Zeiss EVO, Инструкция по эксплуатации, Страница: 41 / 180

ZEISS 3 Product and Functional Description | 3.5 Optional Components and Accessories
If the collector bias is too high, the VPSE detector may receive too much signal and may get satu-
rated. In this case, very bright lines are visible on the image in periodic intervals and proper imag-
ing is no longer possible. Whether a given value for the collector bias is too high, depends on the
specimen, the acceleration voltage, the probe current, and the pressure in the specimen chamber.
Fig. 27: Saturation of the VPSE detector. Bright lines become visible in the microscope image
To eliminate the bright lines in the images, either reduce the collector bias or reduce the chamber
pressure. However, the detector efficiency is reduced by either of these adjustments. You need to
find the optimum parameters for imaging different specimens. It is generally better to reduce the
collector bias, because reducing the chamber pressure can cause new charging effects.
Fig. 28: Charge compensation by adjusting chamber pressure and collector bias. Left: Reducing the collector bias
from 82 % to 78 % results in the elimination of banding effects at 40 Pa. Right: Reducing the pressure in the speci-
men chamber from 40 Pa to 20 Pa results in the elimination of banding effects at a collector bias of 79 %.
Parameter Description
Acceleration voltage
3 kV to 30 kV Possible application range for VPSE G4 detector. However, sufficient
contrast can be obtained only at higher voltages.
3 kV to 7 kV Low voltage application with VPSE G4 detector.
7 kV to 25 kV Standard application for VPSE G4 detector.
Working distance
6 mm to 8 mm For low voltage applications (3 kV to 7 kV)
8 mm to 15 mm For standard applications (7 kV to 25 kV)
Aperture
Instruction Manual ZEISS EVO | en-US | Rev. 10 | 354706-0780-006 41