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This mode of operation typically requires the tank to be filled with Freon-12
at pressures varying from 2 to 3 atm. Because these operating pressures are
greater than 1 atm, the detector must be filled by dilution. Contamination
from air, however, is not a major problem as the optical absorption properties
of air are actually more favorable than those of Freon-12 itself; the only
difficulty is the increase in pressure needed for a mixture of air and Freon
to achieve the same pion momentum threshold as for a pure sample of Freon.
First prepare the gas handling system:
- Make sure that the 60 mil windows are installed and oriented such that
they bulge outwards from interior of the tank.
- Close the valves V2-V4, and the valve on regulator R1.
V1, SV1, and the valve on regulator R2 should be
open.
- Open the valve on the gas supply bottle.
- Adjust R1 to approximately 60 psig.
- Open the valve on R1.
- Check to make sure gauge G1 agrees with the pressure setting
on R1.
- Adjust R2 so that a small flow is detected out the vent of
V1.
- Close V1.
- Adjust R2 to regulate at the required operating pressure.
The tank is now ready for the dilution process. These steps should be
repeated as few times as possible to minimize the quantity of Freon-12 emitted
to the atmosphere.
- Record the tank pressure.
- Open valve V2.
- Monitor the gas pressure until it reaches the required operating pressure.
NEVER let the pressure in the detector exceed 3 atmospheres.
- Record the final pressure.
- Open V3 to vent the tank.
From the recorded pressure readings, the threshold momentum of the mixture
of air and Freon-12 can be calculated (assuming the volume of the tank is
fixed).
Next: Lead Glass Shower Calorimeter
Up: Gas Cerenkov Detector
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Hall-C Staff
2002-11-04
/p Procedures