BEGIN:VCALENDAR VERSION:2.0 PRODID:-//linuxsoftware.nz//NONSGML Joyous v1.4//EN BEGIN:VEVENT SUMMARY:Understanding the link between scrape-off layer and pedestal condi tions at JET using density profile measurements by reflectometry DTSTART:20250527T093000Z DTEND:20250527T110000Z DTSTAMP:20260905T193950Z UID:5808ab55-85ba-47cd-8e2e-050bd4d60a8c SEQUENCE:2 CREATED:20250520T091951Z DESCRIPTION:The confinement of the plasma edge regions\, the pedestal and the Scrape-Off Layer (SOL)\, has a large impact on the stability and effic iency of the entire system but the physics behind them are complex and par tly outside first-principles theory. Empirical scaling laws are a crucial tool in understanding these processes\, and the JET reflectometer provides a unique opportunity to study the pedestal and SOL\, as it has high tempo ral and spatial resolutions. Methods were developed to process and validat e the reflectometer data and to extract and condense each shot to a set of physical parameters. Models that accurately describe all edge profile reg ions were created and improved. It was found that the density at the end o f the high gradient region had a weak correlation with the separatrix dens ity. A large database of shots was created\, from which a selection of sca ns was chosen\, to cover a large range of plasma parameters. By studying t he parameter correlations in the different scans\, it was observed that th e SOL confinement improved in the corner configuration and with higher tri angularity and plasma current\, and degraded with the increase in gas fuel ling and heating power. Only triangularity was seen to have a positive imp act on the pedestal confinement\, with other parameters having a neutral o r negative effect. A temporal analysis of Edge Localised Modes (ELMs) was performed on several shots\, to analyse the timescales of an ELM and how E LMs are affected by the different parameters. It was observed that the ped estal density has a longer recovery (around 30ms) than both pedestal and S OL widths (around 5ms). It was also seen that in certain conditions ELMs c an have a long tail\, associated with a period with near-constant values o f pedestal width and gradient\, and a larger energy loss than normal ELMs. The largest impact of the plasma parameters on ELMs was found to be the E LM shape and timescale. Increased gas fuelling also showed a reduced impac t of ELMs on the profile. LAST-MODIFIED:20250520T092003Z LOCATION:Anfiteatro GA1 (Piso 0 do Pavilhão Central) do IST URL:http://df.vps.tecnico.ulisboa.pt/pt/eventos/understanding-the-link-bet ween-scrape-off-layer-and-pedestal-conditions-at-jet-using-density-profile -measurements-by-reflectometry/ X-ALT-DESC;FMTTYPE=text/html:

The confinement of the plasma edge regions\, the pedestal and the Scrape-Off Layer (SOL)\, ha s a large impact on the stability and efficiency of the entire system but the physics behind them are complex and partly outside first-principles th eory. Empirical scaling laws are a crucial tool in understanding these pro cesses\, and the JET reflectometer provides a unique opportunity to study the pedestal and SOL\, as it has high temporal and spatial resolutions.

Methods were developed to process and validate the reflectometer d ata and to extract and condense each shot to a set of physical parameters. Models that accurately describe all edge profile regions were created and improved. It was found that the density at the end of the high gradient r egion had a weak correlation with the separatrix density. A large database of shots was created\, from which a selection of scans was chosen\, to co ver a large range of plasma parameters.

By studying the paramete r correlations in the different scans\, it was observed that the SOL confi nement improved in the corner configuration and with higher triangularity and plasma current\, and degraded with the increase in gas fuelling and he ating power. Only triangularity was seen to have a positive impact on the pedestal confinement\, with other parameters having a neutral or negative effect.

A temporal analysis of Edge Localised Modes (ELMs) was p erformed on several shots\, to analyse the timescales of an ELM and how EL Ms are affected by the different parameters. It was observed that the pede stal density has a longer recovery (around 30ms) than both pedestal and SO L widths (around 5ms).

It was also seen that in certain conditio ns ELMs can have a long tail\, associated with a period with near-constant values of pedestal width and gradient\, and a larger energy loss than nor mal ELMs. The largest impact of the plasma parameters on ELMs was found to be the ELM shape and timescale. Increased gas fuelling also showed a redu ced impact of ELMs on the profile.

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