7B30.23 - Franck - Hertz : Critical Potential Tube - Low Pressure Helium

Code Number:
7B30.23
Demo Title:
Franck - Hertz : Critical Potential Tube - Low Pressure Helium
Condition:
Excellent
Principle:
Critical Potential in a Gas
Area of Study:
Modern Physics
Equipment:
Tel Atomic Critical Potenial Tube, 0 to 30 VDC Power Supply, 1 - Variacs, 1 - 6 V. Transformer, Volt and Amp Meters, Oscilloscope.
Procedure:

By carefully varying the voltage on the 0 - 2 VAC ripple power supply three different peaks corresponding to three different energies of helium may be shown at one time. Set the tube heater voltage at 4.5 volts and 1.5 amps using the Lambda LA-300 before you make any other connections.  When the other connections are made and turned on, the heater voltage will drop to about 2 volts and the amperage will go up to about 4 to 5 amps when the ripple is set at 2 VAC and the 0 to 30 volt power supply is set to 28 volts.  Slight adjustments to all these settings may be required to get the best oscilloscope trace.  NOTE: MAKE SURE ALL THE POWER SUPPLIES ARE AT MINIMUM OUTPUT BEFORE THEY ARE HOOKED TO THE TUBE AND TURNED ON. THIS WILL INSURE THAT THE TUBE REMAINS UNDAMAGED!!  Note that the oscilloscope hookup that works best for our situation is a little different than the diagram that comes with the tube instruction.  

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