0000000000007612
AUTHOR
A. Nieminen
showing 60 related works from this author
Direct mass measurements of neutron-rich zirconium isotopes up toZr104
2004
Atomic masses of radioactive zirconium isotopes from {sup 96}Zr to {sup 104}Zr have been measured with a relative accuracy of {<=}5x10{sup -7} using a Penning trap coupled to the ion guide isotope separator on-line system. The obtained two-neutron separation energies show strong local correlation in relation to the shape change and shape coexistence between N=58 and 60.
Production of refractory elements close to the Z=N line using the ion-guide technique
1998
Production of neutron-deficient isotopes of refractory elements in the A = 80-88 region was studied using the IGISOL technique and the 165 MeV Si-32 + Ni-nat reaction. Radioactive isotopes of Y through Mo could be produced up to the M-T = + 1 line. New information on the decay of the A = 82 and 85 nuclei, including a more detailed decay scheme and more accurate half-life for Y-82, was obtained. (C) 1998 Elsevier Science B.V. All rights reserved.
Production of neutron deficient rare isotope beams at IGISOL; on-line and off-line studies
2004
This article reports on recent on-line yield measurements employing the light-ion and heavy-ion reaction-based ion guide systems and new results on a-recoil ion transport properties in ion guides with and without electric fields. In addition, the presently used ion guide designs for fusion evaporation reactions are introduced. The present study investigated different schemes for ion extraction from the gas cell. The addition of an extra ring electrode between the traditional skimmer electrode and the exit hole led to transmission independent of the primary beam intensity as opposed to strong intensity dependence observed earlier with the plain skimmer only. Furthermore, the mass resolving p…
Beta decay of $^{56}$Cu
2001
AbstractThe proton-rich isotope 56 Cu was produced at the GSI On-Line Mass Separator by means ofthe 28 Si( 32 S, p3n) fusion–evaporation reaction. Its β -decay properties were studied by detecting β -delayed γ rays and protons. A half-life of 93± 3 ms was determined for 56 Cu. Compared to theprevious work, six new γ rays and three new levels were assigned to the daughter nucleus 56 Ni. Themeasured Gamow–Teller strength values for five 56 Ni levels are compared toshell-model predictions. 2001 Elsevier Science B.V. All rights reserved. PACS: 21.10.-k; 23.40.-s; 21.60.Cs; 27.40.+zKeywords: R ADIOACTIVITY 56 Cu ( β + ) [from 28 Si( 32 S, p3n)]; Measured E γ , I ; Deduced β -intensity and β -st…
Development of a laser ion source at IGISOL
2005
FURIOS, the Fast Universal laser IOn Source, is under development at the IGISOL (Ion Guide Isotope Separator On-Line) mass separator facility in Jyvaskyla, Finland. This new laser ion source will combine a state-of-the-art solid state laser system together with a dye laser system, for the selective and efficient production of exotic radioactive species without compromising the universality and fast release inherent in the IGISOL system. The motivation for, and development of, this ion source is discussed in relation to the programme of research ongoing at this mass separator facility.
Isotope shifts in natural cerium
2003
High resolution crossed beam resonance fluorescence laser spectroscopy has been performed on an atomic beam of naturally occurring cerium, and isotope shifts have been measured in several transitions. Changes in mean square charge radius, δ〈r 2〉, have been extracted using the King plot technique and show the characteristic increase at the N = 82 neutron shell closure. The measurements form the basis for further investigations of radioactive isotopes and isomers on both sides of the shell closure.
Retention of Pb isotopes in glass surfaces for retrospective assessment of radon exposure
2006
Abstract In recent years there has been increasing interest in radio-epidemiological techniques to retrospectively measure the radon dose exposure by determining the activity of 210Pb, the longest-lived 222Rn progeny, in glass surface layers. In this study the diffusion of 39 keV 209Pb+ ions implanted into glass using the IGISOL facility has been studied under conditions that mimic the recoil implantation of 210Pb from 222Rn. The resulting depth distributions of 209Pb were then measured after heat treatment in vacuum at different temperatures by a sputter erosion technique. The diffusion coefficient could be described by an Arrhenius equation D = D0exp(−H/kT) where D 0 = 0.30 - 0.24 + 1.14 …
A new isomer in 125La
1999
Levels in 125La have been studied via β+/EC decay of on-line mass-separated 125Ce using the HIGISOL technique. A new (390 ± 40) ms isomer is definitely attributed to 125La by conversion electron measurements of the 107 keV E3 isomeric transition.
Beam cooler for low-energy radioactive ions
2001
Abstract An ion beam cooler for mass-separated radioactive ion beams has been developed and tested at the IGISOL-type mass separator facility. Technical description and characteristic properties are presented. An energy spread below 1 eV and transmission efficiency of 60% were measured.
The 1+→0+ Gamow–Teller strength of the 58Cug.s.→58Nig.s. transition
2001
The ground-state branch in the beta decay of Cu-58 has been remeasured by using gamma-ray detection combined with ion-guide-based on-line mass separation. The measured value 80.8(7)% is three times more precise and in agreement with the earlier reported value. The deduced Gamow-Teller strength of this transition, to be used for the calibration of the charge-exchange reactions, is 0.0821(7). (C) 2001 Elsevier Science B.V. All rights reserved.
Excited states in 31S studied via beta decay of 31Cl
2006
The beta decay of 31Cl has been studied with a silicon detector array and a HPGe detector at the IGISOL facility. Previously controversial proton peaks have been confirmed to belong to 31Cl and a new proton group with an energy of 762(14) keV has been found. Proton captures to this state at 6921(15) keV in 31S can have an effect on the reaction rate of 30P(p,γ) in ONe novae. Gamma rays of 1249.1(14) keV and 2234.5(8) keV corresponding to the de-excitations of the first two excited states in 31S have been measured. No beta-delayed protons from the IAS have been observed. peerReviewed
Collinear laser spectroscopy of neutron-rich cerium isotopes near theN= 88 shape transition
2003
Laser spectroscopy has been used to measure the isotope shifts of 146Ce and 148Ce relative to 144Ce, Z = 58. The new data, in combination with existing optical data on the stable isotopes and radioactive 144Ce isotope, permits a study of charge radii variations for the even-N Ce nuclei from N = 78 to N = 90. This range covers both the N = 82 shell closure and the N = 88 shape transition region. A marked increase in deformation occurs at N = 88 for elements with Z ≥ 60 but not for those with Z ≤ 56. The new data for Ce (Z = 58) show an intermediate behaviour, resulting in a smooth increase in deformation with Z in the N = 88, 90 region.
Laser spectroscopy of neutron deficient zirconium isotopes
2002
The first optical measurements of the neutron deficient isotopes, 87-89Zr, and also the two long-lived isomers, 87m,89mZr, have been performed using the new technique of collinear laser spectroscopy of cooled, bunched ion beams. Nuclear mean-square charge radii, spins, magnetic moments and quadrupole moments spanning the N = 50 shell closure are reported. The \"kink\" in the charge radii trends at the neutron shell closure is the most pronounced obsd. for any element in the region. [on SciFinder (R)]
Nuclear moments, charge radii and spins of the ground and isomeric states in175Yb and177Yb
2012
This paper reports static moments and changes in mean-square charge radii of 175, 177, 177mYb measured using collinear laser spectroscopy at the IGISOL facility. The moments are compared to predictions made using the Nilsson model to determine the purity of the multi-quasiparticle T1/2 = 11.4 s, Iπ = 8− state of 176Yb and the ground state of 177Yb. The ground-state spins of 175, 177Yb and the T1/2 = 6.41 s, E = 331.5 keV isomeric state in 177Yb, have been measured from the hyperfine structure to be 7/2, 9/2 and 1/2 respectively.
Applications of the total absorption technique to improve reactor decay heat calculations: study of the beta decay of [sup 102,104,105]Tc
2009
The decay heat of the fission products plays an important role in predicting the heat‐up of nuclear fuel after reactor shutdown. This form of energy release is calculated as the sum of the energy‐weighted activities of all fission products P(t) = ΣEiλiNi(t), where Ei is the decay energy of nuclide i (gamma and beta component), λi is the decay constant of nuclide i and Ni(t) is the number of nuclide i at cooling time t. Even though the reproduction of the measured decay heat has improved in recent years, there is still a long standing discrepancy at t∼1000 s cooling time for some fuels. A possible explanation for this disagreement can been found in the work of Yoshida et al. [1], who demonst…
The shape transition in the neutron-rich yttrium isotopes and isomers
2007
Abstract Laser spectroscopy has been used to study 86–90,92–102Y and isomeric states of 87–90,93,96,97,98Y. Nuclear charge radii differences, magnetic dipole and electric quadrupole moments have been obtained. Information on the nature of the Z ≈ 40 , N ≈ 60 sudden onset of deformation has been derived from all three parameters. It is seen that with increasing neutron number from the N = 50 shell closure that the nuclear deformation becomes increasingly oblate and increasingly soft. At N = 60 a transition to a strongly deformed rigid prolate shape occurs but prior to this, although the nuclear deformation is increasing with N, a proportionate increase in softness is also observed.
Studying exotic nuclides close to the N = Z line at the HIGISOL facility
2003
The ion guide [1, 2] for heavy-ion fusion-evaporation reactions (HIGISOL) which was developed by Beraud et al. [3] has been implemented at the IGISOL facility in Jyvaskyla [4]. This system was modified over the past 5 years. Figure 1 shows the present set-up. The HIGISOL takes advantage of the different angular distributions of primary beam and reaction products: the primary beam is stopped in front of the stopping chamber and the reaction products enter the stopping chamber through a thin foil passing the beam stop. This so called “shadow” method removes the plasma effect since the primary beam is not ionising the stopping gas. In order to improve ion optical properties, mainly to reduce t…
R-matrix analysis of theβdecays ofN12andB12
2010
The β decays of 12N and 12B have been studied at KVI and JYFL to resolve the composition of the broad and interfering 0+ and 2+ strengths in the triple-α continuum. For the first time a complete treatment of 3α decay is presented including all major breakup channels. A multilevel, many-channel R-matrix formalism has been developed for the complete description of the breakup in combination with the recently published separate analysis of angular correlations. We find that, in addition to the Hoyle state at 7.65 MeV, more than one 0+ and 2+ state is needed to reproduce the spectra. Broad 03+ and 22+ states are found between 10.5 and 12 MeV in this work. The presence of β strength up to the 12…
Beta-decay half-lives of $^{70}$Kr and $^{74}$Rb
2000
Abstract Beta-decay half-lives of two nuclei close to N = Z line, 70 Kr and 74 Rb, have been measured at the ISOLDE mass-separator facility at CERN. Importance of these half-lives on two ingredients explaining existence and development of the Universe, the astrophysical nucleosynthesis and the Standard Model, are discussed.
A radio frequency ring electrode cooler for low-energy ion beams
2004
We are investigating a new concept for ion confinement while buffer-gas-cooling low-energy ion beams. Instead of applying the well-established technique of Radio Frequency Quadrupoles (RFQs) where the ions are transversely confined by a quadratic-pseudo potential we are using a stack of thin ring electrodes supplied by an RF field (RF funnel) which creates a box-shaped potential well. In Monte Carlo simulations we have investigated the transmission behavior and cooling performance of the RF funnel. First experimental investigations with ion currents up to 20 nA revealed a promising transmission characteristic which qualifies the RF funnel as high-current cooler.
β-decay data requirements for reactor decay heat calculations: study of the possible source of the gamma-ray discrepancy in reactor heat summation ca…
2007
The decay heat of fission products plays an important role in predictions of the heat up of nuclear fuel in reactors. The released energy is calculated as the summation of the activities of allfission products P(t) = Ei λi Ni(t), where Ei is the decay energy of nuclide i (gamma and beta component), λi is the decay constant of nuclide i and Ni(t) is the number of nuclide i at cooling time t. Even though the reproduction of the measured decay heat has improved in recent years, there is still a long standing discrepancy in the t ∼ 1000s cooling time for some fuels. A possible explanation to this improper description has been found in the work of Yoshida et al. (1), where it has been shown that…
Medium-spin structure of neutron-rich Pd and Cd isotopes
2003
Cadmium isotopes are traditionally considered as good examples of nearly spherical, vibrational nuclei, which can be described by quadrupole vibrators in the collective model, as well as the U(5) dynamical symmetry in the interacting boson model (IBM). However, the shape coexistence of more deformed intruder states originating from proton 2p–4h excitation across the Z = 50 major shell is another interesting structural aspect, whose presence in Pd-isotopes has also been demonstrated [1,2].
Beta decay of neutron-rich 118Rh and the lowest excited states in 118Pd
2000
Beta decay of a refractory isotope 118Rh produced in symmetric fission and mass separated by the ion guide technique has been applied for the study of low-lying excited states of 118Pd. The yrast band in 118Pd has been observed up to a 6+ state and the lowest states of the asymmetric γ-band have been identified. The measured half-life of 118Rh is (300±60)ms. The systematics of the excited states in neutron-rich Pd-isotopes implies the saturation towards an O(6) symmetry at N = 70.
Transport of ions in ion guides under flow and diffusion
2000
Abstract A model for ion transport simulations in the ion guide stopping chamber is introduced. Computed transport time distributions are compared to the experimental data obtained in on- and off-line conditions. It is shown that millisecond transport times are feasible and that diffusion of ions is an important mechanism in transport.
On-Line Ion Cooling and Bunching for Collinear Laser Spectroscopy
2002
A new method has been developed for increasing the sensitivity of collinear laser spectroscopy. The method utilizes an ion-trapping technique in which a continuous low-energy ion beam is cooled and accumulated in a linear Paul trap and subsequently released as a short ( $10--20\ensuremath{\mu}\mathrm{s}$) bunch. In collinear laser measurements the signal-to-noise ratio has been improved by a factor of $2\ifmmode\times\else\texttimes\fi{}{10}^{4}$, allowing spectroscopic measurements to be made with ion-beam fluxes of $\ensuremath{\sim}50\mathrm{ions}{\mathrm{s}}^{\ensuremath{-}1}$. The bunching method has been demonstrated in an on-line isotope shift and hyperfine structure measurement on r…
Laser spectroscopy of cooled zirconium fission fragments
2002
The first on-line laser spectroscopy of cooled fission fragments is reported. The $^{\mathrm{96}\mathrm{--}\mathrm{102}}\mathrm{Z}\mathrm{r}$ ions, produced in uranium fission, were extracted and separated using an ion guide isotope separator. The ions were cooled and bunched for collinear laser spectroscopy by a gas-filled linear Paul trap. New results for nuclear mean-square charge radii, dipole, and quadrupole moments are reported across the $N=60$ shape change. The mean-square charge radii are found to be almost identical to those of the Sr isotones and previously offered modeling of the radial changes is critically reviewed.
βdecay of neutron-rich118Agand120Agisotopes
2003
$\ensuremath{\beta}$ decays of on-line mass-separated neutron-rich ${}^{118}\mathrm{Ag}$ and ${}^{120}\mathrm{Ag}$ isotopes have been studied by using $\ensuremath{\beta}\ensuremath{-}\ensuremath{\gamma}$ and $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence spectroscopy. Extended decay schemes to the ${}^{118,120}\mathrm{Cd}$ daughter nuclei have been constructed. The three-phonon quintuplet in ${}^{118}\mathrm{Cd}$ is completed by including a new level at 2023.0 keV, which is tentatively assigned the spin and parity of ${2}_{4}^{+}.$ The intruder band in ${}^{118}\mathrm{Cd}$ is proposed up to the ${4}^{+}$ level at 2322.4 keV. The measured $\ensuremath{\beta}$-decay half…
Laser spectroscopy of radioactive Ti, Zr and Hf isotopes and isomers at the JYFL laser-IGISOL facility
2003
Abstract The recent progress at the laser-ion guide isotope separator on-line facility, JYFL, is presented. At the facility new techniques for studying short-lived radioisotopes by laser spectroscopy have been developed and applied to the study of isotopes in refractory metal elements. In particular, recent results on the spectroscopy of cooled ion beams of radioactive Ti, Zr and Hf isotopes are discussed.
The β-decay approach for studying 12C
2008
6 pags., 3 figs. -- 9th International Conference on Clustering Aspects of Nuclear Structure and Dynamics (CLUSTERS'07) 3–7 September 2007, Stratford upon Avon, UK
Reactor Decay Heat inPu239: Solving theγDiscrepancy in the 4–3000-s Cooling Period
2010
The {beta} feeding probability of {sup 102,104,105,106,107}Tc, {sup 105}Mo, and {sup 101}Nb nuclei, which are important contributors to the decay heat in nuclear reactors, has been measured using the total absorption technique. We have coupled for the first time a total absorption spectrometer to a Penning trap in order to obtain sources of very high isobaric purity. Our results solve a significant part of a long-standing discrepancy in the {gamma} component of the decay heat for {sup 239}Pu in the 4-3000 s range.
Influences on the triple alpha process beyond the Hoyle state
2010
7 pags., 3 figs. -- International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos - IX, 25-30 June 2006, CERN
On the decrease in charge radii of multi-quasi particle isomers
2007
Abstract We report changes in mean-square charge radii, δ 〈 r 2 〉 , magnetic moments and quadrupole moments for three multi-quasi particle isomers; 97m2Y, 176mYb and 178m1Hf. All the isomers are observed to display a decrease in 〈 r 2 〉 compared to the lower-lying nuclear state on which the isomer is built. The decreases in 〈 r 2 〉 occur despite the isomers showing increases in quadrupole moment. Possible mechanisms for the effect, which is now seen for six multi-quasi particle isomers, are discussed.
Character of an 8− isomer of 130Ba
2002
Abstract The static moments and isomer shift of the J π = K π =8 − isomeric state in 130 56 Ba have been measured using the technique of collinear laser spectroscopy. The isomer has been found to have a magnetic dipole moment of −0.043(28) μ N and a static quadrupole moment of +2.77(30) b. These values have been used to assign the state as a two neutron 7 2 + [404]⊗ 9 2 − [514] configuration corresponding to a prolate shape. The half-life of the isomer has been confirmed as 9.54(14) ms. The change in the mean square charge radius was found to be 〈 r 2 〉 130m −〈 r 2 〉 130g–s =−0.0473(30) fm 2 .
High-resolution studies of beta-delayed proton emitters at IGISOL facility
1998
Beta-decays of23Al and41Ti have been studied by applying ion guide techniques, gamma detection and a gas-Si telescope for charged-particle detection. The experimental beta-decay strength of41Ti was found to be quenched by a factor ofq2 = 0.64 compared to our shell model calculations below 8 MeV excitation energy in41Sc. This result is in line with the generally accepted value ofq = 0.77. The isobaric analogue state of the41Ti ground state was measured to contain 10(8)% isospin impurity. This relatively high value could be well reproduced by the shell model calculation in thesdfp space. Gamma-decay of theT = 3/2 isobaric analogue state in23Mg was observed together with its decay by proton em…
Status of HIGISOL a new version equipped with SPIG and electric field guidance
2001
A new HIGISOL chamber devoted to the study of short-lived products from heavy-ion-induced fusion-evaporation reactions is proposed. It enables, via the extraction of ions by means of a SPIG (SextuPole rf Ion Guide), to improve the mass resolving power by a factor 2.5 compared to the previous system using a skimmer-ring assembly. The gas cell was also equiped with an electric field for faster transportation of recoiling ions to the nozzle where they are ejected with the gas jet. The first results obtained both with a radioactive α-source and cyclotron beam will be reported.
Time Characteristics of the Ion Beam Cooler-Buncher at JYFL
2001
A beam cooler for low-energy ion beams was constructed to improve the ion optical properties of radioactive ion beams produced at the IGISOL facility in Jyvaskyla. The beam cooler is a buffer gas filled RF-quadrupole. The delay properties and the possibility to accumulate a continuous IGISOL beam and release it in short bunches is discussed.
Collinear laser spectroscopy of radioisotopes of zirconium
2003
Isotope shifts and hyperfine structures have been measured for radioisotopes of ionic zirconium using on-line laser spectroscopy at the IGISOL facility in Jyvaskyla, where the installation of an ion beam cooler/buncher has significantly improved the experimental sensitivity. Measurements have been made on all the neutron-deficient isotopes from 87Zr to 90Zr, including the isomers 87m,89mZr, and the neutron-rich isotopes from 96Zr to 102Zr. The change in mean square charge radii between the isotopes and the nuclear moments of the odd isotopes have been extracted. The data show a sudden increase in the mean square charge radius at mass A = 100, consistent with an onset of nuclear deformation …
Improvements on Decay Heat Summation Calculations by Means of Total Absorption Gamma-ray Spectroscopy Measurements
2011
The decay heat of fission products plays an important role in predictions of the heat released by nuclear fuel in reactors. In this contribution we present results of the analysis of the measurement of the beta decay of some refractory isotopes that were considered possible important contributors to the decay heat in reactors. The measurements presented here were performed at the IGISOL facility of the University of Jyvaeskylae, Finland. In our measurements we have combined for the first time a Penning trap (JYFLTRAP), which was used as a high resolution isobaric separator, with a total absorption spectrometer. The results of the measurements as well as their consequences for decay heat sum…
Nuclear charge radii of neutron deficient titanium isotopes44Ti and45Ti
2004
Optical isotope shifts of the unstable 44,45Ti isotopes, as well as those of stable 46−50Ti, have been investigated by collinear laser spectroscopy on fast ion beams using an ion guide isotope separator with a cooler-buncher. Changes in mean square charge radii across the neutron 1f7/2 shell are deduced. The evolution of the even-N Ti nuclear radii shows a generally increasing tendency with decreasing neutron number. This behaviour is significantly different to that of the neighbouring Ca isotopes which exhibit a symmetric parabolic behaviour across the shell. The trend of the Ti nuclear radii is consistent with the predictions of the relativistic mean-field theory. The charge radius of 44T…
β-decay ofO13
2005
The beta decay of O-13 has been studied at the IGISOL facility of the Jyvaskyla accelerator centre (Finland). By developing a low-energy isotope-separated beam of O-13 and using a modern segmented charged-particle detector array an improved measurement of the delayed proton spectrum was possible. Protons with energy up to more than 12 MeV are measured and the corresponding log(ft) values extracted. A revised decay scheme is constructed. The connection to molecular states and the shell model is discussed.
New levels in 118Pd observed in the beta-decay of very neutron-rich 118Rh isotope
2006
We investigate the β decay of very neutron-rich 118Rh isotope using on-line mass-separated sources which are produced by applying 25 MeV proton induced symmetric fission of natural uranium at the IGISOL facility. The β–γ and γ–γ coincidence spectroscopy is employed to establish the level scheme of daughter nucleus 118Pd. Five low-lying new levels are identified for the first time with tentative spin and parity assignments based on the even-mass Pd systematics.
Nuclear moments and charge radii of the171Hf ground state and isomer
2000
The magnetic moment, quadrupole moment and mean-square charge radial changes, relative to 172Hf, have been measured for the 171Hf ground state and the ½-[521] isomeric state, using on-line laser spectroscopy. The magnetic moments of the isomer and ground states are found to be + 0.526(16)µn and -0.674(12)µn, respectively. The spectroscopic quadrupole moment of the ground state is found to be +3.463(27) b. No change in mean-square charge radius is observed between the ground state and isomeric state. The observation of an inversion in the odd-even staggering at 171Hf is consistent with the suggested deformation trends.
Isomeric state of 80Y and its role in the rp-process
2003
The HIGISOL facility has been used to investigate carefully the isomeric transition 228.5 keV in 80Y. We have measured the electron internal conversion coefficient for this transition αK = 0.50 ± 0.07 which gives the value for half-life of “bare” isomeric state T 1/2 = 6.8 ± 0.5 s. The isomeric state should play an important role in the rp-process calculations.
Nuclear charge radii and electromagnetic moments of radioactive scandium isotopes and isomers
2011
International audience; Collinear laser spectroscopy experiments with the Sc + transition 3d4s 3 D 2 → 3d4p 3 F 3 at λ = 363.1 nm were performed on the 42−46 Sc isotopic chain using an ion guide isotope separator with a cooler-buncher. Nuclear magnetic dipole and electric quadrupole moments as well as isotope shifts were determined from the hyperfine structure for five ground states and two isomers. Extensive multi-configurational Dirac-Fock calculations were performed in order to evaluate the specific mass-shift, M SMS, and field-shift, F, parameters which allowed evaluation of the charge radii trend of the Sc isotopic sequence. The charge radii obtained show systematics more like the Ti r…
Cooling and bunching of ion beams for collinear laser spectroscopy
2003
A greatly increased sensitivity in collinear laser spectroscopy experiments has been achieved by the application of new on-line ion cooling and bunching techniques. Cooling of a low-energy ion beam to low emittance and low velocity spread is shown to increase the peak efficiency while bunching the beam results in highly efficient background suppression.
Breakup channels forC12triple-αcontinuum states
2009
The triple-alpha-particle breakup of states in the triple-alpha continuum of C-12 has been investigated by way of coincident detection of all three alpha particles of the breakup. The states have been fed in the beta decay of N-12 and B-12, and the alpha particles measured using a setup that covers all of the triple-alpha phase space. Contributions from the breakup through the Be-8(0(+)) ground state as well as other channels-interpreted as breakup through excited energies in Be-8-have been identified. Spins and parities of C-12 triple-alpha continuum states are deduced from the measured phase-space distributions for breakup through Be-8 above the ground state by comparison to a fully symme…
First Precision Mass Measurements of Refractory Fission Fragments
2005
Atomic masses of 95-100Sr, 98-105Zr, and [corrected] 102-110Mo and have been measured with a precision of 10 keV employing a Penning trap setup at the IGISOL facility. Masses of 104,105Zr and 109,110Mo are measured for the first time. Our improved results indicate significant deviations from the previously published values deduced from beta end point measurements. The most neutron-rich studied isotopes are found to be significantly less bound (1 MeV) compared to the 2003 atomic mass evaluation. A strong correlation between nuclear deformation and the binding energy is observed in the two-neutron separation energy in all studied isotope chains.
TAS measurements for reactor physics and nuclear structure
2011
In this contribution we will present recent total absorption measurements of the beta decay of neutron‐rich nuclei performed at the IGISOL facility of the Univ. of Jyvaskyla. In the measurements the JYFL Penning Trap was used as a high resolution isobaric separator. The total absorption technique will be described and the impact of recent results in the fields of reactor physics (decay heat calculations) and nuclear structure will be discussed.
Ground-state spin of 59Mn
2001
Beta decay of $^{59}$Mn has been studied at PSB-ISOLDE, CERN. The intense and pure Mn beam was produced using the Resonance Ionization Laser Ion Source (RILIS). Based on the measured $\beta$-decay rates the ground-state spin and parity are proposed to be $J^{\pi}$ = 5/2$^{-}$. This result is consistent with the systematic trend of the odd-A Mn nuclei and extends the systematics one step further towards the neutron drip line.
JYFLTRAP: a cylindrical Penning trap for isobaric beam purification at IGISOL
2004
Abstract A Penning trap has been installed for isobaric beam purification at the IGISOL-facility at the University of Jyvaskyla. In this paper, the technical details of this new device together with results of the first tests are presented. The mass resolving power, depending on the excitation parameters and the ion species, can be as high as 145 000 and the total transmission has been determined to be 17%. In addition, it is shown that with this experimental setup it is possible to measure atomic masses up to A=120 with accuracies of approximately 50 keV .
Penning trap at IGISOL
2002
The IGISOL facility [1] at the Department of Physics of the University of Jyvaskyla (JYFL) is delivering radioactive beams of short-lived exotic nuclei, in particular the neutron-rich isotopes from fission reaction. These nuclei are studied with the nuclear and collinear laser spectroscopy methods. In order to obtain a meaningful increase, in comparison to a standard level, of precision and sensitivity of such studies an improvement of the radioactive beam quality is necessary. This improvement will be achieved due to a radioactive beam handling which consists of three steps: beam cooling, bunching and (isobaric) purification. The latter means a possibility of obtaining a pure monoisotopic …
Non-analog β decay of 74Rb
2001
The magnitude of the Coulomb mixing parameter δ 1 has been experimentally deduced, for the first time, for the β decay of 74 Rb. The estimated magnitude is derived from the feeding of the non-analog first excited 0 + state in 74 Kr. The inferred upper limit of 0.07% is small compared to theoretical predictions. The half-life was measured to be 64.90(9) ms. 2001 Published by Elsevier Science B.V.
A new pulsed release method for element selective production of neutron rich isotopes near 208Pb
1998
Abstract A new method to reduce the isobaric contamination problem for the production of neutron rich Bi, Pb and Tl nuclei at on-line mass separators, based on the pulsed release of these radioactive species, is presented. The results of a feasibility study are reported.
Total absorption study of theβdecay of102,104,105Tc
2013
The $\ensuremath{\beta}$-feeding probabilities for three important contributors to the decay heat in nuclear reactors, namely ${}^{102,104,105}$Tc, have been measured using the total absorption spectroscopy technique. For the measurements, sources of very high isobaric purity have been obtained using a Penning trap (JYFLTRAP). A detailed description of the data analysis is given and the results are compared with high-resolution measurements and theoretical calculations.
The first cooled beams from JYFL ion cooler and trap project
2002
Abstract A ion manipulation scheme employing a linear radiofrequency quadrupole and a Penning trap is described. It provides means to improve emittance, cool, bunch and mass-purify the existing ion beams from an Ion Guide Isotope Separator while preserving its fast operation. The ion beam cooler is operational and capable to cool ion beam down to eV regime in few ms with at least 60 percent transmission.
Isomeric state of $^{80}$Y and its role in the astrophysical rp-process
2001
5 pages, 7 figures.-- PACS nrs: 21.10.Tg; 23.20.Nx; 27.50.+e.
Wien filter for cooled low-energy radioactive ion beams
2002
A Wien filter for cooled radioactive ion beams has been designed at Ion Guide Isotope Separator On Line technique (IGISOL). The purpose of such device is to eliminate doubly charged ions from the mass separated singly charged ions, based on q=+2→q=+1 charge exchange process in an ion cooler. The performance of the Wien filter has been tested off-line with a discharge ion source as well as on-line with a radioactive beam. The electron capture process of cooled q=+2 ions has been investigated in a radiofrequency quadrupole ion cooler with varying partial pressures of nitrogen. Also, the superasymmetric fission production yields of 68<A<78 nuclei have been deduced.
Collinear laser spectroscopy of ZrII
2003
A new technique involving collinear laser spectroscopy of ion bunches has been used to study the radio-isotopes 87,87m,88,89,89m Zr.
Production of neutron-rich isotopes in fission of uranium induced by neutrons of 20 MeV average energy
2000
In the context of a parameter study conducted by several laboratories for future European radioactive beam facilities based on fast-neutron induced fission, in particular for the SPIRAL-II project at GANIL, we have measured the yields of neutron-rich isotopes in the mass range of 88 to 144. These nuclei were obtained as fission products of natural uranium bombarded by neutrons of 20 MeV average energy emitted by a thick carbon target irradiated by 50 MeV deuterons. Yields have been measured using on-line mass separation with the ion-guide method. Compared with proton-induced fission at 25 MeV the magnitude of cross-sections, except for the symmetric region, is similar. Z-distributions of is…
Status of the ion trap project at IGISOL
2001
The IGISOL fa ility at the Department of Physi s of the University of Jyväskylä (JYFL) is delivering radioa tive beams of short-lived exoti nu lei, in parti ular the neutron-ri h isotopes from the ssion rea tion. These nu lei are studied with the nu lear spe tros opy methods. In order to substantially in rease the quality and sensitivity of su h studies the beam should undergo beam handling: ooling, bun hing and isobari puri ation. The rst two pro esses are performed with the use of an RFQ ooler/bun her. The isobari puri ation will be made by a Penning trap pla ed after the RF- ooler element. This ontribution des ribes the urrent status of the ion trap pro je t and its future prospe ts. The…