Evolution the 2D Spatial Profile of Visible Emission During an ELM in the DIII-D Divertor

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1 Evolution the 2D Spatial Profile of Visible Emission During an ELM in the DIII-D Divertor M. E. Fenstermacher J. Boedo, M. Groth, C.J. Lasnier,, A.W. Leonard J. Watkins and the DIII-D Team presented at the 43 rd APS-DPP Meeting Long Beach, CA Oct Nov 2, 2001 QTYU IOP APS-DPP, /18/01 1

2 Motivation and Outline MOTIVATION - The transient particle and energy loads due to ELMs are a significant problem for the design of divertors in future tokamak reactors. Detailed understanding of the effect of the ELM pulse on the 2D distribution of radiation in the divertor is needed, to validate computer simulations, to investigate mitigation schemes. OUTLINE - A new gated, intensified camera with wavelength filters views the lower divertor tangentially in DIII-D Tomographic reconstruction techniques provide 2D ELM profiles Carbon and deuterium emission during ELM evolution Compare with ELM heat flux profiles. Future Plans - obtain the temporal evolution of 2D divertor emission profile during ELMs. APS-DPP, /18/01 2

3 Summary (1) First 2D images of divertor carbon and D α emission during ELM obtained on DIII-D Vacuum Window /LensPair CCD Cameras A new fast gated, intensified camera is now operating on the tangential view of the lower divertor in DIII-D Front Mirrors Beamsplitt er Rear Lens Pair Air Actuated Filter Housings (6Filter Capacity) Available gate time 1µsec, gain 20, Front Mirrors Vacuum Window /LensPair CCD Cameras Initial data images in D α and CIII visible emission show large changes during ELMs compared with the profiles between ELMs in the divertor Beamsplitt er Rear Lens Pair Air Actuated Filter Housing s (6 Filter Capacity) Substantial broadening of D α at the outer target Transition of CIII emission from strikepoints to X-point Qualitative comparison of TTV data with line integrated measurements and heat flux profiles during ELMs indicates consistency Verification and detailed analysis awaits dedicated experiments. APS-DPP, /18/01 3

4 Summary (2) Dedicated 2002 experiments proposed to study divertor and main chamber SOL ELM effects Optimize large Type-I ELMs at low frequency External triggering of camera with variable delay to synchronize camera gate on ELM evolution Correlate camera images with other fast lower divertor diagnostics Target j sat, n e, t e - Floor probes, 19 channels, 1 MHz Heat flux radial profile - IRTV (line scan), 9.6 khz Line integrate emission - Filterscopes, 6 channels, 100 khz Volume n e and T e - Div. Thomson Scattering, 8 channels, 20 Hz ELM evolution during propagation in the divertor should be measurable Data will provide critical test of ELM simulation models Will attempt to image ELMs simultaneously at midplane SOL and in divertor. APS-DPP, /18/01 4

5 Discharge Parameters and Evolution APS-DPP, /18/01 5

camera for this experiment: DN USN Integration time 6 100 µs Approx.

6 Emission during ELMs obtained in lower divertor of near DN ( D α and CIII - 465nm) and USN discharges (CIII only) Discharges near DN Primary X-point may switch from lower to upper divertor at some times Gated camera for this experiment: DN USN Integration time µs Approx. gain 10 5 K 17 msec field rate (30 frames/sec) Internally triggered (not syncronized to ELMs) Frame time ± 5 ms Near DN USN APS-DPP, /18/01 6

7 Shift of ELM energy from upper to lower divertor is not as sensitive to drsep as for peak time averaged heat flux Lasnier PSI (Eup-Elo)/(Eup+Elo) in+out ELM (Eup-Elo)/(Eup+Elo) in+out Attached (Petrie) (Qup-Qlo)/(Qup + Qlo) Time-average Detached (Petrie) (Qup Qlo)/(Qup + Qlo) Time-average DRSEP (cm) (Qup-Qlo)/(Qup+Qlo) Time-average /rs APS-DPP, /18/01 7

8 Time history shows well matched DN discharges during time of CIII and D α ELM emission images. APS-DPP, /18/01 8

9 Line integrated fast D α shows larger ELMs at OSP (fs03) than at ISP(fs00) in both LSN discharges. APS-DPP, /18/01 9

10 Line integrated fast D α shows larger ELMs at OSP (fs03) than at ISP (fs00) in both DN discharges. D α - DN CIII - DN ELM No ELM NoELM ELM CIII - USN NoELM ELM APS-DPP, /18/01 10

11 ELM Emission Reconstructions - DN APS-DPP, /18/01 11

12 CIII visible emission between ELMs localized near strikepoints High power ELMy plasma with attached divertors 100Hz ELMs vs. 60 Hz camera field rate Between ELM image not verifiable CIII 465nm Tangential view APS-DPP, /18/01 12

13 CIII visible emission during an ELM substantially different from between ELMs Emission near strikepoints reduced more than 2.5x Local emission near X-point increases factor of 20 Profile resembles time averaged detachment profile CIII 465nm Tangential view APS-DPP, /18/01 13

14 Other CIII visible images during ELMs show variety of profiles from different ELMs and timing during an ELM ms ms ms APS-DPP, /18/01 14

15 ELM Emission Reconstructions - USN APS-DPP, /18/01 15

intensity seen on most camera frames 107344

16 Lower diver tor CIII visible emission between ELMs in USN plasma at low intensity Low intensity seen on most camera frames CIII 465nm Tangential view APS-DPP, /18/01 16

17 D α emission between ELMs local to outer strikepoint Consistent with line integrated measurements Some residual ELM effect may remain D α Tangential view APS-DPP, /18/01 17

18 D α between ELMs intensity enhanced by 10x D α Tangential view APS-DPP, /18/01 18

19 D α emission during an ELM shows 15 cm broadening of profile in the outer SOL at the target Broad profile reaches 4 cm flux surface mapped to midplane Intensity 40x higher than between ELMs D α Tangential view APS-DPP, /18/01 19

20 Other D α profiles during ELMs show high intensity at either strikepoint or near the X-point 1670 ms ms 2100 ms APS-DPP, /18/01 20

21 Lower divertor CIII visible emission during an ELM in an USN plasma 10x emission between ELMs Emission (source?) locaized to inner wall and 45 deg. tiles CIII 465nm Tangential view APS-DPP, /18/01 21

22 Comparison with Target Profiles APS-DPP, /18/01 22

23 Lower divertor heat flux in near DN shape shows broad profiles during ELMs Lasnier PSI00 Discharge had drsep sweep from LSN to USN Near DN drsep = 0.5 cm (yellow curve) lower heat flux width is 2.5x broader than time averaged heat flux width Surface energy density, J/cm Separatrix Separatrix Lower Divertor Time-avg q low, DRSEP = 3.8 cm DRSEP = 3.8 cm DRSEP = 2.1 cm DRSEP = +0.5 cm DRSEP = +3.4 cm 98727_1704_elmprof.kal Major Radius, cm APS-DPP, /18/01 23

Target plate Jsat from probes also shows broad profiles during some ELMs Data from upper divertor probes Ion Grad-B drift toward upper divertor Pinj ~ 7

24 Target plate Jsat from probes also shows broad profiles during some ELMs Data from upper divertor probes Ion Grad-B drift toward upper divertor Pinj ~ 7 MW ELMing H-mode See J. Watkins poster LP1.035 for more details USN ELMs [ s] No ELM Avg( s) J. Watkins APS-DPP, /18/01 24

25 Broad D α emission on outer target during ELM similar to broad heat flux profiles observed previously OSP ISP Inner wall 45 tile Floor APS-DPP, /18/01 25

26 CIII intensity near 45 degree tile during ELM is ~10x higher than between ELMs Inner wall 45 tile Floor APS-DPP, /18/01 26

27 Summary and Future Plans APS-DPP, /18/01 27

28 Summary A new fast gated, intensified camera is now operating on the tangential view of the lower divertor in DIII-D Available gate time 1µsec, gain 20,000 Initial data images in D α and CIII visible emission show large changes during ELMs compared to the between-elm profiles in the divertor Substantial broadening of D α at the outer target Transition of CIII emission from strikepoints to X-point Qualitative comparison of TTV data with line integrated measurements and heat flux profiles during ELMs indicates consistency Verification and detailed analysis awaits dedicated experiments. Future plans include external triggering of camera with variable delay to synchronize camera gate on ELM evolution ELM evolution during propagation in the divertor should be measurable Data will provide critical test of ELM simulation models APS-DPP, /18/01 28

29 Gated intensified cameras can be installed on either lower or upper tangential view of the divertors Two gated, intensified cameras are available CCD Cameras Lower divertor systems now use optical relay system without fiber imageguide. Neutron browning effects eliminated Front Mirrors Vacuum Window /LensPair Beamsplitt er RearLens Pair Air Actuat ed Filter Housing s (6Filter Capacity) Images obtained for all DIII-D shots. Similar visible systems now view the upper, baffled divertor on DIII-D. Both systems provide two images at different wavelengths simultaneously Front Mirrors Vacuum Window /LensPair Beamsplitt er CCD Cameras Air Actuat ed Filter Housing s (6 Filter Capacity) Rear Lens Pai r APS-DPP, /18/01 29

30 Future plans include high speed imaging of ELM evolution in the divertor and main chamber SOL THOMSON PHD Use upstream diode to gate cameras Detector View Simultaneously image ELM in main chamber SOL and in lower divertor Follow ELMs through the edge/sol by varying trigger delay PHDUP Compare to codes (UEDGE, B2- Eirene, EDGE2D etc.) CCD Imaging Region APS-DPP, /18/01 30

31 Fast triggering electronics detects ELM pulse at outer midplane and triggers gated cameras after variable delay Gain Variable Gain Amplifier Threshold Level Threshold Comparator & TTL Pulse Time Window Enabler t1 t2 t1 Enable t2 Delay Generator Constant OR Cumulative t (µs) Constant OR Cumulative Camera Gate Generator Optical Transmitter Optical Receiver Camera APS-DPP, /18/01 31

Scrape-off Layer Plasma Flow in L- and H-Mode Plasmas on JT-60U )

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