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

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slide1
基于放射性束的核结构、核天体物理研究刘

Outline

  • Brief introduction to RIB physics
  • 100Sn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
slide3

Rm∝

208Pb

Halo nuclei

Hansen & Jonson, Europhys. Lett., 1987, 4:409.

Halo nuclei

100 sn1
100Sn

GT-strength is unique tool to study wave fct.

pure spin-flip transition

0+ => (pg9/2-1 ng7/2)1+

large decay energy

=> most of GT strength

in b-decay window

Shell model

Grawe et al.

measure:

T1/2

b-endpoint energy

(branching)

=> GT-strength

100 sn2

Gamow-Teller Strength in its Decay

Search for its Isomer

100Sn:

rp process

100 sn3

Gamow-Teller Strength in its Decay

Search for its Isomer

Particle Stability of Neighbours:

key to the rp-process

100Sn:

rp process

the fragment separator frs
the FRagment Separator (FRS)

F4

F2

~109 s-1

ΔE

1st Bρ separation

2nd Bρ separation

identification F2-F4: DE => Z

Br(x,x´,a´) = b gA/q m0c

q = Z

TOF => b

100 sn setting full statistics 15 days

259 100Sn

s = 6pb

103Sb?

99Sn

97In

93Ag

95Cd

100Sn setting (full statistics, 15 days)

Z

N=Z

N=Z+1

N=Z+2

N=Z-1

Te

Sb

Sn

In

Cd

Ag

A/Q

silicon implantation detector and beta absorber simba
Silicon Implantation Detectorand Beta AbsorberSIMBA

7 x-strips

7 x-strips

10 SSSD

60x40x1 mm3

10 SSSD

60x40x1 mm3

100Sn

3 DSSD 60x40x0.7 mm3

Gassiplex+ Mesytec

X SSSD 60x60x0.3 mm3

Y SSSD 60x60x0.3 mm3

R - chain

pixels in implantation zone: 3x60x40 = 7200

implantation
Implantation

RISING

SIMBA

DEGRADER

rising
RISING

+

15 x 7

Germanium detectors

ePhoto~ 11%

@ 662 keV

correlation of implantation and decay
Correlation of Implantation and Decay

require same position within ± 1mm in x,y,z

record all decay triggers within 15 s

(b+ of 3 generations)

Maximum Likelihood analysis

varying the 100Sn half-life

with known: daughter decays,

efficiencies, dead times, background

T1/2 = 1.16 ± 0.20 s

Comparison:

MSU 2007 0.55 s

GSI 1997 0.94 s

100Sn

only 1st decays

+0.70

-0.31

+0.54

-0.26

gamma spectrum after beta decay of 100 sn
Gamma Spectrum after Beta Decay of 100Sn

all events within 4 s after implantation

141

511

436

96

141

436

1297

2048

96

gamma intensities

what do we expect?

Stone, Walters 1985

2003

g intensities

corrected for efficiency

and M1 conversion

511

(pg9/2)-1ng7/2

111 total b+ decays

70 100Sn b+ decays

(pg9/2)-1nd5/2

Gamma Intensities

5 lines add up to 4018 keV ???

slide24

E*(1+) = (2.71 + x) MeV with x ≈ 0.05 MeV

  • because:
  • total sum energy = 2.76(0.43) MeV (Schneider et al.)
  • DMc2- QEC(1+)= 2.6(1.0) MeV (Chartier et al.)
  • one b-delayed proton event:
  • Ep + Sp(100In) = 2.93(0.34) MeV (Audi et al.)
compare to shell model
compare to shell model

Grawe et al.

Nowacki, Sieja

extraction of beta spectrum
Extraction of Beta Spectrum

sum over total energy within 3 s after implantation

in implantation zone + calorimeter

tested (by eye) for uninterrupted tracks

from maximum likelihood

Emax = 3.29 ± 0.20 MeV

QEC = 4.31 ± 0.20 MeV

to excited state

=> I(b+)= 87%

=> log ft = 2.62

100Sn

b spectrum

conv. line?

result of ML analysis

+0.13

-0.19

range of analysis

known log ft values

superallowed GT

100Sn

known log(ft) values

Nuclear Data Sheets

84 (1998) 487

log (ft)

gamow teller strength
Gamow Teller Strength

GT strength of even Sn isotopes

extreme SM

SM truncated

QRPA

FFS

exp.

A. Bobyk, W. Kaminski, I. Borzov 2000

H. Grawe, 2010

why is b gt that large
why is BGT that large?

wave functions must be rather pure

I i > = {(pg9/2)10} 0+

< f I = {(pg9/2)9 (ng7/2)1} 1+

10 protons can transform into a neutron

conclusions
Conclusions

the 100Sn shell gap

is robust

- doubly magic -

6 isomer in 100 sn

5

4

Eg/MeV

3

3 isomer decays after ToF=200ns

decaying within 25 ns ?

2

1

T/ms

0

15

5

20

10

6+ isomer in 100Sn ?

Eg/MeV

what s new
what‘s new?

103Sb

T1/2 < 50 ns !

99Sn

T1/2 > 0.2 ms

97In

95Cd

93Ag

conclusions1
Conclusions
  • first observation of 93Ag, 95Cd, 97In, and 99Sn
  • reduced rate of 103Sb => T1/2 < 50 ns
  • 102Sn: new isomeric state
  • 100Sn: probably no isomer
  • 1stg-spectrum after decay of 100Sn
  • 100Sn decay: T1/2, Ebmax, Eg, BGT
  • superallowed GT transition
  • => dominant configurations (pg9/2)10 =>(pg9/2)9 (ng7/2)1
the 100 sn team

The 100Sn Team

photo taken by Hans Geissel

slide36

Study of N ≥Z proton drip-line nuclei 96,97,98Cd with astrophysical consequencesSpokespersons: A. Blazhev, P. Boutachkov Z. Liu, R. Wadsworth

  • Shell structure near doubly-magic 100Sn
  • Abundance of isomeric states
  • Exotic decay mode
slide38

Neutron-proton pairing

T=1, S=0

T=0, S=1

Tz=0

slide39

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, 014311 (1999)

Experimental signals for T=0 np pairing

Binding energy differences

Deutron transfer reactions

 Rotational properties: delayed alignments in N=Z nucl

Level structure:

92Pd, B. Cederwallet al.Nature 469, 68-71 (2011)

Spin-gap isomer:

96Cd

slide41

E6 Spin gap

T=0

T=0

No T=0

96Cd

Effect of T=0 np interaction in 96Cd

Shell model calculations by H. Grawe

rising s352 experimental setup

Z

A/Q

RISING S352 Experimental Setup

Stopped RISING

Primary beam

124Xe @ 850 MeV/u

Active stopper

96Ag

96 ag

0.27(14) s

new

known: R. Grzywacz et al. PRC 55 (1997) 1126

B(E4; 19+ 15+)

= 0.4(3) W.u.

4168

Counts

SE

4264

B(E2; 19+ 17+)

= 4(3) W.u.

E[keV]

1.58(3) s

78(8) s

B(E3; 13- 10+)

= 0.187 (20) W.u.

96Ag

Tf<1 s

slide44

T1/2 (421) = 0.67  0.15 s(96Cd g.s.)

96Cd 

T1/2(470, 1506, 667) = 0.29-0.10 + 0.11 s

0-0.2 μs

0.2 – 4.5 μs

96Cd

0.2 – 4.5 μs

slide46
Beta decay GT strengths in GF space 100% g9/2 → g9/2, similar to the case of g9/2 → g7/2 seen in 100Sn

16+

15+

BGF = 0.14 with quenching factor of 0.6 (Herndl and Brown NPA627, 35 (1997))

Bexp= [3860(18) *  ] / (f T1/2) = 0.19 + 0.08-0.07 with T1/2 = 0.29 secs

96 cd results b s nara singh z liu et al phys rev lett 107 172502 2011
96Cd ResultsB. S. Nara Singh, Z. Liu et al. ,Phys. Rev. Lett. 107, 172502 (2011)
  • Evidence for the existence of the 16+ E6 “spin-gap” isomer in 96Cd
  • Evidence for the strong influence of the iso-scalar neutron-proton interaction
  • Our work allows to deduce T1/2 = 0.67 ± 0.15 s for the g.s. in 96Cd
results in other nuclei
Results in other nuclei
  • -decaying high-spin isomers were observed in
  • 94Pd
  • 96Ag
  • 98Cd
  • Core-excited states aross the N=Z=50 shell closure
    • identified in 96Ag
    • more in 98Cd
  • Phys. Rev. C 82, 061309(R)(2010)
  • Phys.Rev. C 84,044311 (2011)
  • J.Phys.:Conf.Ser. 205, 012035 (2010)
slide58

GSI现有和将来的实验装置

FAIR (Facility for Antiproton and Ion Research) (Darmstadt, Germany)

350m

~1GeV/u

RISING

ring branch

slide59

DEcay SPECtroscopy (DESPEC)

NEUTRON DETECTOR

GE γ-ARRAY

RADIOACTIVE

BEAM

DSSD IMPLANTATION

DETECTOR

Total Absorption  Spectrometer (TAS)

Fast timing measurements

Compact, flexible and modular geometry

g-factors and quadrupole moments

slide60

AIDA: Advanced Implantation Detector Array

E

8 cm

Veto

24 cm

8 x 8 cm

128 x 128 strips

1 mm (Micron)

3 dssd

beam

www.ph.ed.ac.uk/~td/AIDA

Implantation energy measurement

Decay energy measurement (several layers)

Low threshold: ~40 keV (conversion electron!)

Fast recovery (~µs); ASIC

slide61

ASIC Design Requirements

Selectable gain 20 100020000 MeV FSR

Low noise 12 60050000 keV FWHM

energy measurement of implantation and decay events

Selectable threshold < 0.25 – 10% FSR

observe and measure low energy b, b detection efficiency

Integral non-linearity < 0.1% and differential non-linearity < 2% for > 95% FSR

spectrum analysis, calibration, threshold determination

Autonomous overload detection & recovery ~ ms

observe and measure fast implantation – decay correlations

Nominal signal processing time < 10ms

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

slide62

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
slide64

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

slide66

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, 4p neutron detector
  • 12x 8cm x 8cm DSSSDs
  • 24x AIDA FEE cards
  • 3072 channels (x 3)
  • Design complete
  • Mechanical assembly in
  • progress
slide67

s ?

T=0 J=1

T=0 J=0

np

T=1 J=0

Even-even

Odd-odd

(3He,p)

(3He,p) Transfer Reactions

L=0 transfer – forward peaked

Measure the np transfer cross section to T=1 and T=0 states

Both absolute s(T=0) and s(T=1) and relative s(T=0) / s(T=1) tell us about the character and strength of the correlations

slide69

Many thanks to my collaborators:

Blazhev, P. Boutachkov, , Tom Davinson, L. Livinov,

T.Faestermann,B. S. Nara Singh et al.