Synthesis & study of superheavy nuclei

Transcription

1 20 th Europen School on Exotic Beams, JINR, Dubna, Russia, August 2013 Synthesis & study of superheavy nuclei Dr. Andrey G. Popeko Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research

2 Laboratory of Nuclear Reactions 2

3 BASIC DIRECTIONS of RESEARCH 1. Heavy and superheavy nuclei Synthesis and study of properties of superheavy elements, Chemistry of new elements, Fusion-fission and multi-nucleon transfer reactions, Mass-spectrometry and nuclear spectroscopy of SH nuclei. 2. Light exotic nuclei Properties and structure of light exotic nuclei, Reactions with exotic nuclei. 3. Radiation effects and physical bases of nanotechnology. 4. Accelerator technology.

4 Nobel Lecture, December 8, 2003 by Vitaly L. Ginzburg WHAT PROBLEMS OF PHYSICS AND ASTROPHYSICS SEEM NOW TO BE ESPECIALLY IMPORTANT AND INTERESTING IN THE BEGINNING OF THE XXI CENTURY? 1. Controlled nuclear fusion. 2. High-temperature and room-temperature superconductivity. 3. Metallic hydrogen. 4. Two-dimensional electron liquid 12. X-ray lasers, gamma-ray lasers, superhigh-power lasers. 13. Superheavy elements. Exotic nuclei. 14. Mass spectrum. Quarks and gluons. Quantum chromodynamics. 4

5 SHEs affect: WHY SUPERHEAVIES? Nuclear physics; Electrodynamics of extremely strong fields; Atomic physics; Chemistry; Astrophysical nucleosynthesis; Evolution of planets; Problem is understandable for tax-payers. 5

6 Periodic table of the elements Dmitri Mendeleev (1869) 6

7 238 U + n 1934: search for transurane 239 U* Nn + e + ν Otto Hahn und Lise Meitner

8 1938: discovery of nuclear fission 235 U + 1 n 236 U* Kr Ba + 1 n + 1 n Liquid drop model: G. Gamow, Proc. Roy. Soc. London A 123, 373 (1929), N. Bohr, J.A. Wheeler, Phys. Rev. 56, 426 (1939). 8

9 Irradiation of targets at HFIR reactor (Oak Ridge) Irradiation in the HFIR flux trap Thermal-neutron flux of neutrons/cm² s 31 target positions (10 13 targets typically irradiated) Produces ~35 mg 252 Cf per target (smaller quantities of Bk, Es, Fm) 9

10 22 mg of 249 Bk, 1 M$, 1 year at HIFR ORNL 10

11 Prehistory Wheeler, J. A., Nuclear Fission and Nuclear Stability, chapter 9 in Niels Bohr and the Development of Physics Pergamon Press, London (1955) In so far as one can extrapolate the stability criteria for very heavy nuclei, one is led to expect the existence of nuclei twice as heavy as known nuclear species, that can be created by massive neutron irradiation, and that will live long enough to be studied in the laboratory. The limits to the stability of superheavy nuclei are set primarily by neutron escape (too high a ratio of neutrons to protons) and by spontaneous fission (too high a ratio of Z 2 to A).

12 R-process Explosion 20 кt fissions; N f = exp{n-1} n = 56 Т = 336 ns; last 18 ns 90 % of neutrons; thermonuclear explosion: 50 ns; total time: < 100 ns, total neutron flux: n cm -2 But collection efficiency ! 12

13 Complete Fusion 13

14 The energy is too low 14

15 The energy is too high 15

16 The energy is correct 16

17 LogT SF / s Spontaneous fission half-lives of actinides U Pu Cm Cf Fm 102 HI-fusion 0 SF-isomers 104 LD -10 mf U mf Cm mf Pu Fissility 17

18 History 1966: A. Sobiczewski, F.A. Gareev, B.N. Kalinkin: next magic numbers are Z=114, N=184; 1966: V.M. Strutinsky; shell correction method; 1967: H.B. Meldner: next magic numbers are Z=114, N=184. Accuracy of predictions: Spontaneous fission half-life: T 1/2 10 ±10!! α-decay: T 1/2 10 ±10!! 18

19 A. Sobiczewski, F.A. Gareev and B.N. Kalinkin Physics Letters 22 (1966)

20 Z 26 Z = October h, 4.5 m 2, 4 g/cm 2 Z 21, N

21 1971, Dubna, P. Fowler, Tracks of SHE!?

22 Предсказания энергии связи различных массовых формул для изотопов Sn 22

23 How well do we understand the known nuclei? 232 Th: α-decaying, T 1/2α = sec, 233 Th: β-decaying, T 1/2β = sec; 238 U: α-decaying, T 1/2α = sec, 239 U: β-decaying, T 1/2β = sec; 257 Fm: α-decaying, T 1/2α = sec, 258 Fm: sf-decaying, T 1/2sf = sec.

24 Cross Section / nb Experimental and theoretical cross-sections for 64 Ni Pb 271 Ds + 1n Experiment, 1982 R. Bock et al. C.J. Wong HIVAP, 1997 B. Pustilnik Experiment, 1994 S. Hofmann et al C.M. - Energy / MeV

25 Chart of the Nuclides 25

26 Z=124 Shell corrections N=184 Proton shell: 114 or/and 126, 120? Z=126 Neutron shell: 172 or/and 184? N=184 Z=114 26

27 Theoretical predictions of position of SHE

28 28

29 Andrew Westphal, Space Sciences Laboratory U. C. Berkeley 29

30 Synthesis of SHE at accelerators 1971; Orsay, France; 232 Th + 82 Kr n; σ 4n < 0.5 mb!!! 1971; Dubna, SU; 208 Pb + 70 Zn n; σ 2n < 0.1 mb!!! (1996, GSI, Germany); ; Dubna, SU; deep inelastic or fission reactions of 76 Ge, 136 Xe U; 1975; Dubna, SU; 48 Ca + actinides: 48 Ca-consumtion : mg/h, 200 US$/mg; Total amount: 5 g in SU, 5g in US. 30

31 Cross-section limits for reactions with 48 Ca 31

32 Число протонов Reactions of SHE synthesis Число нейтронов 32

33 Chart of transactinide nuclides

34 Cross sections / nb Cross-sections of Hot (actinide targets) and Cold (Pb or Bi targets) fusion reactions E-3 1E-4 "Cold" "Hot" 1 b 1nb 1pb 100 1/h 1 /10d 1E-5 1E-6 1fb Element number 1 /20y Warm ( 48 Ca + actinide targets) complete fusion reactions 34

35 Reactions of Synthesis Act Ca Projectiles 48 Ca produced by Heavy Ion Accelerator U400 Energy: MeV Intensity: pμa Consumption: mg/h Beam dose: ( ) Target materials producer Isotope enrichment (%) 233 U IAR U Np IAR Pu IAR Pu ORNL Am IAR / ORNL 99.9 Prices per 1 mg 197 Au 0.03 US$ 239 Pu 4 US$ 48 Ca 80 US$ 249 Cf 60,000 US$ 245 Cm IAR Cm ORNL / IAR Bk ORNL Cf ORNL / IAR 97.3

36 On-line separation Focal plane detector Separator Beam Target Beam stop 36

37 FLNR accelerators U400M - 4m heavy ion cyclotron E = MeV/n U400-4m heavy ion cyclotron E = MeV/n U200-2m heavy ion cyclotron E = 3 15 MeV/n IC-100-1m heavy ion cyclotron E = MeV/n Microtron MT-25 - electron accelerator E = 25 MeV DC280 4m cyclotron under construction. 37

38 New 18 GHz Ion sources DECRIS-SC1, SC2

39 FLNR U400 cyclotron 39

40 UNILAC (GSI) 40

41 Design of the superconducting (liquid He free) 18 GHz ECR ion source Running at IC

42 SHIP-target 31 cm 42

43 GANIL Rotating Targets 43

44 249 Cf - target 44

45 45

46 Molten Beam Stop 46

47 Magnetic and electric rigidities Magnetic rigidity: Bρ (T m) = (A E (МeV)) ½ q-1 Deflection in electrostatic dipole : tg(α) = 10-6 (q ε(v/cm) L(cm))/(2 Е(MeV)) Electric rigidity Е/q (МV) Velocity: v (сm/ns) = (Е(МeV)/А) ½. 47

48 22 Ne U 260 No* Nucl Е(МeV) Br (vac. Т m) Br (He, Т m) Br (H 2. Т m) V (cm/ns) E/q vac (MV) 22 Ne No U He H

49 48 Ca Pu * Nucl. Е(МeV) Br (vac. Т m) Br (He. Т м) Br (H 2. Т м) V (cm/ns) E/q vac (MV) 48 Ca Pu He H

50 136 Xe Xe 272 Hs* Nucl. Е(МeV) Br (vac. Т m) Br (He. Т m) Br (H 2. Т m) V (cm/ns) E/q vac (MV) 136 Xe Hs Xe He H

51 The Velocity Filter «SHIP» 51

52 Electrostatic separator VASSILISSA 52

53 Dubna Gas Filled Recoil Separator

54 Research groups at DGFRS and VASSILISSA 54

55 Berkeley Gas-filled Separator 55

56 Gas-filled recoil separator (GARIS) 56

57 Position-Time Correlation 57

58 Focal plane detectors «Additional» detectors, x, γ-, n, «Main» detector Time-of-flight 58

59 focal plane detector Time-of-flight detector VASSILISSA Time resolution: 300 ps (FWHM) TOF 1 TOF BEAM 2 MCP 59

60 Time-of-flight detector SHIP 60

61 Focal plane detector Position resolution: 0.5 mm Energy resolution: 15 кev (FWHM) 61

62 E / MeV E ToF distribution of 252 No ( 48 Ca PbS) TOF / channel 62

63 Focal plane detector GABRIELA GABRIELA - Gamma Alpha Beta Recoil Investigation with the Electromagnetic Analyser 63

64 On-line neutron detector 74 3 He-counters ε = 25 % ν T ( 252 No) =

65 SHIP-trap 65

66 SHIP data taking system 66

67 Methods of identification: generic decay links; cross-bombardments; on-line post separator; quasi-on-line mass analyzer; calorimetric detectors; Ge-γ- detectors; ion traps. We need higher production rates! 67

68 Generic decay links 107 Bh 108 Hs 109 Mt 110 Ds 111 Rg Cn

69 244 Pu + 48 Ca 292 * 114 Total beam dose: Cm + 48 Ca 296 * 116 Total beam dose: Strip # 4 Strip # 5 Strip # * * * Strip # * 4n 30.5 mm Strip # 8 4n * 27.8 mm MeV 4n 46.9 ms 11.7 mm 27.9 mm MeV ms 19.8 mm 4n 19.2 mm MeV 55 ms 20.3 mm 4n 20.7 mm MeV 0.77 s 30.6 mm MeV 4.58 s 11.8 mm MeV 2.42 s 28.3 mm MeV 0.31 s 19.5 mm MeV s 20.8 mm MeV 10.3 s 30.1 mm MeV 18.0 s 11.4 mm MeV 53.9 s MeV s 19.2 mm MeV s 20.6 mm SF 221 MeV (156+65) 14.3 s 30.6 mm SF 213 MeV (171+42) 7.4 s 11.5 mm SF 197 MeV (195+2) 6.9 s 28.5 mm SF MeV 23 s 19.6 mm SF 177 MeV 3.15 s 20.4 mm The beam was switched off June 25, :39 Oct. 28, :24 July 19, :21 May 02, :21 May 08, :54 69

70

71 Conclusion I Yu. Oganessian. Status of the experiment on the synthesis Z=117. JINR SC, Feb.18-19, 2010, Dubna 71

72 Conclusion II 72

73 Conclusion III Heaviest target: 249 Cf Z max = 118 Heavier projectiles ( 50 Ti, 54 Cr, 58 Fe, 64 Ni) Heavier targets ( 251 Cf, 254 Es -???); Symmetric reactions: 136 Xe+ 136 Xe, 136 Xe+ 150 Nd, 150 Nd+ 150 Nd; Multi Nucleon Exchange - Reactions with RIB (??, or colliders technique (K4-K10)): Nucleon transfer reactions ( 136 Xe+ 208 Pb, 238 U+ 248 Cm). 73

74 Confirmations ( ) A/Z Setup Laboratory Publications SHIP GSI Darmstadt Eur. Phys. J. A 32, 251 (2007) COLD PSI-FLNR (JINR) NATURE 447, 72 (2007) 286, BGS LRNL (Berkeley) Phys. Rev. Lett. 103, (2009) 288, TASCA GSI Mainz Phys. Rev. Lett. 104, (2010) 292, SHIP GSI Darmstadt Eur. Phys. J. A 48, 62 (2012)

75 as the result: Pure Appl. Chem., Vol. 83, No. 7, pp , 2011 Discovery of the elements with atomic numbers greater than or equal to 113 (IUPAC Technical Report) The IUPAC/IUPAP Joint Working Party (JWP) on the priority of claims to the discovery of new elements and 118 has reviewed the relevant literature pertaining to several claims. It was determined that the Dubna- Livermore collaborations share in the fulfillment of those criteria both for elements Z = 114 and

76 Provisional Recommendation - Names and Symbols of the Elements with Atomic Numbers 114 and December 2011 A joint IUPAC/IUPAP Working Party (JWP) has confirmed the discovery of the elements with atomic numbers 114 and 116. In accord with IUPAC procedures, the discoverers proposed names as follows: flerovium and symbol, Fl, for the element with Z = 114 and livermorium with the symbol Lv for the element with Z = 116. The Inorganic Chemistry Division recommended these proposals for acceptance. IUPAC seeks your comments. 76

77 The Festive Naming Ceremony of the new chemical elements Flerovium and Livermorium took place on 24 October 2012 in Moscow IUPAC President Prof. Kazuyuki Tatsumi William Goldstein (Livermore), 77

78 Synthesis of transfermium elements Synthesis of Transfermium Elements Year Discovered element Laboratory Pure & Appl. Chem., Vol. 65, No. 8, pp , (1993) No - Nobelium FLNR 1961/ Lr - Lawrencium LBNL/FLNR 1966/ Rf - Rutherfordium FLNR/LBNL 1970/ Db - Dubnium FLNR/LBNL Sg - Seaborgium LBNL/LLNL Bh - Bohrium GSI Hs - Hassium GSI/FLNR Mt - Meitnerium GSI 78

79 Synthesis of Superheavy Elements Year Discovered element Laboratory Pure & Appl. Chem., Vol. 75, No. 10, pp , (2003) Ds - Darmstadtium GSI Pure & Appl. Chem., Vol. 76, No. 12, pp , (2004) Rg - Roentgenium GSI Pure & Appl. Chem., Vol. 81, No. 7, pp , Cn - Copernicium GSI no name RIKEN, FLNR, LLNL Fl - Flerovium FLNR, LLNL no name FLNR, LLNL Lv - Livermorium FLNR, LLNL no name FLNR, LLNL, ORNL no name FLNR, LLNL Z=114, 116: Pure & Appl. Chem., Vol. 83, No. 7, pp , (2011). 79

80 Conclusion IV Mendeleev periodic table of the elements (2012) 80

81 Interesting reactions Reaction: Who? When? 238 U + 64 Ni GSI Pu + 58 Fe FLNR Cm + 54 Cr GSI Cf + 50 Ti GSI Xe Xe FLNR Xe Sn GANIL Cf + 48 Ca??? 251 Cf + 50 Ti??? 252 Cf + 48 Ca????? 254 Es + 48 Ca???

82 Density Proton number Exotic nuclei α α Z=120, A= α-particles n + 60 neutrons n α α Line of -stability n Z > 220 bubble 150 Z > 120 semi-bubble was produced in 249 Cf+ 48 Ca reaction Z < 120 normal Neutron number 82

83 Study of Chemical Properties of New Elements of the Meneeleev Periodic Table 83

84 Periodic table of elements extended up to Z=210

85 GAS PHASE CHEMISTRY WITH ELEMENTS 112 AND 114 Are elements 112, 113 and 114 volatile metals? How do relativistic effects influence the chemistry of E112, E113 and of E114? 85

86 Chemistry of the Element Bk + 48 Ca 281 Rg SF 7.9 s 1.2 s α s 0.22 s α (8) MeV 9.48(11) MeV 9.96 MeV TKE = 218(5) MeV 38 s 1.3 min 7.4 min α Db ms 10 ms α (9) MeV MeV 274 Bh 11.0 s 13 s α (10) MeV 8.43 MeV 11.03(8) MeV MeV 278 Mt 0.74 s 8.1 s α (19) MeV 9.14 MeV 282 Rg 28.3 s 16 s α (10) MeV 9.43 MeV s 1.0 s α (10) MeV 9.56 MeV 112 ms 45 ms α (40) MeV MeV (10) MeV MeV 268 Db α Bh 9.02 MeV 9.8 s 243 Am + 48 Ca α Mt α MeV 0.72 s 280 Rg α MeV 3.6 s 3n α MeV 0.48 s MeV 87 ms SF TKE = 219(5) MeV 33.4 h SF TKE = 205(5) MeV 16 h DGFRS 86

87 Chemistry of the elements 112 & 114 Beam ( 48 Ca; MeV) Target ( 238 U, 242 Pu; 1 mg/cm 2 ) SiO 2 -Filter Ta metal 850 C Capillary with 2 s transport time Cryo On-line Detector (4p COLD) (32 pairs PIN diodes, one side gold covered) Recoil chamber Beam stop Quartz inlay Quartz column T Hg 112 Rn Temperature gradient: 35 C to 184 C Loop Carrier gas He/Ar (70/30) l

88 Trend of sublimation enthalpy within group 12 Element 112 is a noble metal like Hg room temperature As predicted by Bernd Eichler, 1974 (!) 88

89 Decay chain of 268 Db observed with Dubna Gas-filled Recoil Separator in 243 Am + 48 Ca reaction 268 Db SF 205 MeV 23.1 hr Bh MeV s 276 Mt MeV 1.03 s MeV 5.2 s R MeV 0.69 s MeV 125 ms

90 Irradiation of 243 Am-target with 48 Ca-ions 90

91 Taking off thin layer of Cu-catcher ( mg of Cu) 91

92 Chemical isolation of Db Dissolution of the Cu-cuttings in HNO 3 conc. Addition of the La 3+ (0.7 mg), tracers ( 92m Nb, 177 Ta, 167 Tm, 169 Yb) and carriers Nb, Ta (1 g) Precipitation of La(OH) 3 by NH 4 OH (La, Nb, Ta, Db, Ac precipitate; Cu-solution) 3 times (Nb, Ta 99%) Dissolution of the La(OH) 3 in 2M HNO 3 Sorbtion of La, Ac, Nb, Ta, Db on Dowex 50 (cation-exchange resin) Elution of group 5 elements (Nb, Ta, Db) with 2 ml 1M HF Evaporation of the solution to 0.1 ml Pipetting of the 0.1 ml solution on a PE-foil (40 μg/cm 2 ) - 3 hr ( 92m Nb 85 5%) ( 177 Ta 75 5%) 92

93 Detection system 93

94 Translational Kinetic Energy (MeV) Fission fragment Total Kinetic Energy Yukawa + Exponential Nuclear Energy Two - body viscosity A.J. Sierk and J.R. Nix, Phys.Rev. C 21 (1980) 982 (TP) = 0, Z= Z 2 /A 1/3 94

95 Total kinetic energy

96 Counts Total Kinetic Energy distributions of 252 Cf and 268 Db TKE / MeV 96

97 Periodic table of the elements (2006) 97

98 Mass Analyzer of Super Heavy Atoms Dm/m=1000 Ion source Hot catcher Т= 2000К V 0 = 40 кv Magnetic mass-analyser Target Ion beam Detectors 98

99 Mass Analyzer of Super Heavy Atoms (MASHA) 99

100 I, na I, na MASHA test with Xe and Hg isotopes 26.4% Xe M / DM= % Hg 10.1% 16.9% 23.1% 13.2% 29.7% 0.07 a.m.u. 6.8% a.m.u % 2% 3.9% mass, a.m.u. 0.1 M/DM= mass, a.m.u. 100

101 Search for Superheavy Elements in Nature 101

102 To be found in Nature: one of superheavy nuclides would have a lifetime comparable with the age of the Earth, of about y; in the Universe should exist a mechanism leading to the formation of SHE.

103 Search for SHE in Nature Search for SHE in terrestrial matter Search for SHE in meteorites Search for SHE in cosmic rays Investigation of isotopic anomalies 20 years Void result, but many new high sensitive detection methods were developed 103

104 On the Stability of Superheavy Elements against Fission U. Mosel and W. Griener, Z. Physik, 222 (1969) 261

105 Accuracy of predictions for SHE Spontaneous fission: barrier height ± 10% T 1/2sf *10 ±2 ; inertia parameters ± 30% T 1/2sf *10 ±6 ; total: T 1/2sf *10 ±8 α-decay: method, parameters T 1/2α *10 ±2 ; Q α ± 10% T 1/2α *10 ±5 ; total: T 1/2α *10 ±7 β decay: spins, parities -? Q β ± 1 MeV T 1/2β *10 ±3

106 Super-, Hypernova Starting point: Fe, Pb, U; Neutron flux: ; γ-flux; Half-lives: α, β, SF; Time: sec; Density - Expansion; Crossections: (n,γ), (n,f), (n,x), (γ,f), (γ,x), (ν,x).. How heavy elements will be injected into the Universe? 232 Th, 235 U, 238 U, ( 244 Pu?) are present in Nature!

107 Stellar quake of neutron stars or colliding stars Existence of SHE in Nature is not forbidden!

108 Big proportional counters

109 3 He-neutron multiplicity counters

110 Specific SF activity of samples

111 SF and -decay lifetimes R. Smolanćzuk. Phys. Rev. C56 (1997)

112 Log T (seconds) Search for SF of natural Eka Os by detection of fission neutrons decay Age of the Earth Spherical Shell Deformed Shell stable nuclei Neutron number 112

113 Detector installed in Modana (France) Fréjus peak Entrance to the road tunnel Modane France 113

114 Synthesis of new atomic nuclei using targets of a naturally occurring SHE

115 Perspectives 115

116 Allocation of material resources for the priority fields of research and facilities in M$ IBR-2M and spectrometers Nuclotron-M/NICA Cyclotron complex DRIBs-III Information Technologies Other projects TOTAL IBR-2M and spectrometers 116 Other projects Information Technologies 6.7 Cyclotron complex DRIBs-III Nuclotron-M/NICA

117 DRIBs-III Modernization of existing accelerators (U400М & U400) Creation of a new experimental hall ( 2600 m 2 ) Development and creation of next generation set-ups Creation of a high current heavy ion accelerator (A 100, E 10 MeV A, I 10 pµa) : 60 М$

118 FLNR 2016 SHE factory U400R U m 2 IC100 NanoLab DRIBs DC280 MT25 U400M

119

120 New experimental hall

121 DC280 - stand-alone SHE-factory DC280 (expected) E=4 8 MeV/A Ion Ion energy [MeV/A] Output intensity 7 Li O Ar Ca 5 0,6-1, Synthesis and study of properties of superheavy elements; Search for new reactions for SHEsynthesis Chemistry of new elements; 54 Cr Fe Sn Xe U DGFRS-II, Chemistry, Preseparator + Cryo-Detector, +

122 Thank you for your attention! Many thanks to the organizers!! 122