Upload
xerxes
View
27
Download
1
Tags:
Embed Size (px)
DESCRIPTION
Imaging Diagnostics at the H-1 National Plasma Fusion Research Facility. Because of its relatively unhindered viewing access, the H-1 heliac is well suited for the development of plasma imaging systems. - PowerPoint PPT Presentation
Citation preview
Imaging Diagnostics at the H-1 National Plasma Fusion Research Facility
Left: The coherence tomography systemAbove: Plasma emission reconstructions compared with calculated magnetic isosurfaces
Left: The wheel located in the H-1 tank Above: sequence or reconstructions of large scale plasma instability
Above: Photograph of the first electro-optically modulated Doppler coherence-imaging spectrometer installed on the H-1 heliac and drawing showing the plasma cross-section and imaging arrangement.
Left to right: Doppler images obtained using the 16-channel coherence imaging camera, showing the time-evolution of the plasma brightness profile, the plasma flow and ion temperature. Low field argon discharge, 488nm
Measuring isotope ratios
Measurement of H-D isotope intensity ratios in H light gives information about particle fuelling in H-1.
As the intensity ratio changes, the interferogram phase shifts and fringe contrast changes (see figures left). The technique is useful for 2-d imaging and when Doppler broadening blurs the lineshape.
The H-1 multi-view density interferometer
Left: An electronic wideband sweep and fixed grating now replaces the grating-scanned laser beam. This is a turn-key solution that can provide a more rapid plasma sweep. Above: Temporally-multiplexed plasma sweeps of ECH plasma
Left: Layout of the helium supersonic gas injection system and viewing geometry.
Below: integrated 16-channel PMT detector/amplifier package developed at ANU for imaging spectroscopy
16 channel time-resolved image of H-1 ECH plasma pulse in helium emission (471nm). The spatial intensity profile for the gas pulses becomes more edge localised as the temperature increases. Clutter in the filter passband precludes the use of the intrinsic He atomic emission for temperature estimation.
Above left: Measured pulse brightness versus plasma major radius for 471nm and 504nm transitions. Solid lines are expected brightnesses based on CRM model and measured Te and ne profiles. Right: The electron temperature profile inferred from the relative line intensities.
Above: Photo of grating-based scanning interferometer and Gaussian beam model.Left: Tomographic reconstruction of saturated global instability in low-field (0.1T) argon discharge
Coherence imaging systems (Ti, v, B, …)
Coherence imaging systems are high though-put temporal and/or spatial multiplex polarization interferometers for high resolution, high-speed spectroscopic imaging.
Applications includeDoppler spectroscopy (CXRS, divertor)Emission line ratios (Isotopes, He line ratios)Polarization spectroscopy (MSE, Zeeman)Thomson scattering
Systems are installed at the Australian National University, University of Sydney, Consorzio RFX, IPP Greifswald, NFRC Korea, JT-60 JAEA
The 55 channel tomographic coherence imaging system
Helium line ratios for Te
The original multi-view scanning far-infrared interferometer utilized a rotating scanning grating to generate four independent views (sets of chords in a given viewing direction) of the plasma. The multiple views allow phase shift data to be tomographically unfolded to obtain the plasma density contours
Because of its relatively unhindered viewing access, the H-1 heliac is well suited for the development of plasma imaging systems.
To obtain spatial profiles, the complex plasma geometry requires multiple viewing angles and the application of inverse methods (tomography).
Practical considerations require the use of various temporal, spatial and frequency domain multiplexing methods.
This poster describes imaging systems for key plasma parametersScanning interferometry for electron densityCoherence imaging for spectroscopy (Doppler, ratios, polarization etc)Supersonic He injector and atomic emission line ratios for electron temperature
Quad-coherence imaging systems produce quadrature 2-d interference fringe images at the 4-corners of a CCD array. This allows a snapshot of the complex optical coherence.
The ratio of the brightness of transitions from triplet and singlet atomic states of helium is sensitive to plasma electron temperature. A supersonic helium jet has been developed by USyd for probing Te profiles in the H-1 heliac.
Modulated (temporal multiplex) coherence imaging
Static (spatial multiplex) coherence imaging
Above: Layout for quadrant coherence imaging system
Above: Typical 4-quadrant coherence image (leftmost) and extracted 2-d snapshots of the spectral line brightness, temperature and flow speed. Note hollow ion temperature profile and rigid rotation flow profile for low field argon discharge. (Compare with images to left)
Left: Viewing geometry for quadrant coherence imager. Toroidal field coils and helical field coil internal to vacuum tank are visible.