Veeco MPS-3000 CE, Technical Manual

Page: 45 / 96

41
Do not select beam current while in Manual mode.
2. Adjust for a minimum accelerator current.
a. Adjust the accelerator voltage to minimize the accelerator current
(refer to Step 13. on page 39 ). Typically, the accelerator current
should be no more than 10% of the beam current.
•
Excessive accelerator currents may be an indication of mis-
aligned grids or a system pressure above 4 x 10
-2
Pa (3 x 10
-4
Torr).
• Refer to the ion source technical manual for grid alignment
procedures.
b. The excessive accelerator current may be lowered by adjusting the
operating conditions and/or gas flow rate to bring the A/B Ratio
within recommended limits.
When the accelerator-current-to-beam-current ratio exceeds the pro-
grammed A/B Ratio value, an audio alarm will sound, if enabled. An E25
error message will appear on the Accelerator Current display.
Operating the ion source with a high accelerator current could damage the
grids.
3. Adjust the neutralizer emission current until the value is about 100% to
125% of the beam current (refer to Step 9. on page 37 ).
• When the PBN emission current is satisfactory, the MPS-3000
CE PBN should be completely adjusted for Manual mode
operation.
• The user may continue operating in Manual mode or may
select Local mode (refer to “Local Operation” on page 42 ).
PBN Storing Operating Conditions
All adjustable operating conditions are stored automatically in the selected
memory location when the Adjust knob is turned and is the only method of
storing parameters.
PBN Recalling Operating Conditions
Selecting RCL with the MEMORY switch allows the user to view the operat-
ing conditions stored in the unused memory location. After about four sec-
onds, the original parameters will be displayed.
NOTE
NOTE
CAUTION