F R I Bs In Flight Radioactive Ion Beams

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18

Ne Diproton Decay
E.Rapisarda for the Diproton collaboration
RNB7 2006 Cortina dAmpezzo, July 3th 7th 2006
Elisa Rapisarda Università degli studi di Catania
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Two-proton radioactivity (I)

• Two proton radioactivity is a very exotic decay
  mode
• predicted since 1960 Goldansky Nucl. Phys. 19
  (1960)

• Mass of nuclei beyond the drip line
• Pairing in nuclei
• Sequence of single particle levels
• Deformation
• Tunneling process

• It is expected in Z-even PROTON RICH NUCLEI in
  the vicinity or beyond the proton drip line

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Two-proton radioactivity (II)
Sequential emission
Three body decay
2He emission
Two types of 2p emission - ground-state
emission long lived 45Fe, 48Ni, 54Zn
short lived 6Be, 12O, 16Ne, 19Mg - emission
from excited states ß delayed 22Al, 31Ar,
others 14O, 18Ne, 17Ne, 94Ag To be
measured proton energies proton-proton
angle
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Status of the art

• Medium-mass proton drip-line nuclei are very
  promising (45Fe, 48Ni, 54Zn and 94Ag)

First evidence of two-proton radioactivity in the
decay of 45Fe Phys. Rev. Lett. 89 (2002)102501
NO identification of individual protons NO
measurements of their energies NO relative
emission angle
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Status of the art
Search of 18Ne two proton has been already
performed Gomez del Campo PRL 86(2001)43
using the fusion reaction 17FH at 44 MeV
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Two proton decay of Ne
The measured angular distributions cannot
discriminate between direct or two step emission
of 2p or 2He emission
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The Diproton Experiment
Search for DI-PROTON DECAY of excited states of
18Ne

• 35 MeV/A 18Ne beam will interact on a heavy thick
  target
• The 6.15 MeV level should be populated by Coulomb
  excitation (E1 transition)

Proton energy and angle correlations ? di-proton
emission?
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20Ne 9Be(500?m) at 45 AMeV
FRIBs
?? 4msr ?p/p /- 1 Max B? 2.7 Tm
Production Target
Laboratori Nazionali del Sud
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RIBs detected at the final focus
I 10 enA

• 9 of 18Ne over the total produced RIBs rate
• 98 of transmission along the beam line

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The Experimental Setup
20 degrees cave
The Target Holder

• 250 enA of primary beam current
• 60 kHz of secondary beam on the tagging detector
• ? 5 kHz of 18Ne (9 of the total secondary beam)

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The Experimental Setup Tagging
The Si-Strip
Si-Strip X-Y Position
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The Experimental Setup
Detectors inside the scattering chamber
88 THREE-FOLD TELESCOPES ARRAY 50mm-300mm-CsI ?4.
5?16.5
81 TWO-FOLD TELESCOPES ARRAY 300mm-CsI ?4.5?4.5
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Projectile Selection
Identification can be checked looking to the
DE-E scatter plot in forward detectors
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• The procedure have been checked for the 16O

16O 12C alpha Qval 7.149 MeV
E Ecm Qval
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Results

• 250 enA of primary beam current
• 60 kHz of secondary beam on the tagging detector
• ? 5 kHz of 18Ne (9 of the total secondary beam)

Around 100 Fp and 20 Opp events analyzed up to
now
Gomez del Campo et al. PRL 86(2001)43
E2
E1
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Results

• Possible new levels in 18Ne
• 9.9? 0.25 (1-,2)
• 10.8 ? 0.5 (1-,2)
• 13.2 ? 0.5 (1-,2)

Details of the three Opp events in the 6 MeV
region E6.01MeV Ep1.56 MeV Ep2.88MeV
q1124 q2106 f1-42 f2 -6 fo
36 E6.14MeV Ep11.3 MeV Ep2.18MeV
q150 q294 f1 90 E6.51MeV Ep11.66 MeV
Ep2.22MeV q1144 q2114 f1 82 f2 44 fo
65
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Conclusions

• We are able to identify E1 and E2 resonances
  (resolution of about 1 MeV in the excitation
  energy measurement)
• The observation of 3 events O2p in the good
  excitation energy range notwithstanding the not
  perfect efficiency tell us that the branching
  ratio of the 2p decay is not too small
• Observation of three new possible higher energy
  levels in 18Ne
• First example of measurements with exotic beam at
  intermediate energy at LNS

Improvement

• STATISTICS
• Better reconstruction of the reaction kinematics