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Experimental gas jet studies for the IGISOL LIST method and simulation modeling
The IGISOL Laser Ion Source Trap (LIST) is a method in which a supersonic gas jet is used to transport thermalized nuclear reaction products from a gas cell into a sextupole radio frequency ion guide (SPIG) while removing any non-neutral part of the jet by a positively biased repeller electrode. Specific atom species are resonantly re-ionized with laser radiation in the SPIG which enables the study of exotic nuclei without isobaric contamination. In the first part of this work the repelling effect is studied through a series of ion optical Monte-Carlo simulations. The simulations were able to support the hypothesis that the constant collisions between the fast moving buffer gas atoms and the ions provides additional momentum to overcome potential barriers of several tens of volts, explaining the need for high repelling electrode potentials in practice. The simulations were also used to investigate the differences between helium and argon buffer gases and different repelling geometries. The experimental behaviour of the repelling efficiency as a function of repelling potential was qualitatively reproduced. The second part of this work concentrated on the supersonic gas jet formation and the parameters that affect the gas jet properties, in particular the width. For an efficient transportation of atoms from the gas cell to the SPIG the gas jet needs to be well collimated. The gas jet behaviour was investigated with two nozzle shapes and diameters in varying pressure environments by photographing plasma afterglow in the gas expanding from an arc discharge ion guide. It was found that the jet width is strongly dependent on background pressure and independent of the nozzle shape and gas cell pressure. Because the gas jet exhibited a collimated behaviour only with increasing background pressure, a new de Laval type of nozzle was introduced. This nozzle produced a narrow collimated jet structure at background pressures as low as 0.33 mbar. ...
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Fission studies at IGISOL/JYFLTRAP: Simulations of the ion guide for neutron-induced fission and comparison with experimental data Gao, Z.; Solders, A.; Al-Adili, A.; Canete, Laetitia; Eronen, Tommi; Jokinen, A.; Kankainen, Anu; Lantz, M.; Mattera, A.; Moore, Iain; Nesterenko, Dmitrii; Penttilä, Heikki; Pohjalainen, Ilkka; Rakopoulos, V.; Rinta-Antila, Sami; Vilén, Markus; Pomp, S. (EDP Sciences, 2020)For the production of exotic nuclei at the IGISOL facility, an ion guide for neutron-induced fission has been developed and tested in experiments. Fission fragments are produced inside the ion guide and collected using a ...
Experimental studies for the second-forbidden non-unique β-decay of 20F at IGISOL Hukkanen, Marjut (2018)Tähtien evoluution vaiheet perustuvat tähden alkuperäiseen massaan: kevyemmät tähdet, joiden massa on alle kahdeksan Auringon massaa päättävät evoluutionsa valkoisena kääpiönä, kun taas suuremmat tähdet, joiden massa on ...
Fission yield studies with SPIG-equipped IGISOL : a novel method for nuclear data measurements Karvonen, Pasi (University of Jyväskylä, 2010)This thesis work consists of two sections. In the first section, the development of a so-called Laser Ion Source Trap (LIST) device is described. The LIST device is based on a double SPIG (SextuPole Ion Guide) system, ...
Nuclear fission studies with the IGISOL method and JYFLTRAP Gorelov, Dmitry (University of Jyväskylä, 2015)there is no unique model or theory which describes all aspects of this phenomenon. Experimental measurements of nuclear fission product distributions still remains quite a challenging task for modern technologies. In ...
Gas-phase chemistry, recoil source characterization and in-gas-cell resonance laser ionization of actinides at IGISOL Pohjalainen, Ilkka (University of Jyväskylä, 2018)The underlying theme of this thesis focuses on buﬀer gas puriﬁcation and relevant gas-phase ion chemistry which critically aﬀects ion beam purity at gas cell-based radioactive ion beam facilities. The achievement of ...