The Beam Current Regulator is used to insure that the Beam Current does not drift during an analytical run more than the computer can compensate for during the run. It will generally hold the Beam Current to within 1% during a 12 hour run. The Beam Current Regulator is on the lower left hand side of the SEM console.
STEPS TO STABILIZE THE BEAM CURRENT PRIOR TO TURNING ON THE BCR
1. Turn on the electron gun supply and let the filament warm up at normal operating conditions for 60 to 90 minutes. Check that the 1uA switch is depressed and glowing and ensure that the B.C.R. MODE and the REG. ON buttons are off and not glowing.
2. Adjust the raster size potentiometer to point mode.
3. Ensure that your filament and electron gun are aligned.
4. Adjust Condenser 2 to obtain the Sample Current that you intend to use.
TURNING ON THE BEAM CURRENT REGULATOR
5. Press the BCR MODE switch.
6. Peak your filament one last time.
7. Adjust Condenser 2 one last time to your preferred current and let the BCR stabilize for 30 seconds.
8. Adjust the REF ADJ Pot until the red or green L.E.D. turns off
9. Once the L.E.D. is off, press the REG ON button (the button will glow red). The regulator is now locked onto the beam current that you have set for your analysis. Proceed with your analysis
SHUTTING OFF THE BEAM CURRENT REGULATOR
To turn off the Beam Current Regulator, press the REG ON switch so that the light turns off. Then press the B.C.R. MODE so that the light turns off.
