MOSS Spectroscopy Applications in Plasma Physics. John Howard. Plasma Research Laboratory Australian National University. Outline. MOSS spectrometer Principle Doppler measurements on H-1 Polarization Spectroscopy Zeeman effect and MSE Spread spectrum FTS Imaging systems.
MOSS Spectroscopy Applications in Plasma Physics
Plasma Research LaboratoryAustralian National University
High light throughput
High time resolution
MOSS is optimum in the sense that all photons contribute to three independent pieces of information - intensity, shift and contrast.
Flow velocity (shift)
Lines of sight
Central ring conductor
Plasma cross section
Fringe contrast versus time delayArII 488nm, Ti=10, (10), 100 eV
Nominal delay for LiNbO3 ( 25mm)
The Zeeman components are spectrally shifted and circularly polarized when viewed parallel to B. The nett circular polarization is a measure of the intensity weighted longitudinal component of the B field.
By filtering/modulating the polarization state of the plasma light using a spherical quadrature polarimeter, either the coherence (bandwidth) or centre of mass of the spectral line can be varied.
The MOSS spectrometer senses these modulations as contrast or phase variations of the interferometer fringes.
Spherical quadrature polarimeter
Motional Stark Effect.
H or D atoms in a heating beam experience an induced electric field E= v x B that generates a complex spectrum. Viewed transverse to E the Stark split s and p components are polarized respectively perpendicular and parallel to E.
Combined polarimeter/MOSS system for MSE measurements
Spread Spectrum FTS
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.
Power spectrum of interferogram