1. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 RFX-mod thermal measurement system: a possible diagnostic for plasma-wall interaction M. Dalla Palma 1, E. Sartori 2 and the RFX-mod Team 1 Consorzio RFX, EURATOM-ENEA Association, corso Stati Uniti 4, I-35127 Padova, Italy 2 Università degli Studi di Padova, Italy Padova, April 28th 2010

2. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 2 Outline Description of the RFX-mod thermal measurement system Purpose of the activity: correlation of plasma-wall interaction with thermal measurements Approach: 1.development of models for thermal characterization of tiles, vacuum vessel and toroidal support structure 2.development of an integrated thermal model 3.inference of plasma parameters from thermal experimental measurements, by using the integrated model 4.comparison of the deduced plasma parameters with that ones obtained from other measurements RFX past analyses

3. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 3 Thermal measurements on RFX-mod Plasma-Wall Interaction (PWI) diagnostic by correlating thermal fluxes to the thermocouple (TC) measurements The thermal measurement system is important for: Machine diagnostic to control: – the achievement of the operational limits due to high heat fluxes on the graphite tiles – irregular temperature due to localized plasma-wall interaction – temperature increase due to Joule effect in the coils

4. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 4 Thermocouples set on RFX-mod Plasma 8 TCs on the first wall - Integrated System of Internal Sensors (ISIS) [20÷400°C] 228 total TCs on the vacuum vessel rings [20÷200°C] 16 TCs on vacuum vessel sheet [20÷200°C] 16 TCs on the copper shell [20÷180°C] 16 TCs on the copper shell clamping bands [20÷180°C] 16 TCs on the toroidal support structure [20÷60°C] 8 TCs on 4 saddle coils [20÷100°C] 19 TCs on 3 magnetizing coils [20÷200°C]

5. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 5 TCs layout on the external surface of the vacuum vessel θ = 0° 22.5° 67.5° 112.5° 157.5° 202.5° 247.5° 292.5° 337.5° φ = 0° ring 1 φ = 355° ring 72 40°65°100°125°25°180°320°270° θ = 0° External equator, θ = 90° Top GAP on copper shell (112.5°) GAP on copper shell (292.5°) TCs on vacuum vessel rings TCs on vacuum vessel sheet TCs for comparison with other sensors or diagnostics TCs on dense sectors

6. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 6 Planned activity Correlation of plasma wall interaction (PWI) with thermal measurements, in particular: quantification of power density and energy of the uniform distributed and localized PWI localization of the un-uniform and/or wall-locked PWI Approach: 1.development of models for thermal characterization of tiles, vacuum vessel and toroidal support structure by numerical analyses and validation with experimental measurements 2.development of an integrated thermal model simulating heat fluxes from the first wall to the whole toroidal support structure 3.inference of plasma parameters from thermal experimental measurements, by using the integrated model 4.comparison of the deduced plasma parameters with that ones obtained from magnetic measurements and possibly with IR camera measurements of the tile surface temperature.

7. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 7 1. Thermal characterization TilesPlasma

8. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 8 1. Thermal characterization TilesPlasma Rings

9. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 9 1. Thermal characterization TilesPlasma Vessel sheet Copper shell Toroidal structure Rings Shell clamping bands

10. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 10 1. Thermal characterization TilesPlasma Toroidal structure Rings The model parameters are optimized considering: Effective shape and dimensions of tiles, vacuum vessel and toroidal support structure Thermo-physics parameters of materials Thermal contact resistance at the interfaces Heat transfer mechanisms among interfaced structures

11. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 11 1. Thermal characterization TilesPlasma Toroidal structure Rings PWI: radiation and convection

12. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 12 1. Thermal characterization TilesPlasma Toroidal structure Rings Thermal conduction through fixing keys

13. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 13 1. Thermal characterization TilesPlasma Toroidal structure Rings Th. Conduction through vessel supports + Convection (chimney effect) and radiation PWI: radiation and convection Thermal conduction through fixing keys

14. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 14 2. Development of an integrated thermal model Tiles Plasma Toroidal structure Rings Th. Conduction through vessel supports + Convection (chimney effect) and radiation PWI: radiation and convection Th. conduction through fixing keys Thermal results Model validation: comparison with experimental measurements

15. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 15 3. Inference of plasma parameters Tiles Toroidal structure Rings Th. Conduction through vessel supports + Convection (chimney effect) and radiation PWI: radiation and convection Th. conduction through fixing keys Integrated model Thermal measurement s Plasma

16. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 16 Integrated Model 3. Inference of plasma parameters Thermal measurements Plasma quantification of the power density and energy of uniform distributed and localized PWI localization of the un-uniform and/or wall-locked PWI 4. Validation with magnetic and IR camera measurements mode locking region

17. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 17 Past thermal analyses First wall temperatures [°C] Thermal analyses were carried out with the old RFX finite element model simulating experimental sessions of old RFX New thermal analyses are ongoing with finite element models simulating the thermal behaviour of the RFX-mod. The thermal results are compared with the RFX-mod thermal measurements. Vacuum vessel temperatures [°C]

18. 14th IEA RFP Workshop – Padova, April 26th-28th 2010 18 RFX-mod thermal measurement system: a possible diagnostic for plasma-wall interaction M. Dalla Palma 1, E. Sartori 2 and the RFX-mod Team 1 Consorzio RFX, EURATOM-ENEA Association, corso Stati Uniti 4, I-35127 Padova, Italy 2 Università degli Studi di Padova, Italy Padova, April 28th 2010