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

Joel Zylberberg Simon Fraser University

TRIUMF Student Symposium

Aug. 2, 2006

TRIUMF Student Symposium 02/08/2006

2

Outline

Astrophysical importance of 12C()16OThe DRAGON to study nuclear astrophysics

Yield determination at DRAGON

Charge state distributions (CSD’s)Measurements

Simulations

Conclusions

TRIUMF Student Symposium 02/08/2006

3

Astrophysical importance of 12C()16O

Red giant stars

He-Burning

3 12C12C()16O16O or 12C from He-burning?

HST image of red giant Mira

TRIUMF Student Symposium 02/08/2006

4

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

TRIUMF Student Symposium 02/08/2006

5

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

TRIUMF Student Symposium 02/08/2006

6

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

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

CSD evolution

Coupled differential equations solve numerically = charge-changing cross-sectionEquilibrium condition

That was (fairly) simple.What about the recoils?

TRIUMF Student Symposium 02/08/2006

9

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

TRIUMF Student Symposium 02/08/2006

10

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)

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

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

TRIUMF Student Symposium 02/08/2006

13

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)

TRIUMF Student Symposium 02/08/2006

14

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

TRIUMF Student Symposium 02/08/2006

15

Changing fusion cross-section

Resonance phenomenon

As beam loses energy in target, fusion cross-section changes