. Their
Stinger® system, through a separate circulation loop, provides 4 K cooling at points remote from
the GM cryocooler, Figure 13. Their ULV system, Figure 14, provides 4.2 K cooling with nanometer
scale displacement.

CONCLUSION
Emerging technologies need reliable, available commercial products to move them past basic
research and into the real world. Through a strong research and development program, extensive
customer interaction, and proven ability to manufacture and service commercial products, SHI
continues to advance 4 K GM technology to meet this need.

ACKNOWLEDGMENT
We wish to acknowledge the contributions of ColdEdge Technologies, Equal1, Montana
Instruments, and Photon Spot.

REFERENCES
1. Bahl, Sanjeev. “Helium—Macro View Update.” 25 February 2019. Edison Group Website. Web. 20
Aug 2022. <https://www.edisongroup.com/wp-content/uploads/2019/02/HeliumMacroUpdate 2019.
2. Xu, M. and Morie T., “Numerical Simulation of the Second Stage Regenerator in a 4K GM Cryo-
cooler,” AIP Conference Proceedings 1573, 1143 (2014).
3. Morie, T., Shiraishi, T., and Xu, M., “Experimental Investigation of Cooling Capacity of 4K GM Cryo-
coolers in Magnetic Fields,” Physics Procedia, v. 67 (2015), pp. 474-478.
4. Hiratsuka, Y., “A Gifford-McMahon Cryocooler below 2 K with Helium 4,” Cryocoolers 20, ICC
Press, Boulder, CO (2018), pp. 216-222.
5. Xu, M., Bao, Q., Tsuchiya, A., and Li, R., “Development of Compact 2K GM Cryocoolers,” Physics
Procedia, v. 67 (2015), pp. 491-496.