PASCO OS-9257A PRECISION INTERFEROMETER - Manual (Page 22)

Precision Interferometer 012-07137A
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ä IMPORTANT— The Vacuum Cell is not designed to
be heated.
Index of Refraction for Gases—
Measure the indices of refraction for various gases.
Caution: The PASCO Vacuum Chamber is NOT designed
to hold positive pressures. You will need to provide your
own gas chamber.
Fabry-Perot Spectroscopy—
The Fabry-Perot mode is customarily used as a high-
resolution spectrometer. Very close spectral lines, as in
magnetic splitting, can be resolved much more accurately
than with any but the highest quality diffraction gratings.
To replace the spacer:
1. Turn the interferometer
over, and remove the bot-
tom cover.
2. Position the spacer be-
tween the two ball bear-
ings, as shown in Figure
A2. Release the lever, and
check that the spacer is
snugly in place.
3. Replace the bottom panel.
Mirror Care
The mirror and beam-splitter surfaces are precision ground
and coated. Dirt or scratches will distort the fringe pattern,
so handle all optical surfaces with care. Clean the surfaces
occasionally with lens tissue.
Vacuum Cell
Clean the glass windows on the vacuum chamber occa-
sionally with lens tissue.
Storage
Rotate the Micrometer Knob fully IN before storing the
Interferometer.
Micrometer Calibration
The micrometer is calibrated before it is shipped. How-
ever, if recalibration becomes necessary, use the following
procedure:
1. Turn the interferometer
over, and remove the bot-
tom cover.
2. Loosen the two screws
shown in Figure A1. Slide
the bearing surface toward
the pivot to increase mir-
ror movement per turn of
the micrometer dial. Slide
the bearing surface away
from the pivot to decrease
mirror movement per dial
turn. Tighten the screws
and replace the bottom
cover.
Testing your calibration is most easily performed using a
laser light source of known wavelength, as in
Experiment 1.
Micrometer Spacer Replacement
In order to provide extremely fine, backlash-free control of
the movable mirror, the mechanical linkage between the
micrometer and the movable mirror is maintained under a
state of spring-loaded compression. This compression also
holds part of the linkage (a spacer) in place. Under normal use,
the spacer will never fall out of position. However, a sudden
jolt can jar the spacer and the spring loose. In this case, the
micrometer will no longer work, and you'll hear the parts
rolling around inside.
Maintenance
Figure A2. Spacer
Replacement
Lever
arm
Spacer
Loosen
screws and
slide the
bearing
surface as
required.
Figure A1.
Calibration