AHF MAGNETIC LENS CRYOSYSTEMS[Advanced Hydrotest Facility] Page: 4 of 8
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THE CRYOGENIC DISTRIBUTION SYSTEM
The configuration of the lens system lines resembles a crossroad of twelve evenly
spaced one-way roads (the magnet lens beams), each road entering and passing through the
intersection (the object), from right to left, see FIG 1. The baseline distribution system has
a cryoplant at grade level that is connected to the lens lines 50 m below grade (tunnel
level). The outgoing flow of cryogens is divided at tunnel level into clockwise (CW) and
counter clockwise (CCW) transfer-line headers routed around the outer perimeter of the
gallery (assumed 33 m radius, FIG 2) at 3 to 6 m above the tunnel floor. Valve boxes direct
distribution-header flows to the (parallel) individual lens feed lines. The lens-line
connections may be removable bayonet jumpers or hard-plumbed transfer lines. The lens-
line magnet vacuum vessels, rather than transfer lines, supply the insulating vacuum for
cryogen transport between the individual magnets.
FIG 3 is a flowsheet of the lens cryogenic distribution system. Cryoplant supercritical
helium at about 4 atm flows to parallel JT valves, feeding the lens-line magnets with two-
phase helium at 4.43 K and covering the magnets with liquid. Most of the flashed gas and
heat-load boiloff is returned cold to the cryoplant cold end in a low-pressure return line at <
1.2 atm. The balance of the cold gas is returned to compressor suction (0.9 atm) after being
warmed in vapor cooled current leads. Lens-lines' magnet shields are cooled in series.
Cooldown of lens-line magnets and their shields is performed serially until the shields
reach operating temperature. This configuration permits independent cooldown and warm-
up of a single line or of multiple lines in parallel.
Running the tunnel-level-transfer line header in the cross tunnel (63-m radius
assumed) was considered, but requires more transfer line, and thus higher system capital
costs, higher heat loads and higher operating costs.
The cryoplant has been positioned on an axis (y = 0 in FIG 1 and 2) so that the heat
loads, cryogen flows and transfer lines are essentially symmetric about the facility axis.
CRYOSYSTEM CAPACITY AND REQUIREMENTS
TABLE 2 presents the system heat loads and utility requirements for the baseline
design and the three other cases considered. Transfer-line heat loads of 0.5 W/m at 4.43 K
and 1.91 W at 47.5 K were assumed. These distributed numbers include the heat loads for
valves, bayonets, etc. The following margin factors are used in the table: primary (4.43 K)
Cross tunnel (rim - 63
m radius - NTS)
Gallery Limits .
(33 m radius - NTS) -
-10 - \
FIGURE 2. The magnetic lens system. NTS - Not to Scale
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KELLEY, J. P. & MULHOLLAND, G. T. AHF MAGNETIC LENS CRYOSYSTEMS[Advanced Hydrotest Facility], article, June 1, 2001; New Mexico. (digital.library.unt.edu/ark:/67531/metadc721057/m1/4/: accessed September 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.