Chapter 4. Installation Supplies
32
Installation Planning Guide
01-999021-00 A0100
Liquid Helium Supply
Liquid helium storage containers
(dewars) have a normal loss of
helium from boiloff and varies with
the quality of the container, the
distance from the supplier to the
site, and the time between delivery
and use. Also, some boiloff occurs
during the magnet cooldown
process.
of liquid helium recommended at
installation. To prevent unnecessary
loss of the supply, request delivery
just prior to the scheduled visit of
the Varian installation engineer.
An additional amount of liquid
helium should be available for
delivery on short notice in case the initial amount is insufficient to complete the installation.
lists a recommended short-notice supply.
CAUTION:
Specify that supply dewars are made of nonmagnetic materials. A
magnetic supply dewar can be pulled into the magnet, possibly
damaging the magnet or causing the magnet to quench. A magnetic
supply dewar next to the magnet can damage the solenoid of the
magnet.
Liquid helium is transferred from the storage dewar to the magnet dewar using a transfer
tube supplied with the system. The 200-MHz and 300-MHz magnets use a rigid transfer
tube that must be inserted into the storage dewar and magnet dewar simultaneously without
bending. For that reason, we recommend the 100-L dewar. When ordering liquid helium,
be sure that the supply dewar has a diameter less than 70 cm (27.5 in.). The 400-MHz and
long-hold magnets uses a flexible transfer tube that inserts into most sizes of supply dewars.
Liquid Nitrogen Supply
lists the recommended
quantities of liquid nitrogen. Liquid
nitrogen storage containers suffer a
loss of contents from boiloff, so
request delivery of the supply just
prior to the scheduled visit of the
installation engineer. Provide an
adaptor for connecting 9 mm (3/8
in.) ID rubber tubing to the
container. For low-temperature
operation using the variable
temperature accessory, a refrigerant
is required. Most commonly, this is
liquid nitrogen in the VT cooling
bucket.
Table 15. Initial On-Site and Short-Notice Liquid
Helium Supplies
Magnet
(MHz/mm)
Initial Supply
(liters)
Short-Notice
Supply (liters)
200/54
200
150
200/54 LH235
300
300
200/54 LH365
300
300
300/54
200
150
300/54 LH235
300
300
300/54 LH365
300
300
400/54
300
300
400/54 LH365
300
300
Table 16. Initial On-Site Liquid Nitrogen Supply
Magnet Field
(MHz/mm)
Initial Supply
(liters)
200/54
130
200/54 LH235
325
200/54 LH365
325
300/54
130
300/54 LH235
325
300/54 LH365
325
400/54 325
400/54 LH365
325