Hitachi S-4800 manual Preliminary Operation Check of Column Vacuum

3.1Preliminary Operation

3.1.1Check of Column Vacuum

At the beginning of SEM operation, check the evacuation control panel. The following conditions must be met:

(1)Lamps of IP1, IP2 and IP3 RESET switches are lit.

(2)Ion pump readings are better than the followings. IP1: 2 × 10-7Pa

IP2: 2 × 10-6Pa

IP3: 5 × 10-5Pa

(Pressing MODE switch on the Evacuation control panel shifts forward the blinking of status display lamps. Read vacuum when each of IP1 to IP3 lamp is blinking)

If vacuum readings do not satisfy the above conditions, gun baking is required. Refer to “Maintenance” in section 4.

(3)EVAC POWER switch is set at 1 (ON).

(4)TMP POW ON, NORMAL lamps and the lamp of SC EVAC switch are lit.

(5)Vacuum of S.C (specimen chamber) is better than 2x10-3 Pa. (Read vacuum when S.C lamp is blinking)

(6)APT HEAT switch is set at AUTO.

Usually keep the APT HEAT switch on the evacuation control panel at AUTO.

If the objective lens aperture is contaminated, charging will degrade image quality and the image will drift because of micro discharge. Such problems are noticeable at low accelerating

voltages. The aperture is heated to about 150ºC to remove contaminants to one tenth or less of what it would be at room temperature.

The aperture heating will be turned OFF automatically when you press S.C AIR switch to introduce air into the specimen chamber. The 30 minutes wait will be placed automatically before introducing air when S.C AIR is started while APT HEAT switch is ON. The aperture heating will start again when the specimen chamber vacuum recovered by S.C EVAC operation. Note that after the aperture heating turned ON, image drift may be observed for about half an hour.

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