[en] The advent of efficient recoil separator devices coupled to large arrays of germanium detectors and versatile focal plane detection systems has in recent years allowed a wealth of spectroscopic information to be obtained for transfermium nuclei. At the Department of Physics at the University of Jyvaeskylae, the RITU gas-filled separator is employed in conjunction with the GREAT focal plane spectrometer and the JUROGAM array of germanium detectors. Whilst initial studies using these devices concentrated on even-even nuclei, more recent experiments have attempted to study single-particle properties by examining the structure of odd-mass nuclei and multi-quasiparticle states. An overview of the instrumentation used and highlights from the recent experimental campaigns is presented

[en] The addition of modern arrays of silicon and germanium detectors at the target and focal plane positions of recoil separators has led to a wealth of new spectroscopic data concerning the structure of heavy elements. A particular region of interest has been that of the deformed nuclei close to the N=152 subshell gap. Both detailed decay and in-beam spectroscopic studies have provided complementary data on the location and ordering of single-particle states for proton number in the region of Z=100 and neutron number N=152. Instrumentation developments have allowed in-beam studies to be carried out at the unprecedented level of 20 nanobarns. The future prospects for such studies are also bright - new facilities employing high intensity stable beams are under construction and should yield lead to more significant results over the next decade. Additional long-term interest comes from the advent of next generation radioactive beam facilities which may allow limited studies in the heavy element region to be carried out.

[en] Throughout the history of nuclear structure studies, searches for new phenomena have been carried out at the extremes. These extremes can be described in terms of nuclear excitation energy, spin, or in terms of proton or neutron number through the production of exotic nuclei far from stability. One extreme which has always been a centre for activity is that of mass and proton number - the desire to create new chemical elements and understand their nuclear structure. New elements up to proton number Z = 118 have been created in the laboratory, but by nature these experiments cannot provide extensive information concerning nuclear structure. The extremely small production cross sections only allow a handful of atoms to be produced in a particular experiment. Over the past decade or so, experimental techniques have been developed which now allow detailed nuclear structure studies of nuclei with proton number Z of over 100. The current status of the field and some recent highlights from these studies are reviewed.

[en] The study of heavy and superheavy elements has always been one of the cornerstones of nuclear physics studies. These studies are driven by a desire to create new elements and to determine the limits of nuclear stability. Current experiments to synthesize new elements aim at the fabled ‘Island of Stability’ which should be found in the region of the next ‘magic’ numbers for protons and neutrons beyond Z = 82 and N = 126 (²⁰⁸Pb). The island is predicted to be around proton number 114–126 and neutron number 184. In recent years, another approach to understanding heavy nuclear systems has gained momentum, whereby nuclei with a much lower proton number of around 100 are studied in detail. The motivation for and results of such studies will be presented. (paper)

[en] Isomeric states in ²⁵⁴No were investigated using a calorimetric method. Two different isomers were found with half-lives of T_1/2 266±2 ms and T_1/2 = 184±3μs, respectively. The dominant decay path of the 184μs isomer proceeds via states feeding the longer-lived 266 ms isomer. The 266 ms isomer in turn decays via a two-quasi-particle K = 3 band to the ground-state band. The full decay path was observed with the GREAT spectrometer located at the focal plane of the gas-filled separator RITU at the Accelerator Laboratory in Jyvaeskylae. This work sheds light on the two-quasi-particle structure in this transfermium nucleus

[en] The ground-state yrast band in ¹⁷⁶Hg has been observed up to I=10(ℎ/2π) by using the recoil decay tagging (RDT) method. The irregularity of this band indicates that the prolate intruder band, seen in the heavier Hg isotopes near the neutron mid-shell, crosses the nearly spherical ground-state band of ¹⁷⁶Hg above I=6(ℎ/2π)

[en] A comprehensive Geant4 simulation was built for the SAGE spectrometer. The simulation package includes the silicon and germanium detectors, the mechanical structure and the electromagnetic fields present in SAGE. This simulation can be used for making predictions through simulating experiments and for comparing simulated and experimental data to better understand the underlying physics.

[en] The SAGE spectrometer combines a high-efficiency γ-ray detection system with an electron spectrometer. Some of the design features have been known to be problematic and surprises have come up during the early implementation of the spectrometer. Tests related to bismuth germanate Compton-suppression shields, electron detection efficiency and an improved cooling system are discussed in the paper. (paper)

[en] During an experiment at Jyvaeskylae laboratory involving a 27 MeV α beam on a thick ¹⁵⁴Sm target, γ-spectroscopy of ¹⁵⁶Gd was performed using JUROGAM HPGe multidetector array. We will present here experimental results concerning positive parity bands of this nucleus. Level scheme was enriched with more than ten new transitions as well as a new level in a band observed recently.

[en] Very neutron deficient uranium isotopes were produced in fusion evaporation reactions using ⁴⁰Ar ions on ¹⁸²W targets. The gas-filled recoil separator RITU was employed to collect the fusion products and to separate them from the scattered beam and other reaction products. The activities were implanted into a position sensitive silicon detector after passing through a gas-counter system. The isotopes were identified using spatial and time correlations between the implants and the decays. Two α-decaying states, with E_α=(8612±9) keV and T_1/2=(0.51_-0.10^+0.17) ms for the ground state and E_α=(10678±17) keV and T_1/2=(0.56_-0.14^+0.26) ms for an isomeric state, were identified in ²¹⁸U. In addition, the half-life and α-decay energy of ²¹⁹U were measured with improved precision. The measured decay properties deduced for ²¹⁸U suggest that there is no subshell closure at Z=92