3D radiated power analysis of JET SPI discharges using the Emis3D forward modeling tool

• DOI: 10.1088/1741-4326/ad1d10
• Publication Date: 2024-01-10T22:29:12Z
• Authors: B. Stein-Lubrano; R. Sweeney; D. Bonfiglio; J. Lovell; P. Carvalho; L. Baylor; R.S. Granetz; S. Jachmich; E. Joffrin; M. Kong; M. Lehnen; C. Maggi; E. Marmar; E. Nardon; P. Puglia; U. Sheikh; D. Shiraki; S. Silburn
• Keywords: Effective radiated power

Abstract Precise values for radiated energy in tokamak disruption experiments are needed to validate mitigation techniques burning plasma tokamaks like ITER and SPARC. Control room analysis of power ( P rad ) on JET assumes axisymmetry, since fitting 3D radiation structures with limited bolometry coverage is an under-determined problem. In mitigated disruptions, toroidally asymmetric 3D, due fast-growing MHD modes localized impurity sources. To address this problem, Emis3D adopts a physics motivated forward modeling (‘guess check’) approach, comparing experimental data synthetic from user-defined structures. Synthetic observed the Cherab framework best fit chosen using reduced χ 2 statistic. 2D tomographic inversion models tested, as well helical flux tubes simulated JOREK. Two nominally identical pure neon shattered pellet injection (SPI) discharges analyzed. inversions added toroidal freedom fits thermal quench (TQ) current (CQ). pre-TQ, reconstructions statistically fits, but likely over-optimized do not capture structure seen fast camera images. The next-best pre-TQ that extend towards high-field side, consistent flow under magnetic nozzle effect also JOREK simulations. Whole-disruption fractions <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.98</mml:mn> <mml:mo>+</mml:mo> <mml:mn>0.03</mml:mn> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> </mml:math> <mml:mo>−</mml:mo> <mml:mn>0.29</mml:mn> <mml:mn>1.01</mml:mn> <mml:mn>0.02</mml:mn> <mml:mn>0.17</mml:mn> found, suggesting stored may have been fully by each SPI, although efficiencies below SPARC requirements high pulses still within large uncertainties. used SPI simulations, confirms improvements matching experiment changes modeling. Time-dependent peaking factors calculated discussed.