Jutta Steiner

GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Hesse, Germany

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Publications (29)43.34 Total impact

  • Physical Review Letters 05/2014; 112(17):172501. · 7.73 Impact Factor
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    ABSTRACT: For the proposed new heavy ion linac@GSI the installation of a carbon foil stripper section is under discussion. High duty factor as well as high current (but low duty factor) heavy ion beams were used for machine experiments. Long term tests were performed to check the carbon foil durability. Relevant beam parameters have been measured in three measurement campaigns. After beam testing stripper foils were analyzed with different offline methods. Additionally promising results of high current beam irradiation of rotating target wheels will be presented. In the transfer line to the SIS 18 the heavy ion beam is stripped to higher charge states in a thick carbon foil. The stripper foil is loaded with 3 % of the beam power. To avoid evaporation in a single beam pulse, the beam is rapidly swept over its width. Experiences collected during the last decade of foil stripper operation at GSI will be presented.
    Journal of Radioanalytical and Nuclear Chemistry 02/2014; 299(2). · 1.47 Impact Factor
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    ABSTRACT: The electron shell structure of superheavy elements, i.e., elements with atomic number Z ≥ 104, is influenced by strong relativistic effects caused by the high Z. Early atomic calculations on element 112 (copernicium, Cn) and element 114 (flerovium, Fl) having closed and quasi-closed electron shell configurations of 6d(10)7s(2) and 6d(10)7s(2)7p1/2(2), respectively, predicted them to be noble-gas-like due to very strong relativistic effects on the 7s and 7p1/2 valence orbitals. Recent fully relativistic calculations studying Cn and Fl in different environments suggest them to be less reactive compared to their lighter homologues in the groups, but still exhibiting a metallic character. Experimental gas-solid chromatography studies on Cn have, indeed, revealed a metal-metal bond formation with Au. In contrast to this, for Fl, the formation of a weak bond upon physisorption on a Au surface was inferred from first experiments. Here, we report on a gas-solid chromatography study of the adsorption of Fl on a Au surface. Fl was produced in the nuclear fusion reaction (244)Pu((48)Ca, 3-4n)(288,289)Fl and was isolated in-flight from the primary (48)Ca beam in a physical recoil separator. The adsorption behavior of Fl, its nuclear α-decay product Cn, their lighter homologues in groups 14 and 12, i.e., Pb and Hg, and the noble gas Rn were studied simultaneously by isothermal gas chromatography and thermochromatography. Two Fl atoms were detected. They adsorbed on a Au surface at room temperature in the first, isothermal part, but not as readily as Pb and Hg. The observed adsorption behavior of Fl points to a higher inertness compared to its nearest homologue in the group, Pb. However, the measured lower limit for the adsorption enthalpy of Fl on a Au surface points to the formation of a metal-metal bond of Fl with Au. Fl is the least reactive element in the group, but still a metal.
    Inorganic Chemistry 01/2014; · 4.59 Impact Factor
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    ABSTRACT: Chromium is a shiny, hard and malleable metal, which can be cold rolled in good quality to a thickness below a micrometer. Thinner foils can be obtained by electron-beam gun evaporation or by electroplating. Isotopically enriched material typically has not the quality for cold rolling processes. As 50Cr has a natural abundance of only 4.5 % the enriched material is rather expensive so electron-beam deposition is not a good option because of the inherently low yield of the method. In this contribution we present the preparation of self-supporting 50Cr thin films by thermal evaporation out of a tantalum crucible as an alternative to electrodeposition. With the described method we obtained self-supporting films with a thickness between 250 and 620 μg/cm².
    Journal of Radioanalytical and Nuclear Chemistry 01/2014; · 1.47 Impact Factor
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    ABSTRACT: Titanium-50 (50Ti) is an important and often requested ion beam for nuclear physics’ experiments. While natural titanium of very high purity is available in different forms; enriched material can only be bought as the dioxide or the tetrachloride. These compounds cannot be processed from currently available ion sources with a sufficient beam quality and sufficient beam intensity for a long time. We describe here the process of converting titanium dioxide into the metal, the material analysis of the starting material as well as of the reduced material. Despite varying contamination levels of silicon, chlorine, and tin in the primary materials, we obtained high yields of metallic titanium with different contamination levels. The obtained metallic 50Ti was applied at the accelerator UNILAC for the production of a high intensity ion beam for several month of beam time.
    Journal of Radioanalytical and Nuclear Chemistry 01/2014; · 1.47 Impact Factor
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    ABSTRACT: For experiments performed with the HADES spectrometer (High Acceptance Di-Electron Spectrometer) [1] at GSI a very extraordinary target set-up is required. Since these experiments are strongly background-dominated the alignment and mounting of the targets is crucial for the identification of the electron–positron pairs searched for as a decay product of the vector mesons. The positioning of the numerous target discs has to be done with accuracy better than ±200μm and with a minimum of material around the targets.We describe the target design, the production of the different components and the mounting methods. Finally, an outlook on future target designs and ideas is given.
    Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment - NUCL INSTRUM METH PHYS RES A. 01/2011; 655(1):95-99.
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    ABSTRACT: Experiments with the new recoil separator, Transactinide Separator and Chemistry Apparatus (TASCA), at the GSI were performed by using beams of 48Ca to irradiate targets of 206-208Pb, which led to the production of 252-254No isotopes. These studies allowed for evaluation of the performance of TASCA when coupled to a new detector and electronics system. By following these studies, the isotopes of element 114 (288-291114) were produced in irradiations of 244Pu targets with 48Ca beams at compound nucleus excitation energies around 41.7 and 37.5 MeV, demonstrating TASCA's ability to perform experiments with picobarn-level cross sections. A total of 15 decay chains were observed and were assigned to the decay of 288-291114. A new α-decay branch in 281Ds was observed, leading to the new nucleus 277Hs.
    Physical Review C 01/2011; 83(5). · 3.72 Impact Factor
  • Physical Review C. 01/2011; 83:054618.
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    ABSTRACT: The investigation of the distribution of the fusion-barrier height by heavy-ion collisions requires thin self-supporting targets. To increase the accuracy of the measurement the thickness and homogeneity has to be known as precisely as possible.We prepared the self-supporting nickel foils out of the isotopes 58Ni, 60Ni and 61Ni. The resulting targets were between 75 and 105μg/cm² thick. The foils were produced on copper backing by electron-beam gun evaporation and by extracted ion-beam sputtering, both in high vacuum. To obtain self-supporting nickel foils the copper was removed by etching. We will discuss and compare both methods.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2011; 655(1):44-46. · 1.14 Impact Factor
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    ABSTRACT: The fusion-evaporation reaction 244Pu(48Ca,3-4n){288,289}114 was studied at the new gas-filled recoil separator TASCA. Thirteen correlated decay chains were observed and assigned to the production and decay of {288,289}114. At a compound nucleus excitation energy of E{*}=39.8-43.9  MeV, the 4n evaporation channel cross section was 9.8{-3.1}{+3.9}  pb. At E^{*}=36.1-39.5  MeV, that of the 3n evaporation channel was 8.0{-4.5}{+7.4}  pb. In one of the 3n evaporation channel decay chains, a previously unobserved α branch in 281Ds was observed (probability to be of random origin from background: 0.1%). This α decay populated the new nucleus 277Hs, which decayed by spontaneous fission after a lifetime of 4.5 ms.
    Physical Review Letters 06/2010; 104(25):252701. · 7.73 Impact Factor
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    ABSTRACT: TASISpec (TASCA in Small Image mode Spectroscopy) combines composite Ge- and Si-detectors for a new detector setup aimed towards multi-coincidence γ-ray, X-ray, conversion electron, fission fragment, and α-particle spectroscopy of the heaviest nuclei. It exploits the TASCA separator's unique small image focal mode, i.e. the fact that evaporation residues produced in fusion–evaporation reactions can be focused into an area of less than 3 cm in diameter. This provides the possibility to pack detectors in very close geometry, resulting in an unprecedented detection efficiency of radioactive decays in prompt and delayed coincidence with implanted nuclei.
    Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 01/2010;
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    ABSTRACT: Carbon foils are applied as stripper for the heavy-ion accelerator as well as targets in different experiments at GSI. Carbon foils in a thickness range 5–100μg/cm2 are routinely produced with good homogeneity and excellent durability. Foils thicker than 100μg/cm2 used to be purchased.To overcome problems that emerged and intensified in some applications we started to advance our own carbon production towards higher thickness.We describe the production of carbon foils up to a thickness of 600μg/cm2, report on first tests as stripper foils and as targets, and discuss our future plans.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2010; 613(3):425-428. · 1.14 Impact Factor
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    ABSTRACT: At GSI the gas-filled separator TASCA (TransActinide Separator and Chemistry Apparatus) was set up to investigate the chemical and physical properties of the heaviest elements making use of the highest beam intensities available [www.gsi.de/tasca; M. Schädel, D. Ackermann, A. Semchenkov, A. Türler, GSI Scientific Report 2005, GSI Report 2006-1, p. 262]. Appropriate backings and targets have to be developed.Conceivable backing materials are aluminium, titanium, and carbon. Aluminium backings and titanium backings in different thickness and from different companies are produced by cold rolling. Deposition by resistance heating is applied for carbon backings. For experiments in a chemically active atmosphere, beryllium has to be employed as backing, which is commercially available and produced by cold rolling.The task is to find the best material and thickness for backings to withstand two different processes: the electrodeposition, applied for the production of lanthanide and actinide targets at the Institut für Kernchemie, at the Universität Mainz [K. Eberhardt, et al., Contribution to this conference; D. Liebe, et al., Contribution to this conference], on the one hand, and deposition by thermal evaporation and sputtering on the other.We report on first tests with targets of uranium tetrafluoride (UF4) and metallic uranium on various backings. In addition, the behaviour and durability will be described for the different backing–target combinations in a C-beam and in an Mg beam. For the upcoming beam time U, 208PbS, 144Sm, 154Sm, and Gd are required.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2008; 590(1):141-144. · 1.14 Impact Factor
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    ABSTRACT: The Transactinide Separator and Chemistry Apparatus (TASCA) is a recoil separator with maximized transmission designed for performing advanced chemical studies as well as nuclear reaction and structure investigations of the transactinide elements (Z>103) on a one-atom-at-a-time basis. TASCA will provide a very clean transactinide fraction with negligible contamination of lighter elements from nuclear side reactions in the target.For TASCA a new target chamber was designed and built at GSI including the rotating target wheel assembly ARTESIA for beam intensities up to 2 μA (particle). For the production of longer-lived isotopes of neutron-rich heavier actinide and transactinide elements, hot fusion reactions with actinide targets are required. Here, possible target materials range from thorium up to curium or even heavier elements.For the deposition of lanthanide and actinide elements on thin aluminum and titanium backings by means of Molecular Plating (MP), a new deposition cell has been constructed that allows precise temperature control of the organic solvent and stirring of the solution. The electrode geometry ensures homogeneity of the electric field inside the cell. With the new set-up, holmium and gadolinium layers (500 μg/cm2) on 2–5 μm thin titanium backings have been produced with deposition yields of the order of 90%. Systematic investigations are under way to further optimize the deposition conditions for other lanthanide and actinide elements including uranium and plutonium on different backing materials.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2008; · 1.14 Impact Factor
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    ABSTRACT: Lanthanide and actinide targets are prepared at the University of Mainz by molecular plating, an electrochemical deposition from an organic solvent, for heavy-ion reaction studies at GSI. To acquire information about deposition yield, target thickness, and target homogeneity, the following analysis methods are applied.With neutron activation analysis (NAA) the deposition yield and the average thickness of the deposited material is determined. We report on the analytical procedure of NAA performed subsequent to the molecular plating process.Scanning electron microscope (SEM) is used to determine the morphology of the target surfaces. In combination with energy dispersive X-ray spectrometer (EDS), we also could obtain qualitative information about the chemical form of the deposited material. So far, gadolinium, samarium, holmium, and uranium targets have been investigated with SEM/EDS.With radiographic imaging (RI), targets of uranium prepared by molecular plating and by vacuum vaporization are investigated. This method is suitable to obtain information about the spatial distribution, the homogeneity, and the thickness of the target layer deposition.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2008; 590(1):145-150. · 1.14 Impact Factor
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    ABSTRACT: In this contribution we describe the production and application of uranium targets for synthesis of heavy elements. The targets are prepared from uranium fluoride (UF4) and from metallic uranium with thin carbon foils as backing. Targets of UF4 were produced by thermal evaporation in a similar way as the frequently applied targets out of Bi, Bi2O3, Pb, PbS, SmF3, and NdF3, prepared mostly from isotopically enriched material [Birgit Kindler, et al., Nucl. Instr. and Meth. A 561 (2006) 107; Bettina Lommel, et al., Nucl. Instr. and Meth. A 561 (2006) 100]. In order to use more intensive beams and to avoid scattering of the reaction products in the target, metallic uranium is favorable. However, evaporation of metallic uranium is not feasible at a sustainable yield. Therefore, we established magnetron sputtering of metallic uranium. We describe production and properties of these targets. First irradiation tests show promising results.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2008; 590(1):126-130. · 1.14 Impact Factor
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    ABSTRACT: The application of metallic lead and metallic bismuth targets is limited at high beam currents due to their low melting temperature. To permit using increased beam intensity, we have investigated chemical compounds with higher melting temperatures as targets. Their substitution for metallic targets is crucial for increasing the sensitivity of superheavy element experiments. Heating the carbon backing during evaporation proved to be essential for a successful application of PbS targets in a production run for superheavy elements. It turned out that this procedure quite generally leads to an enhancement of the durability of the carbon backings during evaporation of additional material. Such improved 208PbS targets were irradiated with 54Cr and the cross-section for the production of 261Sg was directly compared with the one obtained from metallic 208Pb. The performance of Bi2O3 and BiF3 targets was also tested using the same projectile to determine which compound would be the more promising substitute for metallic bismuth.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2006; · 1.14 Impact Factor
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    ABSTRACT: Often the compound needed out of isotopically enriched material is not readily available. Frequently the isotopically enriched metals are disproportionately expensive compared to the oxide or carbonate. Physical and chemical techniques have to be applied to receive the wanted compound or metal. We describe different procedures to produce 206PbS, 207PbS and 208PbS out of enriched lead, lead nitrate and lead oxide. To obtain the fluorides of 144Sm, 142Nd, 138Ba and 82Sr, chemical techniques are introduced. 48Ca and 144Sm are needed as metal but only the oxide is affordable. The oxides are reduced in a resistively heated tantalum crucible, and the process and the efficiency are discussed.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2006; 561(1):100-103. · 1.14 Impact Factor
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    ABSTRACT: For target preparation at GSI, a focused ion-beam sputter source, as described by Sletten and Knudsen, has been available for a long time. A survey of the sputtering yields of several isotopic materials was given by Folger et al. This method is applied mainly for rare refractive materials where only small target areas and medium uniformities are needed. We present the setup and discuss the method's pros and cons. For some selected isotopic materials we describe the preparation and the achieved thickness. While for the target preparation of rare materials the focused ion-beam sputter deposition is the ideal choice for larger dimensions, for significantly thicker layers or non-sticking materials, we complemented our lab equipment with a magnetron sputtering machine. We show the principle of this method and report first results of target preparation with the apparatus.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2004; 521(1):222-226. · 1.14 Impact Factor
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    ABSTRACT: The use of metallic lead or bismuth targets is limited at high beam currents due to their low melting point. In order to increase the intensity for irradiation, we investigated chemical compound targets with higher melting temperature. The properties of these targets are promising for further increase of the sensitivity in experiments searching for superheavy elements. The target material is controlled in each step of the production process as well as after the irradiation by optical microscopy, weighing, scanning electron microscopy (SEM), and energy-dispersive x-ray analysis (EDX). In some cases also wavelength dispersive x-ray analysis (WDX), and Atomic Force Microscopy (AFM) are applied. We report on the synthesis of the target material, the production of the targets and their application in heavy-ion experiments.
    01/2003;