• General Remarks
1. Wait 30 min for laser to stabilize after turning it on.
2. Sample should be placed at a right angle to the beam.
3. Fixing the distance to the lens = fixing q, do not change during experiment.
4. Do not trust temperature reading in computer: use chart to determine sample
temperature from set-point temperature.
5. Experiments typically run 5-6 hours; use time intervals around 15 sec. If
longer experiment, increase interval. Hold temperatures for around 40 min (until
signal is stable).
• Light Scattering Equipment Set-Up
1. With laser going through everything before the lens, check
to see that the beam hits the middle of the crosshairs on the wall.
2. Add the lens. Move it until the beam is focused on the crosshairs.
3. Add the beamstop. Use the small mirror to see if the laser is hitting the
middle of the beamstop and adjust it.
4. Add the detector. The focal point of the lens should hit at the front of
the detector, which is inside of the piece.
-Use a sample with a lot of scattering.
-Manually move the detector back and forth and approximate where it should be
based upon the focal point of the lens (use a piece of white paper to see this.)
5. Increase the neural density to reduce the beam intensity.
6. Open Bire 1 and 2 with T2 and T3. Hit start. Hit cancel so it doesn't save.
Change the time interval to 2 seconds.
7. The birefringence will be maximum when the detector is correctly positioned.
Move the detector until it is maximum. (It will be overloaded at 10.0.)
8. Lock the detector into place.
9. When not using the set-up, cover all components with plastic bags.
10. Turn off the laser and put away the key.
11. Measure the thickness of the sample and quartz.
Beam splitter: directs part of the beam to detector 2 and part to the polarizer.
Detector 2: Measures instantaneous fluctuations in the intensity of the laser
beam- can be used to determine if there is a problem with the beam itself.
Polarizer: Filters one direction of light (this one is vertical). It is fixed
at allowing the maximum light through.
Lens: Focuses the scattered light down to one point.
Beamstop: Prevents the non-scattered (transmitted) light from reaching the detector.
• Light Scattering Procedure
1. Turn on the
laser with the key.
2. Remove plastic bags from all components.
3. Plug in the temperature control and set the setpoint. Turn on the detector.
4. Wait until the temperature reaches the desired setpoint. Allow 1.5 hours
for the laser to stabilize.
5. Start the experiment (use the program for detector 1 and 2) and save the
file to the appropriate location.
6. Adjust the temperature as desired.
• Shut Down Procedure
1. Turn off the
laser and remove the sample.
2. Cover all of the equipment with the plastic bags and turn off the detector.