Transient sputtering method for estimating ion confinement times in ECRIS plasma
Authors
Date
2018Copyright
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Elektronisyklotroniresonanssi-ionilähteillä (ECRIS) tuotetaan korkeasti varattuja ione-
ja kiihdytinpohjaisen fysiikan tutkimuksen tarkoituksiin. Pitkät ionien säilöntäajat ovat
välttämättömiä korkeasti varattujen ionien tuottamiseksi. Tässä Pro Gradussa testataan
transienttimenetelmää ionien säilöntäaikojen arviomiseksi sputteroimalla.
Tutkielmassa esitellään tarpeellinen tausta plasmafysiikalle, ECR-ionilähteelle ominai-
sille plasmailmiöille, sekä käytännön menetelmille ionien tuottamiseksi ECR-plasmassa.
Kokeellisessa osiossa esitellään sputterointiin perustuva transienttimenetelmä ionien säi-
löntäaikojen arvioimiseksi ionivirtojen transienttien aikavakioista. Aikavakioiden riippu-
vuus ionilähteen operointiparametreistä analysoidaan nojaten teoreettiseen taustaan, ja
sen havaitaan sopivan ionien sähköstaattiseen säilöntämalliin.
Lisäksi työssä tutkitaan ionien tuottoaikoja soveltamalla sputterointimetodia nopeassa
sputteroinnissa. Tuottoaikoja verrataan ionivirtojen saturaatioaikoihin, joita käytetään
tyypillisesti radioaktiivisten ionisuihkujen tuoton rajakriteerinä. Havaitaan, että ionien
tuottoajat ovat merkittävästi lyhyempiä kuin saturaatioajat, mikä on radioaktiivisten
ionisuihkujen tuoton kannalta tärkeä havainto.
...
Electron Cyclotron Resonance Ion Sources (ECRIS) are used for Highly Charged Ion
(HCI) production for accelerator based physics research. A necessary condition for HCI
production are long ion confinement times. In this thesis, a transient sputtering method
for estimating the confinement times is tested.
In this thesis, the necessary background of plasma physics, ECRIS-specific theoretical
plasma phenomena, and practicalities of HCI production with the ECRIS are introduced.
In the experimental section, a transient sputtering method for estimating ion confinement
times based on the ion current transient decay times is presented. The parameter dependence of the decay times is analyzed relying on the theoretical background, and found to
be in accordance with the electrostatic ion confinement model.
Additionally, the ion production times are probed by applying the sputtering method
in a fast sputtering experiment. The production times are compared to the ion current
saturation times, which are typically used as limiting criteria for radioactive ion beam
production. It is observed, that the ion production times are significantly shorter than
the current saturation times, which is an important finding with respect to radioactive
beam production.
...
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- Pro gradu -tutkielmat [29620]
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