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International Workshop on Nuclear Dynamics and Thermodynamics in Honor of Prof. Joe Natowitz

Experimental search for super and hyper heavy nuclei at TAMU cyclotron Zbigniew Majka M. Smoluchowski Institute of Physics, Jagiellonian University. International Workshop on Nuclear Dynamics and Thermodynamics in Honor of Prof. Joe Natowitz

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International Workshop on Nuclear Dynamics and Thermodynamics in Honor of Prof. Joe Natowitz

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  1. Experimental search for super and hyper heavy nuclei at TAMU cyclotron Zbigniew Majka M. Smoluchowski Institute of Physics, Jagiellonian University International Workshop on Nuclear Dynamics and Thermodynamics in Honor of Prof. Joe Natowitz Texas A&M University, College Station, Texas, USA August 19-22, 2013

  2. The question: „How did the world originate?” is the fundamental one in science. Of particular importance is research of the material world i.e. how the elements are made. The elements existing in nature are ordered according to their atomic (chemical) properties in the periodic system (developed by Dimitry Mendeleev and Lothar Meyers) ¤One of unsolved problems in this area of physics is: „What is the heaviest possible stable or metastable nucleus?”

  3. ¤ The heaviest known natural element is uranium (U) with the number of protons Z=92 in its nucleus. (One can find also in natural uranium ores trace quantities of neptunium (Np, Z=93) and plutonium (Pu, Z=94). ¤All elements above U have been produced artificially and are more or less unstable. In 1934 Enrico Fermi proposed the first method to produce new elements. By bombarding a nucleus (Z,N) with neutrons one obtains a new isotope (Z,N+1) which can β-decay thus forming a new element (Z+1,N). The first elements created in a laboratory was neptunium (McMillan) (University of California in Berkeley in 1940-41) (Seaborg discovered plutonium-239 through the decay of neptunium-239 and used for the first time accelerator to create new elements )

  4. New era of SHE creation started in the late-50s newly constructed accelerators were capable to accelerate heavier nuclei than alpha particles. Experimental search for super and hyper heavy nuclei utilizes heavy nuclei collisions (heavy ions collisions) W#2

  5. Lawrence Berkeley National Laboratory (Lawrence Radiation Laboratory) Nobel Prize in Chemistry (1951) Glenn T. Seaborg (1912 – 1999) Edwin Mattison McMillan (1907 – 1991) He created neptunium in 1940, by absorption of neutron into the uranium-239 and a subsequent beta decay. He moved to the radar research at MIT and Glenn T. Seaborgcontinue the work. He was the principal or co-discoverer of ten elements: plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium and element 106, which was named seaborgium in his honor while he was still living

  6. Joint Institute for Nuclear Research – Dubna Flerov Laboratory of Nuclear Reactions (FLNR) Georgy Nikolayevich Flyorov (Flerov) (1913 – 1990) Yu. Ts.Oganessian Elements discovered at JINR: 1963 – element 102, rutherfordium (1964), nobelium (1966), dubnium (1968), seaborgium (1974), bohrium (1976), flerovium (Island of stability) (1999), livermorium (2001), ununtrium - 113 (2004), ununpentium - 115 (2004), ununoctium – 118 (2006), ununseptium - 117 (2010).

  7. GSI Helmholtz Center for Heavy Ion Research– Darmstadt Gesellschaft fuer Schwerionenforschung Peter. Armbruster Sigurd Hofmann Elements discovered at GSI: meitnerium - 109 (1982), hassium - 108 (1984), darmstadtium - 110 (1994), roentgenium – 111 (1994), bohrium - 107 (1981), and copernicium - 112 (1996)

  8. July 12, 2010

  9. The model calculations of SHE were motivated by Glenn Seaborg idea in the1960s who suggested the possibility of an "island of stability„existence. The hypothesis was that the atomic nucleus is built up in "shells" in a manner similar to the structure of the much larger electron shells in atoms. When the number of neutrons and protons completely fills the energy levels of a given shell in the nucleus, the binding energy per nucleon will reach a local maximum and thus that particular configuration will be stronger bound and will have a longer lifetime than nearby isotopes that do not possess filled shells.

  10. Theory: shell model calculations of heaviest nuclei structure W.J. Świątecki (1926 – 2009) A. Sobiczewski 1966: A. Sobiczewski, F.A. Gareev, B.N. Kalinkin - calculated the next magic numbers: Z=114, N=184 1966: W.D. Myers, W.J. Świątecki - calculated the next magic numbers: Z=126, N=184

  11. Frankfurt school (W. Greiner et. al.) pictureof the periodic system of elements (late sixteis) The islands of super heavy elements are shown in vicinty of Z=114, N=184, 196 andZ=164, N=196 Present definition: Super Heavy are nuclei with Z >104 (Rutherfordium, Rf ).

  12. Classical approach to the SHE creation. A complete fusion of the projectile and target nuclei (at the Coulomb barrier energy) A hot fusion (Cf, Pu actinide targets) A cold fusion (Pb, Bi targets) (E*=30-50 MeV1)) (E*=10-15 MeV2)) 48Ca+249Cf->297118->294118+3n No (Z=102) , Sg (Z=108) , 70Zn+208Pb->288112->277112+1n Bh (Z=107) , Co (Z=112) Conclusions: correct selection of the reaction partners (Z,N) correct selection of the collision energy l 1 Y. Oganessian et al., Phys. Rev. C74 (2006) 044602. 2) S. Hofmann et al., Z. Phys. A354 (1996) 229.

  13. Cross section data and extrapolated values for cold fusion reactions (1n-evaporation channel) 1) sER = 1. 0 and 0.5 pico barn for production of Z=1121), 1182. (the net production probability decreases ~ one order of magnitude for each two units of increase in atomic number) .1. Hofmann et al., Eur. Phys. J. A14 (2002) 147. 2. Yu. Ts. Oganessian et al., Phys. Rev. C74 (2006) 044602.

  14. Massive transfer Fusion vER Au SHE U,Th Alternativeexperimental approach to produce Super and Hyper Heavy Elements (SHE/HHE) Here, in contrary to the complete fusion a spectrum of SHE will be wide A „clasical” velocity filter cannot be utilized

  15. A low energy fission of 232 Th (target) + 197 Au (projectile) ZFF1 ≈ 33 ZSHE ≈ 33 + 79 = 112 ZFF2 ≈ 57 ZSHE ≈ 57 + 79 = 136 Note: Fission fragments of target are a „natural” ion sourcewith a wide spectrum of ions Nature itself selects the most appropriate fusion partner

  16. Three generation of experiments for Super Heavy Elements search at Cyclotron Institute, Texas A&M University 2002 – up to now

  17. The first generation of experiments (BigSolexperiments) The large-bore 7-Tesla Superconducting Solenoid – BigSol (magnetic field parallel to the ER velocity vector – a large angle acceptance ) reaction products velocity filter

  18. 136Xe,172Yb,198Pt(15 A.MeV)+ 238U 84Kr, 172Yb(15 A.MeV)+232Th 238U(12 A.MeV)+198Pt, 238U, 232Th 84Kr(24.8 A.MeV)+232Th 84Kr,129Xe,197Au(7.5 A.MeV)+232Th I) T. Materna et al. In: Progress in Research April 1, 2003-March 31, 2004, p.II-17, http://cyclotron.tamu.edu/publications.html

  19. Fall 2006 measuremets: 197Au(7.5 A.MeV)+232Th M. Barbui et. al.., Int. Journal of Modern Phys. E18 (2009) 1043 M. Barbui et al. Journal of Phys., 312 (2011) 082012 M. Barbui et al. AIP Conf. Proc. 1336 (2011) 594 Experiment was discontinueddue to spetrometer He leak.

  20. Motivation for alternative pathways of our SHE search continuation

  21. Alternative pathways of our SHE search: Search for alpha emitting SHE through implantation and decay of recoiling reaction products on a downstream catcher foil. Determine lifetimes from growth and decay observations in beam and out

  22. The second generation of experiments (Passive catcher experiments – a simple system) α - particle bacward wall of Si detectors SHE Passive catcher (60 μm polypropylene) 232Th target A few centimeters 197Au(7.5 A.MeV) beam

  23. Results: Observed alpha particle decay energy distributions, beam-on(left) and beam-off (right) The backward wall of Si detectors detected signals which might be from ≈ 14 MeV α particles. However, it was impossible to exclude another reasons for such signals

  24. The third generation of experiments -2012 (Active catcher experiments) backward wall of gas - Si detectors α α SHE gas - Si Active catcher (~ 100 detectors 232Th target To electronics/logic 197Au(7.5 A.MeV) beam

  25. Active catcher detection unit Aluminium(parabolic shape) light deflecting guide Fast plastic scintillaror Photomupltiplier tube (Hamamatsu Φ = 8 mm) Au + Th collision products (SHE?) Dedicated electronics Generates event trigger α α backward gas - Si detector Deposited heavy fragment within selected energy window in coincidence with alpha particle (detected by gas-Si detector or scintillator ) alpha decay takes place within selected time window.

  26. Model calculations for parameter estimation of heavy product, which is created during a massive transfer* Assumption: 1. Mass transfer occurs in the selected point on the trajectory (usually the point of closest approach). 2. Transferred mass generates transfers of the momentum and angular momentum. 3. Fluctuations of the transferred momentum and angular momentum are included. and the fluctuations in the mass transferred localization are neglected). 4.The estimates do not determine the likelihood of the transfer (*Zbigniew Sosin)

  27. Cyclotron Institute, Texas A&M University, USA M. Barbui, G. Chubaryan, G. Giuliani, K. Hagel, E-J. Kim,T. Materna, R. MurthyJ. Natowitz, L. Quin, P. Sahu, G. Souliotis, R. Wada, J. Wang, S. Wuenschel Dipartimento di Fisica dell'Universitá and INFN Sezione di Padova,Padova, Italy D. Fabris, M. Lunardon,S. Moretto,G. Nebbia, S. Pesentec,G. Viesti, INFN Laboratori Nazionali di Legnaro, Legnaro, Italy M.Cinausero, G. Prete, V. Rizzi University of Michigan, Ann Arbor, MI, USA F. Becchetti, H. Griffin, T. O'Donnel, University of Silesia, Katowice, Poland S. Kowalski, K. Schmidt Smoluchowski Institute of Physics, Jagiellonian University, Krakow, Poland J. Kallunkathariyil, P. Lasko, Z. Majka, R. Planeta, Z. Sosin, A. Wieloch

  28. Back up

  29. Observation in-beam and out of beam of interesting highenergycandidate msec activities Time distributions gated on energy for beam on (left) and beam off. Half-lives determined from fitting both in-beam and out-of- beam data with two components are indicated

  30. Elements 99 and 100 were first identified in the debris of the hydrogen bomb test in 1952 (the process reconstructed was the many neutron capture by uranium which then decayed quickly by beta emission to more stable isotopes of elements 99-einsteinium and 100-fermium). To synthesize elements 95, 96, 97, 98 and 101 it was sufficient to irradiate previously produced heavy nuclei (93,94,99) with neutrons or alpha particles. Neutron irradiation method requires a strong neutron source (nuclear reactor) Seaborg used accelerator (cyclotron) at LBL (by bombarding heavy nuclei with deuterons) alpha particles.

  31. Observed growth and decay of for detected 8.1 MeV alpha particles during a 100ms on, 100 ms off timing sequence. Calculated lines correspond to a half-life of 50 ms.

  32. Calculated halflives vs A for Z ≥108 calculated by Stasczak et al. Phys. Rev. C 87, 024320 (2013)

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