David Eisenberg

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David Eisenberg

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1. 3/28/2012 David Eisenberg David Eisenberg Construction and Application Langmuir Probe For Irvine Torus

2. 3/28/2012 David Eisenberg Irvine Torus R=0.56m, a=0.035m 0 < Bo < 0.25 T 1015 < nion< 1018 m-3 5 < Te < 15 eV 0.1 < Tion < 2 eV Argon

3. 3/28/2012 David Eisenberg Langmuir Probe The Langmuir probe is useful for providing measurements of electron density, temperature and ion density. In essence, the Langmuir probe is nothing more than a sphere, cylinder or in this case disc made out of a conducting substance inserted into a plasma. As the charged plasma particles collide with the disc, it draws electrical current.

4. 3/28/2012 David Eisenberg Theory No Applied Voltage Negative Potential Lighter Electrons have greater velocity Applied Voltage Decreasing Voltage repels electrons Only Electrons with enough velocity to over come potential barrier collide with probe

5. 3/28/2012 David Eisenberg Construction 2-steps Probe Shaft Stainless Steel Body Teflon Plug 2 Metal Caps Copper Wire Glass Tubing SMA Co-ax Connector Probe Tip Tungsten Wire Glass insulation Aluminum covering Ceramic Casing Protects from plasma heat Molybdenum Tip Disc that actually draws current

6. 3/28/2012 David Eisenberg Probe Details

7. 3/28/2012 David Eisenberg Schematic

8. 3/28/2012 David Eisenberg Data Acquisition

9. 3/28/2012 David Eisenberg I-V Trace 1) Ion Saturation Current Positive contributions from Ions 2) Floating Potential No applied Potential Potential any object will obtain undisturbed in Plasma 3) Space Potential Potential of Plasma

10. 3/28/2012 David Eisenberg Electron Temperature

11. 3/28/2012 David Eisenberg Density

12. 3/28/2012 David Eisenberg Floating Potential

13. 3/28/2012 David Eisenberg In the Future Add data to my results Much more at 17T Run experiments with Helium rather than Argon Use probe to help with diffusion experiment Sources Chen, Francis Plasma Physics and Controlled Fusion, Plenum Press, NY 1984 Chan, Lisa “Langmuir Probe Cronstruction” Thanks to Prof. McWilliams, Dr. Edrich, Scott Catanzariti and the rest of the Lab crew that helped with this project.

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