Physics and engineering studies of heat fluxes to ITER plasma-facing components

Brank, Matic (author), Kos, Leon (mentor), Pitts, Richard A. (comentor)

This thesis deals with plasma power deposition to the ITER first wall and bolometer diagnostic systems. In the first part, the assessment of the heat fluxes is presented, taking into an account plasma scenarios predicted during ITER’s operational phase. The focus is on the experimentally verified power decay of the particles conducted along the magnetic field lines, considering exponential profile, the double exponential profile and the edge-localized modes. The photonic power loads to the first wall are also assessed, taking into account the spatially distributed plasma power sources. In the second part, tomography methods were used to reconstruct these plasma power sources. First, an assessment of the synthetic signals was made using bolometers, taking into account experimentally verified measurement errors. Then we arrived at the solution to the reconstruction, i.e., the inverse problem, with the help of the regularisation method of anisotropic smoothness along magnetic surfaces. The results of the numerical analyses confirmed that the heat fluxes to the first wall are within the prescribed engineering limits. The use of the tomography method shows that the currently defined configuration of the bolometers is suitable for the proper reconstruction of plasma power sources. The bolometers will also be able to detect individual power peaks in the plasma. Additional analyses were made of the quality of the reconstruction if specific bolometers were removed from the defined configuration. The reduction in the number of bolometers does not greatly affect the reconstruction; however, there are different possible bolometer-removal scenarios that affect such analyses and only a few were considered. The experimental verification of the tomography method was not possible during this PhD. It is expected that these algorithms will be tested once ITER is in its operational phase.

• Language: English
• Keywords: tokamak, plasma, field-line tracing, first wall of fusion reactor, tomography, bolometer
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FS - Faculty of Mechanical Engineering
• Place of publishing: Ljubljana
• Publisher: [M. Brank]
• Year: 2024
• Number of pages: XXVIII, 151 str.
• PID: 20.500.12556/RUL-163016
• UDC: 533.95:621.039.61:537.612(043.3)
• COBISS.SI-ID: 210534147
• Publication date in RUL: 01.10.2024

Secondary language

• Language: Slovenian
• Title: Fizikalne in inženirske študije toplotnih tokov na plazmi izpostavljenih komponentah v fuzijskem reaktorju ITER

Abstract

Doktorsko delo obravnava odlaganje moči plazme na prvo steno fuzijskega reaktorja ITER in merilni sistem bolometrov. V prvem sklopu je doktorsko delo osredotočeno na preračun toplotnih tokov na površini prve stene, pri čemer so bili za izračun uporabljeni predpisani plazemski režimi, ki so predvideni za uspešno delovanje reaktorja ITER. Osredotočili smo se na eksperimentalno potrjene padce moči delcev, ki se gibljejo vzdolž magnetnih silnic. Ti zajemajo eksponentni profil, dvojni eksponentni profil in robni lokalizirani način. Preučevan je bil tudi vpliv sevanja fotonov na prvo steno reaktorja, pri čemer so bili uporabljeni porazdelitveni profili sevalne moči plazme v reaktorju. V drugem sklopu smo s pomočjo tomografskih metod rekonstruirali omenjene plazemske profile gostote sevalne moči. Pri tem je bil najprej opravljen izračun signalov na merilnem sistemu bolometrov, pri čemer so bili upoštevani eksperimentalno potrjeni faktorji merilnih napak, nato pa je bila za rešitev rekonstrukcije oziroma inverznega problema uporabljena t.i. regularizacija anizotropične gladkosti vzdolž magnetnih silnic. Rezultati numeričnih analiz potrjujejo, da so toplotni tokovi na prvi steni za predpisane plazemske režime znotraj predpisanih inženirskih omejitev. Hkrati je bilo s pomočjo opisane tomografske metode pokazano, da je trenutno definirani merilni sistem bolometrov sposoben rekonstruirati sevalne profile plazme in predvideti lokacijo največjih vrednosti sevalne moči v plazmi. Dodatna analiza je pokazala, da zmanjšanje predpisanega števila bolometrov načeloma ne vpliva na kakovost rekonstrukcije plazme, a je to odvisno predvsem od tega, kateri bolometri so iz merilnega sistema odstranjeni. V okviru doktorskega dela tomografskih algoritmov nismo uspeli eksperimentalno potrditi. Predvideno je, da bodo v času obratovanja fuzijskega reaktorja ITER tovrstni algoritmi testirani.

• Keywords: tokamak, plazma, sledenje magnetnim silnicam, prva stena fuzijskega reaktorja, tomografija, bolometer