Search

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 Jyväskyla. 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. [ABSTRACT FROM AUTHOR]

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 demonstrated that an incomplete knowledge of the β-decay of some Tc isotopes could be the source of the systematic discrepancy. Motivated by [1], we have recently measured the β-decay process of some Tc isotopes using a total absorption spectrometer at the IGISOL facility in Jyväskylä. The results of the measurements are discussed, along with their impact on summation calculations. [ABSTRACT FROM AUTHOR]

We have developed a new experimental setup based at the GANIL/SPIRAL facility in Caen, France to measure one-nucleon transfer reactions in inverse kinematics in order to study the evolution of the single particle structure of exotic nuclei. The setup couples together three state-of-the-art detection systems: the TIARA Si array, the large-acceptance magnetic spectrometer VAMOS and the high-efficiency segmented Ge γ-ray array EXOGAM. In a first experiment, the 24Ne(d,p)25Ne reaction has been studied to probe the N=16 shell closure. Details of the setup, data analysis and preliminary results are presented. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The excited states in 146Gd have been re-investigated with the 144Sm(α,2n) reaction using a modern Ge γ-ray array including a polarimeter. Amongst the non-yrast states populated in this reaction we have identified the aligned 6+ member of the two-phonon octupole quartet from the observation of the E3 branching to the one phonon 3- state. Our results represent the first observation of a 6+→3-→0+ E3 cascade in an even-even nucleus. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The TIARA+VAMOS+EXOGAM set-up has recently been installed at GANIL to study the single-particle structure of exotic nuclei. The unique characteristics of the TIARA array, combined with the large acceptance spectrometer VAMOS and the high efficiency Germanium detector array EXOGAM, has allowed high-resolution measurements of transfer reactions in inverse kinematics using low intensity exotic beams. We will describe the experimental set-up, data analysis and preliminary results of the first experiments using a 24Ne beam from SPIRAL, concentrating in particular on the performance of VAMOS that has been used to detect the heavy fragments after the (d,p), (d,d) and (d,t) reactions. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper presents two original direct mass-measurement techniques developed at GANIL using the CSS2 and CIME cyclotrons as high-resolution mass spectrometers. The mass measurement with the CSS2 cyclotron is based on a time-of-flight method along the spiral trajectory of the ions inside the cyclotron. The atomic mass excesses of 68Se and 80Y recently measured with this technique are -53.958(246) MeV and -60.971(180) MeV, respectively. The new mass-measurement technique with the CIME cyclotron is based on the sweep of the acceleration radio-frequency of the cyclotron. Tests with stable beams have been performed in order to study the accuracy of this new mass-measurement method and to understand the systematic errors. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The basic properties of plasma jets emitted by pulsed capillary discharges (PCD) are investigated. The PCD operates with a ∼2 kA, 10 ns current pulse, in argon in the 0.5–100 Torr pressure range. The electron density in the high pressure range, 20–100 Torr is measured with a time resolved Michelson interferometer and in the low pressure range, below 1 Torr, with a fast Langmuir probe. Characteristic values for the electron density are of order of 1017 cm-3, for high pressure operation, and 1014 cm-3, for the lower pressure range. In this limit, the characteristic electron temperature of the plasma jets is found to be in the 10 to 20 eV range. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The excited states in 146Gd have been re-investigated with the 144Sm(α,2n) reaction using a modern Ge γ-ray array including a polarimeter. Amongst the non-yrast states populated in this reaction we have identified the aligned 6+ member of the two-phonon octupole quartet from the observation of the E3 branching to the one phonon 3- state. Our results represent the first observation of a 6+→3-→0+ E3 cascade in an even-even nucleus. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Transfer reactions offer the possibility to study single-particle structure in exotic nuclei, including the structure of ground states, the structure of excited states, and the location and distribution of single particle strength. The last of these means that the evolution of single particle orbitals away from stability, and the consequent changes in shell structure and collectivity, can be studied in detail. The kinematics of transfer reactions initiated by protons and deuterons, in inverse kinematics, have characteristic features that mean a general-purpose design of array can be applied to a wide range of experiments. Due to resolution considerations, coincident gamma-ray detection is highly desirable or even essential. A new silicon detector array called TIARA has been designed so that it can be used together with the segmented germanium detectors of the EXOGAM array. The setup for TIARA is now complete, having been built by several UK groups, and it was recently commissioned by the extended UK-France-Spain collaboration at GANIL. The EXOGAM gamma-ray detectors can be placed as close as 50mm to the target, covering 2/3 of 4π, so as to give the maximum detection efficiency. Simultaneously, the VAMOS magnetic spectrometer can be coupled to the system at zero degrees, to separate the beam from reaction products and give precise energy and angle measurements. The features of TIARA, as presently installed, are described. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]