H. Frånberg

Paul Scherrer Institut, Aargau, Switzerland

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Publications (16)13.91 Total impact

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    ABSTRACT: A crucial requirement in the development of liquid-metal spallation neutron target is knowledge of the composition and amount of volatile radionuclides that are released from the target during operation. It is also important to know the total amount produced, which could be released if there was an accident. One type is the lead-bismuth eutectic (LBE) target where different radionuclides can be produced following interaction with a high-energy proton beam, notably noble gases (Ar, Kr, Xe isotopes) and other relative volatile isotopes such as Hg and At. The results of an irradiation experiment performed at ISOLDE on a LBE target are compared with predictions from the MCNPX code using the latest developments on the Li`ege Intranuclear Cascade model (INCL4.6) and the CEM03 model. The calculations are able to reproduce the mass distribution of the radioisotopes produced, including the At production, where there is a significant contribution from secondary reactions. Subsequently, a post-irradiation examination of the irradiated target was performed. Investigations of both the tantalum target structure, in particular the beam window, and the leadbismuth eutectic were performed using several experimental techniques. No sign of severe irradiation damage, previously observed in other ISOLDE targets, was found.
    Nuclear Data Sheets 04/2014; 119:292-295. · 2.67 Impact Factor
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    ABSTRACT: Light-particles stable high-intensity beams (p, d, 3,4He...) will be available from the Linac driver accelerator of SPIRAL-2. Yields of neutron-deficient isotopes as well as of neutron-rich isotopes (by means of reactions with secondary neutrons) are compared with those presently available at the SPIRAL-1 facility. We explore, for light beams (Z< 16) asked in the 'white book' of SPIRAL-2 1, the production methods taking into account the in-target yield but also the feasibility of making such beams by the ISOL method (considering reaction, target, thermal and release properties). We discuss some of the tests needed and planned. A comparison with the present and potentially attainable yields at SPIRAL-1 is presented.
    AIP Conference Proceedings. 04/2010;
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    ABSTRACT: In the frame of the SPIRAL II (Système de Production d'Ions Radioactifs Accélérés en Ligne Partie II) project, several developments of stable and radioactive ion production systems have been started up. In parallel, GANIL has the ambition to preserve the existing stable and radioactive beams and also to increase its range by offering new ones. In order to identify the best directions for this development, a new group called GANISOL has been formed. Its preliminary conclusions and the latest developments at GANIL are presented.
    The Review of scientific instruments 02/2010; 81(2):02A909. · 1.52 Impact Factor
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    ABSTRACT: SPIRAL2 is the new project under construction at GANIL to produce radioactive ion beams and in particular neutron rich ion beams. For the past 10 yr SPIRAL1 at GANIL has been delivering accelerated radioactive ion beams of gases. Both facilities now need to extend the range of radioactive ion beams produced to condensable elements. For that purpose, a resonant ionization laser ion source, funded by the French Research National Agency, is under development at GANIL, in collaboration with IPN Orsay, University of Mainz (Germany) and TRIUMF, Vancouver (Canada). A description of this project called GISELE (GANIL Ion Source using Electron Laser Excitation) is presented.
    The Review of scientific instruments 02/2010; 81(2):02A910. · 1.52 Impact Factor
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    ABSTRACT: A gas-filled segmented linear Paul trap has been installed at the focal plane of the high-resolution separator (HRS) at CERN-ISOLDE. As well as providing beams with a reduced transverse emittance, this device is also able to accumulate the ions and release the sample in bunches with a well-defined time structure. This has recently permitted collinear laser spectroscopy with stable and radioactive bunched beams to be demonstrated at ISOLDE. Surface-ionized 39, 44, 46K and 85Rb beams were accelerated to 30keV, mass separated and injected into the trap for subsequent extraction and delivery to the laser setup. The ions were neutralized in a charge exchange cell and excited with a co-propagating laser. The small ion beam emittance allowed focussing in the ion-laser overlap region, which is essential to achieve the best experimental sensitivity. Fluorescent photons were detected by a photomultiplier tube as a frequency scan was taken. A gate (typically 7-12μs wide) was set on the photomultiplier signal to accept the fluorescent photons within the time window defined by the bunch. Thus, using accumulation times of 100ms, the dominant contribution to background due to continuous laser scattering could be reduced by a factor of up to 4×104 .
    European Physical Journal A 01/2009; 42(3):503-507. · 2.42 Impact Factor
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    ABSTRACT: This work has been carried out at GANIL within the ambit of the TARGISOL European collaboration which aims to study the rel-evant variables governing the release of radioactive elements from targets in an ISOL system. This work shows how it has been possible to extract diffusion coefficients for 35 Ar atoms diffusing out of graphite targets from release time measurements by using an analytic description of the release times. The diffusion coefficients and efficiencies are presented and compared with results obtained using a ''con-tinuous" method. Ó 2008 Published by Elsevier B.V. PACS: 29.25.Rm; 66.30.Jt
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 07/2008; · 1.19 Impact Factor
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    ABSTRACT: The IS419 experiment at the ISOLDE facility at CERN dedicated to the measurement of production and release rates of volatile elements from an irradiated Pb/Bi target by a proton beam of 1/1.4 GeV has been completed. The release of He, Ne, Ar, Br, Kr, Cd, I, Xe, Hg, Po and At isotopes was investigated at different target temperatures, ranging from 250 °C to 600 ° C. Three experimental methods were used for the mass-separated, ionized beams: i) implantation of short- and medium-lived isotopes in a tape and on-line detection with a HPGe γ detector; ii) implantation of longer-lived isotopes in Al foils and off-line detection with a HPGe detector; iii) a Faraday Cup used mainly for stable nuclides. The results were compared with predictions from the FLUKA and MCNPX codes using different options for the intra-nuclear cascades and evaporation/fission models. Results show good agreement with calculations for Hg and for noble gases. For other elements such as iodine it is apparent that only a fraction of the produced isotopes is released. The results from FLUKA and MCNPX with the INCL4/ABLA models are in general more satisfactory than those obtained using MCNPX with the standard Bertini/Dresner model combination. Interestingly also significant yields of 204-210At isotopes were observed. At isotopes are produced either by (p, π-xn) charge exchange reactions on 209Bi or by secondary reactions involving 3He and 4He. Despite the non-release of polonium from Pb/Bi targets at typical operation temperatures, a smaller amount of highly radiotoxic Po isotopes can actually be liberated indirectly as decay daughters of the released astatine.
    http://dx.doi.org/10.1051/ndata:07762. 05/2008;
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    ABSTRACT: Among the multiple progresses in radioactive ion beam (RIB) manipulation for physics experiments, the beam cooling and bunching in gas-filled RF traps has become a widely used technique. It is particularly well adapted to precision experiments, such as Penning trap mass spectrometry or collinear laser spectroscopy. At ISOLDE, an rf quadrupole cooler and ion buncher (RFQCB) has been designed and developed to deliver radioactive beams of improved quality among most of the on-line experiments. The results of the first off-line tests have shown that high transmission efficiencies could be achieved with different RIBs of alkali metals, as it was expected. During the later tests that are presented here a special care was dedicated to the reproduction of the on-line experimental conditions of ISOLDE, with a wide range of different RIBs. This contribution will present the latest off-line tests.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2008; 266:4502-4504. · 1.19 Impact Factor
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    ABSTRACT: The heart of every ISOL (isotope separation on-line) facility is its target and ion source system. Its efficiency, selectivity and rapidity is decisive for the production of intense and pure ion beams of short-lived isotopes. Recent progress in ISOL target and ion source technology is discussed at the examples of radioactive ion beams of exotic zinc and tin isotopes that were purified by isothermal chromatography and molecular sideband separation respectively. An outlook is given to which other elements these purification methods are applicable.
    Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 01/2008;
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    ABSTRACT: Refractory elements, i.e. elements with very high melting point and low vapor pressure, cannot be released in atomic form from an ISOL target. Therefore most of these elements are presently not available as ISOL beams. However, when reactive gases are introduced into the target, they may form volatile compounds with the refractory elements, allowing for an easier transport to the ion source. Particularly useful are high-temperature stable fluorides and oxides. By these chemical evaporation methods so far ISOL beams of the refractory elements C, Zr, Hf and Ta have been produced. We discuss how ISOL beams of B, Ti, Nb, Mo, Tc, Ru, W, Re, Os and Ir could be produced in a similar way.
    The European Physical Journal Special Topics 10/2007; 150(1):285-291. · 1.80 Impact Factor
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    ABSTRACT: Radioactive ion beams (RIBs) are of significant interest in a number of applications. Isotope separation on line (ISOL) facilities provide RIB with high beam intensities and good beam quality. An atom that is produced within the ISOL target will first diffuse out from the target material. During the effusion towards the transfer line and into the ion source the many contacts with the surrounding surfaces may cause unacceptable delays in the transport and, hence, losses of the shorter-lived isotopes. We performed systematic chemical investigations of adsorption in a temperature and concentration regime relevant for ISOL targets and ion source units, with regard to COx and NOx on Al2O3 and SiO2. These materials are potential construction materials for the above-mentioned areas. Off-line and on-line tests have been performed using a gas thermochromatography setup with radioactive tracers. The experiments were performed at the production of tracers for atmospheric chemistry (PROTRAC) facility at the Paul Scherrer Institute in Villigen, Switzerland. (c) 2006 American Institute of Physics.
    Review of Scientific Instruments 03/2006; 77(3). · 1.60 Impact Factor
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    ABSTRACT: Radioactive Ion Beams (RIB) are of significant interest in a number of applications. ISOL (Isotope Separation On Line) facilities provide RIB with high beam intensities and good beam quality. An atom that is produced within the ISOL target will first diffuse out from the target material. During the effusion towards the transfer line and into the ion source the many contacts with the surrounding surfaces may cause unacceptable delays in the transport and, hence, losses of the shorter-lived isotopes. We performed systematic chemical investigations of adsorption in a temperature and concentration regime relevant for ISOL targets and ion source units, with regard to COx and NOx on Al2O3 and SiO2. These materials are potential construction materials for the above mentioned areas. Off-line and on-line tests have been performed using a gas thermo-chromatography set-up with radioactive tracers. The experiments were performed at the PROTRAC facility at Paul Scherrer Institute in Villigen, Switzerland.
    01/2006;
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    ABSTRACT: The beam intensities of short-lived carbon isotopes at Isotope Separation On-Line (ISOL) facilities have been limited in the past for technical reasons. The production of radioactive ion beams of carbon isotopes is currently of high interest for fundamental nuclear physics research. To produce radioactive ions a target station consisting of a target in a container connected to an ion source via a transfer line is commonly used. The target is heated to vaporize the product for transport. Carbon in elementary form is a very reactive element and react strongly with hot metal surfaces. Due to the strong chemisorption interaction, in the target and ion source unit, the atoms undergo significant retention on their way from the target to the ion source. Due to this the short lived isotopes decays and are lost leading to low ion yields. A first approach to tackle these limitations consists of incorporating the carbon atoms into less reactive molecules and to use materials for the target housing and the transfer line that only weakly interact with these molecules. Therefore, the adsorption properties of carbon monoxide (CO) and carbon dioxide (CO2) on a range of materials of interest were investigated in thermochromatography experiments at PSI (Switzerland) by using the carbon isotope 11C. The adsorption enthalpy was retrieved for several materials. A second approach consists of the optimization of target materials and structure, both f or the effusion and diffusion of the nuclides of interest. Corresponding on-line experiments were performed at GANIL (France). For the production, diffusion and ionization efficiencies out of different target materials on-line and off-line experiments with carbon and nitrogen isotopes were performed at ISOLDE (CERN). The work performed within this thesis shows that the use of a coated transfer line, fibre felt targets and an electron cyclotron resonance (ECR) ion source would strongly decrease the losses, and provide the experiments with up to 1000 times higher beam currents than today.
  • H. Frånberg, M. Ammann, U. Köster
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    ABSTRACT: Production rates of volatile elements following spallation reaction of 1.4 GeV protons on a liquid Pb/Bi target have been measured. The experiment was performed at the ISOLDE facility at CERN. These data are of interest for the developments of targets for accelerator driven systems such as MEGAPIE. Additional data have been taken on a liquid Pb target. Calculations were performed using the FLUKA and MCNPX Monte Carlo codes coupled with the evolution codes ORIHET3 and FISPACT using different options for the intra-nuclear cascades and evaporation models. Preliminary results from the data analysis show good comparison with calculations for Hg and for noble gases. For other elements such as I it is apparent that only a fraction of the produced isotopes is released. The agreement with the experimental data varies depending on the model combination used. The best results are obtained using MCNPX with the INCL4/ABLA models and with FLUKA. Discrepancies are found for some isotopes produced by fission using the MCNPX with the Bertini intranuclear cascade model coupled with the Dresner evaporation model.
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    ABSTRACT: Compounds of Cr, Fe and Ni were activated with 72 MeV protons at the PSI Phillips cyclotron and with 1.4 GeV protons at ISOLDE-CERN to produce the radiotracer 52g Mn. The release of the latter was measured by isochronal annealing under vacuum for temperatures ranging from 1100 to 2200 ºC. The most promising materials for an efficient production and fast release of short-lived Mn isotopes were found to be CrC x , Cr 2 O 3 and NiO. 1 INTRODUCTION There is high interest in intense and pure radioactive ion beams of 283 ms 50g Mn (an N=Z isotope with spin 0 + decaying by a superallowed Fermi transition) and ≈100 ms 47 Mn, a T z =-3/2 isotope. A precise measurement of the Gamow Teller strength in the β + -decay of the latter could be compared with precision measurements of mirror transitions in the charge-exchange reaction 47 Ti(3 He, 3 H) 47 V (presently under way at RCNP Osaka [1]) to extract information on isospin and mirror symmetry of N≈Z nuclei.