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22-27 October 2018
Mahatma Mandir Conference Centre
Asia/Kolkata timezone
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Divertor impurity seeding experiments at the COMPASS tokamak

23 Oct 2018, 08:30
4h
Mahatma Mandir Conference Centre

Mahatma Mandir Conference Centre

Gandhinagar (nearest Airport: Ahmedabad), India
Poster P1 Posters

Speaker

Dr Michael Komm (Institute of Plasma Physics of the Czech Academy of Sciences)

Description

Partial detachment is the desired regime for the baseline burning plasma scenario in ITER and next–step devices, as it allows to convert the majority of the energy carried by charged particles through the scrape-off-layer (SOL) into isotropic radiation and thus avoids localized heat flux deposition in the divertor region. In order to maintain relevance to ITER and DEMO, a concentrated effort has been initiated at the COMPASS tokamak to achieve detached operation by means of impurity seeding. Series of experiments with impurity injection in the range of 2-9x1020 molecules per second at different locations in the divertor were performed with the aim to cool the plasma and influence the particle and heat transport in the divertor region and provoke partial detachment. Previously reported results [1] were largely extended by injection of nitrogen at the outer divertor target and also by attempts to seed the plasma with neon. The effects on SOL and divertor plasma conditions were monitored by means of horizontal reciprocating probe manipulator located at the outer midplane and by arrays of divertor Langmuir and Ball-pen probes. The radiation in the edge plasma was observed by AXUV bolometers and fast visible cameras. Experiments in L-mode discharges with nitrogen injected at the outer divertor target have shown that the presence of radiating impurity leads to drop of pressure in the divertor. Depending on the magnitude of the seeding, the upstream pressure can be also affected, suggesting possible penetration of nitrogen into the confined plasma region. The target pressure, however drops at faster rate than upstream, which allows to reach the regime of partial detachment. Similar results were obtained by the HFS nitrogen injection, however the change in divertor pressure was more generally more abrupt and was less sensitive to the amount of injected nitrogen. References: [1] M. Komm et al., proceedings of the 44th EPS conference, Belfast (2017) P1.118
Country or International Organization Czech Republic
Paper Number EX/P1-1

Primary author

Dr Michael Komm (Institute of Plasma Physics of the Czech Academy of Sciences)

Co-authors

Mr Alexis Devitre (Universidad de Costa Rica, San Jose, Costa Rica) Mr Igor Khodunov (Department of Applied Physics, Gent University, Gent, Belgium) Dr Jakub Seidl (Institute of Plasma Physics of the CAS) Mr Jaroslav Krbec (Institute of Plasma Physics of the CAS) Dr Jiri Adamek (Institute of Plasma Physics of the CAS) Dr Jordan Cavalier (Institute of Plasma Physics of the CAS) Dr Josef Havlicek (Institute of Plasma Physics of the CAS) Ms Kristina Tomova (Department of Applied Physics, Gent University, Gent, Belgium) MST1 Eurofusion team (See the author list of Meyer H. et al 2017 Nucl. Fusion 57 102014) Mr Martin Imrisek (Institute of Plasma Physics of the CAS) Mr Matej Peterka (Institute of Plasma Physics of the CAS) Mr Matej Tomes (Institute of Plasma Physics of the CAS) Dr Michael Faitsch (Max-Planck-Institut für Plasmaphysik, 85748 Garching b. München, Germany) Dr Miglena Dimitrova (Institute of Plasma Physics of the CAS) Mr Oleg Samoylov (Department of Applied Physics, Gent University, Gent, Belgium) Mr Pavel Hacek (Institute of Plasma Physics of the CAS) Dr Petr Bohm (Institute of Plasma Physics of the CAS) Mr Petr Vondracek (Institute of Plasma Physics of the CAS) Dr Petra Bilkova (Institute of Plasma Physics of the CAS) Dr Radomir Panek (Institute of Plasma Physics of the CAS) Dr Sarah Elmore (Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England) Prof. Tsviatko Popov (Sofia Univ St Kliment Ohridski, Fac Phys, 5 J Bourchier Blvd, Sofia 1164, Bulgaria) Dr Vladimir Weinzettl (Institute of Plasma Physics of the CAS)

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