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Relaxation Curve of Gasses Heated by a CO 2 Laser

Relaxation Curve of Gasses Heated by a CO 2 Laser. by Jonathan Esten 15.03.2000 with Phillip Stewart under direction of Dr. W. Christian. Abstract.

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Relaxation Curve of Gasses Heated by a CO 2 Laser

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  1. Relaxation Curve of Gasses Heated by a CO2 Laser by Jonathan Esten 15.03.2000 with Phillip Stewart under direction of Dr. W. Christian

  2. Abstract This experiment verified the shapes of relaxation curves for pure CO2, our lasing gas, and a 15% CO2 , 15% N2, 70% He mixture similar to the gas used in the laser. Some rough data was taken to demonstrate the pressure dependence of the relaxation curve for the pure gas. A “poor man’s q-switch” was placed in the laser cavity to turn the beam on and off rapidly for data acquisition.

  3. Theory • A gas laser relies on stimulated emission to produce a powerful, coherent beam. A gas cell is placed in the beam path containing the gas that produces the laser light. The gas will heat as the atoms of the gas are stimulated by the energetic laser photons. The gas will then cool in a manner modeled by a pressure-dependent relaxation curve. • In our mixed gas sample, interactions between the Nitrogen and the Carbon Dioxide affect the curve shape. • A cooling spike is observed before the heating curve begins.

  4. Gas Mix Energy Diagram

  5. Apparatus

  6. Apparatus A microphone in the gas cell was used to detect pressure changes. The output of this microphone was connected to an oscilloscope so that traces could be observed. The pure Carbon Dioxide cell used a simple microphone, where the cell used for the gas mixture contains a more precise capacitance microphone.

  7. Data The heating and cooling curves for both the pure gas and the gas mixture were observed on the oscilloscope. Due to a great deal of acoustic ringing, the curves were often noisy at low pressures. Time constraints prevented correction of this problem, so no solid, analyzable data was taken. However! The phenomena expected were evident, so future work should be fruitful.

  8. Data on pure CO2 Despite ringing, some very good curves were seen matching this.

  9. Pressure dependence? Though not entirely dependable, the preliminary data on pure CO2 indicates that the pressure dependence is exponential.

  10. Data on gas mixture

  11. Observations on gas mix data Curves seen showed cooling, then heating, then gradual cooling as expected. Lots of ringing made analysis impossible. Pressure dependence was not easily observed.

  12. Conclusions • The results were promising. The physical phenomena expected were evident in both samples. • Future experimentation could yield concrete data on the exact pressure dependence of both curves. To do so, extra attention must be paid to the following: • Align beam precisely through gas cell. • Connect cell microphones to a digital scope so that data is easily exported to a computer for analysis

  13. That’s It!

  14. Any Questions? Please contact me. Jonathan Esten at joesten@davidson.edu

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