MOSS Spectroscopy Applications in Plasma Physics
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MOSS Spectroscopy Applications in Plasma
Physics
John Howard
Plasma Research LaboratoryAustralian National University
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Outline
• MOSS spectrometer– Principle
– Doppler measurements on H-1
•Polarization Spectroscopy– Zeeman effect and MSE
•Spread spectrum FTS
•Imaging systems
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Fourier Transform Spectroscopy
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MOSS SpectrometerConcept
Instrument
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Advantages of MOSS
•High light throughput•High time resolution •Compact, robust
MOSS is optimum in the sense that all photons contribute to three independent pieces of information - intensity, shift and contrast.
DC Light intensity
atan(odd,even) Flow velocity (shift)
sqrt(odd2+even2) Temperature (contrast)
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MOSS Hardware
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MOSS spectroscopy on H-1
Lines of sight
Plasma cross section
Central ring
conductor
Fringe contrast versus time delayArII 488nm, Ti=10, (10), 100 eV
Nominal delay for LiNbO3 ( 25mm)
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L-H Confinement Transitions
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Heat Modulation Experiments
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Fluctuation Measurements
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Polarization Spectroscopy
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Polarization Spectroscopy
Spherical quadrature polarimeter
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Polarization Spectroscopy
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Spread Spectrum FTS
Spread Spectrum FTS
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Imaging systems
Multiple spatial channels can be multiplexed through an imaging MOSS spectrometer while maintaining high light throughput and low instrument temperature.
Multiple-crystal modulators can be employed for truly 2-D spectral imaging: the spectrum at each spatial position is encoded in the temporal frequency domain.
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Spread spectrum data at 587nm HeI
Plasma light Calibrationlaser pulse
Laser interferogram
Power spectrum of interferogram
time (ms)
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Conclusion
• MOSS spectroscopy is a high throughput alternative to traditional grating spectrometers
• Well suited to plasma Doppler and polarization spectroscopy
• Fully 2-D spectral imaging is possible.
• Facilitates tomography of scalar (intensity) and vector (velocity) fields in H-1NF for force balance, fluctuation and particle/heat modulation studies