Scaling of divertor power footprint width in RF-heated type-III ELMy H-mode on the EAST superconducting tokamak

Abstract

Dedicated experiments for the scaling of divertor power footprint width have been performed in the ITER-relevant radio-frequency (RF)-heated H-mode scheme under the lower single null, double null and upper single null divertor configurations in the Experimental Advanced Superconducting Tokamak (EAST) under lithium wall coating conditioning. A strong inverse scaling of the edge localized mode (ELM)-averaged power fall-off width with the plasma current (equivalently the poloidal field) has been demonstrated for the attached type-III ELMy H-mode as by various heat flux diagnostics including the divertor Langmuir probes (LPs), infra-red (IR) thermograph and reciprocating LPs on the low-field side. The IR camera and divertor LP measurements show that , in good agreement with the multi-machine scaling trend during the inter-ELM phase between type-I ELMs or ELM-free enhanced Dα (EDA). H-mode. However, the magnitude is nearly doubled, which may be attributed to the different operation scenarios or heating schemes in EAST, i.e., dominated by electron heating. It is also shown that the type-III ELMs only broaden the power fall-off width slightly, and the ELM-averaged width is representative for the inter-ELM period. Furthermore, the inverse Ip (Bp) scaling appears to be independent of the divertor configurations in EAST. The divertor power footprint integral width, fall-off width and dissipation width derived from EAST IR camera measurements follow the relation, λint ≅ λq + 1.64S, yielding . Detailed analysis of these three characteristic widths was carried out to shed more light on their extrapolation to ITER.

Turbulent transport regimes and the scrape-off layer heat flux width

“…We estimate v y % hṽ xṽy i f k E ; (20) where k E is the scale length of the resulting v y flows. Combining with Eq.…”

“…5 is the multimachine scaling. For illustration, we employ regression fit #15 in Table III Recent EAST tokamak measurements 20 (not included in the regression fits of Ref. 22) determined k q to be roughly a factor of 2 larger than the multi-machine fits.…”

“…For the machine parameters, B t , B p , a, and R, we employ representative (approximately midrange) values from Table I representative parameters are taken from Ref. 20. The ion charge and mass employed in Fig.…”

“…An international experimental effort to characterize k q in diverted high-confinement (H) mode discharges was carried out, [14][15][16][17][18][19][20][21] and the resulting database has been analyzed in detail. 22 This database yields a nearly linear inverse dependence on plasma current, i.e., k q / 1/I p with rather weak dependences on other parameters.…”

Numerical simulation of laser ablation of molybdenum target for laser-induced breakdown spectroscopic application

“…This leads to series processes of plasma-wall interaction. The first walls of the tokamak devices are subjected to kinds of particle and energy fluxes [1,2]. In addition, they are bombarded by electromagnetic radiation and neutrons are created in the plasma.…”