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UKAEA-STEP-PR(25)312024
A strategy to prevent concentrated deposition of the exhaust power in a fusion device is to seed a localised ‘divertor’ region with impurity gas, which is chosen to radiate predominantly at the cooler electron temperatures associated with the plasma edge. If this impurity travels upstream to the main confined plasma, it can significantly impact…
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UKAEA-CCFE-PR(23)082022
The role of ion-molecule elastic collisions (specifically D+−D2 collisions) in strongly detached divertor conditions has been studied in the MAST-U Super-X configuration using SOLPS-ITER. Two strongly detached steady state solutions, one obtained through a main-ion (D2) fuelling scan and the other through an impurity (N) seeding scan at fixed …
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UKAEA-CCFE-PR(22)232022
In this paper we a first qualitative analysis of the atomic and molecular processes at play during detachment in the MAST-U Super-X divertor, using divertor spectroscopy data. Our analysis indicates a wide operational regime of detachment of the MAST-U super-X divertor, which can be roughly separated in four phases: 1) The ionisation fro…
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UKAEA-CCFE-PR(22)082022
MAST-U has recently started operating with a Super-X divertor, designed to increase total flux expansion and neutral trapping, both predicted through simple analytic models and SOLPS calculations to reduce the plasma and impurity density detachment thresholds. In this study, utilising the SOLPS-ITER code, we are quantifying the possible gain allowe…
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UKAEA-CCFE-PR(24)2372021
Control of the detachment front between the target and the X-point is necessary for minimizing the effect of detachment on the core plasma (core radiation and loss of confinement) and maximizing the divertor functions (reduction of target heat load and sputtering, He pumping). However, such control has been difficult in experiments. The SOLPS-IT…
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UKAEA-CCFE-PR(23)1012021
The role of neutral and charged hydrogenic molecules in detached regimes of tokamak plasmas is investigated using simplified 1D parallel numerical models. Using MAST-Upgrade like conditions, simulations are implemented to study the rollover of target flux in upstream density scan and target temperature scan. It is found that if H2 and H2+ are cons…
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UKAEA-CCFE-CP(23)142021
The high heat fluxes to the divertor during edge localised mode (ELM) instabilities have to be reduced for a sustainable future tokamak reactor. A solution to reduce the heat fluxes could be the Super-X divertor, this divertor configuration will be tested on MAST-U. ELM simulations for MAST-U Super-X tokamak plasmas have been obtained, using JOR…
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UKAEA-CCFE-CP(21)102021
This paper shows experimental results from the TCV tokamak that indicate plasma-molecule interactions involving D+2 and possibly D− play an important role as sinks of energy (through hydrogenic radiation as well as dissociation) and particles during divertor detachment if low target temperatures (< 3 eV) are achieved. Bot…
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UKAEA-CCFE-CP(21)062021
In this work we provide experimental insights into the impact of plasma-molecule interactions on divertor detachment by applying new spectroscopic analysis techniques to the hydrogen Balmer line series to investigate how both atom and plasma-molecule interactions impact particle balance. Our analysis on a representative L-mode TCV density ramp dis…
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UKAEA-CCFE-CP(23)172020
The paper reviews recent SOLPS modelling of long-legged divertors carried out by UKAEA and the University of York. The required upstream density required for detachment is predicted to scale inversely with the total flux expansion of the divertor, but experimentally this was not found to be the case on TCV. Interpretative SOLPS-ITER modelling sugge…
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