Table des Matières
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17
Technical Information
Pump Used in Presence of Magnetic Fields
Figure 48
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 greater, 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.
288/296
1
Purge gas line
2
Pressure regulator
3
Gas purge valve
4
Gas purge port
5
Forevacuum pump
6
Turbopump
7
Vent valve
Purge layout
TV 1001 SEM User Manual / 87-900-973-01 (H)
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