Ulvac EGO-40M Instruction Manual page 48

MULTI-HEARTH ELECTRON BEAM SOURCE ～EGO-４０M～
Trouble symptom
15. The evaporation rate decreases
and is unstable.
Apparently there is no change in
the beam spot size.
16. The beam spot size is too large. A. Decreased high voltage
17. Distorted beam spot or no
symmetrical sweep on both right
and left sides.
18. The emission current is
saturated and cannot be
increased.
Possible cause
A. Oxidization of evaporant.
B. Increased ripple in the high voltage (5%
p-p or more)
B. Excessive ripple in the high voltage.
C. Incorrect dimensions of the emitter
assembly
A. Non uniform magnetic flux distribution.
A. Poor contact of the filament cable or
filament lead.
B. Saturated emission current due to low
setting of the high voltage.
C. Incorrect dimensions of the emitter
assembly
D. Pressure in the vacuum chamber is high. a. Operate at a pressure below 10
Corrective action
a. Change evaporant.
a. Check if oscillation occurs in the high voltage circuit of the power supply.
See its instruction manual.
b. It is likely that radio frequency noise or thyristor noise is superimposed
on the 3-phase power line of the EB gun power supply.
Check the waveform of the input voltage on an oscilloscope.
If noise is observed, insert a line filter.
a. Expansion in the Y-axis direction can be supressed by using a shorter
trimming piece.
a. See item 15.
a. Check the dimensions against Figure 5.1.
a. Check if there is any ferromagnetic material near the unit.
b. Check if there is any device that produces a magnetic flux.
a. Check if the filament setscrew is tight.
b. Check if the filament support is clean.
If contaminated, clean it by rubbing.
c. Check if the filament cable terminal is tight. If loose, retighten it.
d. Check if the screw on the atm. side of the high voltage feedthrough
terminal is tight.
a. Operate the EB Gun within its correct range.
1.0 A max. at 10 kV
0.8 A max. at 8 kV
0.6 A max. at 6 kV
0.4 A max. at 4 kV
a. Check dimensions against Figure 5-1.
41
7．TROUBLESHOOTING
-3
Pa.