American Magnetics AMI Superconducting Magnets - Manual (Page 17)

16
Operation
Persistent operation
Magnet persistent operation (if applicable)
1. Stabilize the magnet current at the desired current level. Current stability is
indicated by zero voltage across the magnet current leads.
2. Record the current level. This is important when returning the magnet to non-
persistent mode operation.
3. De-energize the persistent switch heater power supply output. The magnet
will commence persistent mode operation after the persistent switch cools.
4. Wait one minute to allow the persistent switch to cool.
5. De-energize the power supply system if desired.
6. Verify persistent mode operation of the magnet by observing the voltage
across the magnet when the power supply is de-energized. The voltage should
remain at zero.
Returning from persistent operation
1. To return magnet current control back to the programmer/ power supply
system, energize the programmer/ power supply system.
2. Match the power supply current to the magnet current recorded when magnet
entered persistent mode.
Note
The best method to reestablish the power supply current to the level of the
persistent magnet is to leave the programmer current limit setting unaltered
after switching to the persistent mode.
3. Switch on the persistent switch heater power supply output.
4. Allow 10-15 seconds to allow the switch to transition from the
superconducting to the resistive state.
5. A small magnet voltage may be observed as the magnet current and power
supply currents equalize. This voltage should quickly decay to zero as the
magnet current is controlled by the programmer/ power supply system.
Caution
Matching the magnet current to the programmer/ power supply system current
is important when returning the magnet from persistent operation. Large
!