Prilagodba energije ubrzanih iona za ozračavanje materijala od interesa za fuzijske reaktore

master's thesis

• Title (english): Adjustment of energy of accelerated ions for irradiation of materials of interest for fusion reactors
• Author: Pavao Roko Andričević
• Mentor: Tonči Tadić (mentor)
• Mentor: Damir Bosnar (mentor)
• Committee member: Damir Bosnar (predsjednik povjerenstva)
• Committee member: Tonči Tadić (član povjerenstva)
• Committee member: Tamara Nikšić (član povjerenstva)
• Committee member: Matko Milin (član povjerenstva)
• Committee member: Davor Horvatić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2015-07-10, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract

Jedan od glavnih koraka ka izgradnji fuzijske nuklearne elektrane je pronalazak materijala sposobnih da podnesu dugotrajno intenzivno zračenje neutronima energije 14.1 MeV, dobivenih reakcijom fuzije, a da pritom ne mijenjaju svoja fizička i kemijska svojstva. Da bi se mogle razumjeti i savladati pojave koje uvjetuju vrijeme života i integritet materijala pri takvom neutronskom zračenju potrebno je materijal izložiti uvjetima što sličnijim onima kakvi se očekuju u fuzijskim reaktorima. Jedan od načina je ozračavanjem pomoću dva ili tri ionska snopa MeV-skih energija koji padaju u istu točku. Budući da snop iona gubi energiju vrlo nejednoliko na svojoj putanji u materijalu postižući maksimum na najvećoj dubini, nužna je ugradnja sustava za prilagodavanje i variranje energije ubrzanih iona. Time se nastoji postići što ravnomjernija raspodjela predaje energije iona u materijalu duž cijele putanje, od ulaska u materijal do krajnjeg dosega u materijalu. Diplomski rad je obuhvatio projektiranje tzv. ion beam degradera tj. jednostavnog sustava za mehaničko variranje energije ubrzanih iona MeV-skih energija, korištenjem više metalnih folija razne debljine. Kreiran je izgled ion beam degradera, kruga koji sadrži 8 folija oblika trapeza, te su odredene debljine razlčitih sustava folija za koje je postignut uvijet homogenosti predane energije od ulaska u materijal do maksimalnog dosega, za ozračavanje željeza snopovima teških iona tj. ionima željeza energija 20, 30 i 40 MeV, te lakih iona istog dosega u željezu, tj. protona energija 600 i 700 keV i alfa-čestica energija 2000 i 2500 keV. Osim računa prijenosa energije iona na materijal, izvršen je i račun distribucija kutnog širenja ionskih snopova radi višestrukih raspršenja iona u folijama (small angle multiple scattering) u svrhu odredivanja površine uzorka koji se ozračava, te potvrde poklapanja površina ozračavanja obaju snopova. Odreden je položaj ion beam degradera unutar komore, te njegova brzina okretanja od najmanje 600 okretaja u minuti. Pri ovoj brzini vrtnje neće doći do pregrijavanja folija, a za nju istodobno nije teško zaustaviti vrtnju beam degradera radi potrebe mjerenja struje snopa.

Abstract (english)

One of the major steps towards building a fusion nuclear power plant is finding materials able to withstand prolonged and intensive 14.1 MeV neutron radiation, without it changing their physical and chemical properties. To be able to understand and master the phenomenas which define the time of life and the integrity of the material under such neutron radiation, it is necessary to expose the material to conditions as simmilar as possible to the ones in fusion reactors. One of the ways to achieve that is irradiation using two or three ion beams of MeV energy range, all falling at the same spot. As the ion beam energy deposition loses is very unhomogenuous on its path in the material, achieving its maximum at a maximum depth, it is necessary to install a system for adjusting and varying the energy of accelerated ions. The aim is to get a homogenuous distribution of ion energy deposition in the material along the entire path, from the surface to maximal ion range in the material. This master thesis includes designing a so-called ”ion beam degrader” ie. a simple system for the mechanical variation of energy of accelerated ions, using metal foils of various thickness. The ion beam degrader would be shaped as a circle that contains 8 trapezoid like foils. The thickness of different groups of foils are calculated for irradiation of iron with heavy ions i.e. iron ions of energy 20, 30 and 40 MeV, and light ions of the same range in iron, i.e. protons of energies 600 and 700 keV and alpha-particles of energy 2000 and 2500 keV. In addition to calculating the energy deposition of ions in the material, ions’ small angle multiple scattering distributions were also calculated for the purpose of determination of irradiated areas at the sample, and to confirm that both ion beams will irradiate the same matching area. The position of the ion beam degrader inside the chamber was determined, and its speed of rotation is proposed to be no less than 600 revolutions per minute. At that speed there will be no overheating of the thin foils and it is not difficult to stop spinning because of the need to measure current.

• Keywords: fuzija; fuzijski reaktori; ubrzani ioni
• Keywords (english): fusion; fusion reactors; accelerated ions
• Language: croatian
• URN:NBN: urn:nbn:hr:217:769416
• Study programme: Title: Physics; specializations in: Research; Course: Research; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra fizike (magistar/magistra fizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-04-04 16:03:54