American-magnetics Current Leads for Cryogenic Systems Manual Manuel d'utilisateur télécharger pdf (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

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.

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American-magnetics Current Leads for Cryogenic Systems Manual Manuel d'utilisateur Page 3