Chapter V – Troubleshooting
5-11
C
996-0255 rev. b
Equipment needed:
• 1 oscilloscope (1MΩ input)
• 1 photodiode risetime ~1ns
• 1 Styrofoam high density beam block
• 1 metric Allen wrench set
• 1 English Allen wrench set
1) Turn system off.
2) Locate
λ
/4 plate #1 (closest to Pockels cell) and using a
pencil, mark the holder ring at the 12:00 position. This
will show the initial position of
λ
/4 plate.
3) Loosen set screw holding the
λ
/4 plate #1 and rotate it
approximately 45° in either direction.
WARNING!
Ensure that Q-switch is OFF and green LED on remote box
(RB601) is OFF during free-running operation.
4) Turn system on, open shutter but do not activate the Q-
switch. The system will now lase with a long pulse out-
put.
Re-closing the cavity
1) Turn off the system.
2) Rotate
λ
/4 plate #1 back to its original position (pencil
mark at 12:00). Tighten set screw.
3) Turn on system, open shutter, but leave Q-switch off.
4) To check for free-running, use an IR card, an oscilloscope
or look for green light after the SHG crystal.
5) If free-running is observed tweak on rotational position of
λ
/4 plate #1.
6) If no free-running is observed, gradually increase oscilla-
tor pump voltage on the power unit by 100 V while
continuing to monitor for free-running. If observed,
repeat step 5.
7) Return oscillator pump voltage to normal operational
level. There should now be a 100 V buffer between this
point and where the system free-runs.
8) Continue normal system operation.
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