American Magnetics Current Leads for Cryogenic Systems Manual - Manual (Page 3)

Rev. 5, July 2003 Page 3 of 10
AMI HELIUM VAPOR COOLED CURRENT LEADS
AND SUPERCONDUCTING BUS BARS
Installation, Operation and Maintenance Instructions
I. INTRODUCTION
The American Magnetics, Inc. (AMI) helium vapor cooled current leads and superconducting bus
bars are designed to introduce high currents into liquid helium environments with a minimum of
liquid helium loss. This is accomplished by using the heat capacity of the cold helium boil-off
gas to cool the current leads.
II. SPECIFICATIONS
A. Table 1 lists the specifications and shows dimensional references for AMI standard vapor
cooled current leads. Dimensional references in Table 1 are shown on Figure 1. Custom
designed or special order current leads may have dimensions and specifications that vary
from those listed.
B. A voltage drop of <0.1 volts per lead at the rated current is typical and should not be
exceeded.
C. A pressure drop of approximately 2mm of mercury (0.03 psi) is developed through the
leads at the rated current.
D. AMI superconducting bus bars (optional) are designed to connect the cold end of the
current lead with the magnet terminals. The bus bars are a soldered laminate of Nb
3
Sn/Cu
and will remain superconducting as long as the bottom end of the bus bar is in contact
with liquid helium.
III. INSTALLATION
A. Carefully remove the current leads from the shipping carton and ensure all packaging
material is removed.
B. Position the current leads into the helium dewar and secure them in position either with
the supplied fittings or by bolting through the micarta insulating flange.
CAUTION: Ensure that the bottom of the current lead tube
(vapor inlet) is positioned above the maximum liquid helium level.
Operation of the current leads with a liquid helium level above the
vapor inlet will result in excessive helium loss and could damage
the lead.