The roles of power loss and momentum-pressure loss in causing particle-detachment in tokamak divertors: II. 2 Point Model analysis that includes recycle power-loss explicitly.

In the Part I companion paper, using a simple heuristic model it was demonstrated that, generically, volumetric loss of both pressure-momentum and power are required for particle detachment to occur. The volumetric power-loss fraction, f_pwr-loss, was treated as a freely specifiable quantity; however, part of f_pwr-loss is due to the hydrogenic recycle process at the target and in the present paper an extended 2 Point Model--the 2PM with Recycle--is used that takes this into account explicitly. It is again demonstrated, but now using more physically realistic modeling of both pressure-momentum and power loss, that it is the combination of these two volumetric losses that is the cause of particle-detachment. For practical use, a convenient spreadsheet version is provided for the 2PM with Recycle. It allows the user to specify the magnitudes and time-variation during a discharge of the 3 primary drivers of plasma conditions in the divertor: q_∥u (t), f_radiation ^impurity (t), and n_u (t) (or p_totu (t)), where t (s) is the time in the discharge; it outputs values of plasma quantities at the target, T_et (t), Γ_∥t(t), etc. The 2PM with Recycle Spreadsheet requires little more effort to use than the more familiar and analytic, basic 2PM which does not include hydrogenic recycle power loss explicitly. Comparisons are included here of the 2PM with versus without Recycle showing that, when volumetric momentum-loss is not allowed for, then the two models give radically different results at low values of T_et, i.e. for particle-detachment conditions; however, when momentum-loss is allowed for the results for the 2PM w versus wo Recycle are qualitatively the same and only differ quantitatively by a factor of ≼2, typically. [ABSTRACT FROM AUTHOR]