Operation
37
2) Insure that the second harmonic generator is installed according to
the instructions given above.
3) Install the fourth harmonic generator using the second set of
alignment pins and screw holes. Insure that the harmonic generator
housing is installed such that it is against the second alignment pin.
4) Install the 266 nm dichroic separation mirrors using the alignment
pins and screw holes closest to the beam exit.
5) Adjust the wave plate on the second harmonic generator housing to
maximize the 266 nm energy.
6) Adjust the external screw on the 4HG housing to optimize the crystal
angle, maximizing 266 nm energy.
7) Reinstall the harmonic generator housing cover.
NOTE: DO NOT DISASSEMBLE THE FOURTH HARMONIC
GENERATOR. THE CRYSTALS INSIDE ARE HYGROSCOPIC.
DUST, DIRT AND HUMIDITY WILL DESTROY THE
CRYSTALS.
The Gemini PIV laser is a dual head, independently triggerable system.
The fundamental laser output beams are polarization combined, then
frequency doubled in KTP. The temporally separated visible pulses
must generally overlap each other to produce the best signal in the PIV
experiment.
The alignment is optimized by adjusting the beam from laser 2 to overlap
the beam from laser 1 as shown in Figure 4-7. The beam from laser 1 is
fixed and cannot be adjusted, so beam overlap is optimized by steering
the beam from laser 2. This is an iterative process, switching between
overlap measurements at the laser head and at a distance several meters
from the head. The following procedure provides a tested method to
align the beams from the two laser heads.
The procedures described below require the laser to be operated
with the harmonic head cover open and the interlock defeated.
Stray IR and visible laser radiation may be generated. For safety
reasons room access should be limited and everyone in the room
should wear safety glasses.
Gemini PIV
Alignment
To Next Page
Loading...