Spectrometer apertures and transmission

Sample was flat clean Cu110, tilt 30 degrees, 3 kV max current.

Count rates vs aperture, images saved. 500 eV, pass 50 eV

• 1/1 900 kHz
• 2/1 830
• 3/1 380
• 3/2 285
• 3/3 125
• 4/1 225
• 5/1 350

• Conclusions: exit slit widths, 5:3:1, count rate 2.8:1.8:1, "hot" part of channeltron in center
• Exit slit no effect on image area

• Entrance 5 (1x12) aligned with 4 (1 mm) with 50% more counts
• Entrance 1 (6x12) only 8% more counts than 2 (6 mm)
• Round apertures 6:2:1, count rates 3.7:1.3:1, ideally if lens images sample on slit should be no difference. Angles should be fixed by magnification of 3. This may suggest tweaking lens factors to try to optimize transmission. These results may depend on pass energy....