5 Maintenance of system
22
When baking out the column intense heat will develop. Be careful not
to get in contact with the column to avoid injuries.
A bake out should be done under the following conditions:
• Gun vacuum drops below 7 or 8e-9 mbar.
• Serious problems with beam drift/gun stability.
• If system is vented, or if the IGP has been OFF for more than
24 hrs. User should check gun vacuum before initiating a bake
out.
To perform a bake out follow the following procedure. Start of the
bake out process is only possible for users with supervisor privilege.
STEP 7 ► Turn off the EHT and the gun. Keep column chamber valve open.
STEP 8 ► Remove high-tension cable from column.
In order to avoid any misalignment of the gun head you should try not
to exert any side forces.
STEP 9 ► Insert a round and flat piece of Al foil into column opening. Be careful
not to short out 24 V interlock pins. If you short this contact, it might
cause damage to the power supply.
STEP 10 ► In LEO software, open Tools > Go To Panel > Bake out.
STEP 11 ► Select the time for bake out from Table 1. For maintenance select
Bake out = Overnight and choose Bake out Start to begin.
Table 1 Time for
various bake outs.
Time Functionality
Quick
2 hours heating / 1 hour cooling
Overnight
8 hours heating / 2 hours cooling
Weekend
40 hours heating / 3 hours cooling
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