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:20260915T025516Z UID:5808ab55-85ba-47cd-8e2e-050bd4d60a8c SEQUENCE:1 CREATED:20250520T091941Z DESCRIPTION: The confinement of the plasma edge regions\, the pedestal and the Scrape-Off Layer (SOL)\, has a large impact on the stability and effi ciency of the entire system but the physics behind them are complex and pa rtly outside first-principles theory. Empirical scaling laws are a crucial tool in understanding these processes\, and the JET reflectometer provide s a unique opportunity to study the pedestal and SOL\, as it has high temp oral and spatial resolutions. Methods were developed to process and valida te the reflectometer data and to extract and condense each shot to a set o f physical parameters. Models that accurately describe all edge profile re gions were created and improved. It was found that the density at the end of the high gradient region had a weak correlation with the separatrix den sity. A large database of shots was created\, from which a selection of sc ans was chosen\, to cover a large range of plasma parameters. By studying the parameter correlations in the different scans\, it was observed that t he SOL confinement improved in the corner configuration and with higher tr iangularity and plasma current\, and degraded with the increase in gas fue lling and heating power. Only triangularity was seen to have a positive im pact on the pedestal confinement\, with other parameters having a neutral or negative effect. A temporal analysis of Edge Localised Modes (ELMs) was performed on several shots\, to analyse the timescales of an ELM and how ELMs are affected by the different parameters. It was observed that the pe destal density has a longer recovery (around 30ms) than both pedestal and SOL widths (around 5ms). It was also seen that in certain conditions 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 normal 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 reduced impa ct of ELMs on the profile. LAST-MODIFIED:20250520T091941Z LOCATION:Anfiteatro GA1 (Piso 0 do Pavilhão Central) do IST URL:http://df.vps.tecnico.ulisboa.pt/en/events/understanding-the-link-betw een-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)\, h as a large impact on the stability and efficiency of the entire system but the physics behind them are complex and partly outside first-principles t heory. Empirical scaling laws are a crucial tool in understanding these pr ocesses\, 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 data and to extract and condense each shot to a set of physical parameters . Models that accurately describe all edge profile regions were created an d improved. It was found that the density at the end of the high gradient region had a weak correlation with the separatrix density. A large databas e of shots was created\, from which a selection of scans was chosen\, to c over a large range of plasma parameters.

By studying the paramet er correlations in the different scans\, it was observed that the SOL conf inement improved in the corner configuration and with higher triangularity and plasma current\, and degraded with the increase in gas fuelling and h eating 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 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 conditi ons ELMs can have a long tail\, associated with a period with near-constan t values of pedestal width and gradient\, and a larger energy loss than no rmal ELMs. The largest impact of the plasma parameters on ELMs was found t o be the ELM shape and timescale. Increased gas fuelling also showed a red uced impact of ELMs on the profile.

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