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Recoil charge state distributions in 12C()16O at DRAGON
Joel Zylberberg Simon Fraser University
TRIUMF Student Symposium
Aug. 2, 2006
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Outline
Astrophysical importance of 12C()16OThe DRAGON to study nuclear astrophysics
Yield determination at DRAGON
Charge state distributions (CSD’s)Measurements
Simulations
Conclusions
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Astrophysical importance of 12C()16O
Red giant stars
He-Burning
3 12C12C()16O16O or 12C from He-burning?
HST image of red giant Mira
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The DRAGON
At ISAC-TRIUMF
and p capture reactions: He and H targets
Recoil mass separatorMagnetic dipole: q/m and momentum
Electric dipole: q/m and energy
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Yield calculations at DRAGON
Beam and recoils in several charge states; DRAGON selects one of them
Need to know:Number of recoils
Number of beam ions
Detector efficiency
Charge state fraction Measuring and modeling CSD’s!
)efficiencydetector fraction)( state (chargeparticles) beam(#
detected recoils ofnumber Yield
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Measuring CSD’s
FC4: incident beam currentFC1: after target (all charge states)FCCH: after dipole (only the selected charge state)Target thickness ~ pressure repeat at different pressures
inFC
FCCHq qI
qIF
/
/
4
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Charge-state distributions
Collisions in gas
Electron gain/loss
Equilibrium eventually reached
CSD of C3+ beam in He at 12.8 MeV
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CSD evolution
Coupled differential equations solve numerically = charge-changing cross-sectionEquilibrium condition
That was (fairly) simple.What about the recoils?
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CSDsim code
Want to predict recoil CSD
Perform fit to CSD data to get cross-sections for C and O in He
CSD of 9.6 MeV O3+ beam in He target as a function of target thickness. Data from ERNA (DRAGON-like facility in Germany) [Shurmann et al. NIMA 531 (2004) 428]
Calculate beam CSD numerically
In each step: Add recoilsEvolve CSD of recoils
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CSDsim
What happens during fusion?
2 main scenarios
PU0e: Recoil Picks Up No Electrons (qrecoil = qbeam +2)
PU2e: Recoil Same Charge as Beam ion (qrecoil = qbeam)
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CSDsim
Model agrees with data
Labels:PU0e - no e- capture during fusion
PU2e – recoil picks up both e- during fusion
Predictions converge for thick target
F6/F5 in recoils: data from DRAGON compared to CSDsim predictions
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Summary
DRAGON detects 1 charge state of recoils
CSDsim predicts charge state fractions: first successful modeling of recoil CSD
No electrons captured during fusion, in this reaction (at this energy)12C()16O data analysis improved
12C()16O important in astrophysics
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Acknowledgements
Thanks to:D. Hutcheon & the DRAGON group
D. Shürmann at ERNA
TRIUMF
You, for your attention
Questions? Comments?
HST image of red supergiant Betelgeuse (Alpha Orionis)
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DRAGON data analysis
In this particular reaction PU0e behavior seen (can be modeled)
May not always be PU0e
To improve data analysis:Continue studying CSD’s of recoils (see if always PU0e)
Use a post-stripper (gas or foil)
Use a very thick target
Measure recoil CSD each time a new reaction is measured
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Changing fusion cross-section
Resonance phenomenon
As beam loses energy in target, fusion cross-section changes