Physics of the detached radiative divertor regime in DIII-D

Abstract

This paper summarizes results from a two-dimensional (2D) physics analysis of the transition to and stable operation of the partially detached divertor (PDD) regime induced by deuterium injection in DIII-D. The analysis [1] shows that PDD operation is characterized by a radiation zone near the X-point at T e ∼ 8-15 eV which reduces the energy flux into the divertor and thereby also reduces the target plate heat flux, an ionization zone below the X-point which provides a deuterium ion source to fuel parallel flow down the outer divertor leg, an ion-neutral interaction zone in the outer leg which removes momentum and energy from the flow and finally a volume recombination zone above the target plate which reduces the particle flux to the low levels measured on the plates and thereby also contributes to reduction in target plate heat flux.

Study of the Ionization Rate in the Scrape‐off Layer

“…Pertinent simulation runs demonstrate that in the analysis of contemporary divertor tokamak SOLs, MSI must necessarily be taken into account. In particular, this is true in the case of neutral-gas puffing [8] and for ELMy scenarios [2]. The results obtained have a qualitative character, whereas for a quantitative analysis one would also have to follow the neutral dynamics.…”

Radiative snowflake divertor studies in DIII-D

“…Radiative divertor conditions in DIII-D are routinely accessed with carbon and deuterium radiation using D 2 seeding that increases upstream (and core) density [14,15].…”

“…In the standard divertor, radiation initially peaked in the inner and outer divertor legs, and eventually the radiative front moved to the X-point (e.g., Ref. [15]). In the SFminus, radiation also initially peaked in the divertor legs, however, as the SF-minus was formed, it was broadly distributed throughout R div (m) Standard radiative divertor 150679 Radiative SF-minus divertor the divertor volume, with occasional peaking at the null-points.…”

Doppler coherence imaging and tomography of flows in tokamak plasmas (invited)

“…15 UEDGE numerical simulations of expected flow speeds in the divertor for different core densities corresponding to times of 4000 ms ͑low density case͒ and 4500 ms ͑high density͒ have been undertaken. This behavior, and the reconstructed flow amplitudes, is consistent with earlier observations of near sonic flows in the inboard SOL toward the divertor and into the outboard divertor as the plasma nears detachment.…”