Agilent Technologies 969-8935, User Manual

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17
Technical Information
Pump Used in Presence of Magnetic Fields
268/276 TV 551/701 SEM Navigator User Manual / 87-900-958-01(G )
Pump Used in Presence of Magnetic Fields
Magnetic fields induce eddy currents in the rotor of a turbomolecular
pump that tend to oppose to its rotation.
The result is increased electrical power consumption by the motor,
most of which is dissipated in the rotor.
Since the rotor is not in contact with the stator the above power can
leave the rotor mainly by radiation and hence the rotor may be
overheated while static parts of the pump remain cool.
This effect is strongly dependant from the intensity, time function
and distribution of the magnetic field.
In general, therefore, an increase in pump current can be expected.
If this increase is lower than 50 % of the current value drawn by the
motor in high vacuum operation, no particular problem should be
expected.
However if the effect is grater, than the case should be carefully
reviewed by Agilent's specialist. As a matter of fact, in case of high
magnetic fields, also important forces might be generated and applied
to the rotor.
Accessories and Spare Parts
Tab. 9
Description Part number
Mains cable NEMA Plug, 3m long 969-9958
Mains cable European Plug, 3m long 969-9957
Serial cable and Navigator Software 969-9883
Inlet screen DN 160 969-9304
Inlet screen DN 200 969-9316
Water cooling kit (plastic model) 969-9347
Water cooling kit (metallic model) 969-9337
Air cooling kit for standard rack controller 969-9314
Air cooling kit for Navigator controller 969-9339