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Recoil charge state distributions in 12 C( a,g ) 16 O at DRAGON

Recoil charge state distributions in 12 C( a,g ) 16 O at DRAGON. Joel Zylberberg Simon Fraser University TRIUMF Student Symposium Aug. 2, 2006. Astrophysical importance of 12 C( a,g ) 16 O. The DRAGON to study nuclear astrophysics

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Recoil charge state distributions in 12 C( a,g ) 16 O at DRAGON

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  1. Recoil charge state distributions in 12C(a,g)16O at DRAGON Joel Zylberberg Simon Fraser University TRIUMF Student Symposium Aug. 2, 2006

  2. Astrophysical importance of 12C(a,g)16O The DRAGON to study nuclear astrophysics Yield determination at DRAGON Charge state distributions (CSD’s) Measurements Simulations Conclusions Outline TRIUMF Student Symposium 02/08/2006

  3. Astrophysical importance of 12C(a,g)16O • Red giant stars • He-Burning • 3a 12C • 12C(a,g)16O • 16O or 12C from He-burning? HST image of red giant Mira TRIUMF Student Symposium 02/08/2006

  4. At ISAC-TRIUMF a and p capture reactions: He and H targets Recoil mass separator Magnetic dipole: q/m and momentum Electric dipole: q/m and energy The DRAGON TRIUMF Student Symposium 02/08/2006

  5. 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  Yield calculations at DRAGON Measuring and modeling CSD’s! TRIUMF Student Symposium 02/08/2006

  6. FC4: incident beam current FC1: after target (all charge states) FCCH: after dipole (only the selected charge state) Target thickness ~ pressure  repeat at different pressures Measuring CSD’s TRIUMF Student Symposium 02/08/2006

  7. Charge-state distributions • Collisions in gas • Electron gain/loss • Equilibrium eventually reached CSD of C3+ beam in He at 12.8 MeV TRIUMF Student Symposium 02/08/2006

  8. Coupled differential equations  solve numerically s = charge-changing cross-section Equilibrium condition  CSD evolution That was (fairly) simple. What about the recoils? TRIUMF Student Symposium 02/08/2006

  9. Want to predict recoil CSD Perform fit to CSD data to get cross-sections for C and O in He CSDsim code • Calculate beam CSD numerically • In each step: • Add recoils • Evolve CSD of recoils 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] TRIUMF Student Symposium 02/08/2006

  10. 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) CSDsim TRIUMF Student Symposium 02/08/2006

  11. 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 TRIUMF Student Symposium 02/08/2006

  12. 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(a,g)16O data analysis improved 12C(a,g)16O important in astrophysics Summary TRIUMF Student Symposium 02/08/2006

  13. Thanks to: D. Hutcheon & the DRAGON group D. Shürmann at ERNA TRIUMF You, for your attention Questions? Comments? Acknowledgements HST image of red supergiant Betelgeuse (Alpha Orionis) TRIUMF Student Symposium 02/08/2006

  14. 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 DRAGON data analysis TRIUMF Student Symposium 02/08/2006

  15. Changing fusion cross-section • Resonance phenomenon • As beam loses energy in target, fusion cross-section changes TRIUMF Student Symposium 02/08/2006

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