uu.seUppsala University Publications
Change search
ReferencesLink to record
Permanent link

Direct link
Effect of tungsten off-axis accumulation on neutral beam deposition in JET rotating plasmas
Show others and affiliations
2015 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 57, no 4, 045001Article in journal (Refereed) Published
Abstract [en]

Evidence for low field side accumulation of tungsten is often observed in bolometry and soft x-ray emissivities of highly rotating JET ITER-like wall (ILW) plasmas. Poloidal variation of the density of high-Z impurities, such as tungsten, in the core of NBI heated plasmas is expected from neoclassical theory due to charge displacement and parallel electric field generated by the centrifugal force. We calculate the poloidally asymmetric distribution of tungsten using fluid equations and a 1D transport simulation with the JETTO/SANCO code. Peaking of tungsten on the outboard side of the plasma is found and verified with soft x-ray and bolometry measurements. We then study the effect of a poloidally asymmetric tungsten distribution on the distribution of the NBI heat source by simulations with the Monte Carlo code ASCOT. The simulations show that the poloidally asymmetric tungsten profile redistributes the fast NBI ions radially through shifting their ionization profile and poloidally through enhanced pitch-angle scattering at high energy. The amplitude of the redistribution is in the order of 10% for the highest n(W)/n(e) ratios of similar to 10(-4) measured in recent JET H-mode plasmas. As a result of the scattering of the beam particles, the core heat deposition is changed less than 10%, which does not have a significant impact to the performance of JET plasmas. The modelling is in qualitative agreement with measurements by the vertical neutron camera that sees a broadening in the 2.5 MeV neutron profile when tungsten peaks on the outboard side of the plasma.

Place, publisher, year, edition, pages
2015. Vol. 57, no 4, 045001
Keyword [en]
tungsten, neutral beam, JET, asymmetry, neutron
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-251991DOI: 10.1088/0741-3335/57/4/045001ISI: 000351637700013OAI: oai:DiVA.org:uu-251991DiVA: diva2:811119
Available from: 2015-05-11 Created: 2015-04-28 Last updated: 2015-05-11Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Conroy, Sean
By organisation
Applied Nuclear Physics
In the same journal
Plasma Physics and Controlled Fusion
Physical Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 556 hits
ReferencesLink to record
Permanent link

Direct link