基于放射性束的核结构、核天体物理研究 刘 忠 outline brief introduction to rib...
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![Page 1: 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](https://reader033.vdocuments.pub/reader033/viewer/2022061310/56649d045503460f949d82c9/html5/thumbnails/1.jpg)
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• 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
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Halo nuclei
208Pb
Hansen & Jonson, Europhys. Lett., 1987, 4:409.
Halo nuclei
Rm∝2/1
2 )2/( nS
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100Sn:Gamow-Teller Strength in its Decay
rp process
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Shell Model Orbitals
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100SnGT-strength is unique tool to study wave fct.
pure spin-flip transition0+ => (pg9/2
-1 ng7/2)1+
large decay energy=> most of GT strength in b-decay window
measure:T1/2
b-endpoint energy(branching)=> GT-strength
Shell modelGrawe et al.
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100Sn:Gamow-Teller Strength in its DecaySearch for its Isomer
rp process
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100Sn:Gamow-Teller Strength in its DecaySearch for its IsomerParticle Stability of Neighbours: key to the rp-process
rp process
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key to the astrophysical rp-process
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100Sn history
year where production events quantity
1994 GSI fragm. 124Xe 7 T1/2 E() E() S139
1994 GANIL fragm. 112Sn 11 ident.1996 GANIL fusion 11 m
1998 GSI fragm. 112Sn 1 T1/2 E() E() S192
2007 MSU fragm. 112Sn 14 T1/2
2008 GSI fragm. 124Xe 259 T1/2 E() E() S330
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1st Bρ separation 2nd Bρ separationΔE
identification F2-F4: DE => ZBr(x,x´,a´) = b g A/q m0c
q = ZTOF => b
F2F4
the FRagment Separator (FRS)
~109 s-1
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the FRagment Separator (FRS)
~109 s-1
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100Sn setting (full statistics, 15 days)
A/Q
Z
Te
Ag
Cd
In
Sn
Sb
N=Z+2N=Z+1N=ZN=Z-1
259 100Sn
s = 6pb 103Sb?
99Sn
97In
95Cd
93Ag
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Silicon Implantation Detectorand Beta Absorber
SIMBA
100Sn
pixels in implantation zone: 3x60x40 = 7200
X SSSD 60x60x0.3 mm3
Y SSSD 60x60x0.3 mm3
10 SSSD 60x40x1 mm3
3 DSSD 60x40x0.7 mm3
Gassiplex+ MesytecR - chain
7 x-strips
7 x-strips10 SSSD 60x40x1 mm3
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Implantation
RISING
SIMBA
DEG
RADER
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and how it looks in reality
100Sn
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RISING
+
15 x 7
Germanium detectors
ePhoto~ 11%@ 662 keV
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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 analysisvarying the 100Sn half-lifewith 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
100Snonly 1st decays +0.70
-0.31
+0.54 -0.26
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Gamma Spectrum after Beta Decay of 100Sn
all events within 4 s after implantation
511
141
436
96
1297 2048
141
436
96
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Gamma Intensities
5 lines add up to 4018 keV ???
2003Stone, Walters 1985
(pg9/2)-1ng7/2
(pg9/2)-1nd5/2
what do we expect?
511
g intensitiescorrected for efficiencyand M1 conversion
70 100Sn b+ decays
111 total b+ decays
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E*(1+) = (2.71 + x) MeV with x ≈ 0.05 MeVbecause:
• 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.)
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compare to shell model
Grawe et al. Nowacki, Sieja
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Extraction of Beta Spectrum
100Snb spectrum
conv. line?
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
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
-0.19+0.13
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known log(ft) values
Nuclear Data Sheets 84 (1998) 487
log (ft)
100Sn
superallowed GT
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Decay of the heaviest N=Z doubly magic nucleus 100Sn
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Gamow Teller Strength
A. Bobyk, W. Kaminski, I. Borzov 2000
8.17
81
12
4 2/72/9
refGT
gg
refGT
B
NN
l
lB
ft26951
s86142
ftgg
Ft2B
22VA
GT
.
.
/exp
exp. FFS
QRPA
SM truncatedextreme SM
GT strength of even Sn isotopes
H. Grawe, 2010
6203GT 19B .
.exp .
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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
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the 100Sn shell gap
is robust
Conclusions
- doubly magic -
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3 isomer decays after ToF=200nsdecaying within 25 ns ?
6+ isomer in 100Sn ?
1
5
4
3
2
Eg/MeV
0 2015105 T/ms
Eg/MeV
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what‘s new?
93Ag
103Sb T1/2 < 50 ns !
99Sn
95Cd
T 1/2 > 0.2 m
s
97In
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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
• 1st g-spectrum after decay of 100Sn
• 100Sn decay: T1/2, Ebmax, E , g BGT
• superallowed GT transition
=> dominant configurations (pg9/2)10 =>(pg9/2)9 (ng7/2)1
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The 100Sn Team
photo taken by Hans Geissel
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Shell structure near doubly-magic 100Sn Abundance of isomeric states Exotic decay mode
Study of N ≥ Z proton drip-line nuclei 96,97,98Cd with astrophysical consequences
Spokespersons: A. Blazhev, P. Boutachkov Z. Liu, R. Wadsworth
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T=0, S=1
T=1, S=0
Tz=0
Neutron-proton pairing
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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 diff erences
Deutron transfer reactions
Rotational properties: delayed alignments in N=Z nucl
Level structure: 9 2 Pd, B. Cederwall et a l . Nature 469, 68-71 (2011)
Spin-gap isomer:
9 6 Cd
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Effect of T=0 np interaction in 96Cd
Shell model calculations by H. Grawe
T=0
No T=0
E6 Spin gap
96Cd
T=0
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Primary beam124Xe @ 850 MeV/u
RISING S352 Experimental SetupStopped RISING
Z
A/Q
96Ag
Active stopper
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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+) = 0.187 (20) W.u.
E[keV]
Coun
ts
known: R. Grzywacz et al. PRC 55 (1997) 1126
new
96Ag
4264
4168
SE
Tf<1 s
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96Cd
0.2 – 4.5 μs
96Cd
0-0.2 μs
T1/2 (421) = 0.67 0.15 s (96Cd g.s.)
0.2 – 4.5 μs
T1/2 (470, 1506, 667) = 0.29-0.10 + 0.11 s
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E6 Spin gap
Effect of iso-scalar np interaction in 96Cd, 16+ isomer
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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 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
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96Cd Results
B. 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
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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)
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SMS and IMS
In jection
Septum
E lectronC ooler
(m /q)
(m /q)
(m /q)
(m /q)
>
>
>
SchottkyN oise-P ickups
v 1
(m /q)0
(m /q)0
(m /q)1
v 1
(m /q)1
v 0
In jection
Septumv 0
TO F-D etector
ff
vv
(m /q)m /q2
t= + 2
t
21 (1 )
vv
0 t
SCHOTTKY M A SS SPECTROM ETRY ISOCHRONOUS M A SS SPECTROM ETRY
Cooled Fragments Hot Fragments
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SMS: Broad Band Frequency Spectra
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M.W.Reed et al., PRL 105 172501, (2010)
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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
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NEUTRON DETECTOR
DSSD IMPLANTATIONDETECTOR
GE γ-ARRAY
RADIOACTIVEBEAM
DEcay SPECtroscopy (DESPEC)
Total Absorption Spectrometer (TAS)Fast timing measurementsCompact, flexible and modular geometryg-factors and quadrupole moments
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8 x 8 cm128 x 128 strips1 mm (Micron)3 dssd
24 c
m
8 cm
E
Veto
AIDA: Advanced Implantation Detector Array
ww
w.p
h.ed
.ac.
uk/~
td/A
IDA
Implantation energy measurementDecay energy measurement (several layers)Low threshold: ~40 keV (conversion electron!)Fast recovery (~µs); ASIC
beam
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ASIC Design Requirements
Selectable gain 20 1000 20000 MeV FSRLow noise 12 600 50000 keV FWHM
energy measurement of implantation and decay events
Selectable threshold < 0.25 – 10% FSRobserve and measure low energy , b b detection efficiency
Integral non-linearity < 0.1% and differential non-linearity < 2% for > 95% FSRspectrum analysis, calibration, threshold determination
Autonomous overload detection & recovery ~ msobserve and measure fast implantation – decay correlations
Nominal signal processing time < 10msobserve and measure fast decay – decay correlations
Receive (transmit) timestamp datacorrelate events with data from other detector systems
Timing trigger for coincidences with other detector systemsDAQ rate management, neutron ToF
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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
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AIDA: ASIC schematic
High-speed bufferx10
DC fdbk
shaper
9R
R
Slowcomparator
Clamp comparator(for x10)
PeakHoldpositivePolarity
PeakHoldnegativePolarity
RC filter(with reset)
Fastcomparator
RC filter(with reset)
CM
OS
sw
itches
I thresholdR threshold
I thresholdR threshold
DC fdbk
shaperPeakHold
positivePolarity
PeakHoldnegativePolarity
Fastcomparator
RC filter(with reset)
I thresholdR threshold
4:1 MUX
1
2
2
3 4
4
5
6
6
7
8
9
9
10
10
10
10
1010
11
11
11
11
1111
12
13
14
14
15
16
17
18
18
1919
1919
19
19
19
19
19
19
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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 portsPower
FEE width: 8cmPrototype – air coolingProduction – recirculating coolant
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FEE Assembly Sequence
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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
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(3He,p)
np
Even-even
?s
T=0 J=0
Odd-odd
T=1 J=0
T=0 J=1
L=0 transfer – forward peaked
/1|| 2 iTf
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
(3He,p) Transfer Reactions
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Proton Radioactivity
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Many thanks to my collaborators:
A. Blazhev, P. Boutachkov, , Tom Davinson, L. Livinov, B. T.Faestermann, B. S. Nara Singh et al.