For pressures up to a few 10 mTorr: the integrated differential pumping stage
For gas pressures inside the vacuum chamber up to a few 10 mTorr, a single differential pumping stage is sufficient to ensure long lifetime of the cathode. It is integrated with the gun and is located very close to the cathode. The efficiency of the differential pumping expressed as the ratio between the chamber and the gun pressure, is up to a factor 1000. The pressure inside the gun is kept at a few 10-5 Torr for a chamber pressure of a few 10 mTorr, allowing safe operation of the gun and a long lifetime of the cathode.
For pressures up to a few 100 mTorr: the double differential pumping stage
The scattering of electrons inside the chamber becomes stronger in this pressure range. The mean free path of electrons inside the chamber is reduced. To compensate, the RHEED screen is shifted closer to the sample. In addition, a second differential pumping stage is added between the gun and the chamber. A pumped tube protrudes inside the vacuum chamber and the differential pumping aperture at the end of the tube is located close to the sample. The electron mean free path through the high pressure region is thus limited to about 50 to 100mm, allowing safe RHEED operation up to a few 100 mTorr.
Electron gun power range: 30kev ~ 50kev
Work pressure range: single differential pumping stage 10mTorr,second differential pumping stage 100mTorr
High-performance gun: high brightness, small spots, low dispersion, low air rate
Screen: aluminum plating protective coating
Remote control: for electron beam focusing and deflection and electronic lock function
Electron beam deflection Angle:±15 °
Add: Room 1310, AirChina Plaza, No. 36 Xiaoyun Road, Chaoyang District, Beijing