Absolutely Calibrated Tangential Imaging of DivertorR. J. Maqueda

X Science LLC

Project Objectives (from proposal)

•Develop and implement an absolutely calibrated tangential visible imaging

system for the lower divertor of NSTX-U.

•Use this diagnostic during plasma operations in NSTX-U, validate calibrated

data and make data available for general team use.

•Use data from diagnostic to benchmark edge computer models and obtain

indirect measurements of relevant quantities such as the deuterium neutral

density and impurity densities (carbon and lithium) in the divertor region.

1NSTX-U Non-Lab Diagnostic PlansJuly 26, 2012PPPL

Absolute calibration is only a small component of funded work

• Upgrade of existing diagnostic.

• Photometric calibration to be performed in-vessel

before and after campaigns.

• Physics results from interaction with modeling.

• Strong collaboration with LLNL team members.

• Need to measure window/mirror transmission

(main hardware development effort).

Shot 132595LiI (red)

LiII (green)

lowerX-point

2

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Similar diagnostics used in other experimentsAlcator C-Mod, comparison with onion skin model [S. Lisgo et al., J.

Nucl. Mater. 337-339, 139 (2005)]

Inter-ELM

ELM

DIII-D, measurements during ELMs[M. Groth, et al., Phys. Plasmas 14, 056120

(2007)]

• Many other examples from DIII-D, C-Mod and JET.

• Comparisons with UEDGE/DEGAS and OSM/EIRENE.

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Diagnostic highly relevant to NSTX-U research

Successful operation of the divertor needs development of appropriate

power handling techniques

•Further development of the snowflake divertor.

•Development and assessment of divertor detachment and performance.

•Generation and transport of impurities (and recycling) at the divertor.

•Study of 3-D field effects on divertor physics.

•Development and implementation of edge computer models

(UEDGE/DEGAS or OEDGE/EIRENE).

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Some challenges ahead• Use lambertian source to provide reproducible target plate on some days after

the run, illuminate plate from outside through fiber light guide (similar to TS

system).

• Avoid introducing probe into plasma region but perform all measurements

behind passive plates.

Existing re-entrant tubeLower dome radial port at Bay F

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Summary

• Main physics results from interaction with modeling.

• Strong collaboration with LLNL team members (UEDGE+DEGAS2)

and/or other models (OSM+EIRENE).

• Photometric calibration expected to yield 20% accuracy.

• Bright emission lines (D, LiI @ 678.0 nm) measured at ≥10 kHz

LiII @ 548.5 nm, CII @ 657.8 nm, CIII@ 464.7 nm at ~1 kHz.

Absolutely Calibrated Tangential Imaging of Divertor