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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

Experimental search for super and hyper heavy nuclei at TAMU cyclotron

Zbigniew MajkaM. Smoluchowski Institute of Physics, Jagiellonian University

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¤ One of unsolved problems in this area of physics is:

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)

„What is the heaviest possible stable or metastable nucleus?”

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¤ ¤ 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-239and used for the first time accelerator to create new elements )

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New era of SHE creation started in the late-50snewly constructed accelerators were capable to accelerate

heavier nuclei than alpha particles.

Experimental search for super and hyper heavy nucleiutilizes heavy nuclei collisions

(heavy ions collisions)

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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. Seaborg continue the work.

Lawrence Berkeley National Laboratory(Lawrence Radiation Laboratory)

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

Nobel Prize in Chemistry (1951)

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Yu. Ts.OganessianGeorgy Nikolayevich Flyorov (Flerov) (1913 – 1990)

Joint Institute for Nuclear Research – DubnaFlerov Laboratory of Nuclear Reactions (FLNR)

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).

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Peter. Armbruster

GSI Helmholtz Center for Heavy Ion Research– DarmstadtGesellschaft fuer Schwerionenforschung

Elements discovered at GSI:

meitnerium - 109 (1982), hassium - 108 (1984), darmstadtium - 110 (1994), roentgenium – 111 (1994), bohrium - 107 (1981), and copernicium - 112 (1996)

Sigurd Hofmann

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July 12, 2010

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The model calculations of SHEwere motivated by Glenn Seaborg idea in the 1960s

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.

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W.J. Świątecki (1926 – 2009)

A. Sobiczewski

1966: A. Sobiczewski, F.A. Gareev, B.N. Kalinkin - calculated the next magic numbers: Z=114, N=1841966: W.D. Myers, W.J. Świątecki - calculated the next magic numbers: Z=126, N=184

Theory: shell model calculations of heaviest nuclei structure

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Frankfurt school (W. Greiner et. al.) picture of the periodic system of elements (late sixteis)The islands of super heavy elements are shown in vicinty of Z=114, N=184, 196 and Z=164, N=196

Present definition: Super Heavy are nuclei with Z > 104 (Rutherfordium, Rf ).

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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)

48Ca+249Cf->297118->294118+3n No (Z=102) , Sg (Z=108) ,

70Zn+208Pb->288112->277112+1n Bh (Z=107) , Co

(Z=112)

(E*=10-15 MeV2))(E*=30-50 MeV1))

1 Y. Oganessian et al., Phys. Rev. C74 (2006) 044602.2) S. Hofmann et al., Z. Phys. A354 (1996) 229.

Conclusions: correct selection of the reaction partners (Z,N) correct selection of the collision energy

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ER = 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.

Cross section data and extrapolated values for cold fusion reactions (1n-evaporation channel) 1)

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Au

U,Th

Fusion

SHE

vERMassive transfer

Alternative experimental approach to produceSuper and Hyper Heavy Elements (SHE/HHE)

Here, in contrary to the complete fusiona spectrum of SHE will be wide

A „clasical” velocity filter cannot be utilized

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A low energy fission of 232 Th (target)+

197 Au (projectile)

ZFF1 ≈ 33 ZSHE ≈ 33 + 79 = 112

ZFF2 ≈ 57ZSHE ≈ 57 + 79 = 136

Note: Fission fragments of target are a „natural” ion source with a wide spectrum of ions

Nature itself selects the most appropriate fusion partner

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Three generation of experiments for Super Heavy Elements search

atCyclotron Institute, Texas A&M University

2002 – up to now

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The large-bore 7-Tesla Superconducting Solenoid – BigSol

(magnetic field parallel to the ER velocity vector – a large angle acceptance )

reaction products velocity filter

The first generation of experiments(BigSol experiments)

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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

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Fall 2006 measuremets:

197Au(7.5 A.MeV)+232Th

Experiment was discontinued due to spetrometer He leak.

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

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Motivation for alternative pathways of our SHE search continuation

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Search for alpha emitting SHE through implantation and decay of recoiling reaction products

on a downstream catcher foil.

Determine lifetimes from growth and decay observationsin beam and out

Alternative pathways of our SHE search:

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197Au(7.5 A.MeV) beam

bacward wall of Si detectors

232Th target

Passive catcher(60 μm polypropylene)

α - particle

SHE

The second generation of experiments(Passive catcher experiments – a simple system)

A few centimeters

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Results:

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

Observed alpha particle decay energy distributions, beam-on(left) and beam-off (right)

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197Au(7.5 A.MeV) beam

232Th target

Active catcher(~ 100 detectors

α SHE

backward wall of gas - Si detectors

α

gas - Si

To electronics/logic

The third generation of experiments -2012(Active catcher experiments)

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Active catcher detection unit

Au + Th collision products (SHE?)

α α

backward gas - Si detector

Photomupltiplier tube (Hamamatsu Φ = 8 mm)

Aluminium (parabolic shape) light deflecting guide

Fast plastic scintillaror

Dedicated electronicsGenerates event trigger

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.

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Model calculationsforparameter estimation of heavy product, which is createdduring 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)

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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

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Back up

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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

Observation in-beam and out of beam of interesting high energy candidate msec activities

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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.

Seaborg used accelerator (cyclotron) at LBL

(by bombarding heavy nuclei with deuterons) alpha particles.

Neutron irradiation method requires a strong neutron source

(nuclear reactor)

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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.

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