leblanc_03feb09_1 mpts phase 4 benoit p. leblanc pppl 19 june 2009
TRANSCRIPT
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MPTS Phase 4
Benoit P. LeBlanc
PPPL
19 June 2009
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Outline
• Scope of work for Phase 4• Technical issues• Seven unused fiber bundles• Gradient location database• Previous inputs• A partial suggestion
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Scope of Phase 4 and More
• Install 10 – possibly 12 -- new radial channels– Use 6-filter polychromator – as in phases 1 & 2
• Install two new alignment channels• Rebuild phase-3 polychromators
– Add 1064-nm filter for Rayleigh noise rejection (unlikely)
• Repair MPTS hardware – three items• Calibrate 40-channel system
– Spectral, fast/slow, gain; before Rayleigh/Raman
• Preparation work for high-Te channels– To be implemented in NSTX-U – 10keV (on the back burner)
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Technical Issues
• Plan is to complete more of existing hardware– 7 unused fiber – one bundles sees RF NB– 16 unused sample-and-hold slots– Changes will occur in the polychromator room
• Develop a technique to unglue output end of fiber bundles – tricky but feasible
• Reroute a large number of fiber bundles– Split bundles need to be physical close – order of 6”– Long sequence of activities, which cannot be stopped before
MPTS is back online ≥ 5 months• Upgrade includes the construction of a fourth
polychromator “tower”• All new polychromators and ancillary hardware need to
be ready at the end of FY10 experimental run• Massive calibration work following successful hardware
installation
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Polychromator Stacked in Towers
• Current 3 “tower” each house 10 polychromators
• Each polychromator is attached to a movable shelf– Split bundles need to be
next to each other vertically
• The fourth tower will have 12 shelves
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Seven fiber bundles remain unused
Seven unused bundles indicated in green R= 31.8, 86.4, 96.3, 104.9, 112.5, 154.6, 157.7 cm
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Gradient location database
• 1446 shots from 2008
• Use spline Te and ne profiles to compute the location of maximum gradients, average over times 0.15s – 0.9*max(ts_time)
• Database includes 29 shots suggested by Rajesh Maingi
• Use this data to identify new channel locations
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Location of Te vs. location of ne
Distribution plot
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Location of Te vs. location of ne
Distribution plot redux
Shots suggested by R. Maingi
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Location of Te vs. location of ne
2D histogram plot
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Histogram of Te location
3
1 2 split bundle unused
Phase 1Phase 2Phase 3Unused
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Histogram of ne location
3
1 2 split bundleunused
Phase 1Phase 2Phase 3Unused
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Comments for Team• Rajesh Maingi
– To better resolve the H-mode pedestal gradients, I suggested the spatial resolution be optimized from ~R=141-147cm. Practically this means adding 4-5 channels.
– Shell works best with smaller gap• Jon Menard
– I am concerned about LLD being successful in increasing D pumping– and forcing us to run larger outer gaps to reduce metal influx
– What range of outer gaps would the proposals below support?, i.e.– have good gradient resolution for H-mode for our typical profiles.
– Some of our transport barrier shots are clearly under-resolved in– the core, so this might warrant some additional coverage there.
– Crudely, I tend to think resolving the edge is 2-3x more important– than the core programmatically
• Joel Hosea– Good documentation of pedestal foot, re ELMS
• Ben LeBlanc– The outermost bundle “sees” the BN limiter – antenna was moved inward in 2004– The bundle will not be instrumented at this time.
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Use Existing Data to Estimate Error
• Found among 2008 shots six pairs of successive plasmas: (S217 open & S218 open), followed by (S217 open & S218 Shut)
• Check shots for similar time evolution etc.• Took data between 0.05s and 0.5s -- avoid saturation• Compare data with both shutters open – Tef0, dTef0,
nef0 – with data with one shutter closed – Tef1, dTef1, nef1
• Select radial positions with raw signal (S218 shot/open) of 0.3 or 0.5.
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Fiber Bundle divided in Two
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Fiber Bundle divided in Three
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A Suggestion…Revision June 2009
• Propose 10 new channels, but will aim at 12– Cannot fit more channels in the schedule
• One new radial channels at R=154.6 cm (unused FB)• One new radial channels at R=31.8 cm (unused FB)• Four to six(?) new radial channels in “pedestal” region
– Done by splitting instrumented bundles in two• No unused bundles available
– Location of higher-resolution channels to be chosen by team/experts’ recommendation
• 2008 data suggest centering around 141 cm
– How far in before splitting bundles is no longer useful
• Four to six in the core and ITB region– Four unused bundles in the core region
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Edge Pedestal Density
Phase 1Phase 2Phase 3Unused
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Te ITB Profile
Phase 1Phase 2Phase 3Unused