VARIAN Products

3 keV Off Axis Electron Gun with Supply
2.75" O.D. Mounting Beam Energy 0 to 3.000V Spot Size 1mm
Incl. 981-2125 Gun 981-2145 Power Supply 981-2147 AES Module Cable Kit	EUR 7 395

The LEED/Auger electron gun produces a finely controlled primary beam over the energy range from 200 eV to 3 keV at beam currents from 1.0 µA to 30 µA in the Auger mode. In the LEED mode, beam energy ranges from 3 eV to 1.5 keV. (Current level is typically 1 µA at 100 eV.) Electrical isolation and shielding ensure that no beam current is lost through leakage paths. This makes it possible to take direct beam current measurements with the gun power supply. This feature is particularly important because a critical relationship exists between the electron beam parameters and the interpretation of the data obtained. Further, for LEED mode operation, an accelerating voltage is applied to the first anode; this design provides maximum beam current while operating within the lower beam energy range of the LEED technique.

Another key design feature of the gun lens system permits the electron beam to remain in focus over the entire energy range with a single setting of the focus control. This is made possible by programming the focus electrode by the electron beam potential. The beam diameter is less than 1 mm above 50 eV; between 5 eV and 50 eV, beam diameter is less than 2 mm.

The gun design includes a filament assembly which is mounted at an angle 13° off the main gun axis so that there is no line of sight between filament and sample. This minimizes the possibility of sample contamination from the filament and also reduces the light reflection from the sample onto the screen. (A deflector assembly brings the electron trajectory onto the gun main axis.)

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