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Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E Impact of N 2 on carbon chemistry in JET S. Brezinsek, Y. Corre and TFE.

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Presentation on theme: "Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E Impact of N 2 on carbon chemistry in JET S. Brezinsek, Y. Corre and TFE."— Presentation transcript:

1 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E Impact of N 2 on carbon chemistry in JET S. Brezinsek, Y. Corre and TFE

2 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E JET experiments associated with N 2 injection High density divertor operation to approach type III ELMy H-mode: integrated scenario development for ITER Hybrid scenario studies with impurity seeding type I ELMy H-mode: operation window with small ELMs in perspectives for ITER Compatibility of advanced tokamak scenarios with the ITER like-Wall: power load reduction and (semi-detached) divertor operation for JET Benefit: High density divertor operation at acceptable divertor conditions Penalty: Reduction of the confinfement Study of the N 2 scavenger effect: avoid carbon in remote areas Good compromise needed!

3 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E Type III ELMy H-mode experiment N 2 blow GIM10 GIM11 gas form Observation and configuration NII light TFE 2005

4 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E First observation of CN molecules in JET Two spectra: prior and post injectionDifference spectrum CN bands appear only directly at the wall Nitrogen and oxygen remain also on inner viewing lines Minor reduction of Carbon lines at this injection level and location Increase of high-n Balmer lines => increase of local density This line-of-sight shows no signifcant recombination (~ 5-10 eV)

5 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E JET: N 2 + could not be found in the spectrum! No N 2 and N 2 + spectral lines observed TEXTOR: N 2 + spectra could be well identified (local gas blow ) JET and TEXTOR: N 2 could not be observed!

6 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E Type III ELM regime with N-seeding: Integrated scenario: hybrid type III ELM - High N (>2.5) and low Ip (1.7MA) at q 95 ~3.2 - self-generated non-inductive current - stability properties (q close to unity) Hybrid scenario: Reference Hybrid D-fuel. Hybrid type III with N seeding N ~2.6 f rad ~50% P=22MW H98 (y,2) * 0.83 N ~2.6 f rad ~25% P=20MW H98 (y,2) * High radiative fraction (75% for ITER) - Reduced heat load (transient and stationary) - Reduced erosion (PFC lifetime) Hybrid Scenario with N 2 seeding

7 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E Radiative Feed-back N-seeded Type III Feed-forward 100% deutérium #68505 #68532 #68747 #68515 #68739 #68746 N =0.75x10 22 N =1.58x10 22 N >2.1x10 22 N-seeding Feed-forward Type III Type I #68743 #68742 drops ~10% Hybrid type III (best pulse) f rad (baseline in between ELMs) H 98(y,2) * Maximum f rad with D-fuelling Type III ELM regime (f rad >40%) N-seeding enables to reach higher f rad for similar H 98 * Conclusion: achieve hybrid type III ELM Operational space

8 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E Bolometer channel Radiated power Z axis A. U.(%) #68515 #68532 bottom top (e) High D-fuelling (f) D+N-fuelling N2N2 D2D2 P rad div /P tot = 23% 35% P rad bulk /P tot = 10% 15% separatrix

9 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E CN emission Far SOL Near SOL

10 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E CN distribution #68515 CN pattern#68532 CN pattern ReferenceN 2 injection CN appears with some delay

11 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E Reduction due to N2 injection #68515 CD pattern#68532 CD pattern ReferenceN 2 injection Hydrocarbon chemistry (outer divertor) Hydrocarbons reduced during strong D 2 and N 2 injection

12 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E Carbon ion flux (total sputtering yield) Reduction due to N2 injection #68515 CII pattern#68532 CII pattern ReferenceN 2 injection Carbon reduced during strong D 2 and N 2 injection

13 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E Wrong orientation #68515 D pattern#68532 D pattern ReferenceN 2 injection Incident deuterium flux D remains almost constant => no strong sign of recombination

14 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E #68515 NII pattern#68532 NII pattern ReferenceN 2 injection Nitrogen flux during injection Certain amount of nitrogen from previous discharges (at SP) 2 cleaning discharges performed

15 Joint SEWGs-TFE meeting S. Brezinsek22/07/2008 TF E Summary CN observed in different experiments N 2 and N 2 + not observed in any experiment Hybrid scenario: Reduction of chemical sputtering (CH) observed at high D 2 and N 2 fluxes Reduction of total carbon yield (CII) observed at high D 2 and N 2 fluxes Strong emission of CN observed in the SOL (away from the N 2 injection) Role of local plasma temperatures (experiments close to detachment) Role of local surface temperatures (experiments cool down the target) Scavenger of hydrocarbons?


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