MOSS Spectroscopy Applications in Plasma

Physics

John Howard

Plasma Research LaboratoryAustralian National University

Outline

• MOSS spectrometer– Principle

– Doppler measurements on H-1

•Polarization Spectroscopy– Zeeman effect and MSE

•Spread spectrum FTS

•Imaging systems

Fourier Transform Spectroscopy

MOSS SpectrometerConcept

Instrument

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)

MOSS Hardware

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)

L-H Confinement Transitions

Heat Modulation Experiments

Fluctuation Measurements

Polarization Spectroscopy

Polarization Spectroscopy

Spherical quadrature polarimeter

Polarization Spectroscopy

Spread Spectrum FTS

Spread Spectrum FTS

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.

Spread spectrum data at 587nm HeI

Plasma light Calibrationlaser pulse

Laser interferogram

Power spectrum of interferogram

time (ms)

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