SPECTROSCOPY OF TRANSFERMIUM ISOTOPES AT DUBNA: RESULTS AND PLANS

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1 SPECTROSCOPY OF TRANSFERMIUM ISOTOPES AT DUBNA: RESULTS AND PLANS Yu. Ts. Oganessian, A.V. Yeremin, O.N. Malyshev, A.G. Popeko, A. Lopes-Martens, K. Hauschild Super Heavy Nuclei and O. Dorvaux International Symposium Texas A & M University, College Station TX, USA March 31 - April 02, 2015

2 Introduction. Types of the spectroscopy experiments Experimental set up at FLNR JINR. Past, present and future. Experiments at FLNR JINR. Results and plans.

3 Main goal of our activity: Preparation of the experiments at SHE Factory. Spectroscopy of superheavy nuclei in decay chains of the 287 Fl and isotopes 1. Model experiments using high resolution alpha spectroscopy (15-17 kev) to study decays of Rf (Z=104) and Db (Z=105) Isotopes and daughter nuclei. 2. Full scale experiments aimed to spectroscopy studies of 287 Fl, and daughter nuclei. Five Ge detectors, thick tunnel detectors ofr detecting CE.

4 1. In beam gamma ray and electron spectroscopy 2. Focal plane α γ - β spectroscopy After separation, the nuclei are implanted in a silicon detector where their decay is studied RDT Prompt gamma-ray Spectroscopy in e nc 7 a t Dis kv kv 5 0 Beam Magnetic Deflection Quadrupole magnetic +100 kv kv -100 kv focusing II Beam Electrostatic Stop deflection +100 kv 3 1 rs e t Me 9 Quadrupole Target magnetic Wheel focusing I Time of Flight detector Positionsensitive detector array Decay and isomeric α, γ and electron spectroscopy

In beam gamma ray and electron spectroscopy Recoil Decay Tagging (RDT) method: (spectroscopy at the target position) Method to investigate rotational bands - transition rates, deformation parameters,

5 In beam gamma ray and electron spectroscopy Recoil Decay Tagging (RDT) method: (spectroscopy at the target position) Method to investigate rotational bands - transition rates, deformation parameters, moments of inertia, which can be compared with theoretical predictions. SEPARATOR RDT Main limitation γ background from fission => I beam ~ 50 pna => σ > 10 nb. I+8 I+6 I+4 I+2 I Nilson quantum numbers [N n z Λ]Ω π [622]5/2+ [624]7/2+ [734]9/2-

6 Recoil Decay Tagging (RDT) Information on the position of the next spherical «gap» Confirm the existence of deformed states (Z=102,104 ): rotational bands 1j15/2 2p3/2 2f5/ Midshell deformed nuclei N=152, Z=102 2f7/2 1i13/2 1h9/2 102 N=162, Z= s1/2 2d3/2 Important disadvantage: ER formation cross section should be more than tens of nanobarns déformation ε 2

Gamma and electron spectroscopy at the focal plane of the separators: Beam Target Separator detection Study of the decay properties of heavy nuclei- isomeric and ground states, α, γ and β

7 Gamma and electron spectroscopy at the focal plane of the separators: Beam Target Separator detection Study of the decay properties of heavy nuclei- isomeric and ground states, α, γ and β spectroscopy of mother (implanted) and daughter products of the evaporation residues. Single particle level structure in Fm-Sg region when moving away from the N=152 towards the N=162 shell. Excitation energy, spin and parity of nuclear levels.

8 Decay (focal plane) studies α-γ (CE) - decay measurements à transitions gs(mother) à gs (daughter) à Q-value à transitions gs(mother) à excs (daughter) followed by γ, CE à E * excited levels à Multipolarity of transition(s) to gs or excs à spin and parity assignments à Q-value (if gs not or weakly populated) (à excs (daughter) might be isomeric ) à transitions isoms (mother) à isoms, excs, gs (daughter) à E * isomeric levels à spin and parity assignments (correlation between life-times and spin/parity differences) ER-γ(CE) decay measurements à transitions isoms(mother) à excs, gs (mother) à E * isomeric levels à spin and parity assignments

Focal plane α γ - β spectroscopy BEFORE: Information about nuclear structure Alpha decay fine structure and half - life measurements Performed@GSI 208Pb(50Ti,3n)255Rf σ ~ 0.

9 Focal plane α γ - β spectroscopy BEFORE: Information about nuclear structure Alpha decay fine structure and half - life measurements Performed@GSI 208Pb(50Ti,3n)255Rf σ ~ 0.2 nb Z=104 α α Study isomeric states & the properties of the daughter nuclei Z=102 F.P. Heβberger et al. Eur. Phys. J A12(2001)57 Electron detection crucial : Ø ae=n(electron)/n(gamma) >Transition multipolarity

10 Nuclear spectroscopy of the isotopes of transfermium elements (last results and possible experiments) Proton number Neutron number

11 Presently Working Experimental Set Ups in the World Dubna Gas Filled Separator (Russia) SHIP (Darmstadt, Germany) Berkeley Gas Filled Separator (USA) GARIS (Saitama, Japan) VASSILISSA (Dubna, Russia) LIZE3 (GANIL, France) RITU (JYFL, Finland) FMA (Argonne, USA) JAERI-RMS (Tokai, Japan) TASCA (Darmstadt, Germany) Gas - filled Vac. V filter Gas - filled Gas - filled Vac. E filter Vac. V filter Vac. V filter Gas - filled RDT Vac. RMS Vac. RMS Gas - filled Focal plane Focal plane Focal plane Focal plane RDT Focal plane Heavy element research Spectroscopy studies 11

12 Spectroscopy of transfermium elements at Dubna: Preconditions High intensity heavy ion beams with good energy resolution pµa cyclotron U400. Experimental set up recoil kinematic separator VASSILISSA with good background conditions at the focal plane Sophisticated detector systems at the focal plane- GABRIELA, Neutron detector

13 Experimental set-up VASSILISSA + (α,γ,β)-detector array VASSILISSA set up at experimental hall of the U400 cyclotron

Detector systems at the focal plane of experimental set up GABRIELA: Gamma Alpha Beta Recoil Investigation with the Electromagnetic Analyser Detection of α, β, γ

14 Detector systems at the focal plane of experimental set up GABRIELA: Gamma Alpha Beta Recoil Investigation with the Electromagnetic Analyser Detection of α, β, γ with high efficiency and resolution Neutron detector (62 3 He counters) and Silicon array at the focal plane Detection of α, SF and neutrons with high efficiency

Nuclear spectroscopy of transfermium elements at Dubna: 50 Ti + 208 Pb 22 Ne + 242 Pu 22 Ne + 238 U 48 Ca

Published results Published results Fm253 In progress In progress : 40 Ar + 182 W Future experiment

15 Nuclear spectroscopy of transfermium elements at Dubna: 50 Ti Pb 22 Ne Pu 22 Ne U 48 Ca Pb 48 Ca Bi Rf256 Rf257 Lr Ne U 22 Ne U or 48 Ca Pb No251 No257 Published results Published results Fm253 In progress In progress : 40 Ar W Future experiment Planned experiments U218 U220 U221 Failure from 210 Pb target Th Ne Pb 22 Ne Bi 40 Ar Hf 15

16 Some experimental results, obtained at FLNR JINR. 251 No sec 253 No 5/2+ γ µ s sec Fm 279 γ γ γ β 71 γ 58 α 8001 β α Fm Lr 2.5 sec 30 sec Md

Spectroscopy of transfermium elements at Dubna: Perspectives Reconstruction of the U400 cyclotron and creation of the new DC280 cyclotron. Modernization of the VASSILISSA experimental set up.

17 Spectroscopy of transfermium elements at Dubna: Perspectives Reconstruction of the U400 cyclotron and creation of the new DC280 cyclotron. Modernization of the VASSILISSA experimental set up. Energy filter Velocity filter The goal: high production rate of slow ER s from asymmetric combinations High beam current; Efficient separation; Efficient detection; Optimized targets; Reduction of background.

18 Way to the asymmetric combinations Achievement: neutron rich isotopes, that could not be reached in more symmetric combinations. Disadvantage: very broad energy and angular distributions of recoils => low transmission of kinematic separators Possible solutions Modernization of the kinematic separator, design for asymmetric combinations Increase of beam intensity (I Ne ~ 2.5 pma)

19 What can be (presently) achieved by decay studies? Advantages of Dubna => Acces to less neutron-deficient nuclei 78 Pt, 79 Au, 80 Hg, 81 Tl, 82 Pb, 83Bi targets «cold fusion» 90 Th, 92 U, 94 Pu, 95 Am, 96Cm targets «hot fusion» Bh 254 Bh 255 Bh 256 Bh 257 Bh 258 Bh 259 Bh 260 Bh Present limits σ 3-5 nb for decay σ nb for prompt 261 Bh 262 Bh 263 Bh 264 Bh 265 Bh 266 Bh 267 Bh 268 Bh Sg 253 Sg 254 Sg 255 Sg 256 Sg 257 Sg 258 Sg 259 Sg 260 Sg 261 Sg Sg Sg Sg Sg 264 Sg 265 Sg 266 Sg 267 Sg Db 252 Db 253 Db 254 Db 255 Db 256 Db 257 Db 258 Db 259 Db 260 Db 261 Db 262 Db 263 Db 264 Db 265 Db 266 Db Rf 251 Rf 252 Rf 253 Rf 254 Rf 255 Rf 256 Rf 257 Rf 258 Rf 259 Rf 260 Rf 261 Rf 262 Rf 263 Rf 264 Rf 265 Rf Lr 250 Lr 251 Lr 252 Lr 253 Lr 254 Lr 255 Lr 256 Lr 257 Lr 258 Lr 259 Lr 260 Lr 261 Lr 262 Lr 263 Lr 264 Lr No 249 No 250 No 251 No 252 No 253 No 254 No 255 No 256 No 257 No 258 No 259 No 260 No 261 No 262 No 263 No Md 245 Md 246 Md 247 Md 248 Md 249 Md 250 Md 251 Md 252 Md 253 Md 254 Md 255 Md 256 Md 257 Md 258 Md 259 Md 260 Md 261 Md Fm 244 Fm 245 Fm 246 Fm 247 Fm 248 Fm 249 Fm 250 Fm 251 Fm 252 Fm 253 Fm Fm 255 Fm 256 Fm 257 Fm 258 Fm 259 Fm 260 Fm

20 Improvements to experimental set up : First stage years Improvement of slow ERs transmission 1) New ion optical scheme => 2 x efficiency modernization of the existing set up. 2) ToF : thinner windows => less straggling Second stage years Improvement of detector array 1) New Si detectors : larger + more strips => 2 x ERs detection efficiency, higher CE detection efficiency 2) Modified Ge detector => higher gamma detection efficiency

21 First stage Velocity filter for asymmetric combinations (modernization of VASSILISSA) High transmission for asymmetric combinations (beams of 12 C, 14,15 N, 16,18 O, 20,22 Ne) movable plates of electrostatic deflectors Availability for symmetric combinations ( 136 Xe Xe 272 Hs*) 50 cm long plates, high electrostatic field strength (decrease of the distance between plates) Time of Flight detector 10 Movable plates Distance in Meters Quadrupole Lenses II Electric Deflector II Magnetic Deflector II Magnetic Deflector III Positionsensitive detector array 0 1 Magnetic Deflector I Beam Stop Electric Deflector I Beam Target Wheel Quadrupole Lenses I

GABRIELA 2015: Gamma detection efficiency estimations for new detector set up Clover detector Preliminary GEANT4 detector arrangement including a Clover and 4 EUROGAM phase-i.

22 GABRIELA 2015: Gamma detection efficiency estimations for new detector set up Clover detector Preliminary GEANT4 detector arrangement including a Clover and 4 EUROGAM phase-i. These surround the 10x10 cm 2 implantation detector (in blue) and its PCB (green). Right : A first estimate of the achievable singles efficiency as a function of photon energy f or a distributed source.

23 Design of new detector chamber finished Manufacturing is now running Clover detector at CSNSM Orsay

24 Comparison of the gamma detection efficiency E gamma (kev) GABRIELA 2009 GABRIELA % 34 % % 26 % % 22 % % 17 % % 14 %

25 Experiments in years Reaction Goal Improvements Transmission Old New 22 Ne( 197 Au,5n) 214 Ac Transmission measurements 22 Ne( 206 Pb,4n) 224 U Spectroscopy of U isotopes 40 Ar( 208 Pb,3n) 245 Fm Transmission measurements 50 Ti( 208 Pb,2n) 256 Rf Study of SF of 256 Rf 22 Ne( 197 Au,5n) 214 Ac Transmission measurements March 2014 DSSD 100x mm 2 DSSD 100x100 mm April 2014 DSSD 100x mm 2 15 April 05. May 2014 Neutron detector April 05. May 2015 DSSD 100x mm 2 Experiments with new detector chamber and new detector array second half of year 2015

26 Model experiments using high resolution alpha spectroscopy (15-17 kev) to study decays of Rf (Z=104) and Db (Z=105) Isotopes and daughter nuclei with the use of U400 cyclotron. 50 Ti beam intensity 0.5 pµa (experiment).

27 F.P.Heßberger et. al., Z. Phys. A 359, (1997) 50 Ti Pb 257 Rf + 1n Excitation functions for evaporation residue production in irradiations of 208 Pb with 50 Ti. The lines are to guide the eye

28 Spectrum of alpha-particles attributed to 257 Rf from 50 Ti Pb at Eproj = ( ) A MeV a) correlated to evaporation residues b) correlated to daughter decays (Ealpha = kev)

29 Arrangement of the experiment 50 Ti Pb 257 Rf + 1n Formation cross section of 257 Rf ~ 10 nbarn Target thickness ~ at/cm 2 Beam intensity of 50 Ti ~ 3x10 12 pps. If ε transmission ~ 40 % 300 events per day 10 days about 3000 events.

30 Preparation for full scale experiments aimed to spectroscopy studies of 287 Fl, and daughter nuclei at SHE factory. 48 Ca,beam intensity about 2.5 pµa.

31 Nuclear spectroscopy of transfermium elements What we have at present? Experiment Dubna Gas Filled Separator

32 Yu. Ts. Oganessian et al., Total integral flux (beam energies MeV) 2.5х10 19

33 All together 31 chains registered 48 Ca Am n

34 48 Ca Am n DGFS: 2.5х10 19 Beam energies МeV, 31 chains

35 Nuclear spectroscopy of transfermium elements What we have at present? Experiment TASCA, GSI, Darmstadt

36 TASISpec A highly efficient multi-coincidence Spectrometer for nuclear structure investigations of the heaviest nuclei Nuclear Instruments and Methods in Physics Research A 622 (2010)

37 [28] Yu. Ts. Oganessian et al., Phys. Rev. C 87, (2013) D. Rudolph et. al., PRL 111, (2013)

38 TASCA GSI, Darmstadt Beam energies 242 and 245 MeV, 22 chains 16 gamma quanta

39 Proposed decay schemes of 280 Rg 276 Mt (a) and 276 Mt 272 Bh (b).

40 Nuclear spectroscopy of transfermium elements What we have at present? Theory

41 E Baldini-Neto, B V Carlson and D Hirata, J. Phys. G: Nucl. Part. Phys. 32 (2006)

42 Jolos R.V. 2- center oscillator model

43 Arrangement of the experiment 48 Ca Am n Formation cross section of ~ 8 pbarn Target thickness ~ at/cm 2 Beam intensity of 50 Ti ~ 1.5x10 13 pps. If ε transmission ~ 40 % 1 event per day (U400) 3 events per day (DC280, SHE factory) 100 days integral flux about 10 20, about 300 events (optimistic case). If 22 chains 16 gamma quatna (TASCA, GSI) 300 chains 215 gamma quanta.

44 Expectations Detection of alpha and gamma decays from ground and excited states of odd odd isotopes , , 280 Rg, 276 Mt, 272 Bh Alpha detection efficiency 70 % Gamma detection efficiency (energy range from 100 to 500 kev) from 34 % to 14 %. Probability of the registration of alpha gamma correlation % In the case of 300 events of we will have real possibility to measure gamma transitions from excited levels.

45 Energy (MeV) 48 Ca Pu 287 Fl +3n

46 Arrangement of the experiment 48 Ca Pu 287 Fl +3n Formation cross section of ~ 4 pbarn Target thickness ~ at/cm 2 Beam intensity of 50 Ti ~ 1.5x10 13 pps. If ε transmission ~ 40 % 1 event per 2 days (U400) 3 events per 2 days (DC280, SHE factory) 100 days integral flux about 10 20, about 150 events (optimistic case).

The people A.V. Yeremin, M.L. Chelnokov, V.I. Chepigin, A.V. Isaev, I.N. Izosimov, D.E. Katrasev, A.N. Kuznetsov, A.A. Kuznetsova, O.N. Malyshev, A.G. Popeko, Yu.A. Popov, E.A. Sokol, A.I. Svirikhin, FLNR, JINR, Dubna, Russia K.

Rubert LPSC Grenoble, France J. Piot GANIL, France D. Tonev, E. Stefanova, P. Detistov Institute for nuclear research and nuclear energy, Sofia, Bulgaria B. Andel, Z.

47 The people A.V. Yeremin, M.L. Chelnokov, V.I. Chepigin, A.V. Isaev, I.N. Izosimov, D.E. Katrasev, A.N. Kuznetsov, A.A. Kuznetsova, O.N. Malyshev, A.G. Popeko, Yu.A. Popov, E.A. Sokol, A.I. Svirikhin, FLNR, JINR, Dubna, Russia K. Hauschild, A. Lopez-Martens, K. Rezunkina CSNSM, IN2P3-CNRS, F Orsay Campus, France O. Dorvaux, B. Gall, F. Dechery, H. Faure, Z. Asfari IPHC, IN2P3-CNRS, F Strasbourg, France J. Rubert LPSC Grenoble, France J. Piot GANIL, France D. Tonev, E. Stefanova, P. Detistov Institute for nuclear research and nuclear energy, Sofia, Bulgaria B. Andel, Z. Kalaninova Comenius University of Bratislava, Slovakia S. Hofmann, J. Maurer, S. Heinz GSI. Darmstadt, Germany D. Pantelica, C. Nita IFIN-HH, Bucharest, Romania S. Mullins, P. Jones, S. Ntshangase, ithemba LABS, South Africa J. Gehlot IUAC, New Dehli, India

48 Thank you for your attention!

The neutron multiplicity study at spontaneous fission of short-lived isotopes (z > 100) using VASSILISSA recoil separator

The neutron multiplicity study at spontaneous fission of short-lived isotopes (z > 100) using VASSILISSA recoil separator Svirikhin A.I. Joint Institute for Nuclear Research, Dubna, Russia Manipal University,