Philips CM12 manual Centering the Beam, Alignment of the Thermionic Gun

Erwin Sabio Philips CM12 Alignment & Setup Manual Page 9

Column Alignment

Centering the Beam

1.To center the beam more easily, adjust the intensity knob [9] to find the cross over i.e. the brightest and more focused beam setting. (Note: if the intensity knob is a little hard to control, press the FINE button [10] to spread or concentrate the beam more slowly.)

2.Check to see if the center of the beam coincides with the black dot on the screen.

3.Use the X & Y shift knobs [15] to center the beam.

Alignment of the Thermionic Gun

1.Adjusting the tilt of the gun ensures that the beam of electrons is directed to the center of the sample area. Start by centering the cross-over beam as described earlier.

2.Undersaturate the gun by going to MODE > CONFIGURATION and turning the Filament Knob [18] counter-colckwise until the shadow of the filament becomes visible in the beam as in Figure 9.

Figure 9 The shadow of the filament becomes visible at low saturation.

Figure 10 The STIG, DF, and ALGN buttons activate the multi-function knobs.

3.Press the ALGN button to the right of the multifunction knobs [21] then select GUN > TILT from the menu that appears onscreen. At this point the multifunction X/Y knobs become active and now be used to adjust the tilt of the gun.

4.Adjust the multifunction X/Y knobs until the shadow of the gun in the beam becomes centered and as symmetric as possible.

5.Once the gun has been tilted correctly, press the ALGN button again to exit the gun alignment mode.