Search results for "ydinreaktiot"

Fission yield studies with SPIG-equipped IGISOL : a novel method for nuclear data measurements

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, providing the possibility to improve the elemental selectivity of the IGISOL method via highly discriminative laser ionization occurring outside the ion guide. The improved selectivity enables the production of isotopically pure beams. The double SPIG can be used without laser ionization and replaces the conventional skimmer electrode. In this work, the SPIG is compared to the skimmer and is shown to remarkably improve both the efficiency and beam quality of the IGISOL facilit…

Ydinfuusion fysikaaliset perusteet energiantuotannossa ja fuusiolaitteiden kehitys

2016

Kahden atomin, joiden massaluku on alle 60, yhdistymistä yhdeksi atomiksi kutsutaan fuusioksi. Tämän ydinreaktion seurauksena vapautuu valtavasti energiaa ja sen valjastamista ihmiselle hyödyllisen muotoon on tutkittu yli 50 vuoden ajan. Keskeisin tavoite tälle pro gradu -tutkielmalle oli selvittää lämpöydinfuusion fysikaaliset perusteet, minkälaisia merkittäviä läpimurtoja fuusiotutkimuksessa on saavutettu ja toisaalta minkälaisia ratkaisemattomia ongelmia energiantuottoon kykenevän fuusiovoimalan edessä on. Edistysaskelien ja ratkaisemattomien ongelmien osalta keskitytään menestyksekkäimpään koelaitteeseen, tokamakiin. Tähän mennessä erilaisia koejärjestelmiä on ehdotettu useita, mutta to…

Nuclear fission studies with the IGISOL method and JYFLTRAP

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 the present work nuclear fission is studied from the radioactive ion beam production point of view. Some models suggest that the neutron-induced fission can be more favorable for production of neutron-rich nuclides than the proton-induced fission. The general idea of this thesis is to compare all aspects of both approaches in connection with the IGISOL method. A new technique to determine independent fission product yields was suggested for the comparison. This technique has be…

Electron spectroscopy with the SAGE spectrometer

2016

A device called the SAGE (Silicon And GErmanium) spectrometer, designed for in-beam electron spectroscopy, is introduced in this work. A detailed description to the technical aspects of the device is given along with several examples of analytical procedures related to work done with the device. The radial ltering method and veto/add-back algorithms are tools for improving the quality of the electron-gamma data whilst the time-gate selection procedure helps in determining absolute internal conversion coe cients without reference points. Two very di erent types of experiments with results obtained from the electron data are introduced and analysed. Coulomb excitation is used to probe 154Sm a…

γ decay of excited states in 198Rn identified using correlated radioactive decay

1999

The low-lying level structure of the neutron-deficient isotope 198Rn has been studied for the first time, using the 166Er(36Ar,4n) reaction at a beam energy of 175 MeV. Evaporation residues were selected using an in-flight gas-filled separator, RITU, and implanted at the focal plane into a 16-element position-sensitive, passivated ion-implanted planar silicon detector. Prompt γ rays in 198Rn were observed at the target position using the JUROSPHERE array of 24 Compton-suppressed germanium detectors, and were identified by the subsequent radioactive decay of associated recoiling ions in the silicon detector. Isotopic assignments of the nuclei produced were made on the basis of the energy and…

Measurement of an Excess in the Yield of J/ψ at Very Low pT in Pb-Pb Collisions at √sNN = 2.76 TeV

2016

We report on the first measurement of an excess in the yield of J=ψ at very low transverse momentum (pT < 0.3 GeV=c) in peripheral hadronic Pb-Pb collisions at √sNN=2.76  TeV, performed by ALICE at the CERN LHC. Remarkably, the measured nuclear modification factor of J=ψ in the rapidity range 2.5 <y< 4 reaches about 7 (2) in the pT range 0–0.3 GeV=c in the 70%–90% (50%–70%) centrality class. The J=ψ production cross section associated with the observed excess is obtained under the hypothesis that coherent photoproduction of J=ψ is the underlying physics mechanism. If confirmed, the observation of J=ψ coherent photoproduction in Pb-Pb collisions at impact parameters smaller than twice the nu…

Nuclear Data and Experiments for Astrophysics

2022

Nuclear astrophysics aims to understand the origin of elements and the role of nuclear processes in astrophysical events. Nuclear reactions and reaction rates depend strongly on nuclear properties and on the astrophysical environment. Nuclear inputs for stellar reaction rates involve a variety of nuclear properties, theoretical models, and experimental data. Experiments providing data for nuclear astrophysics range from stable ion beam direct measurements to radioactive beam experiments employing inverse kinematics or indirect methods. Many properties relevant for astrophysical calculations, such as nuclear masses and β-decays, have also been intensively studied. This contribution shortly i…

Gauge theory phase diagrams from holography

2014

The science case of the FRS Ion Catcher for FAIR Phase-0

2019

The FRS Ion Catcher at GSI enables precision experiments with thermalized projectile and fission fragments. At the same time it serves as a test facility for the Low-Energy Branch of the Super-FRS at FAIR. The FRS Ion Catcher has been commissioned and its performance has been characterized in five experiments with 238U and 124Xe projectile and fission fragments produced at energies in the range from 300 to 1000 MeV/u. High and almost element-independent efficiencies for the thermalization of short-lived nuclides produced at relativistic energies have been obtained. High-accuracy mass measurements of more than 30 projectile and fission fragments have been performed with a multiple-reflection…

Production cross section and decay study of $^{243}$Es and $^{249}$Md

2019

In the study of the odd-$Z$, even-$N$ nuclei $^{243}$Es and $^{249}$Md, performed at the University of Jyv\"askyl\"a, the fusion-evaporation reactions $^{197}$Au($^{48}$Ca,2$n$)$^{243}$Es and $^{203}$Tl($^{48}$Ca,2$n$)$^{249}$Md have been used for the first time. Fusion-evaporation residues were selected and detected using the RITU gas-filled separator coupled with the focal-plane spectrometer GREAT. For $^{243}$Es, the recoil decay correlation analysis yielded a half-life of $24 \pm 3$s, and a maximum production cross section of $37 \pm 10$ nb. In the same way, a half-life of $26 \pm 1$ s, an $\alpha$ branching ratio of 75 $\pm$ 5%, and a maximum production cross section of 300 $\pm$ 80 nb…