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PERSISTENT SURVEILLANCE FOR PIPELINE PROTECTION AND THREAT INTERDICTION Determination of Carbon Release Mechanisms in the DIII-D Divertor from Analysis.

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Presentation on theme: "PERSISTENT SURVEILLANCE FOR PIPELINE PROTECTION AND THREAT INTERDICTION Determination of Carbon Release Mechanisms in the DIII-D Divertor from Analysis."— Presentation transcript:

1 PERSISTENT SURVEILLANCE FOR PIPELINE PROTECTION AND THREAT INTERDICTION Determination of Carbon Release Mechanisms in the DIII-D Divertor from Analysis of C I Line Profiles Presented by Phil West a for Ralph Isler b and Neil Brooks a a General Atomics b ORNL DSOL ITPA Toronto November, 2006

2   components of the 3 P- 3 P o Zeeman triplet of C I are used to determine the carbon production mechanism Physical sputtering: o Asymmetric line shape o Only a small red wing with respect to the rest frame wavelength because most atoms move toward the collection optics. o Peak is shifted by -0.1 to -0.2 Å from the rest frame wavelength Chemical sputtering: o Nearly symmetric line shape o Peak shifted by only -0.03 to - 0.04 Å owing to the near thermal release of parent hydrocarbon.   

3 Helium plasmas provide a good test for modeling profiles when physical sputtering is dominant. The red wing (  is the result of reflections from the divertor tiles The Thompson formula, with E impact = 400 eV, is a good fit except near . An additional 9% contribution from chemical sputtering gives the best fit to the source profile.

4 C I from the porous plug ( during methane injection) comes mainly from molecular dissociation. Porous plug - methane breakup Two Gaussian Representation of Symmetric Component 97% - 0.35 eV 3% - 5.0 eV Outer strike point: Attached L-mode Thompson =10% Total Cold symmetric peak (aka chemical sputtering) dominates T S1 = 0.35 eV

5 When divertor detaches C I Doppler shift drops to near zero Detached Case (solid): n e /n GW ~ 0.7 Div Thomson near OSP: n e DIV ~2 x 10 20 m -3 T e DIV ~ 1.3 eV after t=3.0 s Attached Case (dashed): n e /n GW ~ 0.2 Div Thomson near OSP: n e DIV ~2 x 10 19 m -3 T e DIV ~ 15. eV after t=3.0 s Suggests that C I emission in detached case is recombination dominated Inner Strike Zone Outer Strike Zone

6 Summary Cold, symmetric peak present in all cases studied ( detached, attached, high and low NBI power) Thompson peak prominent only in high power NBI, attached cases In detached, high density, cold divertor cases, Doppler shift of cold symmetric peak drops to values much lower than expected for chemical sputtering, probably a sign that recombination dominates the C I emission.


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