This paper presents analyses of deuterium atomic and molecular emission and their contribution to the total radiation in DIII-D high-recycling ohmic plasmas:.•Measurements of Lyman-alpha intensity ...and Lyman-Werner bands (attempted) in DIII-D divertor plasma utilizing new divertor SPRED.•In high-recycling conditions, measured Fulcher-alpha band intensity 100x lower than Dalpha line intensity indicating negligible role of molecular radiation.•In high-recycling conditions, EDGE2D-EIRENE predicts measured peak electron temperature, but broader profiles; measured electron density is underpredicted by simulations by 2–3x.•Standalone EIRENE predictions, upgraded for calculations of Lyman-Werner intensities, predicted 50x lower Lyman-Werner band emission than Ly-alpha emission, corroborating negligible role of molecular emission in high-recycling conditions.
The contributions of deuterium molecular emission to the total deuterium radiation was assessed in DIII-D ohmically-confined plasmas in high-recycling divertor conditions. Radial profiles of the deuterium Ly-α line intensity across the low-field side divertor leg were obtained with the recently installed divertor Survey Poor Resolution, Extended Spectrometer 1. A high-resolution spectrometer was used to measure the poloidal profiles of the deuterium Balmer-α and the deuterium Fulcher-α band intensity in the visible wavelength range. The scrape-off layer plasma and neutral distributions were simulated using the edge fluid EDGE2D-EIRENE 2, and the numerical solutions constrained utilizing Thomson scattering and Langmuir probe measurements at the low-field side midplane and the divertor target plate. The studies show that for these conditions molecular emission plays a negligible role in the total radiative power balance of the low-field side divertor, but molecular processes are important when evaluating deuterium Balmer-α line intensity for code-experiment validation.
•The magnitude of the isotope effect is determined by the pressure in the sub-divertor.•Pumping of gas within the JET divertor is effective near the outer target only.•The re-distribution of the ...neutrals due to drifts decreases the throughput.•The total decrease of the throughput reduces the isotope effect.
Experiments in JET-ILW Ohmic confinement mode plasmas show that the line-averaged detachment onset density in deuterium discharges is approx. 10% lower than in hydrogen discharges. The magnitude of the isotope effect on the detachment onset density depends on the divertor geometry, the magnetic configuration and the throughput of the sub-divertor/divertor cryopump system. Simulations with the edge fluid code EDGE2D-EIRENE revealed that the pumping of neutral gas within the JET divertor is effective near the outer divertor target only. The studies show that the magnitude of the isotope effect is determined by the molecular pressure in the sub-divertor pumping plenum.
According to the simulations, operating in vertical configurations or closer proximity of the strike point increases the molecular pressure (and thus throughput) in front of the outer pumping plenum by up to 15% compared to the horizontal configuration, thus producing a stronger isotope effect on the detachment onset density. Similarly, EDGE2D-EIRENE predicts that plasma, hence neutral, redistribution due to E × B drifts in favourable BT configurations (ion B × grad(B) towards the divertor) decreases the throughput. The total decrease of the throughput reduces the isotope effect on the detachment onset density, and decreases the detachment onset density for both isotopes.
We report the identification of a localized current structure inside the JET plasma. It is a field-aligned closed helical ribbon, carrying current in the same direction as the background current ...profile (cocurrent), rotating toroidally with the ion velocity (corotating). It appears to be located at a flat spot in the plasma pressure profile, at the top of the pedestal. The structure appears spontaneously in low density, high rotation plasmas, and can last up to 1.4 s, a time comparable to a local resistive time. It considerably delays the appearance of the first edge localized mode.
•Comparisons are made between EDGE2D-EIRENE simulations that use a new CHEM database for He II with the existing ADAS database.•This allows lower simulated electron temperatures to be reached (~2 eV) ...close to the divertor target plates.•At temperatures of ~ 2 eV in He (~ 1 eV in D) intense recombination-driven radiation becomes important.•This study shows the importance of the highest quality atomic data in edge transport modelling.
The influence of the ITER-like Wall (ILW) with divertor target plate made of tungsten (W), on plasma performance in JET H-mode is being investigated since 2011 (see F. Romanelli and references ...therein). One of the key issues in discharges with low level of D fuelling is observed accumulation of W in the plasma core, which leads to a reduction in plasma performance. To study the interplay between W sputtering on the target plate, penetration of W through the SOL and edge transport barrier (ETB) and its further accumulation in plasma core predictive modelling was launched using a coupled 1.5D core and 2D SOL code JINTRAC (Romanelli, 2014; Cenacchi and Taroni, 1988; Taroni et al., 1992; Wiesen et al., 2006). Simulations reveal the important role of ELMs in W sputtering and plasma density control. Analyses also confirm pivotal role played by the neo-classical pinch of heavy impurities within the ETB.
The 3D edge plasma transport code EMC3-EIRENE 1 was successfully adapted to the single null configuration of JET. A test bed with the well established 2D edge plasma code EDGE2D-EIRENE 2,3 was ...prepared to check the adaptation of the EMC3-EIRENE code and isolate any discrepancies when compared. While both codes solve essentially the same set of reduced Braginskii’s fluid equations, they use very different numerical techniques: a 3D Lagrangian Monte Carlo method in EMC3 and a 2D Eulerian finite differences scheme in EDGE2D. The results should be very similar as both codes are iteratively coupled to the same kinetic neutral particle Monte Carlo code EIRENE 4. We show that both codes are in a fairly good quantitative agreement regarding both midplane and target plasma profiles as well as transition from low to high recycling regime with increasing core plasma density.
► A continuous integration of the development of analysis codes at JET was achieved. ► The maintenance of the highly available and traceable system was greatly rationalised. ► Historical ...configurations of the analysis chain can be automatically retrieved now. ► The tools for the new framework are provided with unit tests and documentation.
At the JET experiment data from routine diagnostics is analysed automatically by a suite of codes within minutes after operation. The maintenance of these interdependent codes and the provision of a consistent state of the physics database over many experimental campaigns against a backdrop of continuous hardware and software updates, requires well defined maintenance and validation procedures. In this paper, the development of a new generation of maintenance tools using distributed version control and a work-flow following the principle of continuous integration 1 is described.
A discrepancy in the divertor radiated powers between EDGE2D-EIRENE simulations, both with and without drifts, and JET-ILW experiments employing a set of NBI-heated L-mode discharges with step-wise ...density variation is investigated. Results from a VUV/visible poloidally scanning spectrometer are used together with bolometric measurements to determine the radiated power and its composition. The analysis shows the importance of D line radiation in contributing to the divertor radiated power, while contributions from D radiative recombination are smaller than expected.
Simulations with W divertor plates underestimate the Be content in the divertor, since no allowance is made for Be previously deposited on the plates being re-eroded. An improved version of EDGE2D-EIRENE is used to test the importance of the deposited layer in which the sputtering yield from supposed pure Be divertor plates is reduced to match the spectroscopic signals, while keeping the sputtering yield for the Be main chamber walls unchanged.
•Shortfall in the EDGE2D-EIRENE simulated JET divertor radiated power studied.•Atomic and molecular electron power loss terms independently scaled in EIRENE.•Strong sensitivity found to the atomic ...electron power loss term.•Allows access to lower temperature divertor parameter space.•EDGE2D-EIRENE simulations include D2 molecular radiation for the first time.
A discrepancy in the divertor radiated powers between EDGE2D-EIRENE simulations and JET-ILW experiments employing a set of NBI-heated L-mode discharges with step-wise density variation is investigated. The analysis shows the importance of the contributions from the deuterium fuel to the divertor radiated power, making these discharges ideal for this study. Molecular radiation losses from D2 molecules have been included for the first time and the present simulations allow the atomic and molecular electron power loss terms in EIRENE to be independently scaled in order to understand their importance in determining the simulated electron temperatures and distribution of radiated power.
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