SPECS EBE-1, Manual

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Installation
3.5 HV conditioning
When the high voltage is raised for the first time or the first time after baking or out-
gassing, the emission current may be seen to jump periodically. Small sparks may even
be seen or heard. Provided that the amount of time between these is generally increas-
ing and the strength of the sparks is gradually decreasing, such disturbances may be re-
garded as part of the normal conditioning process and can be ignored. They can occur
because of local outgassing causing brief arcing or because of small sharp edges leading
to field emssion. The resulting arc generally rounds off the sharp edge thereby elimin-
ating the problem.
3.6 Setting up rod position
Make sure the flux monitor cables are disconnected from the instrument before
carrying out the procedure below.
During outgassing there could be arcing to the flux electrode which would otherwise
damage the flux electronics.
Before evaporating with a rod for the first time, drive the rod into its fully forward pos-
ition using the thimble drive. The rod will now stick right through the evaporation
zone. Set the e-beam voltage for instance to 1000 V using the “beam control”. Set the
range switch to 20 mA. Slowly increase the filament current (see conditioning the fila-
ment if this is the first time) until the emission current reads 10 mA and read just the
“beam control” to maintain 1000 V as necessary. 10 W of power is now being dissipated
in the rod. The rod may be driven in and out if desired, to warm it throughout and out-
gas it. Higher powers may be used for higher temperature materials.
Now, gradually withdraw the rod. The emission current will stay constant and then sud-
denly begin to drop as the tip of the rod leaves the evaporation zone. Drive the rod 3
mm forward again (1 full turn of the thimble). This is the ideal position for evaporation
from rod and ensures that the electrons strike only the tip of the rod.
8 EBE-1