Title - $10.99


Procedure of De Energize QE300 Magnet


Prepare the magnet:


  • Refill LHe at least 75% full
  • Check Liquid Nitrogen level 50% or more
  • There is no ice block on all three ports.


Prepare Power Stick


  • Check all the pins of the Power Lead, make sure all pins are OK.
  • Clean the copper connection. Make sure it has good contact.
  • Connect the diodes and tighten the screws
  • Measure the two big copper leads, It should be 85 Ohm.
  • Connect A and B connectors to the Power Lead. A A, and B B.
  • Check the following connections:

B1 C B5 short

B10 C A1 100 Ohm ---- Common to Main Heater

B10 C A2 100 Ohm ----Common to Y Heater

B10 C A4 100 Ohm ---- Common to Z3 Heater

B10 C A3 100 Ohm ---- Common to X Heater


Prepare the following Tools:

  • Gloves, None Magnetic Tools, He gas
  • Shorting Plug
  • Unplug Stick
  • #2 and #4 rubber stopper


Start to De-engergize the magnet. If started, there is no way to stop it !!!


  • Open the Liquid Helium upstacks, use #4 and #2 to cover the hole.
  • Use unplug tool to take the shorting plug out, and then insert the power stick, make sure it seats very well.
  • Connect B to B on the power stick
  • Connect A to A on the power stick
  • Connect the Voltmeter to two copper connector and set to Volts measurement and in 2 Volts scales.
  • Make sure the 9 volts battery is good in the box.


  • Switches all up to start no red lights!!!!!


  • Remove the rubber stopper on the exhaust LHe port.


  • Turn on the Z2 heater first for 10 seconds and then turn off.


  • Turn on the Z0 Heater Main heater The voltmeter should down about 0.5 Volts




The following Guide is from Joe BAhnan:

The other two wires coming out of the 10 pin connector are pot taps for measuring DC voltage. Heres a quick guideline:


1.  Make sure you have 80% Lhe.

2.  Connect diodes to energizing lead.

3.  Pull shorting plug and insert energizing lead into NMR. Caution of cold gases boiling off when inserting room temp e-lead.

4.  Connect the 2 ten pin connectors to top of e-lead noting plug "A" and "B".  Connect the two wires coming from connector B to a volt meter set up for DC.

5.  Connect power supply.

6.  Remove any carbon burst discs if any are present as not to burst in a quench.

7.  Increase power supply voltage until main switch opens; when the volt meter jumps from zero to about 1.2VDC the switch has opened and the magnet is de-energizing.

8.  Allow the volt meter to run down to zero ( about 3-4 hours usually).

9.  Confirm field is gone with small bit of ferrous material before removing diodes and/or lead.


Call John Davidson or I with any questions and please be safe. Joe Bahnan cell 908 578 9299.












This note is from Oxford Magnet Manual:


The magnet may be discharged by connecting a pair of diodes across the terminals as shown in the following figure. Switch on the Z0 and Z2 shim coil switch heaters and then the main coil heater. The magnet will discharge at a rate determined by the forward voltage drop of the diodes. Care should therefore be taken no to disconnect the diodes before the discharge is complete. The diodes must be capable of carrying the full operating current of the magnet and must be fixed to an adequate heat-sink.





























Pins Plug

1 B10 (L) Heater and resistor Common

2 A1 Main

3 A6 Z0

4 A5 Z1

5 A3 X

6 A2 Y

7 ZX

8 B8 Main Coil Start

9 B8 Maint Coil Start

10 B4 B5 Shims (+Ve) current input

11 B9 ZY

12 A10 XY

13 A9 R2

14 A8

15 B2 Shims (-Ve) Current Rrturn

16 B7 Main Coil End

17 B7 Main Coil End

18 A4 Z3


Note: 1 -18 are the pin numbers. The first letter is for the connector A or B. The second number is A=1, B=2, C=3, D=4, E=5, F=6, H =7, J=8, K=9 and L=10.



Diodes for de-energize the magnet. Discontinued 150KR80A ,replaced by 45LR120D.


Adjustable Power supply. There are two pins to connect the two plugs.

Plugs, Plug A connect to A port and Plug B connect B port on the power Lead.




DE-energize ALOX 300 Magnet (Mercury 300)

1. Liquid helium is full, Liquid ntrogen 80%

2. Power leads (from John Davidson)

a. remove the left colume (the right one is for LHe refilling); b. Unplug the shorting plug; c. insert the power lead. make sure it seat well. d. connect the diodes pack, connect the A and B plug. Plug the power supply (start at 3 VDC). then increase to 6 VDC, the volemeter jump from 0.0000Volts to 0.9096, then decreases. The de-energization started. about one hour, it goes to about 0.0050VDC.

Unplug the power lead and replace the shorting plug. Use N2 gas to release vacuum. until the the red plate drop.





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