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Experiments on synthesis of the heaviest elements at RIKEN

Experiments on synthesis of the heaviest elements at RIKEN. The 6th China-Japan Joint Nuclear Physics Symposium May 17th, 2006, Shanghai, China. Kouji Morimoto RIKEN (The Institute of Physical and Chemical Research) Japan. Table of Contents. Introduction (research region)

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Experiments on synthesis of the heaviest elements at RIKEN

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  1. Experiments on synthesis of the heaviest elements at RIKEN The 6th China-Japan Joint Nuclear Physics Symposium May 17th, 2006, Shanghai, China Kouji Morimoto RIKEN (The Institute of Physical and Chemical Research) Japan

  2. Table of Contents • Introduction (research region) • RIKEN facility (GARIS) • Results 208Pb + 70Zn → 277112 + n 209Bi + 70Zn → 278113 + n • Future plans and Summary

  3. 272Rg 14 chains 278113 2 chains 271Ds 14 chains 265Hs 10 chains Reactions studied by GARIS 116 176 115 114 113 112 Rg Ds Mt 170 Hs 277112 2 chains Bh Sg Db Rf 162 a Lr SF No b+ or EC Md Fm b- New ! Es Cf 152

  4. RIKEN Accelerator Research Facility RIBF facility (under construction) Present facility

  5. Beam Energy Monitor GARIS RILAC Facility CSMAcc. Tanks RILAC Acc. Tanks RFQ-Linac 18GHz ECR Ion Source ±0.2%

  6. Principle of Operation for Gas Filled Recoil Separator Magnetic Field Vacuum Bρ= 0.0227 ・A ・(v/v0) / q [Tm] In the gas. When 1 < v/v0 < Z2/3 qav = (v/v0)・Z1/3 Bρ= 0.0227 ・A ・Z-1/3 [Tm] Trajectory depends only on A and Z of ion, does not depend on Initial charge state or velocity. Heavy Ion q-1 q q+1 Magnetic Field He Gas Continues atomic collision with gas q

  7. 20 208Pb 18 209Bi Bohr’s theorem 16 169Tm 14 198At 271Ds 208Pb 12 272Rg qav 265Hs 209Bi 212Ac 10 192Bi 203Fr 8 208Pb 204Fr 234Bk 254No 6 255Lr 245Fm 209Bi 4 30 5 25 20 15 10 v0: Bohr velocity (v/v0)Z1/3 Estimation of the equilibrium charge states

  8. RIKEN GARIS(Gas-filled Recoil Ion Separator)

  9. G A R I S Detectors Target Dipole magnet Beam

  10. Rotating target system Beam Elastic f = 300 mm, w = 3000 rpm Target thickness：　200～450μｇ/cm2 Evaporated on to 30μg/cm2 carbon foil after irradiated

  11. CCD #3 CCD #2 CCD #1 CCD #4 CCD #4 CCD #1 CCD #2 CCD #4 CCD #1 CCD #2 CCD #3 Target chamber Top view Side view

  12. 140 l/s MBP To GARIS Projectiles MBP 280 l/s Projectiles TMP 150 l/s TMP 280 l/s 10-2 10-1 100 101 102 Vacuum [Pa] Differential pumping system Top view Side view Orifice : f 25 mm

  13. PSD SSD box ions Focal Plane Detectors α TOF 6 cm α

  14. Yield Estimation • Cross Section (σ): 0.1 pico-barn (10-37 cm2) • Target Thickness (T): 400μg/cm2of 209Bi (1.2x1018atoms/cm2) • Beam intensity(I): 0.5 particleμA(3x1012ions/cm2) • Total efficiency(ε): 0.8 Y/s = εｘ σ ｘ Ｔ ｘ Ｉ = 2.9・10-7/s = 1 event / 40 day

  15. 272Rg 14 chains 278113 2 chains 271Ds 14 chains 265Hs 10 chains 277112 2 chains Reactions studied at GARIS 116 176 115 114 113 112 Rg Ds Mt 170 Hs Bh Sg Db Rf 162 a Lr SF No b+ or EC Md Fm b- Es Cf 152

  16. 208Pb + 70Zn → 277112 + n J. Phys. Soc. Jpn., to be submitted K. Morita, K. Morimoto, D. Kaji et al.

  17. Experimental condition 208Pb(70Zn, n)277112 period 2004/4/2 ～ 2004/5/24 Beam Energy 346 MeV at target half depth Total Dose 4.4x1018 Target Thickness 450 μg/cm2 number of events 2 s0.44+0.59-0.29 pb Irradiation time 693 Hours (28.9 Days) Beam Intensity 1.76x1012 /s (0.3 p-mA) Total counting rate ～1 cps

  18. Reaction energy for 208Pb(70Zn, n)277112

  19. Observed events at RIKEN in 208Pb + 70Zn reaction Strip #8 Strip #11 34.42 MeV 23.33 mm 35.13 MeV 18.45 mm 277112 CN 277112 CN 16-April-2004 E (70Zn) = 349.5 MeV 11.09 ± 0.07 MeV 1.10 ms 23.57 mm 11.32 ± 0.04 MeV 1.22 ms 18.31 mm 273Ds 273Ds 11.14 ± 0.04 MeV 0.52 ms 23.45 mm 11.15±0.07MeV (2nd trig. PSD+SSD) 39.9 ms 20.18 mm 269Hs 269Hs 9.17 ± 0.04 MeV 14.19 s 23.34 mm 9.25 ± 0.07 MeV(PSD+SSD) 0.270 s 19.03 mm 265Sg 265Sg 8.71 ± 0.04 MeV 23.02 s 23.45 mm 8.70 ± 0.04 MeV 79.9 s 18.05 mm 261Rf 261Rf 22-May-2004 E (70Zn) = 349.5 MeV 197.3 MeV 2.97 s 23.41 mm 156.3 MeV 8.3 s 18.50 mm

  20. 32.04 MeV 18.06 mm 277112 CN Observed events at GSI in 208Pb + 70Zn reaction 11.45 MeV 280 ms 17.85 mm 24.09 MeV 26.06 mm 273Ds 277112 CN 09-Feb-1996 E(70Zn) = 343.8 MeV 11.08 MeV 110 ms 17.77 mm 11.17 MeV 1406 ms 26.03 mm 269Hs 273Ds 9.23 MeV 19.7 s 17.81 mm 11.20 MeV 310 ms 26.01 mm 265Sg 269Hs 4.60 MeV 7.4 s 17.57 mm 9.18 MeV 22.0 s 26.16 mm 261Rf 265Sg 8.52 MeV 4.7 s 17.96 mm 0.2 MeV 18.8 s 27.33 mm 257No 261Rf 05-May-2000 E (70Zn) = 346.1 MeV 8.34 MeV 15.0 s 17.91 mm 153 MeV 14.5 s 26.70 mm 253Fm

  21. 277112 t = 1.0 ms 273Ds t = 0.24 ms RIKEN GSI 269Hs t = 14 s 265Sg t = 32 s 261Rf t = 7.6 s 10ms 1000s 1ms 0.1s 10s T_decay/s

  22. 209Bi + 70Zn → 278113 + n J. Phys. Soc. Jpn., Oct. 2004 K. Morita, K. Morimoto, D. Kaji et al.

  23. 272Rg 14 chains 278113 2 chains 271Ds 14 chains 265Hs 10 chains Reactions studied by GARIS 116 176 115 114 113 112 Rg Ds Mt 170 Hs 277112 2 chains Bh Sg Db Rf 162 a Lr SF No b+ or EC Md Fm b- New ! Es Cf 152

  24. 209Bi(70Zn, n)278113 Experimental condition period 2003/9 ～ Beam Energy 349 MeV at target half depth Total Dose 5.5x1019 Target Thickness 450 μg/cm2 number of events 2 Cross section 31（+53-25）　fb Irradiation time 240Days Beam Intensity  3x1012 /s (0.5 - 0.8pμA) Total counting rate ～2 cps

  25. 36.75 MeV TOF 44.61 ns 30.33 mm 36.47 MeV TOF 45.69 ns 30.08 mm 209Bi + 70Zn → 278113 + n 278113 CN 278113 CN a a 1st chain 11.68MeV (PSD) 344μs 30.49 mm 11.52 MeV (PSD) 4.93ms 30.16 mm 23-July-2004 18:55 (JST) 274Rg 274Rg a a 11.15 MeV 6.149+5.003 (PSD+SSD) 9.260 ms 30.40 mm 0.88+10.43=11.31 MeV (PSD+SSD) 34.3 ms 29.61 mm 270Mt 270Mt a a 2nd chain 10.03 MeV 1.136+8.894(PSD+SSD) 7.163 ms 29.79 mm 2.32 MeV (escape) 1.63 s 29.45 mm 2-April-2005 2:18 (JST) 266Bh 266Bh a a 9.08 MeV (PSD) 2.469 s 30.91 mm 9.77 MeV (PSD) 1.31 s 29.65 mm Wilk et al. 9.29±0.1 MeV0.87 sec 262Db 262Db Table of Isotopes T1/2 34±4 sec S.P. ～33% : α～64% 204.05 MeV(PSD) 40.9 s 30.25 mm 192.32 MeV(PSD) 0.787 s 30.47 mm s.f. s.f.

  26. 5 5 a1 a1 0 0 5 5 a2 a2 0 0 Counts / 100 keV 5 5 a3 Counts / bin a3 0 0 5 5 a4 a4 0 0 5 5 a5 a5 0 0 8 9 10 11 12 100ms 10ms 1s 100s 10000s E / MeV Tdecay α 252Md ← 256Lr ← 260Db ← 264Bh ← 268Mt ← 272Rg α３ α５ α４ α２ α１ t=5.5ms α１ α１ α２ t=30ms α２ t=1.3s α３ α３ α４ α４ t=5.7s α５ t=27s α５ (sec)

  27. N=165 278113 278113 t = 2.6 ms N=163 274Rg t = 21.8 ms RIKEN 1st event N=161 270Mt t = 0.82 s 2nd event N=159 266Bh t = 1.89 s N=157 262Db t = 20.8 s 10ms 1000s 1ms 0.1s 10s T_decay/s

  28. 50 Total (High gain) Beam-like particles 100 40 0.3 cps 10 1 278113 0 10 20 30 EER [MeV] Target-like particles Total [ ROI = 8 - 12MeV ] 20 5 4.2x10-3 cps 10 0 8 9 10 11 12 Counts per 0.01 MeV 0 Anti-coincidence with TOF detectors 0 20 40 60 80 100 5 TOF [ns] Light charged particles 6.3x10-4 cps 0 Mass gate 8 9 10 11 12 30 ER-α correlation (DP = ±1 mm, Dt = 60 s) 20 5 Counts 278113 a4 a3 a2 a1 10 0 0 8 9 10 11 12 100 200 300 0 Energy / MeV Mass

  29. Summary for the 113 experiments • 2 atoms of 278113 were produced by 209Bi(70Zn,n) reaction. • 278113(a)→274Rg(a)→270Mt(a)→266Bh(a)→262Db(SF) • Identification was based on • connected to theknown decays266Bh(a)→262Db(SF) • reaction energy systematics • cross section systematics • Z & A of 278113 are largest ones among the isotopes whose Z & A were determined experimentally produced by “cold fusion” reaction.

  30. 86Kr Future plan 82Se 118 294 76Ge Cold Fusion Reaction 117 116 289 290 292 70Zn 68Zn 176 115 287 288 64Ni 114 287 288 289 286 283 113 283 284 278 238U + 58Fe 112 277 283 284 285 Rg 272 279 280 269 270 271 273 280 281 Ds 268 275 276 Mt 170 238U + 48Ca 269 Hs 267 277 Bh 266 267 271 272 238U + 40Ar Sg 265 266 Db 267 268 232Th + 40Ar N=162

  31. SHE chemistry using GARIS as a pre-separator RIKEN GARIS Gas-jet transport system He gas (with aerosol) Differential pumping section Focal plane Primary beam Evaporation residues Beam stopper Gas inlet Mylar window Teflon capillary SHE nuclides Chemistry apparatus Rotating target D2 10 cm Elastic scattering monitor Q1 Q2 D1 0 1 2 m Chemistry system coupled to a recoil separator for nuclear physics studies Open new frontiers in SHE chemistry Chemical experiments under extremely low background conditions Stable and high gas-jet transport efficiency Chemical reactions with a large variety of chemical reagents H. Haba et al Gas-jet transport system coupled to GARIS in collaboration with the TASCA community at GSI (TransActinide Separator and Chemistry Apparatus)

  32. α spectrum of 255No α spectrum of 245Fm σ = 150 nb σ = 15 nb He pressure: 127.7 kPa He flow rate: 2.0 L/min TKCl: 640 oC Beam dose: 1.3 × 1016 Aerosol collection: 60 s Counting time: 11940 s He thickness: 60 mm He pressure: 89.2 kPa He flow rate: 5.0 L/min TKCl: 618 oC Beam dose: 3.9 × 1017 Aerosol collection: 1.5 s Counting time: 20950 s H. Haba The α spectrum of 255No is very complicated. Only the α-peak of 245Fm is clearly identified.

  33. Summary 265Hs 10chains 271110 (Ds)14 chains 272111(Rg)14 chains 2771122 chains 2781132 chains 208Pb,209Bi(HI,1n) reaction 1mb 100nb RIKEN 10nb 1nb 100pb 10pb 1pb 0.1pb 102 104 106 108 110 112 114 100 Atomic Number

  34. Collaborators • Kosuke Morita RIKEN • Kouji Morimoto RIKEN • Daiya Kaji RIKEN • Takahiro Akiyama RIKEN, SaitamaUniv. • Nozomi SatoTohoku Univ. • Akira Yoneda RIKEN • Takatoshi Ichikawa RIKEN • Hidetoshi Kikunaga RIKEN • Toshimi Suda RIKEN • Atsushi Yoshida RIKEN • Tetsuya Ohnishi RIKEN • Hiromitsu Haba RIKEN • Eiji Ideguchi Univ. of Tokyo • Akira Ozawa Univ. of Tsukuba, RIKEN • Takayuki Yamaguchi Saitama Univ. • Hiroyuki Koura JAERI • Fuyuki Tokanai Yamagata Univ. • Y. –L. ZhaoIHEP Beijing • Xu IMP Lanzhou • Hisaaki Kudo Niigata Univ. • Shin-ichi GotoNiigata Univ. • Keisuke Sueki Univ. of Tsukuba • Kenji Katori RIKEN

  35. 20 272Ds 10 273111 4 2 s (pb) 278112 1 0.5 279113 0.3 0.2 0.1 5 10 15 20 Ex of C.N. (MeV) Excitation Energy Calculated threshold of fission after 1n emission Masses of Beams & Targets Audi & Wapstra, Nucl. Phys A565, 1 (1993) Masses of Compound Nuclei Myers & Swiatecki, Nucl. Phys. A601, 141 (1996)

  36. Future Plans Near future New element (>113) search present system Chemistry GARIS + gas-jet In the next Gamma-ray spectroscopy (α-γ coincidence) present system + gamma-ray detector Direct Z and A measurement GARIS + re-accelerator + dE - E detector

  37. Summary of the Future Plans Near future New element (>113) search present system Chemistry GARIS + gas-jet Almost ready Should be develop In the next Gamma-ray spectroscopy present system + gamma-ray detector Direct Z and A measurement GARIS + re-accelerator + dE E detector

  38. ・Research in future ーScience of heavy elementsー 1)Searching for new elements 2)Spectroscopic study of heaviest elements 3)Chemistry of heaviest elements 4)Development of the new detectors for SHE study

  39. 1)Searching for the new elemets Z=113 exp. continue 209Bi + 70Zn → 278113 + n Z=114 exp. start 208Pb + 76Ge → 283114 + n Z=115 exp. start 209Bi + 76Ge → 284115 + n ??? Z=120 exp.238U + 64Ni → 299120 + 3n GARIS upgrade cf. DUBNA 244Pu + 58Fe → 299120 + 3n

  40. 20 272Ds 10 273111 4 2 s (pb) 278112 1 0.5 279113 0.3 0.2 0.1 5 10 15 20 Ex of C.N. (MeV) Calculated threshold of fission after 1n emission Masses of Beams & Targets Audi & Wapstra, Nucl. Phys A565, 1 (1993) Masses of Compound Nuclei Myers & Swiatecki, Nucl. Phys. A601, 141 (1996)

  41. いつどの位実験を行ったのか event 7月23日 4月2日

  42. Summary • 208Pb(58Fe,n)265Hs, 208Pb(64Ni,n)271Ds,209BiPb(64Ni,n)272Rg, 208Pb(70Zn,n)277112, and 209Bi(70Zn,n)278113 reactions have been studied. • Independent confirmations of synthesis of elements 108, 110, 111, and 112 • Optimum reaction energies for (HI,n) reactions were studied • New synthesis of 113th element

  43. 5 5 a1 a1 0 0 5 5 a2 a2 0 0 Counts / 100 keV 5 5 a3 Counts / bin a3 0 0 5 5 a4 a4 0 0 5 5 a5 a5 0 0 8 9 10 11 12 100ms 10ms 1s 100s 10000s E / MeV Tdecay α 252Md ← 256Lr ← 260Db ← 264Bh ← 268Mt ← 272Rg α３ α５ α４ α２ α１ t=5.5ms α１ α１ α２ t=30ms α２ t=1.3s α３ α３ α４ α４ t=5.7s α５ t=27s α５ (sec)

  44. 5 5 a1 a1 0 0 5 5 a2 a2 0 0 Counts / 100 keV 5 5 a3 Counts / bin a3 0 0 5 5 a4 a4 0 0 5 5 a5 a5 0 0 8 9 10 11 12 100ms 10ms 1s 100s 10000s E / MeV Tdecay α 252Md ← 256Lr ← 260Db ← 264Bh ← 268Mt ← 272Rg α３ α５ α４ α２ α１ t=5.5ms α１ α１ α２ t=30ms α２ t=1.3s α３ α３ α４ α４ t=5.7s α５ t=27s α５ (sec)

  45. 5. Summary 1. SHE chemistry using GARIS as a pre-separator ・ Development of a gas-jet chamber coupled to GARIS ・ Model experiments with 206Fr and 245Fm 2. Search for SHE nuclides for chemical experiments ・Investigation of the 232Th + 40Ar reaction Future plans ・26Mg(238U,3n)261Rf (Z=104) ・27Al(238U,3n)262Db (Z=105) ・30Si(238U,3n)265Sg (Z=106) ・34S(238U,3n)269Hs (Z=108) ・48Ca(238U,3n)283112 (Z=112) 3. New chemistry techniques ・Flow-electrolytic column ・Gas chromatograph column coupled to the gas-jet chamber

  46. W. J. Swiatecki, K. Siwek-Wilczynska, and J. Wilczynski PRC (2004) RIKEN

  47. Machine-times (This 5 years) 265Hs(Z=108) 3 days　（10） 271Ds(Z=110) 40 days　（14） 272Rg(Z=111) 50 days　（14） 277112 29 days　（2） 278113 173 days　（2）

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