laser-induced fluorescence for plasma diagnostics designing and testing an optical probe for...
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Laser-Induced Fluorescence for Plasma Diagnostics
Laser-Induced Fluorescence for Plasma Diagnostics
Designing and Testing an Optical Probe for Advanced Plasma Studies
Stephanie Sears
Advisor: Dr. Walter Gekelman
OverviewOverview
What is a plasma?What is a plasma? What kind of plasma was used for this research?What kind of plasma was used for this research? How was this plasma generated?How was this plasma generated? What exactly is LIF?What exactly is LIF? How was the experiment constructed?How was the experiment constructed?
The laserThe laser The probeThe probe Data CollectionData Collection
What were the results?What were the results? What were some of the problems?What were some of the problems? How does this contribute to further research in plasma physics?How does this contribute to further research in plasma physics? What is the next step?What is the next step? ConclusionsConclusions
Helium Plasma
Neon Plasma
Specifics of Our Plasma
• Fully-ionized argon (ArII)
• Dimensions=
• Density=
• Approximate electron temperature=
• Predicted ion temperature=
Creating the Plasma
• The plasma is pulsed
• Field Strength=
• Created with an electron beam
The Machine Schematic
North South
Machine Specifications
• 18 meters in length, 1 meter in diameter• 90 magnetic coils generate fields between 0.05 and 4 kG
• Barium oxide-coated nickel cathode• Molybdenum mesh anode• 0.55 meter cathode-anode separation• 450 radial ports• 60 rotating flanges• 4 mechanical pumps• 2 turbo pumps• 2 portable vacuum stations• Computer controlled stepping motors• Available working gases include helium, neon, argon, and hydrogen
The Machine Itself
The Cathode
The Anode
Inside the Chamber
What is Laser-Induced Fluorescence (LIF)?
Allowed Transitions of Argon II
Simple Energy-Level Diagram
Theoretical Spectrum
Actual, Doppler-Broadened Spectrum
Illustration of the Doppler Effect
Relation of Optical Intensity to Wavelength
Why is this worth looking at?
The Experimental Set-Up
Timing Diagram
The Laser
The Probe(Original Design)
Actual Design
Data Collection
The Data
Interpreting the Data
Problems To Overcome
• Very low signal-to-noise ratio
• Huge amount of scattered light
• Poor alignment of fiber with laser sheet
• The laser itself
Ways to Improve LIF Observation
• Better Filter
• Amplifier
• Better Probe Design
Design for a Future Probe
Conclusions
Acknowledgements and Thanks
• Dr. Walter Gekelman-Advisor
• Stefan Grunspan and Brett Jacobs-UCLA students
• Marvin Drandel-LAPD technician
• Everyone else on the UCLA plasma team
• Fellow REU students and friends
The EndThe End