The Facility for Rare Isotope Beams (FRIB) should garner a lot of attention in 2022 when it first delivers the intense beams that scientists will use to study everything from nuclear astrophysics to fundamental interactions and applications for society including in medicine, homeland security and industry. But the facility is already quietly serving as a world-class research, teaching and training center for Michigan State University (MSU), the facility’s host, combining cryogenics, accelerator and superconducting radio frequency sciences and technology. For example, FRIB’s state-of-the-art cryogenic infrastructure, ranging from small helium systems to a large 2 K plant supporting the FRIB accelerator, is accessible to MSU’s engineering and physics programs, providing a wide range of opportunities for students interested in many aspects of cryogenic engineering.

The education program is known as the MSU Cryogenic Initiative, a collaboration between the university’s College of Engineering and FRIB specialists. It’s designed to provide courses, research and training for those seeking advanced degrees in cryogenic, mechanical or process engineering. Rigorous accelerator science, superconducting magnet and superconducting radio frequency programs are also being developed and implemented.

“MSU is the ideal place for the Cryogenic Initiative,” says Dr. Peter Knudsen, senior cryogenic process engineer, “especially given that the accelerator is located on the campus itself.” The purpose of the program, he says, is to provide opportunities for students to clarify and refine understanding of their engineering curriculum; exercise analytical skills and creativity in design; pursue critical and practical research and development; and gain hands-on experience in hardware construction and implementation. “The need for properly trained staff is often unrecognized. Although a degree from a good institution is foundationally important, by itself, it is simply not enough to ensure a functional system, let alone a cost-effective, reliable and efficient one. The apprenticeship model is not only critical for skilled trades but for professional engineers.”

Students entering the program have the opportunity to learn about the newest technology in cryogenic systems through exposure to the FRIB machine. “Advanced cryogenic systems are anticipated to play an important role not only in accelerators but many aerospace applications,” says Professor Rao Ganni, director for the MSU Cryogenics Initiative. “But many of the components required for helium systems are adopted—with little or no changes—from conventional industries like refrigeration, gas processing or air separation. This leaves a lot of opportunity for research, leading to advancement and new designs.”

Cryogenic engineering often involves dealing with fluid non-idealities, material extremes and very energy-intensive processes. This is especially true of 4.5 K and 2 K refrigeration processes, according to Ganni. Large 4.5 K and 2 K helium refrigerators typically require ~250 W/W and ~850 W/W respectively, though it is not uncommon for a 2 K system to require ~1,000 W/W or greater. In comparison, residential air conditioning units often operate between 50 and -10°C, requiring ~0.25 W of input power for every 1 W of cooling provided.

Helium refrigeration, Ganni says, is the most practical and cost-effective solution to cool superconducting magnets and/or superconducting radio frequency (SRF) cavities to 4.5 K or 2 K (sub-atmospheric) for modern particle accelerators. The FRIB 4.5 K cold box is designed to support a maximum capacity of an equivalent of 18.5 kW at 4.5 K for four different types of simultaneous loads: 4.5 K refrigeration, 4.5 K liquefaction, a cold compressor at 30 K and 35 to 55 K thermal shield loads. Ganni says he selected the cold box’s design to ensure a well-balanced system, capable of efficiently supporting varying fractions of the different load types and a varying capacity. The cold box expands upon methods his team developed at Thomas Jefferson National Accelerator Facility (CSA CSM) for its 12 GeV helium refrigeration system [1].

Other FRIB systems also advance previous state-of-the-art installations. The compressor system, for example, uses compressors developed by Ganni, under NASA funding, for the 20 K helium system used in Chamber A at the agency’s Johnson Space Center [2]. Ganni says the overall project, under the leadership of NASA’s Jonathan Homan, allowed the realization of a compressor system capable of operating over an unprecedented range [3], so that full advantage of a “Ganni Cycle Floating Pressure Process” could be achieved. Overall, and as demonstrated by the JLab 12 GeV system [4], Ganni says the refrigeration system at FRIB is expected to operate efficiently from 30 to 100 percent of the maximum (exergetic) capacity and for any selected load type combination using the Ganni Cycle. The 2 K cold box utilizes the most up-to-date cryogenic centrifugal technology and implements a full sub-atmospheric compression process that provides optimal efficiency and a minimum capital and equipment footprint [5].

Major sub-systems were installed before the building occupancy date (BOD) in March 2017, including the main 4.5 K cold box, compressors, oil removal and liquid nitrogen. And most warm interconnecting piping, critical parts of the tunnel-shaft cryogenic transfer line sections, and the tunnel cryogenic distribution sections were placed in position before the BOD.

None of the equipment, including the distribution system, was put into storage or double-handled, according to Ganni, instead arriving “just in time” and installed into planned locations. The 2 K cold box sub components were purchased in advance to minimize project cost and risk and are in the process of being assembled at FRIB. Engineers also sucessfully commissioned and performance tested the warm compressor system and the 4.5 K cold box before the end of 2017. The team plans to cool the first linac segment, along with the first three cryomodules, to 4.5 K in early 2018.

The distribution system is extensive, consisting of interconnecting transfer lines between cold boxes and lines for the three LINAC segments from the cold box room down into the tunnel. As expected for large 2 K helium systems, there are many sub-systems, such as helium gas storage, helium purifier, liquid nitrogen, liquid helium storage and (sub-atmospheric process) “guard” vacuum. There are also supporting facility systems, such as cooling water, instrument air and electrical power. And, thanks to the existing infrastructure at MSU, many support services, from compressor alignment to 4160 V electrical, are readily available on-site.

FRIB will operate as a scientific user facility for the Office of Nuclear Physics, part of the US Department of Energy’s Office of Science (DOE-SC). It is funded by the DOE-SC, MSU and the state of Michigan, supporting the mission of the Office of Nuclear Physics in DOE-SC. More information about the educational and research opportunities in cryogenic mechanical and process engineering offered through the MSU Cryogenic Initiative is available at https://frib.msu.edu/cryoinitiative, or by contacting Peter Knudsen (knudsen@frib.msu.edu) or Rao Ganni (ganni@frib.msu.edu). https://frib.msu.edu.

References
[1] V. Ganni et al., “Application of JLab 12 GeV Helium Refrigeration System for the FRIB Accelerator at MSU,” Advances in Cryogenic Engineering, Vol. 59, 2014.
[2] J. Homan et al., “Commissioning of a 20 K Helium Refrigeration System for NASA-JSC Chamber-A,” Advances in Cryogenic Engineering, Vol. 59, 2014.
[3] P. Knudsen et al., “Commissioning and Operational Results of the 12 GeV Helium Compression at JLab,” Advances in Cryogenic Engineering, Vol. 61, 2016.
[4] P. Knudsen et al., “Modifications to JLab 12 GeV Refrigerator and Wide Range Mix Mode Performance Testing Results,” Proceedings of the 26th International Cryogenic Engineering Conference–International Cryogenic Materials Conference 2016, 2017.
[5] P. Knudsen and V. Ganni, “Process Options for Nominal 2-K Helium Refrigeration System Designs,” Advances in Cryogenic Engineering, Vol. 57, 2012.