Use of lithium capillary structures in Ohmic discharges of T-10 Tokamak

Мұқаба

Дәйексөз келтіру

Толық мәтін

Аннотация

The results of experiments at the T-10 tokamak using lithium capillary-porous structures are presented. It is shown that lithium sputtering under conditions of graphite diaphragms can significantly reduce deuterium recycling and the level of impurities in the plasma. At the same time, recycling increases significantly five discharges after the start of the day of the experiment, and the effect of reducing the level of impurities persists for 150—300 discharges. The results of using a capillary-porous structure with lithium filling as a movable rail diaphragm in the T-10 configuration with tungsten main diaphragms are presented. The introduction of a lithium diaphragm into the SOL region makes it possible to reduce recycling and obtain discharges with an effective plasma charge approaching unity. In this case, the effect increases as the lithium sputtered in the chamber is accumulated. It is shown experimentally that a capillary-porous structure with lithium filling can be used as a main diaphragm with longitudinal plasma heat fluxes up to 3.6 MW/m2. However, a necessary condition is the complete impregnation of the porous structure with lithium and the prevention of extrusion of lithium into the discharge as a result of the interaction of the current flowing to the diaphragm with the toroidal magnetic field. Experiments have shown that to obtain discharges with a small lithium admixture, a strong gas injection of deuterium or impurity is required to reduce the temperature of the plasma periphery and effective cooling of the diaphragm below 450 Å°C. Otherwise, the diaphragm transfers into a strong evaporation mode with high lithium flows, which lead to a significant increase in the lithium concentration in the plasma. Strong evaporation reduces the heat inflow and stabilizes the diaphragm temperature.

Толық мәтін

Рұқсат жабық

Авторлар туралы

V. Vershkov

National Research Center “Kurchatov Institute”

Хат алмасуға жауапты Автор.
Email: V.Vershkov@fc.iterru.ru
Ресей, Moscow

D. Sarychev

National Research Center “Kurchatov Institute”

Email: V.Vershkov@fc.iterru.ru
Ресей, Moscow

D. Shelukhin

National Research Center “Kurchatov Institute”

Email: V.Vershkov@fc.iterru.ru
Ресей, Moscow

A. Nemets

National Research Center “Kurchatov Institute”

Email: V.Vershkov@fc.iterru.ru
Ресей, Moscow

S. Mirnov

Troitsk Institute for Innovation and Fusion Research

Email: V.Vershkov@fc.iterru.ru
Ресей, Moscow

I. Lyublinski

Dollezhal Research and Development Institute of Power Engineering

Email: V.Vershkov@fc.iterru.ru
Ресей, Moscow

A. Vertkov

Dollezhal Research and Development Institute of Power Engineering

Email: V.Vershkov@fc.iterru.ru
Ресей, Moscow

M. Zharkov

Dollezhal Research and Development Institute of Power Engineering

Email: V.Vershkov@fc.iterru.ru
Ресей, Moscow

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1. JATS XML
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2. Fig. 1. Scheme of the experiment with lithium deposition on T-10.

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3. Fig. 2. Determination of the amount of lithium by the duration of the temperature plateau: a - before the experiment; b - after five lithiations.

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4. Fig. 3. Time evolution of the average plasma density after valve disconnection in a series of discharges after lithiation: 1 – first discharge after lithiation (61390); 2 – second discharge after lithiation (61391); 3 – tenth discharge after lithiation (61399); 4 – twenty-third discharge after lithiation (61412).

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5. Fig. 4. Change in the density decay time in a series of discharges after lithiation.

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6. Fig. 5. Time evolution of the total number of particles in the cord after switching off the gas inlet in the second pulse after lithium deposition.

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7. Fig. 6. Radial distributions of losses recorded by the pyroelectric bolometer and AXUV sensors in discharges before and after lithium deposition. Solid black line – pyroelectric bolometer before lithiation; red dotted line – after lithiation; black dotted line with dots – AXUV before lithiation; red dotted line – AXUV after lithiation.

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8. Fig. 7. Changes in some discharge characteristics during an experimental campaign with lithium deposition. In the two lower right figures CIIIA, OIIА and CIIIC, the designation A means measurements in the diaphragm section, and the designation C means measurements in the section opposite the diaphragm.

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9. Fig. 8. Schematic diagram of the arrangement of tungsten and lithium diaphragms on the T-10.

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10. Fig. 9. Construction of a lithium diaphragm. 1 — lithium layer impregnating a molybdenum grid; 2 — molybdenum grid; 3 — lithium container; 4 — tungsten felt layer; 5 — molybdenum tube with heater; 6 — mounting bracket.

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11. Fig. 10. Location of thermocouples on the lithium diaphragm.

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12. Fig. 11. Lithium diaphragm glow: left - at the beginning of the campaign; middle - in the middle; right - at the end.

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13. Fig. 12. Experimental dependence of the diaphragm glow in a Taylor discharge on its temperature. The solid line is an exponential with an increment of 23°.

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14. Fig. 13. Changes in discharge characteristics in the experimental campaign depending on the intensity of the LiI line glow.

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15. Fig. 14. Dependence of the reciprocal of the OII line glow intensity on the LiI line glow intensity.

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16. Fig. 15. Dependence of the effective plasma charge on the intensity of the LiI line glow.

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17. Fig. 16. Dependences of the signals of the central chord AXUV and the glow of the WI line in the cross-section of the diaphragm location on the intensity of the LiI line.

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18. Fig. 17. Change in the WI line glow in the first pulses after lithium deposition.

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19. Fig. 18. Results of the experiment with the introduction of a lithium diaphragm into the plasma from pulse to pulse with its subsequent removal.

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20. Fig. 19. Comparison of plasma characteristics in three series of experiments with deep diaphragm insertion.

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21. Fig. 20. Time evolution of radial profiles of bolometric losses in pulse 71474.

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22. Fig. 21. Time evolution of the central electron temperature in pulses 71473 and 71474.

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23. Fig. 22. Radial distributions of soft X-ray emission for two moments of pulse 71474.

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24. Fig. 23. Typical time course of the heating discharge of thermocouple T2, located on the reverse side of the lithium diaphragm.

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25. Fig. 24. Dependence of the maximum increase in heating of thermocouple T2 on the distance to the last closed surface for a series of 30 cm diaphragm insertions. Squares are temperature increases. Line is an exponential with an increment of 2 cm.

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26. Fig. 25. Photograph of the diaphragm at the moment of the start of droplet ejection and after 1 ms with the toroidal magnetic field directed clockwise when viewed from above.

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27. Fig. 26. Photograph of the diaphragm at the moment of the start of droplet ejection and after 1 ms with the toroidal magnetic field directed counterclockwise when observed from above.

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28. Fig. 27. Change in plasma characteristics after disabling the gas inlet at different radial positions of the diaphragm.

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29. Fig. 28. Changes in discharge characteristics when turning the gas starter on and off.

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30. Fig. 29. Evolution over time of density, voltage on the gas inlet valve and glow of the LiII line in a series of discharges with a lithium diaphragm at a radius of 30 cm.

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31. Fig. 30. Dependence of the evolution of the average density on the LiII line glow for discharge 71666.

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32. Fig. 31. Time variation of average density, LiII line glow and diaphragm current in a series of discharges with a lithium diaphragm at a radius of 30 cm. Solid red line — discharge 72157, diaphragm at 32 cm, initial temperature 300 °C; Dotted black line — discharge 72158, diaphragm at 30 cm, initial temperature 300 °C; Dashed green line — discharge 72161, diaphragm at 30 cm, initial temperature 300 °C; Short dashed violet line — discharge 72162, diaphragm at 30 cm, initial temperature 376 °C; Short dashed blue line — discharge 72165, diaphragm at 30 cm, initial temperature 390 °C.

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33. Fig. 32. Photograph of the diaphragm glow observed tangentially by a high-speed color camera, showing the two lines along which the data was read.

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34. Fig. 33. Glow intensities in the red region, taken for the photo in Fig. 32 along the red line. Red solid line — discharge 72157, aperture at 32 cm, initial temperature 300 °C; black dotted line — discharge 72160, aperture at 30 cm, initial temperature 300 °C; green dash-dotted line — discharge 72161, aperture at 30 cm, initial temperature 300 °C; violet, short dotted line — discharge 72162, aperture at 30 cm, initial temperature 376 °C; blue short dash-dotted line — discharge 72165, aperture at 30 cm, initial temperature 390 °C.

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35. Fig. 34. Calculated changes in the temperature of the lithium diaphragm over time in a series of pulses with a diaphragm at a radius of 30 cm. Red circles - discharge 72158, diaphragm at 30 cm, initial temperature 300 °C; purple triangles - discharge 72161, diaphragm at 30 cm, initial temperature 300 °C; blue stars - discharge 72162, diaphragm at 30 cm, initial temperature 376 °C; black squares - discharge 72165, diaphragm at 30 cm, initial temperature 390 °C.

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36. Fig. 35. Heating of the diaphragm in the discharge according to thermocouple T2 when the initial temperature changes.

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37. Fig. 36. Profiles of chord signals of pyroelectric bolometers and semiconductor AXUV sensors for the lithium-dominated discharge 71673. Rectangles are pyroelectric bolometer data, circles are AXUV data (magnified by 1.54 times), stars are the difference between them.

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38. Fig. 37. Comparison of the energy retention times dependence on the density when the T-10 is operating with carbon, tungsten, and lithium diaphragms. Circles are data with lithiation, triangles are previous data with graphite diaphragms without lithium, and an asterisk is with tungsten diaphragms without lithium.

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39. Fig. 38. Dependences on the discharge current of the maximum achievable densities in ohmic discharges when operating the T-10 with diaphragms: carbon - blue triangles, tungsten - purple stars and lithium - red circles.

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