Superconducting Technology Assessment - nitrd

Large Cryocoolers
There are two European manufacturers of large machines, Linde in Germany and Air Liquid in France. There are a
few Japanese manufacturers, but their track record is not as good as the Europeans. Dresden University in Germany
is one of the few places in the world doing research on efficient refrigeration cycles. A system capable of handling
kW level heat loads cools portions of the Tevatron accelerator at Fermilab in Illinois. The conceptual design of a single
large system has been initiated under the HTMT program (Figure 6.6).
RSFQ PEs
1m
SRAM
77 0 k
4 0 k
50
SIDE VIEW
Fiber/Wire
Interconnects
1m
3m
HRAM/DRAM
Data Vortex
0.5
Figure 6-6. Concept for a large-scale system including cryogenic cooling unit for supercomputers 7 .
6.4.2 COOLING – READINESS
The technology for the refrigeration plant needed to cool large systems, along with its associated mechanical and
civil infrastructure, is understood well enough to allow us to make technical and cost estimates. Small space and
commercial cryocoolers are available, but engineering changes are needed for use in large-scale systems. Larger
units and their components have been made in much smaller numbers and may require further development.
6.4.3 COOLING – ISSUES AND CONCERNS
Vibration can be a serious problem for superconducting electronics if the total magnetic field is not uniform and
reproducible. The cryocooler itself can be mounted with flex mounts on the cryostat vacuum vessel, which has
more mass and is, therefore, more stable than the cooled device.
The reliability issues can be mitigated by using smaller cryocooler units around a central large-scale cryogenic cooling
unit. This approach adds modularity to the system and allows for local repair and maintenance while keeping the
system running. However, the design issues resulting from the management of many cryocoolers working together
are not yet well explored.
7
HTMT Program Phase III Final Report, 2002
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