The Superheavy Element Search Campaigns at TASCA

GSI SCIENTIFIC REPORT 2012 PHN-ENNA-EXP-01 The Superheavy Element Search Campaigns at TASCA J. Khuyagbaatar1,2, A. Yakushev1, Ch.E. Düllmann1,2,3, H. Nitsche4, J. Roberto5, D. Ackermann1, L.-L. Andersson2, M. Asai6, H. Brand1, M. Block1, D.M. Cox7, M. Dasgupta8, X. Derkx2,3, A. Di Nitto3, J. Dvorak2, K. Eberhardt2,3, P.A. Ellison4, N.E. Esker4, J. Even2,3, M. Evers8, C. Fahlander9, U. Forsberg9, J.M. Gates4, N. Gharibyan10, K.E. Gregorich4, P. Golubev9, O. Gothe4, J.H. Hamilton11, D.J. Hinde8, W. Hartmann1, R.-D. Herzberg7, F.P. Heßberger1,2, J. Hoffmann1, R. Hollinger1, A. Hübner1, E. Jäger1, J. Jeppsson9, B. Kindler1, S. Klein3, I. Kojouharov1, J.V. Kratz3, J. Krier1, N. Kurz1, S. Lahiri12, B. Lommel1, M. Maiti12, K. Miernik5, S. Minami1, A. Mistry7, C. Mokry2,3, J.P. Omtvedt13, G.K. Pang4, P. Papadakis7, I. Pysmenetska1, D. Renisch3, D. Rudolph9, J. Runke1, K. Rykaczewski5, L.G. Sarmiento9, M. Schädel1,6, B. Schausten1, D.A. Shaughnessy10, A. Semchenkov13, J. Steiner1, P. Steinegger14, P. Thörle-Pospiech2,3, E.E. Tereshatov10, T. Torres De Heidenreich1, N. Trautmann3, A. Türler14, J. Uusitalo15, D. Ward9, N. Wiehl2,3, M. Wegrzecki16, V. Yakusheva2 1 GSI, Darmstadt, Germany, 2HIM, Mainz, Germany, 3U. Mainz, Germany, 4LBNL+UC Berkeley, CA, USA, 5ORNL / UT Knoxville, USA, 6JAEA Tokai, Japan, 7U. Liverpool, UK, 8ANU, Canberra, Australia, 9Lund U. Sweden, 10LLNL, USA, 11Vanderbilt U, USA, 12SINP, Kolkata, India, 13U. Oslo, Norway, 14U. Bern+PSI Villigen, Switzerland, 15U. Jyväskylä, Finland, 16ITE Warsaw, Poland Successful experiments on the synthesis of elements with Z=114-118 in 48Ca-induced reactions with actinide targets were first performed at the DGFRS in Dubna [1]. Results for Z=114 (Fl) and Z=116 (Lv) nuclei have been later on confirmed by other groups [2-4]. Using doubly-magic 48Ca for the synthesis of yet heavier elements is not possible due to the lack of sufficient amounts of target materials for elements beyond Cf. Thus, several attempts to produce element 120 in reactions with projectiles beyond 48Ca have been carried out at DGFRS and SHIP [5-7]. The separator TASCA and its detection systems were significantly upgraded since the experiment on 288,289Fl [3] was performed [8]. In the past two years, two experiments on the synthesis of elements beyond Z=118 have been undertaken at TASCA using the reactions 50Ti + 249Bk → 299119* and 50Ti + 249Cf → 299 120*. To verify the performance of the setup, element 117 was also synthesized. The first attempt to form element 120 at TASCA was performed in August-October 2011. The search for element 119 was performed in two series from April to September 2012. The beam energies from the UNILAC, average initial target thicknesses (d) [9], and accumulated beam doses for each reaction are given in Table 1. These Beam Cf Ti 299 120 299 249 Bk 48 Ca References [1] Y. Oganessian, Radiochim. Acta 99, 429 (2011) [2] L. Stavsetra et al., PRL. 103, 132502 (2009) [3] Ch.E. Düllmann et al., PRL. 104, 252701 (2010) [4] S. Hofmann et al., EPJ. A 48, 62 (2012) [5] S. Hofmann et al., GSI Scientific Report-2007, 131 (2008) [6] Yu.Ts. Oganessian et al., PRC. 79, 024603 (2009) [7] S. Hofmann et al., GSI Scientific Report-2011, 205 (2012) [8] see GSI Scientific Report-2011, pages-206, 212, 217, 218, 251-253 (2012) [9] J. Runke et al., J. Radioanal. Nucl. Chem. (accepted) Table. 1. The parameters of the experiments. For details, see text. Target CN Date Elab (MeV) d (µg/cm2) 249 50 values are preliminary. Beam doses were deduced from beam current measurements in front of the target. 85% of the beam doses were estimated to be on the target. Subsequent to the months-long experiments on elements 119 and 120, an experiment on the synthesis of element 117 in reaction 48Ca + 249Bk → 297117* was successfully performed. In about one month of experiment time, the Bk target was bombarded by 48Ca ions at three different beam energies. The final data analyses of all these experiments are currently ongoing. We are grateful for support by the GSI directorate, ion source, accelerator, and experiment electronics staff. 119 297 117 25.08-12.10.2011 306 13.04-03.07.2012 23.07-03.09.2012 300 26.09-09.10.2012 270 515 440 Beam dose Beam dose on target 1.1·1019 0.9·1019 4.2·1019 3.6·1019 0.6·1019 0.5·1019 19 0.4·1019 0.2·1019 09.10-22.10.2012 274 0.5·10 22.10-29.10.2012 268 0.3·1019 GSITemplate2007 131