Magnet Support Assemblies and Lambda Plates

Magnet Support Assemblies

AMI magnet support assemblies are designed to suspend superconducting magnets in liquid helium dewars with the minimum input of heat to the helium. Helium is transferred into the dewar by inserting a transfer tube through the 3/8 inch I.D. O-ring sealed helium fill fitting. Low helium consumption vapor-cooled current leads are installed on the assembly. The structure of the support assembly uses fiberglass support tubes and copper radiation baffles to minimize thermal conduction and radiation heat transfer into the liquid helium. A mating electrical connector with 10 ft. of cable is provided for instrumentation hook-up.

All magnet support assemblies are custom designed to interface with your dewar and magnet. An AMI Technical Sales Representative is available to help you define the support assembly design requirements.

Lambda Plates

The addition of a lambda plate to the magnet support assembly allows superconducting magnet operation below 4.2K. Typically, the field strength of a superconducting magnet can be increased by more than 10% if the operating temperature is reduced from 4.2K to 2.2K. A lambda plate will maintain the magnet at reduced temperature for extended periods of time and is a cost effective way to obtain higher magnetic fields.

Each lambda plate assembly includes a throttle valve operated from the dewar top and a vacuum pump port. The throttle valve allows a small amount of liquid helium to enter a low pressure region within the lambda plate. The lower pressure in this region causes the liquid helium to flash to a gas which cools the lambda plate. Heat is transferred from the liquid helium remaining in the magnet well section of the dewar to the lambda plate until a equilibrium temperature is reached.

A carbon glass resistor temperature sensor is included for monitoring the magnet temperature. The low pressure, vacuum region is maintained with a customer supplied vacuum pump attached to the vacuum pump port. For proper lambda plate operation, the dewar must be designed with a thermally isolated magnet well section.

Call your AMI Technical Sales Representative for more information regarding lambda plate operation and available configurations.

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