DSSSD for b decay investigations of heavy neutron-rich isotopes
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DSSSD for decay investigationsof heavy neutron-rich isotopes
J. Benlliure
Universidad de Santiago de Compostela, Spain
Rising ‘04
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Motivation
-decay investigation of heavy neutron-rich nuclei: half lives Q values -delay gamma emission -delay neutron emission
Production of heavy neutron-rich nuclei incold-fragmentation reactions (S227): 197Au(950 A MeV)+Be 238U(1000 A MeV)+Be136Xe(1000 A MeV)+Be208Pb(1000 A MeV)+Be
Nuclear structure and astrophysics around N=126 and Z=82
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Experimental method
-decay with half lives larger than the implantation rate (DSSD): implantation-decay time correlation implantation-decay position correlation implantation surface implantation range
Identification and implantation of fast-heavyneutron-rich isotopes (FRS): fission contamination charge states implantation range
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Suppression of fisssion pollution
Slits behind the target
238U(1000 A MeV)+Be
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Charge states in the MUSICs: Z identification
Correlated measurement with two MUSICs with a stripper in between
E Music 1 E Music 2
E M
usi
c 1
E Music 2 E
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Charge states in the FRS: A/Q identification
Difference between B1 and B2 with a degrader and a stripper at S2
O-1
O-2
1-O O-O
E MUSIC
E d
egra
der
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Identification matrix
More than 30 new isotopes
A/Z
194W 2h 41 min
186Lu 10 h 45 min
A/Z
z
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Implantation range
Monoenergetic degrader at S2: larger implantation surface at S4 smaller dispersion in the implantation range
Achromatic degrader Monoenergetic degrader
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Implantation range
Estimated implanted isotopes for a setting centered on 192W in 1 mm thickness silicium with a monoenergetic degrader at S2
Silicium thickness (m)
ch
arg
e s
tate
s
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Detector setup for half lives measurement
Implantation-decay correlations with large background (half lifes similar to the implantation rate):
implantation-decay time correlation: active catcher implantation-decay position correlation: granularity implantation of several ions: thickness and area energy of the implanted ion and the emitted
Active catcher for implantation-decay correlations
4 double-side silicon-strip detectors
- surface 5x5 cm2
- thickness 1 mm - 2x16 3.125 mm strips - manufactured by MICRON
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Experimental setup at S4
Detectors: Ionisation chamber (rejection of reactions in the stopper) 2 plastic scintillator detectors (implantation) 4 double-side silicon-strip detectors
Electronics: 10 carts x 16 charge sensitive preamplifiers from GANIL one channel per strip (implantation signals saturated) 16 channel spectroscopic amplifiers CAEN N568B
DAQ: 3x32 channel multievent peak sensing CAEN ADC V785
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Implantation procedure
E MUSIC 2
E M
US
IC 3
E S
C43
(ch
ann
els)
E SC42 (channels)
MUSIC 1
SC4SC42
SC43
MUSIC 2
MUSIC 3
Reaction rejection Stopper thickness
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Implantation procedure
Setting centered on186Lu
Produced Implanted
MUSIC 1
SC4SC42
SC43
MUSIC 2
MUSIC 3
Sc43Sc42
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DSSD response: energy resolution
Energy resolution (1%)Energy spectra
3 source
239Pu E->5148,85 keV
241Am E-> 5478,38 keV
244Cm E->5794,88 keV
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DSSSD response: position correlation
SC
42
(m
m)
Silicon strip
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DSSSD response: hit multiplicity
multiplicity 2 multiplicity 3
multiplicity 4 multiplicity 5
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Summary and future plans
- Propose dedicated experiments to investigate the north-east of the chart of the nuclides
- New preamplifiers (double gain)
- - Additional detectors to improve detection efficiency
Summary-Validation of the production and identification of heavy neutron-rich isotopes:
-Cold fragmentation-Charge states discrimination-Production cross section determination
-Around 35 new heavy neutron-rich isotopes in the region Z=71->78 has been discovered-Optimum setup for position and time correlation:
-Implantation procedure-Position correlation-Energy resolution-Time correlation (in progress)
Future plans