Neutron-Rich Nuclei Production Project using Multinucleon Transfer Reaction (KISS Project)

1. Oct. 24, 2011 DCEN2011 Experimental project for production of neutron-rich nuclei by multinucleon transfer reaction (KISS project) Y.X. Watanabe (KEK) for KISS collaboration Collaborators KEK H. Miyatake, S.C. Jeong, H. Ishiyama, N. Imai, Y. Hirayama, K. Niki, M. Okada, M. Oyaizu, Y.X. Watanabe RIKEN M. Wada, T. Sonoda, Y. Ito, Y. Matsuo K.U. Leuven P. Van Duppen, Y. Kudryavsev, M. Huyse

2. Astrophysical nucleosysnthesis by r-process H. Grawe et al., Rept. Prog. Phys. 70 (2007)1525. A Observed solar r-abundance distribution 3rd peak (A~195) N=126 2nd peak N = 126 (Waiting point) Z Nuclear characteristics (T1/2, Sn, …) N = 82 r-process • Better understanding of r-process scenario • Actual r-process path • Astrophysical Nn-T condition • Duration time passing through waiting point • Actinide element production rate A half of elements heavier than Fe is considered to be produced by rapid neutron capture process (r-process) Fe N Lifetime measurements around N=126 → Astrophysical environments of r-process

3. 5×108 years ≤T1/2 30 days ≤T1/2 < 5×108 years 10 minutes ≤T1/2 < 30 days T1/2 < 10 minutes unknown 136Xe + 198Pt MNT Lifetime measurements around N=126 nuclei 83 209Bi 82 204Pb 207Pb 208Pb 206Pb 81 203Tl 205Tl 207Tl 80 196Hg 198Hg 199Hg 200Hg 201Hg 202Hg 204Hg 206Hg 79 197Au 205Au atomic number 78 194Pt 195Pt 196Pt 198Pt 204Pt 77 193Ir 203Ir 76 192Os 202Os 75 201Re 74 200W 116 117 118 119 120 121 122 123 124 125 126 neutron number • five-year project since FY2010: Lifetime measurements of N=126 nuclei • Multinucleon transfer (MNT) reaction to access N=126 nuclei • C.H. Dasso et al., Phys. Rev. Lett. 73 (1994) 1907. • V. Zagrebaev and W. Greiner, Phys. Rev. Lett. 101 (2008) 122701. • L. Corradi et al., J. Phys. G: Nucl. Part. Phys. 36 (2009) 113101. • From 203Ir down to 200W by 136Xe+198Pt MNT reaction

4. KEK Isotope Separation System (KISS) @ RIKEN Detection system - 3 detection stations - Tape-transport system - Multi-layered plastic scintillators - Ge detectors - Lifetime measurements - b-decay spectroscopy Focusing chamber - Electric-Q triplet - Electric deflector - Slit - Monitors Extraction chamber - Electric lens - Monitors ISOL (Ion Separator On-Line) - Electric-Q doublet - Magnetic dipole - Magnetic-Q doublet 136Xe beam from RIKEN ring cyclotron Gas catcher system - Target (iso-pure 198Pt) - Gas cell (Argas) - Laser resonance ionization - SPIG (SextuPole Ion Guide) Ar gas Lasers MNT reactions

5. Points of project Aimed reaction channels are very rare. • Estimation of • are very important subjects • from theoretical and experimental point of view Absolute cross sections Isotopic distribution • Small production yields as well as short lives • Efficient collection • Fast extraction • → Efficient measurements Gas catcher system Low background detection system • A lot of contaminants • → Isotopic separation (Z) • ISOL → Mass separation (A) Laser resonance ionization

6. + + + + Laser resonance ionization (Z selection) gas flow ISOL (A separation) 136Xe 9 MeV/A Gas catcher system — Laser resonance ionization + ISOL — P. Van Duppen, Nucl. Instrum. Meth. B126 (1997) 66. Yu. Kudryavtsev et al., Nucl. Instrum. Meth. B267 (2009) 2908. SPIG (SextuPole Ion Guide) Gas cell filled with 0.5 atm. Ar gas Beam diameter : ̴ f1 mm emittance : ̴ 10p mm · mrad Ar gas 198Pt 2nd chamber 6×10-2 Pa TMP 1600 L/s Extraction chamber 10-5 Pa TMP 1500 L/s Ion source chamber 37 Pa Screw Pump 175 L/s VRF ̴ VSPIG Separations of Z and A are achieved by laser resonance ionization and ISOL, respectively. V0 ̴ 60 kV

7. 160 120 80 40 0 1400 1200 1000 800 600 400 200 0 5 cm 4 3 2 1 0 1.0 f10 cm 0.8 3 cm 0.6 0.4 0.2 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 Gas cell design - Efficient collection and rapid extraction - Calculated transport time profile Cross-sectional view of stopping distribution (202Os fragments) Ar gas 0.5 atm. extracted yields (a.u.) (mm) transport time ( msec ) (mm) Mean transport time = 253 ms Transport efficiency : etra = 56% laser Top view of gas cell Evaluated survival probabilities of radioactive nuclei laminar flow Ar gas survival probability ion collector electrode exit hole (f1 mm) 136Xe beam 198Pt target Stopping efficiency : estop = 87 % half-life (sec) Survival probability : esur = 72% (T1/2 = 500 msec) Simulation by hydrodynamic calculations

8. Frequency tunable dye lasers l1 dye laser ScanMate2E excimer laser LPX240i excimer laser LPX240i Gas cell dye laser FL3002 l2 Laser resonance ionization - Element selection - Schematic diagram of laser system setup atomic energy levels (extracted fragment) Combination of two laser wavelengths for ionization is intrinsic to each element ionization autoionizing state (AIS) Z selection EI l2 Stable isotopes (Z = 69–78) laser Ex l1 : 210 – 450 nm Intermediate state l2 : 350 – 660 nm l1 laser l1andl2 tuning for the most efficient ionization-schemes of radioactive isotopes g.s.

9. 200W: production rate = 0.11 pps ~1 × 104 particles/day b-decay detection rate: ~160 counts/day beam on beam on beam off beam off beam on beam on beam on beam off beam off beam off beam off beam on Lifetime with 10% error T1/2 (predicted by KUTY) Au 1 day Pt Ir 1 h Os Re 1 min 200W W Toff Ton tape movement (50cm) 0.5 s Ta 1st station Hf 1 s waiting nuclei Toff = T1/2× 3 switch Lu 0.1 s 2nd station Yb 10 ms switch switch 121 124 120 123 126 122 125 3rd station N Detection system Detection station Ge detectors for X rays Tape transport system (eX = 60% for 70 keV X-ray) Plastic scintillators for brays (eb = 80%) 3 detection stations 3rd 2nd 1st Limitation of lifetime measurements Beam Switching box from ISOL Ge detectors for g rays (eg = 20% for 500 keVg-ray) Beam Beam-on/off time-sequence Ton = T1/2× 2

10. Multinucleon transfer (MNT) reaction 64Ni (6.1 MeV/A) +238U L. Corradi et al., Physical Review C59 (1999) 261. projectile-like fragments -1p 0p -2p -3p -4p -5p -6p 6n pick-up Experimental data Calculations (GRAZING code) A. Winther, Nuclear Physics A572 (1994) 191; A. Winther, Nuclear Physics A594 (1995) 203. • Rather large cross sections (~1 mb) for 6p-stripping channels • Up to 6n-pick-up channels for pure neutron transfer (0p)

11. 198Pt 208Pb Production distribution 136Xe+198Pt @ 7 MeV/A s (mb) s (mb) s (mb) s (mb) 104 104 104 104 103 103 103 103 82 82 82 82 102 102 102 102 80 80 80 80 10 10 10 10 198Pt evaporation 1 1 1 1 78 78 78 78 Atomic number Atomic number Atomic number Atomic number 10-1 10-1 10-1 10-1 76 76 76 76 10-2 10-2 10-2 10-2 10-3 10-3 10-3 10-3 74 74 74 74 10-4 10-4 10-4 10-4 126 126 126 126 124 124 124 124 122 122 122 122 120 120 120 120 114 114 114 114 118 118 118 118 116 116 116 116 Neutron number Neutron number Neutron number Neutron number 136Xe+208Pb @ 7.3 MeV/A 208Pb evaporation

12. 202Os 202Os 201Re 200W 200W 199Ta 136Xe : 9 MeV/A, 2 pnA 198Hf 198Pt : 12 mg/cm2 197Lu Excitation functions and yields Excitation functions for production of N = 126 isotones Expected yields for N = 126 isotones 102 10-1 10 10-2 1 10-3 cross section after evaporation (mb) Measurement limit 10-1 Yield (pps) 10-2 10-4 10-3 10-5 10-4 10-6 5 6 7 8 9 10 11 196 12 197 13 198 199 200 201 202 10-5 203 204 Elab (MeV/A) Mass (A) s ~0.1 mb for 202Os s ~1mb for 200W 5.0 pps for 202Os 0.1 ppsfor 200W calculated by GRAZING code (http://personalpages.to.infn.it/~nanni/grazing)

13. 208Pb 198Pt 208Pb 198Pt MNT with RIB 136Xe beam 198Pt target 208Pb target 10 10 10 10 83 83 83 83 5 5 5 5 82 82 82 82 81 81 81 81 0 0 0 0 80 80 80 80 79 79 79 79 -5 -5 -5 -5 78 78 78 78 -10 -10 -10 -10 77 77 77 77 Atomic number Atomic number Atomic number Atomic number 76 76 76 76 -15 -15 -15 -15 75 75 75 75 74 74 74 74 -20 -20 -20 -20 73 73 73 73 -25 -25 -25 -25 72 72 72 72 71 71 71 71 -30 -30 -30 -30 144Xe beam 116 116 116 116 117 117 117 117 118 118 118 118 126 126 126 126 125 125 125 125 119 119 119 119 124 124 124 124 123 123 123 123 122 122 122 122 121 121 121 121 120 120 120 120 Neutron number Neutron number Neutron number Neutron number

14. 144Xe + 198Pt : Cross sections s (mb) s (mb) 104 104 82 82 103 103 80 80 144Xe+198Pt @ 7.2 MeV/A 136Xe+198Pt @ 7 MeV/A 102 102 78 78 10 10 Atomic number Atomic number 76 76 1 1 10-1 10-1 74 74 198Pt 198Pt 10-2 10-2 130 130 128 128 126 126 124 124 118 118 122 122 120 120 72 72 Neutron number Neutron number 10-3 10-3 10-4 10-4

15. 140, 144Xe + 198Pt : Yields Expected yields of N=126 isotones (E~9 MeV/A, optimized target thickness) Expected beam intensities of Xe isotopes (Proton-induced fission of U at the total fission rates of 1014 Hz) 104 1011 e = 0.01 140Xe 109 102 108 waiting nuclei 1 Yield (pps) 107 136Xe+198Pt 140Xe+198Pt 144Xe+198Pt 10-2 Beam intensity (pps) 144Xe 106 Measurement limit fragmentation (238U+Be) 105 10-4 104 10-6 204 202 200 198 196 194 103 146 144 142 140 (W) (Hf) (Yb) 138 (Er) (Os) (Pt) 136 Mass (A) Mass(A) 198Hf, one of the waiting nuclei, would be accessed by using RIB 140Xe

16. 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 Mass number Mass number Mass number Understanding of MNT reactions ( L. Corradi et al., Phys. Rev. C66 (2002), 024606. ) 58Ni + 208Pb Isotopic distributions of PLFs (protonstripping channels) calculation -6p -5p -4p -3p -2p -1p 0p Independent single-nucleon transfer modes + one pair transfer mode + particle evaporation For better description Absolute cross sections ← Pair transfer Isotopic distributions ← Energy dissipation (Evaporation)

17. Experiment with VAMOS at GANIL 198Pt (1.3 mg/cm2) SSD IC DC2 DC1 MWPC 136Xe (8 MeV/A) VAMOS • MWPC • Drift Chambers 2 • Ionization Chamber • Silicon Wall 34° ~ grazing angle EXOGAM 12 (or 11) clovers Suppression shield configuration B with full Compton suppression PLF Trajectory Path length, Angles, Br Velocity Total kinetic energy Mass, Atomic number, Charge TLF g-rays ~500 keV total photo-peak efficiency ~10%

18. Cross section measurements for 136Xe + 198Pt Cross sections to produce PLFs and TLFs by MNT reactions of 136Xe+198Pt s (mb) TLF s (mb) PLF 4p pick-up 198Pt 136Xe 3p pick-up g-transitions are known (Z=75~77) Calculated by GRZAING code ( A. Winther, program GRAZING, http://personalpages.to.infn.it/~nanni/grazing ). • PLF : fragments are detected by VAMOS (s > 1 mb ↔ 4-proton pick-up channels) • TLF : g-rays are detected by EXOGAM (s > 10 mb ↔ 3-proton pick-up channels) • Unknown g-decay scheme • Systematic tendency of gamma transitions over isotopic chains • New isotope 202Os

19. Investigation of astrophysical environment of r-process Lifetime measurements for nuclei around N=126 Nuclear production by MNT reactions of 136Xe+198Pt Rare events, Large contaminants KEK Isotope Separation System (KISS) at RIKEN Gas catcher system : Efficient collection, Fast Extraction Laser resonance ionization + ISOL : Z & A separation Low-backgrounddetection system : 10% error for 200W Nuclear production by MNT reactions with neutron-rich RIB 198Hf, one of waiting nuclei, would be accessed by using RIB 140Xe Better description of MNT reactions Pair transfer, Energy dissipation Absolute cross sections and isotopic distributions will be measured by VAMOS at GANIL for 136Xe+198Pt system Summary

21. Q-value

22. ~99.7% contaminations s (mb) 202Os 202Os ~0.3% atomic number Contaminations 136Xe + 198Pt Isobaric distribution (A=202) s (mb) 198Pt atomic number isobar N=126 neutron number Z and A separations are essential for the lifetime measurements of rare channel products.

23. 198Pt 202Os 136Xe 9 MeV/A ~65° 12 mg/cm2 Angular distribution Yield (a.u.) ~10° < 0.5 MeV/A ~ Angle ( degree ) Kinematic condition for 202Os Energy distribution Low energy, wide energy spread Large and wide emission angle Yield (a.u.) Energy ( MeV/A ) It would be difficult to separate and collect efficiently by using a spectrograph.

24. = = 0.17 0.9 6.8% for 202Os (T1/2 = 2.38 s predicted by KUTY) 5.0% for 200W (T1/2 = 423 ms predicted by KUTY) Total efficiency of gas catcher system Total efficiency = estop × etrans× esurv × eLIS × eSPIG stopping survival transport Total efficiency half-life (sec) KUTY : T.Tachibana, M. Yamad, Proc. Inc. Conf. on exotic nuclei and atomic masses, Arles, 1995, p763.

25. FY FY FY FY FY FY Time schedule Gas-catcher system will be installed in this March Off-line test of laser resonance ionization is in progress Mass separator will be installed in the early months of the next FY Measurements (136Xe+198Pt) Construction, R&D

26. Channeltron for secondary electron detection Ions Electrode ~ 350 V/cm Filament : Ni, Ir… Ionization chamber ( Vacuum ) Control PC Wave meter l1 l0 l2 Power meter Photo detector for timing tuning R&D for laser resonance ionization Pump lasers : Excimer laser (Lambda Physik LPX240i) 100 mJ/pulse @ 200 Hz Frequency tunable dye lasers (Lambda Physik FL3002 l2 :10mJ/p, ScanMate2E+SHG l1 :1mJ/p) FL3002 for VIS. FL3002 for VIS., l2 ScanMate2E for UV, l1 Excimer lasers

27. AIS AIS 800 700 600 500 400 300 200 100 0 658 656 646 650 652 654 648 660 Rhenium ionization ( Z = 75, A=185, 187 ) 1st step 417.253nm fix 2nd step scan Ionization energy : Ei = 63181.6 cm-1 ( = 7.83 eV) 融点：3459K 649.84 nm 652.22nm 654.64nm Ionization limit AIS Ei l2 < 655.78 nmで IPを越える l2 (nm) 500 6F0 (J=7/2) 1st step scan w/o 2nd step 1st step 208.6265nm • Ex = 47932.55cm-1 • l1 = 208.6265 nm • (SHG) • l0 = 417.2530 nm (fundamental) 400 300 200 6S (J=5/2) 100 417.24 417.26 417.20 417.22 417.30 417.28 l0 (nm)

28. 2nd stepのパワー依存性測定 1st step 417.253nm, 28.4mJ/p (飽和している) l2 power (mJ/p@f10mm) l1 power (mJ/p@f10mm) 2nd step 2nd step l2 power (1016photon/cm2 pulse) l1 power (1014photon/cm2 pulse) Power dependence 1st stepのパワー依存性測定 2nd step 2.2mJ/p(飽和している) 2nd step 2nd step 2 mJ/p(<10mJ/p) 100mJ/p(<1mJ/p), l1 = 208.6265nm, l2 = 652.218nmでイオン化するのが効率良い。 ガスセル入り口(f10mm)で必要なパワーは、 1st : 100mJ/p(<1mJ/p), 2nd : 2 mJ/p(<10mJ/p)

29. 1st step 417.900nm fix 2nd step scan 1000 800 AIS 408.186nm 408.217nm 408.266nm 408.434nm 409.520nm 600 AIS 400 Ionization limit 200 0 409 409.5 410 408.5 408 l2 (nm) 1st step scan w/o 2nd step 1st step 208.950 nm 400 300 200 100 0 417.88 417.92 417.80 417.84 417.96 l0 (nm) Iridium ionization ( Z = 77, A=191, 193 ) Ionization energy : Ei = 72323.9 cm-1 ( = 8.97eV) 融点： 2739K AIS Ei l2 < 408.74 nmで IPを越える 10 (J=11/2) • Ex = 47858.45cm-1 • l1 = 208.950 nm • (SHG) • l0 = 417.900 nm (fundamental) 4F (J=9/2)

30. l2 power (mJ/p@f10mm) 4 7 8 9 0 1 2 3 5 6 10 1400 2nd step 408.217nm (1st 17mJ/p) 1200 1000 2nd step 408.434nm (1st 17mJ/p) 800 600 2nd step 408.217nm (1st 3mJ/p) 400 200 0 1.2 1.6 0 0.4 0.8 2.0 2.4 2.8 l2 power (1016photon/cm2 pulse) Power dependence 2nd stepのパワー依存性測定 1st stepのパワー依存性測定 l1 power (mJ/p@f10mm) 120 160 40 80 0 800 2nd step 408.434nm (1.15mJ/p) 600 400 2nd step 408.217nm (1.18mJ/p) 200 0 0 0.4 0.8 1.2 1.6 2.0 l1 power (1014photon/cm2 pulse) 3 mJ/p(<10mJ/p) 100mJ/p(<1mJ/p), 1st : 208.950nm, 2nd : 408.434nmでイオン化するのが効率良い。 ガスセル入り口(f10mm)で必要なパワーは、 1st : 100mJ/p(<1mJ/p), 2nd : 3mJ/p(<10mJ/p) 今後、W (Z=74), Ta (Z=73), Os (Z=76)等の共鳴イオン化様式を探索予定

31. E2, E3実験室におけるKISS設置予定（上から見た図） 絶縁トランス(<100kV) 高電圧プラットホーム(~60kV) t50mm絶縁シート 5808 高電圧防護柵(予定) 一次ビームライン整備 2011年度内希望 ゲートバルブ 一次ビームモニターチャンバー Ar gas セル50kPa@高電圧 絶縁ダクト EQダブレット 差動排気用真空槽 40Pa@高電圧 Dipole Mag. 引出しチャンバー レーザー光 J3　→ E2 E2 MQダブレット 2010年度3月設置予定 　高電圧プラットホーム Ar gas セルハウジング真空槽 Ar gas セル 　引出しチャンバー 2011年度設置予定 高電圧防護柵 　引出しチャンバーより下流ライン J3にレーザ装置(E2の地下) E3 測定用チャンバー