Time-resolved%20Tomographic%20Spectroscopy%20System - PowerPoint PPT Presentation
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Time-resolved%20Tomographic%20Spectroscopy%20System
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85Mm length) translated perpendicular to viewing chord. ~10-15 locations along length of chord. chords scanned individually. all scans compiled to a 'generic' scan. ... – PowerPoint PPT presentation
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Title: Time-resolved%20Tomographic%20Spectroscopy%20System
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Time-resolved Tomographic Spectroscopy System for
H-1NF
F. Glass J. Howard
Plasma Research Laboratory Australian National
University
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Introduction
- Encouraged by results of a single-view Modulated
Optical Solid State (MOSS) spectrometer. - MOSS spectrometer is a robust, compact
Fourier-transform device. - The line-integrated measurement leans to
tomography. - Several challenges in implementing
-flexible emission collection system. - many
views -gt many spectrometers? - thorough
calibration. - interpretation of measurements
(tomographic inversions).
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Overview
- Goals
- create time-resolved images of emitted
intensity, ion temperature of a poloidal
cross-section. - initial estimates of bluk flow
speeds simultaneously from several directions. -
better estimate of force balance in H-1NF.
- System Design - Light Collection, Light
Processing, Signal Analysis - Calibration - spatial response, in-situ, MOSS
spectrometer. - Results - first data
- Future Work
- Conclusion
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System Design Light Collection
- Flexible system which optimises light throughput
and maximises number of channels. - Five 45 sectioned viewing modules mounted on
800mm diameter rotatable wheel (200 rotation
range). - Each module - 11 parallel views embedded in
module. - Total of 55 angularly views channels.
- Each view
- coupling lens 15mm dia. 12.5mm aperture.
- mirror polished stainless steel, 11 different
angles. - optical fibre 1mm core dia., teflon jacketed,
aperture restricted.
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System Design Light Collection
- Stray light reduction diffuse blackened
stainless steel. - thin sheet viewing dumps.
- optical fibre apertures.
- Rotation using external stepper motor gear set
and internal sprocket engaging holes on wheel
side.
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System Design Light Processing
- Fourier-transform device using optical
solid-state modulation techniques. - Measures line intensity, species' temperature
and flow speed simultaneously. - Time-resolved measurements on large number of
channels.
- Input 8x8 array of fibres.
- Detection 8x8 multi-anode photomultiplier
assembly. - Issues
-detector cross-talk -instrument calibration
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Calibration Spatial Response
- Need to know where and how much the views are
seeing. - -gt tomography
- -gt insitu calibration
- Pre-installation scan
- thin fluorescent tube (3mm dia. 85Mm length)
translated perpendicular to viewing chord. - 10-15 locations along length of chord.
- chords scanned individually.
- all scans compiled to a 'generic' scan.
- Response curves characterised by Gaussian fit
parameters - -gt profile of height and width parameters.
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Calibration Insitu
- Remove variations between channels in total
transmission. - Compensate for any long term variaton.
- Understanding of stray light effects.
- 3 thin fluorescent tubes (3mm dia. 85Mm length)
installed perpendicular to wheel's viewing plane.
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Calibration Insitu
- Measured calibration
- Simulated calibration
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Calibration MOSS Spectrometer
- Account for spatial variations in
lithium-niobate crystal birefringence. - Multi-anode photomultiplier assembly
'cross-talk'. - system is field-widened.
- laser light through an initial channel - measure
intensity and contrast - measure other channels individually and
referenced to initial channel. - Laser pulse -gt per shot baseline.
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Results First Data
- Argon plasma (488nm line).
- 48 active channels.
- Shows transition.
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Future Work
- Initial work on tomographic inversions to be
completed - poloidal cross-section images of intensity and
ion temperature. - Estimates of bulk flow speeds from several
directions simultaneously.
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Conclusion
- Designed, manuactured and installed light
collection and spectrometer sub-systems. - Performed initial and insitu calibration of
system. - Obtained first data using argon discharge.
- Demodulated signals to give intensity and ion
temperature time-evolution in 5 seperate views of
plasma.
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