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Author:Hirvijoki, Eero
Title:Assessment of the performance of active NPA design in ASDEX Upgrade tokamak using the ASCOT code
Aktiivisen NPA:n suorituskyvyn arviointi ASDEX Upgrade-tokamakissa ASCOT-koodin avulla
Publication type:Master's thesis
Publication year:2010
Pages:82      Language:   eng
Department/School:Informaatio- ja luonnontieteiden tiedekunta
Main subject:Ydin- ja energiatekniikka   (Tfy-56)
Supervisor:Salomaa, Rainer
Instructor:Kurki-Suonio, Taina
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  94   | Archive
Keywords:fusion
fast ions
NBI
current drive
active NPA
ASDEX Upgrade
ASCOT
fuusio
nopeat ionit
NBI
virranajo
aktiivinen NPA
ASDEX Upgrade
ASCOT
Abstract (eng): Before fusion is to provide commercial electricity, the current concept of inductive current drive has to be abandoned and new steady state methods adopted.
The neutral beam current drive (NBCD) is the best candidate so far but, unfortunately, despite of good theoretical prejudices, the efficiency of the method has proven disappointing.

It is a common thought that the fast ions from NBCD itself would enhance plasma micro-turbulence, and ruin the performance.
Thus a new, so-called active NPA diagnostics is to be installed in ASDEX Upgrade to reveal more information about the fast ion population generated by NBCD.

The method utilizes NB-generated neutral density to enhance charge exchange rate in the plasma core and, thus, a higher signal from the core region is expected than in traditional NPA.
However, before the current design is finalized, simulations have to be done to verify the performance of the diagnostic.

A Monte Carlo orbit following code ASCOT was updated to allow simulation of active NPA signal and a totally new code, NID, was implemented to provide the 4D NB-generated neutral density required in the active NPA simulations.
As a result, probably the first of its kind synthetic NPA camera was implemented.

With ASCOT it was then possible to compare the performance of the traditional and active NPA in ASDEX Upgrade.
The study focused on ions from the 93 keV current drive beams, 6 and 7 from injector 2, while the neutral cloud was provided by the 60 keV beam 3 from injector 1.
The results demonstrated that, with a careful choice of the detector sightline, active NPA would yield almost local measurements of the fast ion spectrum inside the plasma.
Abstract (fin): Ennen kuin fuusio voidaan valjastaa kaupalliseen sähköntuotantoon, nykyinen induktiivinen virranajomenetelmä täytyy vaihtaa tasaiseen, jatkuvaan menetelmään.
Tähän mennessä paras vaihtoehto on korkeaenergisten neutraalien hiukkasten injektoiminen (NBCD), mutta hyvistä teoreettisista ennusteista huolimatta virran generoiminen nopeilla hiukkasilla on osoittautunut tehottomaksi.

Yleisesti ajatellaan, että NBCD:n tuottamat nopeat ionit, joihin menetelmä perustuu, aiheuttavat plasmaan mikroturbulenssia ja siten heikentävät menetelmän tehokkuutta.
Jotta näiden nopeiden ionien populaatiosta saataisiin parempi kuva, ASDEX Upgrade tokamakiin on suunniteltu asennettavan uusi aktiivinen neutraalihiukkasdiagnostiikka (active NPA).
Menetelmä hyödyntää neutraalisuihkujen luomaa neutraalipilveä, joka kasvattaa varauksenvaihtoreaktioiden taajuutta plasman keskustassa.
Ennen suunnitelmien viimeistelyä diagnostiikan suorituskyky on kuitenkin varmistettava simuloimalla.

Monte Carlo -pohjainen radanseuranta koodi ASCOT päivitettiin sopivaksi aktiivisen NPA signaalin simulointiin.
Lisäksi rakennettiin täysin uusi koodi, NID, laskemaan neutraalisuihkuista syntyvä neutraalitiheys aktiivisen NPA signaalin simuloimiseksi.
Tuloksena on todennäköisesti ensimmäinen laatuaan oleva synteettinen NPA kamera.

Tämän jälkeen ASCOT mahdollisti perinteisen ja aktiivisen NPA:n suorituskykyjen vertailun.
Tutkimus keskittyikin ASDEX Upgrade:n 93 keV virranajosuihkujen 6 ja 7 tuottamiin ioneihin 60 keV suihkun tuottaessa neutraalitiheyden aktiivista diagnostiikkaa varten.
Tulokset osoittivat, että huolellisella detektorin katselusuunnan valinnalla, aktiivinen NPA mittaus pystyisi tuottamaan lähes paikallisia mittauksia nopeiden ionien spektristä.
ED:2010-11-19
INSSI record number: 41339
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