Tokai Radioactive Ion Accelerator Complex (TRIAC)

An ISOL-based radioactive nuclear beam (RNB) facility, Tokai Radioactive Ion Accelerator Complex (TRIAC), has been jointly developed by High Energy Accelerator Research Organization (KEK) and Japan Atomic Energy Agency (JAEA). The facility started to supply RNBs for experiments in 2005 and RNBs including fission fragments with energies up to 1.1MeV/A are available in the present. Several experimental studies were performed successfully using ⁸Li beams with various energies.     

Towards direct mass measurements of nobelium at SHIPTRAP

The Penning-trap mass spectrometer SHIPTRAP allows precision mass measurements of rare isotopes produced in fusion-evaporation reactions. In the first period of operation the masses of more than 50 neutron-deficient radionuclides have been measured. In this paper the perspectives for direct mass measurements of rare isotopes around nobelium are discussed and the achievable precision is addressed. The temporal stability of the magnetic field, an important issue for the long measurement times resulting from the low production rates, was investigated and the time-dependent uncertainty due to magnetic field fluctuations was determined. Based on the present performance direct mass measurements of nobelium isotopes are already feasible. With several technical improvements heavier elements between Z=102–105 will be in reach.     

Precision mass measurements of radioactive nuclei at JYFLTRAP

The Penning trap mass spectrometer JYFLTRAP was used to measure the atomic masses of radioactive nuclei with an uncertainty better than 10 keV. The atomic masses of the neutron-deficient nuclei around the line were measured to improve the understanding of the rp-process path and the SbSnTe cycle. Furthermore, the masses of the neutron-rich gallium ( ) to palladium ( ) nuclei have been measured. The physics impacts on the nuclear structure and the r-process paths are reviewed. A better understanding of the nuclear deformation is presented by studying the pairing energy around .     

Independent fission yields with JYFLTRAP

A novel method to determine independent yields in proton induced fission employing ion counting after a Penning trap has been developed. A satisfactory agreement with previous measurements was found for independent yields of Cs isotopes in 50 MeV proton induced fission.     

Commissioning of the MAGNEX large-acceptance spectrometer

The MAGNEX large-acceptance spectrometer has been commissioned with beams from the Tandem accelerator at INFN-LNS Catania. The optics were tested with elastically-scattered ⁷Li, ¹⁶O and ⁴⁸Ti beams with various apertures mounted after the target. The momentum dispersion was verified to be in agreement with the optics calculations. A demonstration of the particle identification capabilities of the PSD start detector and the focal plane detector was given by a measurement of the ²⁷Al(⁷Li,⁶Li)²⁸Al transfer reaction at a mean angle of 25°. The measured charge state distribution of ⁴⁸Ti ions is in agreement with predictions for a gold stripping foil. Preliminary results of the software reconstruction of incident angle and excitation energy, obtained through matrices based on a 3D-interpolation of the measured field maps, are encouraging.     

Carbon-cluster mass calibration at SHIPTRAP

A carbon-cluster ion source has been installed and tested at SHIPTRAP, the Penning-trap mass spectrometer for precision mass measurements of heavy elements at GSI. Carbon-cluster ions ¹²C_n ⁺, 5 ≤n ≤23, were produced by laser-induced desorption and ionization from a carbon sample. They were tested for the first time as reference ions in an on-line mass measurement of the radionuclides ¹⁴⁴Dy, ¹⁴⁶Dy and ¹⁴⁷Ho. In addition, carbon clusters of various sizes were used for an investigation of the systematic uncertainty of SHIPTRAP covering a mass range from 84 u to 240 u. The mass-dependent uncertainty was found to be negligible for the case of (m-m _ref)< 100 u. However, a systematic uncertainty of 4.5 ×10^-8 was revealed.     

On the spectroscopy of atomic electrons (positrons)in the energy range of 10 to 50 MeV from heavy-ion collisions at intermediate energies

The feasibility of the spectroscopy of dynamically ionized electrons (positrons) from heavy-ion collisions at intermediate energies, e.g. Pb+Pb at 60 AMeV has been studied. We propose a magnetic toroid spectrometer for lepton spectroscopy in an energy range between 5 and 50 MeV. Special emphasis was laid on large solid angles, on broad-band characteristics and on a good suppression of secondary events. The device is a versatile compact-size instrument for lepton detection in in-beam experiments at a moderate energy resolution of %. Received: 28 December 1999 / Accepted: 29 March 2000     

An RF quadrupole–time-of-flight system for isobar-separation and multiplexed low-energy Rare-Isotope Beam experiments

A novel system consisting of RF quadrupole and time-of-flight sections is proposed, in which ions can be cooled, bunched, mass separated with a resolution sufficient to differentiate between isobars, and guided to different experimental setups, e.g. for precision mass measurements or mass-resolved decay spectroscopy. It enables multiplexed operation of several connected experiments and interleaved measurements using different nuclides in one connected experiment. Such a system could be employed advantageously at in-flight facilities, at which experiments with stopped exotic nuclei are made possible using gas-filled stopping cells, such as SHIPTRAP at GSI, or potentially at ISOL facilities. First results for individual stages of the system are presented.     

The heavy-ion magnetic spectrometer PRISMA

PRISMA is a magnetic spectrometer installed at Laboratori Nazionali di Legnaro (Italy) and designed for A=100–200, E=5–10 MeV-per-nucleon beams, and for possible use with the proposed radioactive beam facility SPES. The foremost features of the instrument are presented, along with the outline of two data analyses exemplifying the effectiveness of PRISMA-CLARA in studies of reaction dynamics.     

Characterization of a miniature Paul-Straubel trap

Frequency standard applications and ultra-high resolution spectroscopy of a confined single ion require traps of drastically reduced dimensions (about or below 1 mm). These small dimensions increase the sensitivity of the trapping behavior to imperfections in the trap geometry and to patch potentials. For the aim of the metrological laser interrogation of a single Ca⁺ ion, a miniature cylindrical ring trap was built. In order to optimize the laser cooling process and to reach strong binding conditions, the boundaries of the stability diagram and the zones of low confinement as well as the ion motion properties were characterized. Received 14 November 2000 and Received in final form 1st February 2001     

The HERMES Recoil Detector

The HERMES Collaboration installed a new Recoil Detector to upgrade the existing spectrometer to study hard exclusive processes which provide access to generalised parton distributions (GPDs) and hence to the orbital angular momentum of quarks. The HERMES Recoil Detector mainly consists of three components: a silicon detector surrounding the target cell inside the beam vacuum, a scintillating fibre tracker and a photon detector with three layers of tungsten and scintillator bars in three different orientations. All three detectors are located inside a solenoidal magnet which provides a 1T longitudinal magnetic field. The Recoil Detector was installed in January 2006 and data taking will last until July of 2007.     

Analysis of solids by secondary ion and sputtered neutral mass spectrometry

A mass spectrometer is described, which allows the analysis of sputtered neutral and charged particles as well as of residual gas composition. This combined SIMS, SNMS, and RGA instrument consists of a scanning primary ion beam column, an electron impact ionizer, an electrostatic energy filter and an rf quadrupole mass analyzer.Various examples of surface and bulk analysis are presented which demonstrate the beneficial complementary features of these techniques. These are, in particular: a substantial reduction of the matrix effect and fewer complications with samples of low electrical conductivity in SNMS, and the possibility of measuring the depth distribution of gases included in small cavities in the solid in the SNMS/RGA mode. SIMS, on the other hand, allows in many cases higher detection sensitivities.EURATOM Association     

Measurement of the transverse kinetic energies of argon recoil ions produced in 120 MeV -Ar collisions

Measurements were carried out to deduce the transverse kinetic energies of highly charged argon recoil ions produced in single collisions of 120 MeV ions with argon atoms in which the post collision charge states of the projectiles were not determined. A time of flight spectrometer was designed and fabricated to detect the charge states of recoils. Experimental procedures for optimizing the spectrometer for extraction, transmission and detection of recoils are described. A simple approach for determining the transverse kinetic energy of the recoil ions from FWHM of the peaks is reported. This method is shown to be independent of the choice of collision partners and requires only the knowledge of the physical values of “optimized parameters” of time-of-flight spectrometer used in the experiment. The transverse kinetic energy of the recoil ions determined from the present approach is found to vary from 0.03 eV for to 4.02 eV for Ar¹⁰⁺. These values are compared with the results reported by earlier workers and are shown to follow a q²-behaviour up to a charge state q =8+ of the recoil ions. Received: 5 February 1998 / Revised: 8 June 1998 / Accepted: 11 June 1998     

Mass measurements of neutron-deficient radionuclides near the end-point of the rp-process with SHIPTRAP

Direct mass measurements of nuclides near to the supposed end-point region of the astrophysical rp-process were performed at SHIPTRAP, the Penning trap mass spectrometer at GSI Darmstadt. The masses of 24 nuclides were measured with relative uncertainties between 5 ^. 10^-8 and 2 ^. 10^-7 . Three of them, ¹⁰⁷Sb , ¹¹¹I and ¹¹²I , were determined experimentally for the first time. The data analysis and mass evaluation are presented in detail.     

Energy distribution of ions produced by excimer-laser ablation of solid and molten targets

2 . The measurements reveal components with different charge-to-mass ratio and distinct components with the same charge/mass ratio. The most probable kinetic energy has values of several tens of eV for singly charged ions, and is larger by a factor exceeding 2 for doubly charged ions. The role of target material and state, solid or liquid, laser photon energy and fluence has been investigated and is discussed in comparison to the findings of previous investigations. An estimate of the electrostatic plasma potential in PLA, based on electron loss rate arguments, is presented to account for the high ion energies observed. Received: 9 March 1998 / Accepted: 27 November 1998 / Published online: 24 February 1999     

Development of a Fourier-Transform Ion-Cyclotron-Resonance detection for short-lived radionuclides at SHIPTRAP

The Penning-trap mass spectrometer SHIPTRAP at GSI is designed to provide clean and cooled beams of singly charged radioactive ions produced in fusion-evaporation reactions and separated in-flight by the velocity filter SHIP. The scientific goals include mass spectrometry, atomic and nuclear spectroscopy, and chemistry of transuranium species which are not available at ISOL- or fragmentation facilities Penning-trap based mass measurements on radionuclides relies up to now on the destructive time-of-flight ion-cyclotron-resonance method. One of the main limitations to the experimental investigations is the low production rate of most of these exotic nuclides, for which the use of this detection scheme is not applicable. A sensitive and non-destructive method, like the narrow-band Fourier Transform ion-cyclotron-resonance technique, is ideally suited for the identification and characterization of these species. A new cryogenic trap setup for SHIPTRAP exploiting this detection technique as well as some results of first preparatory tests are presented.     

High-precision masses of 29-33Mg and the N = 20 shell “closure”

High-precision mass measurements have been performed on the exotic magnesium isotopes ^29-33Mg using the MISTRAL radiofrequency spectrometer, especially suited for very short-lived nuclides. This method, combined with the powerful tool of resonant laser ionization at ISOLDE, has provided a significant reduction of uncertainty for the masses of the most exotic Mg isotopes: a relative error of 7×10^-7 was achieved for the weakly produced ³³Mg that has a half-life of only 90ms. Moreover, the mass of ³³Mg is found to change by over 250keV. Verifying and minimizing binding energy uncertainties in this region of the nuclear chart is important for understanding the lack of binding energy that is normally associated with magic numbers.     

Determination of90Sr in environmental samples with resonance ionization spectroscopy in collinear geometry

A new, fast technique for trace analysis of the radioactive isotopes⁸⁹Sr and⁹⁰Sr in environmental samples has been developed. Conventional mass separation is combined with resonance ionization spectroscopy in collinear geometry, which provides high selectivity and sensitivity. In addition, a chemical separation procedure for sample preparation has been developed. The described technique was used to determine the⁹⁰Sr content in 870 m³ air samples collected near Munich during and shortly after the Chernobyl reactor accident in April 1986. The content of⁹⁰Sr was measured to be 1.4 mBq per m³, corresponding to 1.6 × 10⁹ atoms of⁹⁰Sr per sample. This value is in good agreement with the results of radiochemical measurements.This publication comprises part of the Dissertations of J. Stenner and K. Zimmer     

Gas-phase conformational and energetic properties of deprotonated dinucleotides

Ion mobility experiments and molecular modeling calculations were used to investigate the gas-phase conformations and folding energetics of 16 deprotonated dinucleotides. [M-H]^- ions were formed by MALDI and their collision cross-sections measured in helium using ion mobility based techniques. Cross-sections of theoretical structures, generated by molecular mechanics/dynamics calculations, were compared to the experimental values for conformational identification of the dinucleotides. Temperature dependent measurements and kinetic theory were also used to obtain energetic and dynamic data concerning the folding properties of the dinucleotides. Three distinct families of conformations, with significantly different collision cross-sections, were identified: a “stacked” family in which the two nucleobases stack; an “H-bonded” family in which the two nucleobases stay in the same plane and are hydrogen-bonded to each other; and an “open” family in which the two nucleobases are separated from each other. At temperatures ≥ 300 K these conformers rapidly interconvert in most systems, but they can be separated and individually observed in the lower temperature (80-200 K) experiments. The types and relative amounts of each conformer observed, and the temperature at which they can be separated, are base and sequence dependent. Theoretical modeling of the temperature-dependent data was used to determine isomerization barrier heights between the various conformers and yielded values between 0.8-12.9 kcal/mol, depending on the dinucleotide. Received 17 May 2002 Published online 13 September 2002