Fig. 3: Power and particle balance shows additional volume long-legged divertor drives power and particle losses.

Particle (a–c) and power (d–f) balance comparisons between different divertor shapes as function of core Greenwald fraction. a–c Particle balance showing the ion target flux (lower outer divertor) - black, total ionisation source - magenta, Molecular Activated Recombination (MAR - orange) and Electron-Ion Recombination (EIR - cyan) ion sinks (both ion sinks are integrated over the divertor chamber) for the Super-X Divertor (SXD) (a), Elongated Divertor (ED) (b) and Conventional Divertor (CD) (c). d–f Power balance showing hydrogenic power losses \({P}_{{{{\rm{loss}}}}}^{{{{\rm{hydro}}}}}\) (orange, integrated over the divertor chamber), target power deposition P_target (black, obtained from spectrocopically inferred temperatures and Langmuir probe particle fluxes) and estimated power flow into the divertor chamber (magenta, \({P}_{{{{\rm{div}}}}}\approx {P}_{{{{\rm{loss}}}}}^{{{{\rm{hydro}}}}}+{P}_{{{{\rm{target}}}}}\)) assuming that the divertor chamber power losses are dominantly hydrogenic, in agreement with imaging bolometry measurements³⁴. Under the assumption that the lower and upper divertors are similar (consistent with Langmuir probe results³⁴), \({P}_{{{{\rm{div}}}}}\), \({P}_{{{{\rm{loss}}}}}^{{{{\rm{hydro}}}}}\) and P_target have been multiplied by two to obtain integrated values of the upper and lower outer divertors. The results are derived from a probabilistic sample obtained from a Bayesian spectroscopic analysis, showing the median and the 68% equal-tailed confidence interval (shaded region). See Methods section for more information about the analysis and uncertainty propagation.