1. Progress on the 40 Ca(α,  ) 44 Ti reaction using DRAGON Chris Ouellet Supervisor: Alan Chen Experiment leader: Christof Vockenhuber ● Background on the 40 Ca( α,  ) 44 Ti reaction ● 40 Ca( α,  ) 44 Ti using DRAGON ● Current work ● Future goals

2. Background on the 40 Ca(α,  ) 44 Ti reaction ● 44 Ti is considered signature of the α -rich freezeout during the expansion phase of a core collapse supernova (D. Arnett, Princeton University Press, 1996) ● The reaction has been agreed as key to production of 44 Ti (The et al. ApJ 1998) ● Its half life is very well determined (59.2 ± 0.6 yr) (I. Ahmed, et al. Phys Rev Lett. 1998) ● Detection of its decay in supernova remnants (A.F. Ayudin et al. Astronomy and Astrophysics 1994) allows for the rare calculation of the absolute total yield of a specific nuclide in a stellar nucleosynthesis event

3. COMPTEL observed 1.16 MeV  -rays from the decay of 44 Ti in the young supernova remnant Cas A (1994)

4. Background (Con't) ● Excess in presolar grains of 44 Ca relative to other isotopes indicate significant 44 Ti production in supernova (L.R. Nittler, et al. ApJ 1996) ●  -ray spectroscopy in the 70's of this reaction determined many of the levels and some resonance strengths (e.g. J.J. Simpson, et al. Phys Rev C 1980) ● These prompt  -ray studies only partly cover the energy region of interest ● Direct measurement is favorable

5. 44 Ti Energy Levels

6. ● A recent (2000-2005) experiment involved activation of a 4 He gas target by 40 Ca beam and implantation of the recoils into a solid target ● The yield was then measured using the 44 Ti/Ti ratio obtained through AMS (Nic VIII conference proceedings)

7. 40 Ca( α,  ) 44 Ti using DRAGON ● DRAGON allows detection of both the recoils and the  -rays ● First data run end of May 2005 to test beam feasibility ● 44 Ti recoils were detected and we measured the charge state distribution of the 40 Ca beam ● A modified microwave source with a solid Ca sputter target produces >20 enA with very low 40 Ar contamination (<0.5%) ● The accelerator gives DRAGON 40 Ca7+ however ED1 is insufficiently powerful to bend the resulting recoils through the separator ● An additional silicone nitride foil was installed post gas target to boost the charge states of the beam

8. ● Windowless gas target (H,He) surrounded by BGO  -ray detector array ● Focal plane silicon strip detector or ion chamber for recoil identification ● High beam suppression: typical ratios are 1-100 recoils / 10 13 beam ions

9. Charge State Distributions After Gas

10. Ion Chamber Schematic

11. Ion Chamber Singles Spectrum (1127 keV/u)

12. IC  -Coincidence Spectrum

13. IC  -Time of Flight-Coincidence Spectrum

14. Box projection method

15. Current Analysis ● Goal is to produce an excitation function ● Check the system by measuring the strong and well- established resonances around 1127 keV/u at various target pressures (1 – 8 Torr) ● The data we've taken covers a range of energies from 850 keV/u to 1150 keV/u ● Tabulate recoils and calculate yields

16. Preliminary Excitation Function

18. Summary and Future Goals ● Produced clean 40 Ca beam ( 20 enA) ● Installed CSB to boost the charges states of the recoils, making it acceptable to the spectrometer ● Clearly identified 44 Ti using the ion chamber, both in coincidence with the BGO array and in TOF through the separator ● Covered a large range of energy and have seen resonances ● Detailed analysis including  -ray spectra is ongoing ● Additional beam time is slotted to cover the low energy region ● Ti charge state distribution will be measured using stable Ti beam