ITER Wide Angle Viewing System Synthetic Measurements

Transcription

1 ITER Wide Angle Viewing System Synthetic Measurements M. Kocan, M. H. Aumeunier, M. De Bock, V. Martin, R. Pitts, R. Reichle, A. Sirinelli, G. Vayakis, M. Walsh, C. Watts, L. Zabeo Port Plugs & Diagnostics Integration Division ITER Organization Disclaimer: The views and opinions expressed herein do not necessarily reflect those of the ITER Organization Page 1

2 ITER construction site April 2017 Diagnostics building close to completion First diagnostics to be installed in 2019 Assembly hall Diagnostics building Tokamak Page 2

3 ITER visible/infrared wide angle viewing system (WAVS) 15 visible and IR views monitoring the first wall and the divertor Protects the plasma facing components from overheating Will generate ~100 GB of data per second In this presentation focus on synthetic IR measurements Why are the WAVS synthetic IR measurement important? ITER all-metallic environment (Be, W) interpretation of IR measurements challenging Machine protection algorithms can misinterpret the reflections as local overheating and trigger fast termination of plasma false positives can induce fatigue to ITER or hamper experimental programmes Limited spatial resolution can lead to underestimation the of peak surface temperature risk of components damage Synthetic data guide the design development (mirror temperatures, pixel resolution, camera frame rate, software) Page 3

4 Synthetic IR data production workflow Heat load specifications parallel heat flux Plasma equilibrium First wall & divertor geometry Field line tracing first wall and divertor surface heat load Heat transfer simulations surface temperature Plasma facing components structure and properties Raytracing synthetic IR images IR diag. specs Surface optical properties Page 4

5 Synthetic IR data production workflow Heat load specifications parallel heat flux Plasma equilibrium First wall & divertor CAD Field line tracing first wall and divertor surface heat load Heat transfer simulations surface temperature Plasma facing components structure and properties Raytracing synthetic IR images IR diag. specs Surface optical properties SOLPS Kukushkin FED 2011 Equilibrium: DINA code (15MA baseline burning plasma) Kocan JNM2015 Page 5

6 Synthetic IR data production workflow Heat load specifications parallel heat flux Plasma equilibrium First wall & divertor geometry Field line tracing first wall and divertor surface heat load Heat transfer simulations surface temperature Plasma facing components structure and properties Raytracing synthetic IR images IR diag. specs Surface optical properties OUTER DIVERTOR q surf [MW/m 2 ] INNER DIVERTOR q surf [MW/m 2 ] Wetted by plasma Page 6

7 Synthetic IR data production workflow Heat load specifications parallel heat flux Plasma equilibrium First wall & divertor geometry Field line tracing surface heat load Full 3d field of the real surface temperature Heat transfer simulations surface temperature Plasma facing components structure and properties Raytracing synthetic IR images IR diag. specs Surface optical properties Be W Be W ANSYS Page 7 T surf

8 Synthetic IR data production workflow Heat load specifications parallel heat flux Plasma equilibrium First wall & divertor geometry Field line tracing surface heat load Heat transfer simulations surface temperature Plasma facing components structure and properties Raytracing synthetic IR images IR diag. specs Surface optical properties Inner target SPEOS code Page 8

9 Various instrumental effects are studied separately rather than trying to build a comprehensive ITER IR simulator In this presentation examples of the impact of: (1) Spatial resolution limitations (2) Reflections (3) Temperature of the diagnostic mirrors Page 9

10 Spatial resolution limitations example for the divertor view dropped dropped Divertor monoblocks implemented in the model 30% overheating imposed on selected T 10-20% T >20% of monoblocks ( delamination effect) of nominal T nominal T Optical blur taken into account Based on these results FoV reduced by 1/3 areas with poor resolution were sacrificed in favor of improved spatial resolution Page 10

11 Impact of reflections Uniform emissivity ε=0.2(w), ε=0.3(ss), ε=0.15(be), emission model cos 0.6 (θ) Reflectivity models: (1) diffuse, (2) reflective: DIFFUSE SURFACE 2% Lambertian, 98% specular Unknown emissivity (ε=1) Known emissivity Emissivity unknown Unknown emissivity (ε=1) SPECULAR SURFACE Known emissivity Emissivity known False hot spots due to reflections on specular surfaces can lead to significant overestimation of the surface temperature Experimental characterization of the surface emissivity and reflectance as a function of the surface roughness and temperature is needed Page 11

12 Impact of the mirror temperature (stray light effect) typical range Results important e.g. to make decision whether the IR camera diagnostic will need heat plasma exchanger to cool the mirrors Beginning of life (mirrors R spec =99%) PORT PLUG (T = C) TARGET: 10% ERROR optical path End of life (mirrors R spec =95%) mirrors from 200 C Useful signal Stray light from environment Stray light from mirrors to camera TARGET: 10% ERROR Page 12

13 Summary Further details on ITER IR synthetic images in: M.H. Aumeunier, Nuclear Materials and Energy (2017) M. Kocan, Phyica Scripta Phys. Scr. T167 (2016) General conclusion: interpretation of IR measurements in ITER will be challenging, especially if to be done in real time Further work: Experimental study of the PFC surface properties and mirror degradation process in ITER-relevant conditions Combine instrumental effects (optical blur, reflections, mirror temperature, stray light, etc.) to make prediction about the ultimate diagnostic performance Modelling of the time-dependent phenomena (instantaneous increase of the surface temperature due to plasma motion, MARFEs, UFOs etc) to support the development of the pattern recognition software Page 13

14 General issue: lack of manpower Looking for volunteers to collaborate on the vis-ir modelling (field line tracing & raytracing) Code infrastructure already in place so excellent topic for PhD or postdoc Possibility to join through the ITER Project Associate scheme ( Open IPA call for ITER vis-ir support (application deadline soon!) Page 14

15 Thank you for your attention Page 15