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First results from Transmission Grating Imaging Spectrometer
D. Kumar, D. Stutman, K. Tritz, M. FinkenthalPlasma Spectroscopy Group,
Department of Physics and Astronomy,The Johns Hopkins University.
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Device Setup• Motivation– Provide impurity
measurements for Multi-Energy Soft Xray system
– Impurity monitor in itself• Detection– CsI coated MCP– Phosphor screen– CMOS imaging system
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• Design advantages– Survey spectrometer
(30 A – 700 A)– Robust to neutrons– Provide spatial impurity
distribution• Beam excited charge exchange emission
• Electron excited emission (edge and core)
• Frame exposure = 380 ms
Device Setup
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Grating details
• Free standing Grating dimensions– 1 mm x 1 mm– 200 nm period
• NIST calibrations
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Calibration through PID spectra
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Al IV 161 A
Ne I 736
Ne II 461 A
24 A
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NSTX results – typical spectrum
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NSTX results – ohmic spectrum
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Ohmic shot – spatial profile (edge)
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Typical shot – spatial profile(Edge + CX + core)
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BIG QUESTION – WHAT ABOUTCOPPER, MOLY, IRON?
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Copper
• No Copper observed.• Reason – The absence of Cu XIX doublet lines
(2p63s – 2p63p) at 273 A and 303 A.
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Molybdenum
• 74 A Mo peak correlates with (Mn like Mo)– Some shots where DIM observed Mo– No LITER and strike points on LLD
• However, no effect of Mo on Zeff
• Data is noisy:
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Lithium
• Spatial profile of the ohmic spectrum at 135 A confirms that some Li does get into the plasma.
• With NBI, the spatial profile indicates that there is something in addition to charge exchange.
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Iron
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• Metals observed sometimes in the second frame when Prad
rises.
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WHAT ABOUT OXYGEN, CHLORINE?
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Oxygen
• MCP needs to be calibrated for proper calculations
• From C VI 182 and O VIII 293 A:
• From C VI 521 and O VIII 293 A:
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2.5
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Chlorine (SPRED)
C IV 312 A
Cl XV 237 A
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Chlorine (accumulation)
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Summary of Cl
• The presence of 237 A Cl XIV along with Cl XV lines at 384 A and 415 A clearly confirms Cl
• Cl emission substantially brighter with NBI• Cl seems to accumulate (towards core) with
time• SPRED indicates presence of Cl at least since
March 2007
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Conclusion
• Results – C, O, Cl, Li, Fe, Mo (?), Cu• Future direction– Geometric modeling– High speed readout– After run – Calibration of MCP efficiency
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Acknowledgements
• PPPL– L. Roquemore– R. Kaita– V. Soukhanovskii– C. Skinner– S. Gerhardt– G. Zimmer– NSTX 2nd shift – John, Jerry &
Ron– VPL – Tommy– J. Winston– J. Dong– J. Wertenbaker
• SSL, Berkeley– J. Lepson
• NIST– C. Tarrio
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