RFX-mod thermal measurement system: a possible diagnostic for plasma-wall interaction

114th IEA RFP Workshop – Padova, April 26th-28th 2010

RFX-mod thermal measurement system:a possible diagnostic for plasma-wall interaction

M. Dalla Palma1, E. Sartori2

and the RFX-mod Team

1 Consorzio RFX, EURATOM-ENEA Association, corso Stati Uniti 4, I-35127 Padova, Italy2 Università degli Studi di Padova, Italy

Padova, April 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 parametersfrom 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


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


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]


TCs layout on the external surface of the vacuum vessel

θ = 0°

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


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 structureby numerical analyses and validation with experimental measurements

2. development of an integrated thermal modelsimulating heat fluxes from the first wall to the whole toroidal support structure

3. inference of plasma parametersfrom 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.


1. Thermal characterization

TilesPlasma



TilesPlasma Rings



TilesPlasma

Vessel sheet

Copper shell

Toroidal structure

Rings

Shell clamping bands



TilesPlasmaToroidal 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




Rings

PWI: PWI: radiation and radiation and

convectionconvection




Rings

Thermal Thermal conduction conduction

through through fixing keysfixing keys




Rings

Th. Conduction through vessel

supports+

Convection (chimney effect)

and radiation


supports+


and radiation

PWI: PWI: radiation and radiation and convectionconvection

Thermal Thermal conduction conduction



2. Development of an integrated thermal model


Rings


supports+


and radiation


supports+


and radiation


Th. Th. conduction conduction


Thermal results

Model validation: comparison with

experimental measurements


3. Inference of plasma parameters

TilesToroidal structure

Rings


supports+


and radiation


supports+


and radiation


Th. Th. conduction conduction


Integrated modelIntegrated model

Thermal measurements

Plasma


Integrated Integrated ModelModel

3. Inference of plasma parameters

Thermalmeasurements

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 lockingregion


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]


RFX-mod thermal measurement system:a possible diagnostic for plasma-wall interaction

M. Dalla Palma1, E. Sartori2

and the RFX-mod Team

1 Consorzio RFX, EURATOM-ENEA Association, corso Stati Uniti 4, I-35127 Padova, Italy2 Università degli Studi di Padova, Italy

Padova, April 28th 2010

RFX-mod thermal measurement system: a possible diagnostic for plasma-wall interaction

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