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Spectroscopy of hydrocarbon in low temperature plasmas : Results from JT-60U T. Nakano J apan A tomic E nergy A gency, Ibaraki, Japan. 6-9/11/2006 ITPA.

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Presentation on theme: "Spectroscopy of hydrocarbon in low temperature plasmas : Results from JT-60U T. Nakano J apan A tomic E nergy A gency, Ibaraki, Japan. 6-9/11/2006 ITPA."— Presentation transcript:

1 Spectroscopy of hydrocarbon in low temperature plasmas : Results from JT-60U T. Nakano J apan A tomic E nergy A gency, Ibaraki, Japan. 6-9/11/2006 ITPA DSOL Meeting Univ.of Toronto, Canada

2 Hydrocarbon in divertor Hydrocarbon : Chemical reaction with H, producing C x H y Y chem > Y phys ( Low impact energy ), determining the life time of carbon plates Source of impurity Co-deposition with T => Tritium inventory => Wall pumping Molecular Assisted Recombination => Sink of H + (Ex. CH 4 + H + => CH H, CH e - => CH 3 + H) Measurement of yield : Ion flux <= Langmuir probe C x H y flux <= Spectroscopy Difficulties in detached plasma : Particle flux measurement ( Probe ) Limited availability of CH emission rate (Spec.)

3 Local gas-puff system Gas injection : CH 4, CD 4, C 2 H 4 and C 2 H 6 at 3x x10 19 /s Spectroscopy : CH, CD and C 2 viewing chords: Gas-puff nozzle Background ( 10cm toroidally apart ) T e : 80 o toroidally apart X 2 CFC : Toyo tanso CX-2002 Used since 1997 NBI-heated Plasma exposure 11 hrs

4 Example of LEP measurement T e = 70 eV, = 3.7x10 18 / 1.6x10 16 ~ 230 View for the gas-puff port View for Background Injected CD 4

5 Results : CH 4, CD 4 injection Weak temperature dependence Similar results from PISCES-A ( T e < 25 eV ) Small isotope effect between CH 4 and CD 4,,leading in No isotope difference between Y CH4 and Y CD4 ( previously reported data ) detach

6 Intense CD emission around outer strike point in detached plasma Attached Detached MARFE Suggesting CxHy molecules dissociate/ionize/CX around the outer strike point even in detached plasmas  Langmuir probe still a good measure. Density ramp-up No C x H y puff

7 No significant change of  CD emission rate during detachment MARFE LEP : X 1 (CH 4 / CD) : X 0.1 CD : X1.5  Y CH4 : x 15 !!  suggesting D 0 + C reaction : X1.5

8 ` LEP at detachment much higher than model calculation Attached : T e > 20 eV, measured LEP is close to modeled Detached: LEP trend is similar to CX rate coef. Detach

9 Model for CH 4 processes Definition : Rate equation : Ex. for CH 2 Steady-state solution ( dX/dt = 0 ) is used.

10 ` LEP at detachment much higher than model calculation Attached : T e > 20 eV, measured LEP is close to modeled Detached: LEP trend is similar to CX rate coef. Detach

11 Summary Finished LEP data production by the local gas-puff method for CH, CD and C 2 for CH 4, CD 4, C 2 H 4, C 2 H 6 in attached condition. At detachment, LEP does not change significantly. CD intensity becomes strong at the strike point ( x 1.5).  ion becomes significantly low ( x 0.1 )  D 0 + C chemical erosion at the strike point   CD4 becomes high ( x 1.5 ) CD 4 loss process is unknown; CX is suggested.

12 JT-60U all carbon machine Dome Baffle Pump Diverot plates Divertor plates speed: 25.6 m 3 /s Feedback-controlled D 2 puff Surface area : ~ 200 m 2 Vessel volume : ~110 m 3 Baking temperature : 300 o C 150 o C ( ~ 2003 )

13 Results : CH 4, CD 4 injection Suggesting C 2 H y is sputtered by chemical reaction with CH 4 and C tile Strong temperature dependence CH 4 / C 2 CD 4 / C 2

14 Results : C 2 H 4 and C 2 H 6 injection C 2 H 4 / CH > C 2 H 6 / CH C 2 H 4 / C 2 < C 2 H 6 / C 2, indicating break-up process: probability of CH and C 2 production

15 Reasons for LEP data production Essential data for spectroscopic measurement of Y chem Wide variety of LEP for CH 4 ~ 50% difference <= LEP affected by transport, due to divertor geometry Need to measure Y chem including C 2 H y <= No systematic LEP data for C 2 H y

16 LEP: Loss Events / Photon = reciprocal of the number of photons emitted until a molecule is lost. CH and C 2 measured (recent works): T e ~ 40eV T e ~ 10eV Motivation for heavier hydrocarbon yield Only CH measured (works so far) :


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