Synthesis of New Elements and New Approaches in SHE Research

Transcription

1 ECOS Town Meeting Orsay 2014 Synthesis of New Elements and New Approaches in SHE Research Michael Block GSI Darmstadt and Helmholtz Institute Mainz

2 Courtesy Ch.E. Düllmann Superheavy Elements Current Status Z 114 Bh Hs Mt Ds Rg Cn α α α Fl α Lv α 100?????? Recent results from Dubna in dicussion D. Ackermann N SF α β + EC β -

3 Courtesy Ch.E. Düllmann Superheavy Elements The hottest Topics Z SF No, 255 Lr a N b + EC b -

4 Nuclear Shells: Magic Numbers in SHE? M. Bender et al., Phys. Lett. B 515 (2001) 42

5 Courtesy Ch.E. Düllmann / A. Yakushev Cross Sections for SHE Synthesis cross section / barn 1E-6 Projectile Target 48 Ca,..., 70 Zn Pb/ 209 Bi 1E-7 1E-8 1E-9 1E-10 1E-11 1E-12 1E-13 1E-14 1E C,..., 26 Mg U Bk 48 Ca U,..., 249 Cf atomic number Z

6 Requirements Some Facts and Figures Beam intensity: present: 6 x pps (1µA p ) for typical beams 48 Ca, 50 Ti, future: 6 x pps (10µA p ) feasible Ø But: need for high power targets (talk by J. Piot) Due to low intensities radioactive beam Targets: intensities not competitive yet! mg/cm 2 thickness about Ø 10 Intensity mg of material of 10 9 needed pps corresponds for typical target to wheel geometries Problem: limited 0.5 availability µg / cm 2 targets actinide material Recoil separator High transmission (for synthesis: short separation time) low background (beam suppression, shielding of n, γ)

7 Synthesis, separation and identification of SHE Beam ( 48 Ca, 50 Ti) Target ( 243 Am, 249 Bk, 249 Cf) TASCA TransActinide Separator and Chemistry Apparatus Particle Detector (α; e - ; SF) Photon Detector (γ; X) Detection of decay chain 288 Fl Impant 6.5 MeV 242 ms α 9.98 MeV 284 Cn 130 ms SF MeV Ch.E. Düllmann et al., PRL 104 (2010)

8 ... DSSSD State-of-the-Art Stop Detector Array 6900 pixels Target Chamber 144 mm side view 48 mm Digital DAQ acces to lifetimes down to 100 ns Amplitude 1800 Eα1 τ Eα Time / channel 50Ti beam

9 How to synthesize element 120? 249Cf + 50Ti 299Ubn Courtesy Ch.E. Düllmann

10 Z 109 Hs Bh Mt 264Hs 0.5ms 262Sg Sg ms Db Rf Search for Element 119: 50 Ti+ 249 Bk calculated decay properties by A. Sobiczewski Mt ms 265Hs 266Hs 267Hs 269Hs 269Hs 270Hs 271Hs 2 ms 34 s 261Rf 68 s 2 ms 49 ms 265Sg 16 s 263Rf ~8 s Rg 0.4s 264Bh 265Bh 266Bh 267Bh 1 s 263Sg s 1 s 264Sg 37 ms 261Db 262Db 263Db 2 s 260Rf 21 ms 27 s 262Rf 2 s? Rg 1.6ms 269Ds 270Ds 271Ds Ds 0.2ms 0.1ms 1.1ms 268Mt 42 ms ~1 s 15 s 266Sg 0.4 s 270Mt 0.5 s 12s 267Sg ~1min 266Db 22min 7.6 s 267Db 1.2 h Rg 6 ms 273Ds 0.2ms ~4 s 1.2 s 274Mt0.45 s 270Bh 271Bh 272Bh 61 s 268Db 16 h 267Rf 1.3 h ms 277Cn Cn 0.6ms 12 s 271Sg 2.4 m 270Db 23 h 275Mt 9.7ms 276Mt 6 s 275Hs 0.15 s ms 278Rg 279Rg 280Rg 0.17 s 0.17 s 3.6 s 274Bh 0.9 m Courtesy Ch.E. Düllmann 279Ds s 278Mt 5.2 s N s 281Rg 26 s s s s 282Cn 283Cn 284Cn 285Cn 0.8ms s 282Rg 0.5 s 281Ds 9.6 s ms 0.1 s ms s s 34 s s s ms 30ms ms ms 18 ms 18 ms 53ms ms s 0.2ms 0.2ms ms ms α SF

11 Courtesy Ch.E. Düllmann 2012: Search for element Ti+ 249 Bk Element 119 Status of element 119 search campaign in 2012 at GSI: beam dose: particles 40 TB of data (analysis is ongoing) Sensitivity 70 fb for one event (preliminary) Current status of data analysis yields no evidence for detection of element 119

12 Chain 1 ER (4) 55.9 ms 10.31(4) 2.98 s 8.86(2) 178 s 9.42(3) 6.79 s 8.84(3) 45.1 s 7.89(3) 1.34 h h Element 117 confirmation and discovery of a new long-lived isotope Energy (kev) Event- by- event analysis pixel X=103, Y= Energy (kev) Time (s) days Ampl Pile-up chan / 17ns days Time (s) Random Probability for ER-α-α-α-α-α-α-SF chain with E α =( ) MeV with same Δt s as in chain 1: <5*10-15 decay event beam off J. Khuyagbaatar et al., Phys. Rev. Lett. 112, (2014) SF

13 : 4 decay chains from DGFRS 2 TASCA chains Tot. J. Khuyagbaatar et al., Phys. Rev. Lett. 112, (2014) Rg 278 Mt 274 Bh 270 Db 266 Lr

14 Courtesy Ch.E. Düllmann Cross Sections for SHE Synthesis cross section / barn 1E-6 Projectile Target 48 Ca,..., 70 Zn Pb/ 209 Bi 1E-7 reach 10 fb cross section 13 C,..., 26 Mg limit U Bk 48 Ca U,..., 249 Cf 1E-8 1E-9 1E-10 1E-11 1E-12 1E-13 1E-14 1E-15 Ø future synthesis attempts should be able to atomic number Z Z= Ti Bk 70 fb

15 Importance of Masses for Z > 100 high-precision mass measurements provide accurate absolute binding energies to map nuclear shell effects anchor points to fix decay chains Studies the nuclear structure evolution Benchmark theoretical nuclear models

16 SHIPTRAP: Probing the Strength of Shell Effects δ 2n (N,Z) = 2B(N,Z) B(N-2,Z) B(N+2,Z) 337 (2012) 1207 No Experimental Muntian (mic-mac) Z=114 N=184 Möller FRDM Z=114 N=184 TW-99 Z=120 N=172 SkM* Z=126 N=184

17 CryoCell Setup Cryo Cell DC-Cage RF-Funnel 40K 20mbar He 450mm 400mm Gas Cell DC-Cage 300K RF- Funnel 60mbar He 320mm Advantages compared to 1st generation gas cell: Larger stopping volume and Coaxial injection of reaction products Higher cleanliness due to cryogenic operation Larger gas density at a lower absolute pressure C. Droese et al. NIM B 338, 126 (2014)

18 Laser Spectroscopy of the Heaviest Elements Methods: Search for atomic levels hyperfine spectroscopy Measurement of isotopic shifts Motivation: relativistic and QED effects Nuclear moments & spins changes in mean square charge radii

19 Search for Atomic Transitions Nobelium Theoretical predictions for the 1 S 0-1 P 1 - transition in the element nobelium (Z=102) Calculations benchmarked by comparison to homologs Uncertainties large from compared to experimental resolution Experiment: two step RIS with non-resonant second step excitation search for 1 P 1 level in range predicted by different theories [1],[2]: S. Fritzsche, Eur. Phys. J. D 33 (2005) 15 [3]: A. Borschevsky et al., Phys. Rev. A 75 (2007) [4]: Y. Liu et al., Phys. Rev. A 76 (2007) [5]: P. Indelicato et al., Eur. Phys. J. D 45 (2007) 155 [6]: J. Sugar, J. Chem. Phys. 60 (1974) 4103 determine IP from Rydberg series

20 Resonant Ionization Laser Spectroscopy of Nobelium Buffer Gas Recoil Beam + + Pulsed Filament (Tantal) Desorption of 254 No from Ta: ν 2 ν 1 Laser Beams + 10 cm evaporation temperature 1350(20) K α Detector - M.Laatiaoui et al., Eur. Phys. J. D 68 (2014) 71 H. Backe et al., Eur. Phys. J. D 45, 99 (2007)

21 SHIP October 2014 Homolog Yb (Z =70) 112 Sn( 48 Ca,5n) 155 Yb (t 1/2 =1.75 s, α) Laser on Laser 2 λ 2 = 351nm Laser 1 λ 1 = nm

22 Superheavy Elements (SHE): a new collaboration in Proposal to integrate new "Superheavy Element" subcollaboration in FAIR submitted to Board of Representatives (Summer '14) Focus: synthesis, nuclear structure, atomic physics, nuclear chemistry experiments in region Z 100 Existing facilties: SHIP, TASCA, SHIPTRAP, Chemistry beamline Developments for high-intensity cw-linac ongoing (HIM, GSI, U Frankfurt) Complementary to existing NUSTAR activities at Super-FRS Organizational Structure: Spokesperson: R.-D. Herzberg (Univ. Liverpool) Deputy: M. Block (GSI/HIM) Technical Director: A. Yakushev (GSI) Currently includes 9 German and 17 international institutes Endorsed by NUSTAR Collaboration Committee: Sept. 25, 2014 submitted to FAIR management: Oct. 27, 2014 Ivan Strašík and O. Boine-Frankenheim Collimation Concept for Beam Halo Losses in SIS 100 8th Machine Advisory Committee

23 Staged Approach towards cw linac for SHE Full performance test of sc cw LINAC HLI proof of principle 2. Full performance test of a shorter sc cavity energy variation (by Ampl & Phase) 8 gaps simpler design easier to fabricate 3. Advanced Demonstrator up to 4.61 A/Q = 6 5 sc CH-Cavity, 5 sc Solenoid possible to place in HLI@GSI Material courtesy of V. Gettmann / W. Barth cooperation: GSI, HIM, Uni Frankfurt Ivan Strašík and O. Boine-Frankenheim Collimation Concept for Beam Halo Losses in SIS 100 8th Machine Advisory Committee

24 First components October 2014

25 Conclusions and Perspectives Recent attempts on synthesis of elements 119 and 120 yield cross section limits down to 70 fb New attempts demand high-intensity stable beams x-ray finger printing provides practical method to pin down odd-z elements 113, 115, 117 unambiguously High-precision mass measurements add powerful tools to map strength and location of shell closures laser spectroscopy probes relativistic effects on the atomic structure and gives access to nuclear properties (spins, moments) Thank you for your attention!