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A LASER SCATTERING DIAGNOSTIC

TO STUDY THE ANOMALOUS FLUX DISSIPATION OF AN FRC Onnie Luk Advisor: Tobin Munsat. A LASER SCATTERING DIAGNOSTIC. Some Preliminaries…. FRC: Field-Reversed Configuration Magnetic configuration for plasma confinement Fusion energy research My summer project

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A LASER SCATTERING DIAGNOSTIC

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  1. TO STUDY THE ANOMALOUS FLUX DISSIPATION OF AN FRC Onnie Luk Advisor: Tobin Munsat A LASER SCATTERING DIAGNOSTIC

  2. Some Preliminaries… • FRC: Field-Reversed Configuration • Magnetic configuration for plasma confinement • Fusion energy research • My summer project • Design a laser diagnostic instrument for fluctuation measurement in FRC experiment at Los Alamos National Laboratory

  3. What is Plasma? • 4th state of matter • Ionized gas with its motion controlled by electromagnetic fields • 99% of all baryonic matter in the universe is made up of plasma • Stars • Interstellar gas • Interplanetary space (solar wind)

  4. + 1 2 + He4 Neutron Deuterium Tritium + + + + 3 + What is Fusion? • Need • high temperature (~100 million K) to fuse atoms • good confinement • ITER: fusion experiment under construction

  5. Alternate Magnetic Confinement Configuration • Field-Reversed Configuration (FRC) • What's so great about FRC? • Potential fusion reactor • Simpler design than tokamak with better wall interaction • Can possibly refuel tokamaks • Study fast magnetic reconnection (basic science)

  6. FRX-L: an FRC Experiment • Field Reversed Experiment-Liner • Located at Los Alamos National Laboratory • Anomalous flux dissipation observed; possibly caused by lower hybrid drift instability • Expected characteristic of the density fluctuation: • λ = 26 μm • Guess: • ñ/n = 1%

  7. Plasma Detectors θ Laser Radius of Curvature Beam Diameter z φ d mλ Beam Divergence Wavefront Diffraction Grating Gaussian Beam Study of Density Fluctuation – Laser Scattering Diagnostic

  8. Design Consideration: Laser • Wavelength: 632.8nm (HeNe) • High power: 17mW • Beam pointing stability: <0.002° • small compared to scattering angle θ • Beam diameter: 0.96mm • not too big and not too small • Beam divergence: 0.05° • Polarization: Linear

  9. Design Consideration: Detector • Power ratio : 2 x 10-5 • Scattered power Ps: 3x10-7 W • Size: Φ 0.23 mm • compact, with active area similar to beam size (~ Φ2mm) • Fast-responding: ≥ 20 MHz(fNyquist of digitizer) • Noise Equivalent Power (NEP): 2.82x10-11 W • as low as possible • Signal-to-Noise Ratio (SNR): 1.2x104 • SNR = Ps/NEP > 10

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