基于放射性束的核结构、核天体物理研究 刘 忠 Outline Brief introduction to RIB physics 100 Sn 区域奇异核衰变 远离稳定线核素质量测量 ( 直接质子放射性核 ) Nuclear Detectors R&D for RIB physics Outlook

Halo nuclei 208 Pb Hansen & Jonson, Europhys. Lett., 1987, 4:409. Halo nuclei Rm∝

100 Sn: Gamow-Teller Strength in its Decay rp process

Shell Model Orbitals

100 Sn GT-strength is unique tool to study wave fct. pure spin-flip transition 0 + => (  g 9/2 -1 g 7/2 )1 + large decay energy => most of GT strength in  -decay window measure: T 1/2  -endpoint energy (branching) => GT-strength Shell model Grawe et al.

100 Sn: Gamow-Teller Strength in its Decay Search for its Isomer rp process

100 Sn: Gamow-Teller Strength in its Decay Search for its Isomer Particle Stability of Neighbours: key to the rp-process rp process

key to the astrophysical rp-process

100 Sn history

1 st Bρ separation2 nd Bρ separation ΔEΔE identification F2-F4:  E => Z B  (x,x´,  ´) =  A/q m 0 c q = Z TOF =>  F2 F4 the FRagment Separator (FRS) ~10 9 s -1

the FRagment Separator (FRS) ~10 9 s -1

100 Sn setting (full statistics, 15 days) A/Q Z Te Ag Cd In Sn Sb N=Z+2N=Z+1N=Z N=Z Sn  = 6pb 103 Sb? 99 Sn 97 In 95 Cd 93 Ag

Silicon Implantation Detector and Beta Absorber SIMBA 100 Sn pixels in implantation zone: 3x60x40 = 7200 X SSSD 60x60x0.3 mm 3 Y SSSD 60x60x0.3 mm 3 10 SSSD 60x40x1 mm 3 3 DSSD 60x40x0.7 mm 3 Gassiplex+ Mesytec R - chain 7 x-strips 10 SSSD 60x40x1 mm 3

Implantation RISING SIMBA DEGRADER

and how it looks in reality 100 Sn

RISING + 15 x 7 Germanium detectors  Photo ~ 662 keV

Correlation of Implantation and Decay require same position within ± 1mm in x,y,z record all decay triggers within 15 s (  + of 3 generations) Maximum Likelihood analysis varying the 100 Sn half-life with known: daughter decays, efficiencies, dead times, background T 1/2 = 1.16 ± 0.20 s Comparison: MSU s GSI s 100 Sn only 1st decays

Gamma Spectrum after Beta Decay of 100 Sn all events within 4 s after implantation

Gamma Intensities 5 lines add up to 4018 keV ??? 2003 Stone, Walters 1985 (  g 9/2 ) -1 g 7/2 (  g 9/2 ) -1 d 5/2 what do we expect? 511  intensities corrected for efficiency and M1 conversion Sn  + decays 111 total  + decays

E*(1+) = ( x) MeV with x ≈ 0.05 MeV because: total sum energy = 2.76(0.43) MeV (Schneider et al.)  Mc 2 - Q EC (1 + )= 2.6(1.0) MeV (Chartier et al.) one  -delayed proton event: E p + S p ( 100 In) = 2.93(0.34) MeV (Audi et al.)

compare to shell model Grawe et al.Nowacki, Sieja

Extraction of Beta Spectrum 100 Sn  spectrum conv. line? from maximum likelihood E max = 3.29 ± 0.20 MeV Q EC = 4.31 ± 0.20 MeV to excited state =>I(     = 87% => log ft = 2.62 sum over total energy within 3 s after implantation in implantation zone + calorimeter tested (by eye) for uninterrupted tracks range of analysis result of ML analysis

known log(ft) values Nuclear Data Sheets 84 (1998) 487 log (ft) 100 Sn superallowed GT

Decay of the heaviest N=Z doubly magic nucleus 100 Sn

Gamow Teller Strength A. Bobyk, W. Kaminski, I. Borzov 2000 exp. FFS QRPA SM truncated extreme SM GT strength of even Sn isotopes H. Grawe, 2010

why is B GT that large? wave functions must be rather pure I i > = {(  g 9/2 ) 10 } 0 + < f I = {(  g 9/2 ) 9 ( g 7/2 ) 1 } protons can transform into a neutron

the 100 Sn shell gap is robust Conclusions - doubly magic -

3 isomer decays after ToF=200ns decaying within 25 ns ? 6 + isomer in 100 Sn ? E  /MeV T/  s E  /MeV

what‘s new? 93 Ag 103 Sb T 1/2 < 50 ns ! 99 Sn 95 Cd T 1/2 > 0.2  s 97 In

Conclusions first observation of 93 Ag, 95 Cd, 97 In, and 99 Sn reduced rate of 103 Sb => T 1/2 < 50 ns 102 Sn: new isomeric state 100 Sn: probably no isomer 1 st  -spectrum after decay of 100 Sn 100 Sn decay: T 1/2, E  max, E  B GT superallowed GT transition => dominant configurations (  g 9/2 ) 10 =>(  g 9/2 ) 9 ( g 7/2 ) 1

The 100 Sn Team photo taken by Hans Geissel

Shell structure near doubly-magic 100 Sn Abundance of isomeric states Exotic decay mode Study of N ≥ Z proton drip-line nuclei 96,97,98 Cd with astrophysical consequences Spokespersons: A. Blazhev, P. Boutachkov Z. Liu, R. Wadsworth

T=0, S=1 T=1, S=0 T z =0 Neutron-proton pairing

N=Z nuclei, unique systems to study np correlations T=0 Pairing may become Important in A>80 N=Z nuclei A. L. Goodman, PRC 60, (1999) Experimental signals for T=0 np pairing Binding energy differences Deutron transfer reactions Rotational properties: delayed alignments in N=Z nucl Level structure: 92 Pd, B. Cederwall et al. Nature 469, (2011) Spin-gap isomer: 96 Cd

Effect of T=0 np interaction in 96 Cd Shell model calculations by H. Grawe T=0 No T=0 E6 Spin gap 96 Cd T=0

Primary beam MeV/u RISING S352 Experimental Setup Stopped RISING Z A/Q 96 Ag Active stopper

0.27(14)  s 1.58(3)  s 78(8)  s B(E4; 19 +  15 + ) = 0.4(3) W.u. B(E2; 19 +  17 + ) = 4(3) W.u. B(E3; 13 -  10 + ) = (20) W.u. E  [keV] Counts known: R. Grzywacz et al. PRC 55 (1997) 1126 new 96 Ag 96 Ag SE T f <1  s

96 Cd  0.2 – 4.5 μs 9 6 Cd μs T 1/2 (421) = 0.67  0.15 s ( 96 Cd g.s.) 0.2 – 4.5 μs T 1/2 (470, 1506, 667) = s

E6 Spin gap Effect of iso-scalar np interaction in 96 Cd, 16 + isomer

Beta decay GT strengths in GF space 100% g 9/2 → g 9/2, similar to the case of g 9/2 → g 7/2 seen in 100 Sn B GF = 0.14 with quenching factor of 0.6 ( Herndl and Brown NPA627, 35 (1997)) B exp = [3860(18) *   ] / (f T 1/2 ) = with T 1/2 = 0.29 secs

96 Cd Results B. S. Nara Singh, Z. Liu et al., Phys. Rev. Lett. 107, (2011) Evidence for the existence of the 16+ E6 “spin-gap” isomer in 96 Cd Evidence for the strong influence of the iso-scalar neutron-proton interaction Our work allows to deduce T 1/2 = 0.67 ± 0.15 s for the g.s. in 96 Cd

Results in other nuclei  -decaying high-spin isomers were observed in 94 Pd 96 Ag 98 Cd Core-excited states aross the N=Z=50 shell closure identified in 96 Ag more in 98 Cd Phys. Rev. C 82, (R) (2010) Phys.Rev. C 84, (2011) J.Phys.:Conf.Ser. 205, (2010 )

SMS and IMS

SMS: Broad Band Frequency Spectra

M.W.Reed et al., PRL , (2010)

FAIR (Facility for Antiproton and Ion Research) (Darmstadt, Germany) ~1GeV/u 350m ring branch GSI 现有和将来的实验装置 RISING

H. Geissel et al. NIM B 204 (2003) 71 Comparison of FRS and Super-FRS -High primary beam intensity ~10 12 ion/s for 238 U -increase in transmission for fission products (a factor of 10) -cleaner beams due to the higher number of stages

NEUTRON DETECTOR DSSD IMPLANTATION DETECTOR GE γ-ARRAY RADIOACTIVE BEAM DEcay SPECtroscopy (DESPEC) Total Absorption  Spectrometer (TAS) Fast timing measurements Compact, flexible and modular geometry g-factors and quadrupole moments

8 x 8 cm 128 x 128 strips 1 mm (Micron) 3 dssd 24 cm 8 cm EE Veto AIDA: Advanced Implantation Detector Array Implantation energy measurement Decay energy measurement (several layers) Low threshold: ~40 keV (conversion electron!) Fast recovery (~µs); ASIC beam

ASIC Design Requirements Selectable gain MeV FSR Low noise keV FWHM energy measurement of implantation and decay events Selectable threshold< 0.25 – 10% FSR observe and measure low energy  detection efficiency Integral non-linearity 95% FSR spectrum analysis, calibration, threshold determination Autonomous overload detection & recovery ~  s observe and measure fast implantation – decay correlations Nominal signal processing time < 10  s observe and measure fast decay – decay correlations Receive (transmit) timestamp data correlate events with data from other detector systems Timing trigger for coincidences with other detector systems DAQ rate management, neutron ToF

Schematic of Prototype ASIC Functionality Note – ASIC will also evaluate use of digital signal processing Potential advantages decay – decay correlations to ~ 200ns pulse shape analysis ballistic deficit correction

AIDA: ASIC schematic

AIDA: status Systems integrated prototypes available - prototype tests in progress Production planned Q3/2010 Mezzanine: 4x 16 channel ASICs Cu cover EMI/RFI/light screen cooling FEE: 4x 16-bit ADC MUX readout (not visible) 8x octal 50MSPS 14-bit ADCs Xilinx Virtex 5 FPGA PowerPC 40x CPU core – Linux OS Gbit ethernet, clock, JTAG ports Power FEE width: 8cm Prototype – air cooling Production – recirculating coolant

FEE Assembly Sequence

Prototype AIDA Enclosure Prototype mechanical design Based on 8cm x 8cm DSSSD evaluate prior to design for 24cm x 8cm DSSSD Compatible with RISING, TAS, 4  neutron detector 12x 8cm x 8cm DSSSDs 24x AIDA FEE cards 3072 channels (x 3) Design complete Mechanical assembly in progress

( 3 He,p) np Even-even  T=0 J=0 Odd-odd T=1 J=0 T=0 J=1 L=0 transfer – forward peaked Measure the np transfer cross section to T=1 and T=0 states Both absolute  (T=0) and  (T=1) and relative  (T=0) /  (T=1) tell us about the character and strength of the correlations ( 3 He,p) Transfer Reactions

Proton Radioactivity

Many thanks to my collaborators: A.Blazhev, P. Boutachkov,, Tom Davinson, L. Livinov, B.T.Faestermann, B. S. Nara Singh et al.