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We get the best transfer efficiencies when the transfer lines from the Liquifier to the magnet are sufficiently cold. We have tested two modes (paths) to pre-cool the system: the slow (Figure 1 left) and the fast (Figure 1 right) pre-cooling as well as a combination of these two modes which allows us to reduce the slow pre-cooling time.
Figure 1: Slow (left) and fast (right) pre-cooling paths.
The fast pre-cooling transfer efficiencies are about 47-49% which does not allow filling the entire magnet volume using just one Liquifier. Nevertheless, higher efficiencies of about 54% can be obtained with the fast pre-cool if the Liquifier pressure is reduced to 3.5 PSI at the expense of nearly 2 hours (~8L) where the Liquifier is not producing while reaching the set pressure. With the fast pre-cooling the last part of the the transfer line is not re-cooled (see Figure 1). Although the fast pre-cooling has a lower transfer efficiency the procedure could be performed when the magnet needs to be filled immediately and the slow pre-cool hasn't been done because none of the Liquifiers are near full.
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