Monday Physics Meeting, 05/05/08 1

XP-815 – Characterization of divertor heat flux width and mid-plane SOL widths

J-W. Ahn1, R. Maingi2, J. Boedo1, V. Soukhanovskii3, R. Maqueda4, S. Zweben5

1University of California – San Diego

2Oak Ridge National Laboratory

3Lawrence Livermore National Laboratory

4Nova Photonics

5Princeton Plasma Physics Laboratory

Monday Physics Meeting, 05/05/08 2

Motivation and goals of the experiment

Topics of investigation in FY08 (all in H-mode)

(1) To find dependence of λq (target), λTe and λne (upstream) on plasma parameters (Ip, nebar and Power)

(2) To develop SOL width scalings(3) To find the relation between SOL widths and the edge

turbulence characteristics

Monday Physics Meeting, 05/05/08 3

Fast probe vs TS measurement

Both diagnsotics are well validated against each other Fast probe data in FY08: limited due to some technical difficulties (eg, Low power H-mode access, LCFS position control, tip arcing, etc)

Use TS data to complement probe data

Monday Physics Meeting, 05/05/08 4

Ip scan result 1 – Fast probe Te and ne decay lengths

0

5

10

15

20

25

30

35

0 2 4 6 8 10 12 14

machfit2_midmap_128794_man_lrdfit04Ip=1.0MA, NBI=1.4MW, Te=0.7cmIp=0.8MA, NBI=1.4MW, Te=1.3cm

Te (e

v)

R-Rsep midplane (cm)

0

0.5

1

1.5

2

2.5

0 2 4 6 8 10 12 14

Ip=1.0MA, NBI=1.4MW, ne=1.1cmIp=0.8MA, NBI=1.4MW, ne=0.94cm

ne (1

e13

cm-3

)

R-Rsep midplane (cm)

1MA 0.8MA: Te increases by a factor of ~2 but λne unchanged: λq also increases by a factor of ~2 (0.9cm vs 1.6cm)therefore, λTe dominates λq??

Monday Physics Meeting, 05/05/08 5

Ip scan result 2 – IR heat flux decay lengths

1MA 0.7MA: q increases by more thana factor of 2 Fast probe Te and ne data incomplete use TS data

Monday Physics Meeting, 05/05/08 6

Ip scan result 3 – TS profiles

TS profiles seem to indicate: Ip↓ λTe↑ & λne unchanged However, TS data points too sparse, does not allow for scale length fitting To Ensemble TS data points as a function of R-Rsep

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Ip↓ λTe↑ & λne unchanged consistent with fast probe result

Ip scan result 4 – λTe & λne from TS data

Monday Physics Meeting, 05/05/08 8

Density scan result 1 – λq unchanged with <ne> ↑

nebar increase by ~40% λq stays remarkably similar Fast probe data does not show consistent trend

0

0.5

1

1.5

2

0 2 4 6 8 10 12 14

machfit2_midmap_128340_man_lrdfit04

128340, <ne>=3.8e13cm-3, ne=0.8cm128339, <ne>=4.3e13cm-3, ne=1.0cm128338, <ne>=4.8e13cm-3,ne=1.4cm128342, <ne>=4.6e13, ne=0.6cm

Den

sity

(1e1

3cm

-3)

R-Rsep midplane (cm)

Monday Physics Meeting, 05/05/08 9

Density scan result 2 – TS profiles

Although some decay length variation seen, no consistent tendency is observed

Monday Physics Meeting, 05/05/08 10

Density scan result 3 – λTe & λne from TS data

Considering the uncertainty of R-Rsep for each TS profile, therefore responsible for the data scatter of the ensembled TS data, λTe and λne seem to stay unchanged with nebar increase from 4.1 to 5.6e13

Monday Physics Meeting, 05/05/08 11

Power scan result 1 – λq↓ with Power ↑

PNBI↑ λq ↓ No fast probe data obtained for power scan

Monday Physics Meeting, 05/05/08 12

PNBI↑ λTe ↓ & λne unchanged

Power scan result 2 – λTe & λne from TS data

Monday Physics Meeting, 05/05/08 13

Ip, nebar, and Power scan to confirm dependence of λq, λTe, and λne were completed

λq data robust λTe and λne data from fast probe + TS

λq has a strong dependence on Ip (-) and power (-) nebar does not affect any scale length λq variation primarily comes from λTe λne seems unchanged by any parameter scan

Summary and future work

More data point and confidence SOL Scaling Relation between SOL widths and the edge turbulence characteristics Analysis of GPI data and probe Isat data underway