The heaviest elements can exclusively be produced in actinide-target based nuclear fusion reactions with intense heavy-ion beams. Ever more powerful accelerators deliver beams of continuously increasing intensity, which brings targets of current technology to their limits and beyond. We motivate efforts to produce targets with improved properties, which calls for a better understanding of targets produced by molecular plating, the current standard method. Complementary analytical methods will help shedding more light on their chemical and physical changes in the beam. Special emphasis is devoted to the aspect of the optimum target thickness and the choice of the backing material.

J. Khuyagbaatar,1,2,* A. Yakushev,2 Ch. E. Düllmann,1,2,3 D. Ackermann,2,† L.-L. Andersson,1 M. Asai,4 M. Block,2 R. A. Boll,5 H. Brand,2 D. M. Cox,6,‡ M. Dasgupta,7 X. Derkx,1,3 A. Di Nitto,3 K. Eberhardt,1,3 J. Even,1,§ M. Evers,7 C. Fahlander,8 U. Forsberg,8 J. M. Gates,9 N. Gharibyan,10 P. Golubev,8 K. E. Gregorich,9 J. H. Hamilton,11 W. Hartmann,2 R.-D. Herzberg,6 F. P. Heßberger,1,2 D. J. Hinde,7 J. Hoffmann,2 R. Hollinger,2 A. Hübner,2 E. Jäger,2 B. Kindler,2 J. V. Kratz,3 J. Krier,2 N. Kurz,2 M. Laatiaoui,2 S. Lahiri,12 R. Lang,2 B. Lommel,2 M. Maiti,12,‖ K. Miernik,5 S. Minami,2 A. Mistry,6,¶ C. Mokry,1,3 H. Nitsche,9,** J. P. Omtvedt,13 G. K. Pang,9 P. Papadakis,6,14 D. Renisch,3 J. Roberto,5 D. Rudolph,8 J. Runke,2 K. P. Rykaczewski,5 L. G. Sarmiento,8 M. Schädel,2,4 B. Schausten,2 A. Semchenkov,13 D. A. Shaughnessy,10 P. Steinegger,15,16 J. Steiner,2 E. E. Tereshatov,10,†† P. Thörle-Pospiech,1,3 K. Tinschert,2 T. Torres De Heidenreich,2 N. Trautmann,3 A. Türler,15,16 J. Uusitalo,14 D. E. Ward,8 M. Wegrzecki,17 N. Wiehl,1,3 S. M. Van Cleve,5 and V. Yakusheva1 1Helmholtz Institute Mainz, 55099 Mainz, Germany 2GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany 3Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany 4Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan 5Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA 6University of Liverpool, Liverpool L69 7ZE, United Kingdom 7The Australian National University, Canberra, ACT 0200, Australia 8Lund University, 22100 Lund, Sweden 9Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA 10Lawrence Livermore National Laboratory, Livermore, California 94551, USA 11Vanderbilt University, Nashville, Tennessee 37235, USA 12Saha Institute of Nuclear Physics, Kolkata 700064, India 13University of Oslo, 0315 Oslo, Norway 14University of Jyväskylä, 40351 Jyväskylä, Finland 15Paul Scherrer Institute, 5232 Villigen, Switzerland 16University of Bern, 3012 Bern, Switzerland 17The Institute of Electron Technology, 02-668 Warsaw, Poland

Khuyagbaatar, J.; Yakushev, A.; Düllmann, Ch E.; Ackermann, D.; Andersson, L. L.; Asai, M.; Block, M.; Boll, R. A.; Brand, H.; Cox, D. M.; Dasgupta, M.; Derkx, X.; Di Nitto, A.; Eberhardt, K.; Even, J.; Evers, M.; Fahlander, C.; Forsberg, U.; Gates, J. M.; Gharibyan, N.; Golubev, P.; Gregorich, K. E.; Hamilton, J. H.; Hartmann, W.; Herzberg, R. D.; Heßberger, F. P.; Hinde, D. J.; Hoffmann, J.; Hollinger, R.; Hübner, A.; Jäger, E.; Kindler, B.; Kratz, J. V.; Krier, J.; Kurz, N.; Laatiaoui, M.; Lahiri, S.; Lang, R.; Lommel, B.; Maiti, M.; Miernik, K.; Minami, S.; Mistry, A.; Mokry, C.; Nitsche, H.; Omtvedt, J. P.; Pang, G. K.; Papadakis, P.; Renisch, D.; Roberto, J.

The isotopic distribution of nuclei produced in the 50 Ti + 249 Cf reaction has been studied at the gas- filled recoil separator TASCA at GSI Darmstadt, which separates ions according to differences in magnetic rigidity. The bombardment was performed at an energy around the Bass barrier and with the TASCA magnetic fields set for collecting fusion-evaporation reaction products. Fifty-three isotopes located “north-east” of 208 Pb were identified as recoiling products formed in non-fusion channels of the reaction. These recoils were implanted with energies in two distinct ranges; besides one with higher energy, a significant low-energy contribution was identified. The latter observation was not expected to occur according to kinematics collisions or quasifission. The present observations are discussed within the framework of two-body kinematics passing through the formation of a composite system.

Experiments aimed at studying the chemical stability of the novel Sg(CO)6 molecule, first synthesized in 2013, have been performed. Comparison studies with the stabilities of the lighter homolog molecules Mo(CO)6 and W(CO)6 were also performed. In separate experiments, exploratory studies with the goal to identify chemical synthesis routes for these compounds that feature higher chemical yields than previous approaches were carried out. 1. Research Objectives Studying fundamental chemical properties of such heaviest elements at the extremes of the periodic table is an exciting perspective for the chemistry community. These elements' electronic shell structure is strongly influenced by relativistic effects induced by the high nuclear charge. Therefore, the prediction of chemical properties of new elements at the very edge of the periodic table is not straightforward. Highly sensitive chemical investigations are required at the single-atom-at-a-time level to benchmark our theoretical understanding of those effects. The low production rates and short half-lives complicate and limit the applicability of standard chemical procedures and the selection of accessible chemical systems. Gas phase chemical studies on single atomic or single molecular species and their adsorption interaction with stationary surfaces have proven very successful [1,2]. Increasing relativistic effects seem to govern the chemistry of Cn [3,4] and Fl [5,6]. Such effects can also be probed in low oxidation state compounds of lighter transition metal transactinides, Rf, Db, Sg, Bh, Hs, Mt, and Ds, but such compounds were previously out of reach. Only in 2014, our observed formation and high volatility of group 6 hexacarbonyls including Sg(CO)6 [7] opened the door for such studies. As a next step, the study of the compounds thermal stability appears uniquely possible based on our preparatory work with lighter homologs [8]. 2. Research

The experimental program of the future facility for Antiproton and Ion Research (FAIR) project requires a high number of cooled anti-protons per hour [1]. The FAIR proton injector linac has to deliver a 70 MeV, 35 mA pulsed proton beam at a repetition rate of 4 Hz. During recent machine investigations at GSI a high current proton beam was achieved in the Universal Linear Accelerator (UNILAC) [2]. In preparation for this the ion source was equipped with a newly developed 7-hole extraction system and optimized for single charged hydrocarbon beam (isobutane gas) operation. This beam was accelerated to 1.4 MeV/u and cracked in a new pulsed gas stripper into protons and charged carbon ions. The new stripper setup injects high density gas pulses synchronous with the transit of the beam pulse close to the beam trajectory. With this setup a proton (up to 4.3 mA) as well a carbon beam (up to 9.5 mA) intensity record at beam energy of 1.4 MeV was achieved. The proton beam was accelerated up to 3.6 MeV/u inside the first Alvarez-section with full transmission. The paper will present beam measurement in comparison to the former beam investigations using a 2 mA proton beam in the entire UNILAC.

The GSI UNILAC will serve as part of an injector system for the future FAIR facility, currently under construction in Darmstadt, Germany. For this, it has to deliver short-pulsed, high-current, heavy-ion beams with highest beam quality. An upgrade for the 1.4 MeV/u gas stripper is ongoing to increase the yield of uranium ions in the desired charge state. The new setup features a pulsed gas injection synchronized with the beam pulse transit to increase the effective density of the stripper target while keeping the gas load for the differential pumping system low. Systematic measurements of charge state distributions and energy-loss were conducted with U-ion beams and different stripper gases, including H2 and He. By using H2 as a stripper gas, the yield into the most populated charge state was increased by over 50 %, compared to the current stripper. Furthermore, the high gas density, enabled by the pulsed injection, results in increased mean charge states.

In the context of an advanced machine investigation program supporting the ongoing UNILAC (Universal Linear Accelerator) upgrade program, a new uranium beam intensity record (≈10 emA, U) at very high beam brilliance was achieved last year in a machine experiment campaign at GSI. The UNILAC as well as the heavy ion synchrotron SIS18 will serve as a high current heavy ion injector for the new FAIR (Facility for Antiproton and Ion Research) synchrotron SIS100. Results of the accomplished high current uranium beam measurements applying a newly developed pulsed hydrogen gas stripper (at 1.4 MeV/u) will be presented. The paper will focus on the evaluation and analysis of the measured beam brilliance and further implications to fulfil the FAIR heavy ion high intensity beam requirements.

Rudolph, Dirk; Forsberg, Ulrika; Düllmann, C. E.; Golubev, Pavel; Heßberger, F.P.; Khuyagbaatar, J.; Kratz, J. V.; Sarmiento, Luis; Yakushev, A.; Ackermann, D.; Andersson, L.; Block, M.; Brand, H.; Cox, D.; Derkx, X.; Di Nitto, A.; Eberhardt, K.; Even, J.; Fahlander, Claes; Gates, J. M.; Gerl, J.; Gregorich, E. K.; Gross, C. J.; Herzberg, R.-D.; Jäger, E.; Kindler, B.; Krier, J.; Kojouharov, I.; Kurz, N.; Lommel, B.; Mistry, A.; Mokry, C.; Nitsche, H.; Omtvedt, J. P.; Papadakis, P.; Runke, J.; Rykaczewski, K.; Schädel, M.; Schaffner, H.; Schausten, B.; Thörle-Pospiech, P.; Torres, T.; Traut, T.; Trautmann, N.; Türler, A.; Ward, A.; Wiehl, N. Published in: GSI Report

Thirty correlated α-decay chains were observed in an experiment studying the fusion-evaporation reaction 48Ca + 243Am at the GSI Helmholtzzentrum für Schwerionenforschung. The decay characteristics of the majority of these 30 chains are consistent with previous observations and interpretations of such chains to originate from isotopes of element Z = 115. High-resolution α-photon coincidence spectroscopy in conjunction with comprehensive Monte-Carlo simulations allow to propose excitation schemes of atomic nuclei of the heaviest elements, thereby probing nuclear structure models near the 'Island of Stability' with unprecedented experimental precision.

Khuyagbaatar, J.; Yakushev, A.; Düllmann, Ch. E.; Ackermann, D.; Andersson, L.-L.; Block, M.; Brand, H.; Cox, D. M.; Even, J.; Forsberg, Ulrika; Golubev, Pavel; Hartmann, W.; Herzberg, R.-D.; Heßberger, F. P.; Hoffmann, J.; Hübner, A.; Jäger, E.; Jeppsson, J.; Kindler, B.; Kratz, J. V.; Krier, J.; Kurz, N.; Lommel, B.; Maiti, M.; Minami, S.; Mistry, A. K.; Mrosek, Ch. M.; Pysmenetska, I.; Rudolph, Dirk; Sarmiento Pico, Luis; Schaffner, H.; Schädel, M.; Schausten, B.; Steiner, J.; De Heidenreich, T. Torres; Uusitalo, J.; Wegrzecki, M.; Wiehl, N.; Yakusheva, V.

U. Forsberg, D. Rudolph, L.-L. Andersson, A. Di Nitto, Ch.E. Düllmann, J.M. Gates, P. Golubev, K.E. Gregorich, C.J. Gross, R.-D. Herzberg, F.P. Heßberger, J. Khuyagbaatar, J.V. Kratz, K. Rykaczewski, L.G. Sarmiento, M. Schädel, A. Yakushev, S. Åberg, D. Ackermann, M. Block, H. Brand, B.G. Carlsson, D. Cox, X. Derkx, J. Dobaczewski, K. Eberhardt, J. Even, C. Fahlander, J. Gerl, E. Jäger, B. Kindler, J. Krier, I. Kojouharov, N. Kurz, B. Lommel, A. Mistry, C. Mokry, W. Nazarewicz, H. Nitsche, J.P. Omtvedt, P. Papadakis, I. Ragnarsson, J. Runke, H. Schaffner, B. Schausten, Yue Shi, P. Thörle-Pospiech, T. Torres, T. Traut, N. Trautmann, A. Türler, A. Ward, D.E. Ward, N. Wiehl, 1 Lund University, 22100 Lund, Sweden 2 Helmholtz Institute Mainz, 55099 Mainz, Germany 3 Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany 4 GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany 5 Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA 6 Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA 7 University of Liverpool, Liverpool L69 7ZE, United Kingdom 8 Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan 9 University of Warsaw, 00681 Warsaw, Poland 10 University of Tennessee, Knoxville, Tennessee 37996, USA 11 University of Oslo, 0315 Oslo, Norway and 12 Paul Scherrer Institute and University of Bern, 5232 Villigen, Switzerland (Dated: February 11, 2015)

October 23, 2015 (Location: KBW Lecture Hall, GSI) TIME TOPIC Speaker Page 09:00 Welcome T. Stöhlker, Research director of GSI Scientific highlights from gas-filled (and other) separators ◆ Chair: A. Türler (PSI/Bern) 09:10 Status and perspectives of SHE syntheses at RIKEN GARIS H. Haba (RIKEN) 2 09:35 First ionization potential measurement of heaviest actinides T. Sato (JAEA, Tokai) 2 10:00 First observation of an atomic level for the element nobelium M. Laatiaoui (HIM, Mainz) 3 10:25 Coffee 10:45 Status on the chemical investigations of flerovium at TASCA L. Lens (Univ. Mainz) 3 11:10 MARA, a new in-flight recoil separator for nuclear spectroscopy J. Uusitalo (JYFL) 4 11:35 New short-lived 221 U and the mass-surface ear N =126 J. Khuyagbaatar (HIM/GSI) 4 12:00 Enhanced fission stability of K isomers in superheavy nuclei: the case of 254 Rf H. David (GSI) 5 12:25 Lunch 13:15 Workshop Photo