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VI Incontro Nazionale Gruppo Italiano Astrofisica
Nucleare Teorica e Sperimentale (GIANTS),
Perugia Nov. 2006
Measurement of the 3He(4He,g)7Be with ERNA
Mario De Cesare
- Dipartimento di Scienze Ambientali, Seconda
universitá degli studi di Napoli
- INFN sezione di Napoli
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• Abundance determination of 7Li in the Big Bang
  nucleosynthesis

7Be g
3He
3He 4He
n p
4He
7Be e-
7Li
There is more 7Li observed in the universe than
expected

• High energy solar neutrino flux determination
  (F(8B)) coming from the pp-chain

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Measurements of radiative capture reaction cross
sections by means of the detection of the recoil
nuclei
leaky beam / recoils 102
beam / recoils 1014
Beam
Separator
Recoils Leaky
BeamRecoils
Ions identification
Windowless gastarget
Beam
g detection
coincidence
ECM 0.5 3 MeV

• Low enough detection and ion identification
  energy threshold
• High and well known detection efficiency

ECM 1.1- 3 MeV
DE-E detector
ECM 0.5 1.1 MeV
TOF-E detector
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Sq Nq7Be NP NT e
Nq7Be NP NT s e fq
s

• Target thicknes
• Energy loss
• 3He(16O,p)18F

DE dE/dX
DX
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by DE-E ionization-chamber telescope
ECM 1.1-3 MeV
Bethe and Bloch
DE a m Z2/E
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ELab 3 MeV 4He2 ECM 1.3 MeV

Matrix DE-Erest
7Be2
Leaky of 4He
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TOF-E detector set up
Start and Stop detectors
D t L/v e v (2E/m)1/2
ECM 0.5-1.1 MeV
Dt L (m/2E)1/2
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Results
1) Time resolution MCP - PGAC 2.3 ns
ELab 7 MeV 12C2
MCP - Si 0.7 ns
Counts
Ch
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2) Position dependent efficiency
ELab 1 MeV 7Li1
The 100 efficiency is within 15 mm of the optic
axis
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ELab 2.8 MeV 4He2 ECM 1.2 MeV

3) Matrix TOF-E
TOF (a.u.)
Leaky of 4He
7Be2
E (a.u.)
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• The 100 efficiency is within 15 mm of the optic
  axis

Calculation has shown that the electrons have a
radius of 30 mm on the 20 mm radius of the MCP
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Conclusion and Outlook

• There are already measurements for the
  3He(4He,g)7Be in the ECM 1.1- 3 MeV
• A TOF-E detector is a suitable detector for
  measuring 3He(4He,g)7Be at ECM 0.5-2.0 MeV
• Time resolution between MCP and Silicon is 0.7 ns
• The 100 efficiency is within 15 mm of the optic
  axis
• 3He(4He,g)7Be astrofisical factor measurements at
  low energy will start by the end of the year