Recent Progress for Lanzhou GasFilled Recoil Separator 2012

Recent Progress for Lanzhou Gas-Filled Recoil Separator 报告人：张志远 中科院近代物理研究所 2012超重核合成机制与性质研讨会 Institute of Modern Physics, Chinese Academy of Sciences

Outline v Introduction of the Lanzhou gas-filled recoil separator v First fusion reaction experiment: 175 Lu(40 Ar, n)215 -x. Ac v First superheavy nuclei experiment: 208 Pb(64 Ni, n)271 Ds v New detector system and the performance in the 40 Ca+175 Lu and 40 Ca+169 Tm experiments v Summary Institute of Modern Physics, Chinese Academy of Sciences 2

Introduction G FS L Location Gas-filled recoil separator in Lanzhou Institute of Modern Physics, Chinese Academy of Sciences HIRFL-CSR 3

Schematic View Dh : the dipole magnet with horizontally focusing ability Qv and Qh : the vertically and horizontally focusing quadrupole magnets, respectively Institute of Modern Physics, Chinese Academy of Sciences 4

Technical Parameters Table 1 Technical parameters of the gas-filled separator Parameters Values Configuration Q v Dh Q v Q h Total length 6. 5 m Angular acceptance 25 msr Dispersion 0. 73 cm/% Dh magnet Bending radius 1. 8 m Central trajectory length 1. 6 m Bending angle 52° Entrance angle -45° Exit angle 22° Maximum magnetic rigidity 2. 9 T·m Qv magnet Effective length 667 mm Aperture radius 120 mm Maximum field gradient 6. 8 T/m Qh magnet Effective length 500 mm Aperture radius 85 mm Maximum field gradient 8. 9 T/m Institute of Modern Physics, Chinese Academy of Sciences 5

Comparison Table 2 Comparison of the gas-filled separators Configuration Length / m Solid angle / msr Bending angle /deg B max / T m Dispersion / cm/% DGFRS@JINR DQh. Qv 4. 0 6 23 3. 1 0. 75 GARIS@RIKEN DQh. Qv. D 5. 8 12. 2 45+10 2. 2 0. 97 BGS@LBNL Q v Dh D 4. 6 45 25+45 2. 0 RITU@Jyväskylä Qv. DQh. Qv 4. 7 10 25 2. 2 1. 0 HTM DQh. Qv 3. 5 13. 3 30 2. 4 0. 9 SIM DQv. Qh 3. 5 4. 3 30 2. 4 0. 1 Q v Dh Q v Q h 6. 5 25 52 2. 9 0. 73 TASCA @GSI GFSL@HIRFL The subscripts h and v stand for horizontally and vertically focusing, respectively. * HTM : High Transmission Mode * SIM : Small Image-size Mode Institute of Modern Physics, Chinese Academy of Sciences 6

Position Sensitive Silicon Detector Active area： 58 mm * 58 mm Strip Number： 16 (vertical) Width of one strip： 3. 6 mm Thickness： 300 m Manufacture: CANBERRA ØEnergy resolution (FWMH)： ~50 ke. V (212 Po-8. 785 Me. V) ØPosition resolution (FWMH)： ~1. 5 mm (ER- ) Institute of Modern Physics, Chinese Academy of Sciences 7

First fusion reaction experiment : 175 Lu(40 Ar, xn)215 -x. Ac 175 Lu(40 Ar, xn)215 -x. Ac 实验目的： 1. 探索谱仪运行最佳条 件，为超重核实验做 准备 2. 反冲余核在焦平面探 测器上的分布 3. 充气气压对余核平衡 电荷态的影响 4. 余核 211, 210 Ac传输效 率 Institute of Modern Physics, Chinese Academy of Sciences 实验条件： 1. 175 Lu靶厚 0. 53 mg/cm 2 2. 40 Ar束流能量 177 Me. V，靶中心能量 175 Me. V 3. 流强 2. 8× 1011 s-1 4. 氦气气压 0. 7~1. 0 mbar 5. 磁刚度 ~1. 7 Tm 8

4 n-5 n 2 n-3 n p 2 n-p 3 n 2 n- 3 n First fusion reaction experiment: 40 Ar + 175 Lu -> 215 Ac* 211, 210 Ac α 1 215 Ac* 7. 5 Me. V, 0. 25~0. 35 s 207, 206 Fr α 2 6. 8 Me. V, 15~16 s 203, 202 At α 3 Institute of Modern Physics, Chinese Academy of Sciences 203 At 6. 1 Me. V, 7. 4 min 202 At 6. 2 Me. V, 184 s 9

On-line spectra 210, 211 Ac T 1/2=0. 24± 0. 01 s Institute of Modern Physics, Chinese Academy of Sciences P=0. 84 mbar B =1. 73 Tm 10

Equilibrium charge state qave (helium gas) Bohr (overestimate) A. Ghiorso et al (LBNL) Y. Oganessian et al (Dubna) 余核平衡电荷态受以下几方 面因素的影响： 1. 余核核电荷数 (Z) 2. 余核飞行速度 (v) 3. 余核核外电子排布 (4 f, 5 f) 4. 气体种类 (He, H 2) 5. 气体压强 (Pressure) Y. Oganessian et al (Dubna) K. Gregorich et al (LBNL) LBNL Exp. Data K. Morita et al (RIKEN) Institute of Modern Physics, Chinese Academy of Sciences 11

Equilibrium charge state “density effect” Institute of Modern Physics, Chinese Academy of Sciences 12

Transmission Efficiency 175 Lu(40 Ar, xn)215 -x. Ac u Beam intensity： 1 e A u Helium gas pressure： 0. 84 mbar u Magnetic rigidity： 1. 73 Tm u Counting rate of the decay of 211, 210 Ac： 300 counts/min u Detection efficiency： 50% u Abundance of 175 Lu： 97% u Production cross section of 211, 210 Ac： 68. 8 b Vermeulen D, et al. Z. Phys. A, 1984, 318(157). u Transmission efficiency： 14% Institute of Modern Physics, Chinese Academy of Sciences 13

First superheavy nuclei experiment: 208 Pb(64 Ni, n)271 Ds Beam： 64 Ni 19+ (HIRFL-SFC) Energy： 317. 1 Me. V Intensity：~100 pn. A (6. 6× 1011 ions/s) Beam time: 01/15/2011 ~ 01/21/2011 7 days 03/15/2011 ~ 03/26/2011 12 days Total dose： 6. 4× 1017 ions Beam energy at the centre of target: 313. 3 Me. V Excitation energy of the compound nucleus: 14. 4 Me. V 指导合作： 张焕乔（中国原子能科学 研究院） B =2. 01 Tm 任中洲（南京大学） 周善贵（中科院理论物理 研究所） Helium gas P=0. 8 mbar …… Institute of Modern Physics, Chinese Academy of Sciences 14

Rotating Target System u. To avoid the melting of 208 Pb target, the rotating target system and sandwiched target were prepared in the experiment. u. During the irradiation, the target wheel rotated at the speed of 600 rpm. Institute of Modern Physics, Chinese Academy of Sciences 15

Schematic Diagram of Data Acquisition N 568 B Amplifier 1~20 Me. V Accelerator Beam Chopper Scaler 5~200 Me. V ADC CAMAC Institute of Modern Physics, Chinese Academy of Sciences 16

One -decay chain assigned to 271 Ds Known data 208 Pb(64 Ni, Institute of Modern Physics, Chinese Academy of Sciences n)271 Ds (Z=110) 18

Comparison with other laboratory data Decay energy Institute of Modern Physics, Chinese Academy of Sciences Decay time 19

Probability of Accidental Coincidence 208 Pb(64 Ni, n)271 Ds (Z=110) v Counting rate: u 25 s-1 in the focal plane detector u 3. 5 s-1 in the -decay energy range (7 -11 Me. V) v Probability of accidental coincidence u 3 mm position window，309 pixels u EVR- 1: 1. 1× 10 -3 u EVR- 4: 7. 1× 10 -2 u EVR- 5: 2. 7× 10 -1 u EVR- 1 - 4 - 5: 2. 1× 10 -5 Institute of Modern Physics, Chinese Academy of Sciences 20

New Detector System TOF detector Si-box detector stop detectors veto detector light f l i o c Re path side detector Si-box: Stop detector: 50 mm× 3 (active area), position-sensitive detectors (each has 16 vertical strips), 300 m (thickness) Side detector: 50 mm× 8 (active area), non-position-sensitive detectors, Veto detector: 50 mm× 3 (active area), non-position-sensitive detectors TOF detector (Multi Wire Proportional Counter): 80 mm× 180 mm (active area), 0. 5 m mylar window, isobutane gas (2 mbar) Institute of Modern Physics, Chinese Academy of Sciences 21

Silicon-box detector Time-of-flight detector Focal plane detector Photos Micro-Channel Plate detector Institute of Modern Physics, Chinese Academy of Sciences Multi-Wire Proportional Counter 22

40 Ca+175 Lu->215 Pa* Signals obtained from both MWPC and Si-box Total spectrum of silicon detector Institute of Modern Physics, Chinese Academy of Sciences 209, 210 Ra 210, 211 Ac 211, 212 Ra 208, 209 Fr 210, 211 Fr 207, 208 Rn, 203 At 205, 206 Rn 206, 207 Fr u. Observed in the bombardment 40 Ca+175 Lu with an energy of 4. 83 Me. V/u u. Without the veto detector u. With old beam dump, the total counting rate of stop detector was up to 300 events/s -decay spectrum 23

40 Ca+169 Tm->209 Ac* u. Observed in the bombardment 40 Ca+169 Tm with an energy of 4. 84 Me. V/u u. Three veto detectors mounted downstream of the stop detector u. With the improvement of beam dump, the total counting rate decreased to 120 events/s Institute of Modern Physics, Chinese Academy of Sciences 24

40 Ca+169 Tm->209 Ac* All E<10 Me. V signals Energy spectrum from the stop detector E<10 Me. V signals obtained from both stop detector and TOF E<10 Me. V signals anti-coincident with TOF signals E<10 Me. V signals obtained from both stop detector and veto detector with no TOF signals E<10 Me. V signals anti-coincident with TOF and veto signals E<10 Me. V signals obtained from both stop detector and side detector with no TOF and veto signals Institute of Modern Physics, Chinese Academy of Sciences 25

204 Fr 205 Fr 206 Fr 203 m. Rn 205, 206 Rn 200 Po 201 At 204 Rn 40 Ca+169 Tm->209 Ac* -decay spectrum The data for Ca+Lu and Ca+Tm experiments are analyzed in progress. Institute of Modern Physics, Chinese Academy of Sciences 26

Institute of Modern Physics, Chinese Academy of Sciences