CLOUD CHAMBER:
DEMONSTRATE FOG FORMATION BY EXPANSION, NEED FOR NUCLEI.
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Schematic of the cloud chamber setup.
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INSTRUCTIONS:
- CHECK OIL LEVEL IN PUMP BEFORE STARTING (Oil should show in the window at
the end of the blue pump housing)
- Setup as shown above. Use a 1/4" vertical slit slide in the
projector. The slit should cover about 1/3 the width of the tank and
all of the height. Turn on the slit lamp.
- With valves closed, turn on pump and evacuate holding tank
- Leave pump running (DO NOT TURN PUMP OFF WITH VACUUM IN HOLDING TANK -
RELEASE VACUUM BY OPENING BOTH VALVES BEFORE TURNING PUMP OFF).
- With inlet valve closed, open exhaust valve to drop pressure the modest
amount. Usually, if the tank has not been nucleated recently, no cloud
will form.
- Close the exhaust valve and open the inlet valve. Light a match and
by opening the exhaust valve slightly, let a little LITTLE smoke in through
the inlet. Close both valves.
- Now with some nuclei inside, opening the exhaust valve and lowering the
pressure a modest amount will produce a fog. More pressure drop = more
dramatic fog.
QT Movie of a
cloud forming.
�2000.
John Hart, University of Colorado