Radiative response on massive noble gas injection for runaway suppression in disruptive plasmas [Elektronische Ressource] / von Bernhard Reiter

Bernhard Reiter

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• Physik

Informations

• Publié par: ludwig-maximilians-universitat_munchen
• Publié le: 01 janvier 2010
• Nombre de lectures: 45
• Langue: Deutsch
• Poids de l'ouvrage: 31 Mo

Extrait

Radiative Response on Massive Noble Gas
Injection For Runaway Suppression
in Disruptive Plasmas
Dissertation
der Fakult¨at fu¨r Physik
der Ludwig-Maximilians-Universit¨atMu¨nchen
von
Bernhard Reiter
aus Traunstein
Mu¨nchen, 21. Mai 2010Erstgutachter: Prof. Dr. H. Zohm
Zweitgutachter: Prof. Dr. F. Krausz
Datum der mu¨ndlichen Pru¨fung: 16.09.2010Zusammenfassung
In einem disruptiven Tokamakplasma entsteht durch abruptes Ku¨hlen ein relativ starkes
elektrisches Feld, welches Elektronen in das relativistische Geschwindigkeitsregime be-
schleunigen kann. Relativistische Elektronen, die sogenannten Runaways, akkumulieren
EnergieenimMeVBereich, vermehrensichmultiplikativundk¨onnenerheblichenSchaden
anrichten, wenn sie auf die Wand des Vakuumgef¨aßes treffen, was insbesondere fu¨r Fu-
sionsreaktoren der n¨achsten Generation ein ernsthaftes Problem darstellt.
Diese Dissertation verfolgt das Prinzip der abrupten Erh¨ohung der Elektronendichte
im gesamten Plasma durch lokale, massive Injektion von Edelgasen. Die sich daraus
ableitende Erh¨ohung der Reibungskr¨afte soll Runaway-Population unterdru¨cken. Die
Tatsachen, dass der Prozess auf kleinen, disruptionstypischen Zeitskalen abl¨auft und
gleichzeitig die Verteilung der injizierten Materie im dreidimensionalen Raum charakter-
isiert werden soll, stellt die Diagnostizierungsmethoden in einem solchen Experiment vor
hohe Anforderungen.
Um Einblicke in die Wechselwirkungsdynamik zwischen der kalten Materiefront und
dem heissen Plasma zu erlangen, wurde im Zuge dieser Arbeit ein System zur Messung
breitbandiger elektromagnetischer Strahlung aufgebaut. Die Diagnostik basiert auf der
AXUV-Technologieundumfasst176Sichtlinien, derenr¨aumlicheAnordungdieErfassung
der helikalen Strahlungspropagation erlaubt.
Diese Arbeit er¨offnet den Einblick in die Dynamik und die große Asymmetrie der
Strahlungsverteilung unter der Ausbildung komplexer filament¨arer Strukturen. Eine der-
artige Charakterisierung der Strahlungspropagation erlaubt es ausserdem, Ru¨ckschlu¨sse
auf die Trajektorien der Ionen zu treffen.
Die Ergebnisse dieser Arbeit fließen direkt ein in die weitere Entwicklung von In-
jektionsverfahren zur effektiven Runaway-Unterdru¨ckung in zuku¨nftigen Fusionsanlagen
wie ITER.Abstract
In a disruptive tokamak plasma, rapid cooling induces a high electric field, which po-
tentially pushes electrons into the relativistic velocity regime. Relativistic electrons, the
so-called runaways, accumulate many MeV, they multiply quickly andcancause substan-
tial damage when they hit the wall of the vacuum vessel. This constitutes a big challenge
in particular for fusion devices of the next generation.
Thisthesis followstheprincipleofrapidlyincreasing theelectrondensity uptovalues,
where the retarding collisional force leads to a suppression of runaway population. The
method of injecting high amounts of noble gas particles locally into the plasma is put
into practice in the ASDEX Upgrade fusion test facility. The prerequisite for the success
of this approach is the spatially uniform redistribution of the injected particles on short
timescales typical for disruptions.
In the framework of this thesis, a multi-channel photometer system was built with
the intention of diagnosing the spatial propagation of radiation. The new diagnostic
employs the AXUV technology and is equipped with 176 lines of sight. It is made up
by toroidally spaced detectors, which allows for unfolding the helical transport times.
This thesis reveals the asymmetric radiation evolution growing from a highly dynamic
zone of interaction between cold injected matter and hot plasma. Complex filamentary
structures in the plasma periphery formed during the injection process are analysed and
characterised.
The results of this thesis directly support the further development of methods for
future experiments on runaway suppression, which are of great value for next generation
devices like ITER.Acknowledgements
I am very grateful to Prof. Hartmut Zohm, who made it possible for me to carry out this
thesis at the Max Planck Institute of Plasma Physics in Garching. I kindly acknowledge
also for his stimulating comments on the manuscript of this thesis.
IwouldliketothankverymuchDr. GabriellaPautasso,whoalsosupportedthemanuscript
and generously assisted my work.
Many thanks to Dr. Thomas Eich for buying all the nice diagnostic equipment and mak-
ingcomments onseveral talks performedinthecourseofthework andalso onsome parts
of this manuscript.
Many thanks to Dr. Josef Neuhauser, who was very interested in my results and inspired
me in very helpful discussions. Sincere thanks for the comments on this manuscript.
Thank you goes to Dr. Ralph Dux and to Prof. A. Kallenbach for their suggestions and
comments on the manuscript of this thesis.
I am indebted to Dr. Asher Flaws, who supported me for generating the very first tomo-
gramswithmydiagnostic. Hisgroundworkhelpedmealotforcomingfastertosuccessful
disruption analysis.
Thank you goes also to Dr. Tilman Lunt. He provided the codes for the impressive 3-D
visualisation of the vessel and adjusted the CMOS camera according to my wishes.
I am very grateful to Dr. Mark Maraschek, who adjusted his programs to my diagnostic
and helped in many questions regarding data acquisition as well as magnetic mode anal-
ysis.
I wish to thank also Dr. Valentin Igochine and Dr. Anja Gude, who allowed me to use
their setup for diode calibration. Thanks also to Dr. J. C. Fuchs for providing magnetic
equilibrium data.
Thank you goes to Dr. Martin Balden, for helping me with the focused ion beam mi-
croscopy and the EDX device.
In addition, I am indebted to all the technicians for their support. Especially, Heinz Wolf
forgiving methepossibility ofusinghislaboratory. TheteamofDr. Albrecht Herrmann,
for their help during the installation times inside the vessel, Michael, Florian and Gabi.
In particular, of course, Wolfi Zeidner, who measured the camera positions many many
times. I am very grateful to the electricians, forth and foremost Ludwig Kammerloher,
who perfectly tackled the problems came about through many unforseen issues. Thanks
also to GeraldSellmair, Thomas Schwarz, Horst Eixenberger andGeroldSchramm. Also,many thanks to the DAQ group of Dr. Karl Behler, especially Andreas Lohs and Helmut
Blank.
Many thanks to Christian Vogel, for helping me to plan the excursions of graduate stu-
dents during our time as students representatives.
Finally, Idedicate this work to my family, which has supported me as long as Ican think.
stBernhard Reiter Munich, 21 May 2010