Laser-Induced Fluorescence for Plasma Diagnostics Designing and Testing an Optical Probe for Advanced Plasma Studies Stephanie Sears Advisor: Dr. Walter Gekelman

Overview  What is a plasma?  What kind of plasma was used for this research?  How was this plasma generated?  What exactly is LIF?  How was the experiment constructed? The laser The laser The probe The probe Data Collection Data Collection  What were the results?  What were some of the problems?  How does this contribute to further research in plasma physics?  What is the next step?  Conclusions

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

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