AMI vapor cooled current leads are the industry standard for introducing high currents into the liquid helium dewar environment. State-of-the-art techniques provide the most efficient way to transfer high currents from 300K to 4.2K. Standard and custom designs from 25 amperes to 75,000 amperes have been built and used.

The heat capacity of helium vapor is used in these counterflow leads to minimize the liquid helium consumption for a specified operating current. Leads of this type have been shown to evaporate 2.8 x 10-3 liters per hour per ampere for each lead pair when operated at the design current (40% less at zero current). AMI leads are expected to provide this performance under normal conditions, however a more conservative value of 3.2 x 10-3 liters per hour per ampere is recommended for system design calculations. A voltage drop of less than 0.2 volts per lead pair at the rated current is typical. A pressure difference of approximately 2 mm of mercury (0.03 psi) is developed through the leads at the rated current.

Break-away vapor cooled current leads are available and represent a popular configuration for persistent magnet operation. Break-away leads are supplied in two sections so that the upper section can be detached from the lower section during persistent magnet operation. Helium consumption is significantly reduced because current lead thermal paths are eliminated. Automatic lead retractors can be incorporated for automation and control of the break-away lead configuration.

AMI can provide custom vapor cooled current leads for many combinations of current ratings, sizes, lengths, and mounting configurations. An AMI Technical Sales Representative is available to help you define your current lead requirements. Available features include:

View the Current Lead brochure (PDF)
View the Current Lead Manual (PDF)