Study of the 40 Ca a g 44 Ti reaction

Study of the 40 Ca(a, g)44 Ti reaction at stellar temperatures with DRAGON Christof Vockenhuber for the DRAGON collaboration Vancouver, B. C. , Canada

Collaboration L. Buchmann, J. Caggiano, J. M. D’Auria, B. Davids, A. Hussein, D. A. Hutcheon, D. Ottewell, M. M. Pavan, C. Ruiz, G. Ruprecht, M. Trinczek, C. Vockenhuber DRAGON collaboration at TRIUMF, Vancouver, BC, Canada A. Chen, C. Ouellet, J. Pearson Mc. Master University, Hamilton, ON, Canada M. Paul Hebrew University / Weizmann Institute, Israel poster – No Number W. Kutschera, A. Wallner University of Vienna, Austria D. Frekers University of Münster, Germany B. Laxdal, M. Marchetto, K. Jayamana, ISAC operators TRIUMF staff, Vancouver, BC, Canada A. M. Laird, R. Lewis University of York, England H. Crawford, L. Fogarty, E. Ó’Conner, B. Wales, Summer students from Canada and Ireland Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Role of 44 Ti in Astrophysics n laboratory half-life of 60. 0 +/- 1. 0 years n decay through electron capture, if ionized half-life becomes longer n detected in space by g-ray satellites and in pre-solar grains n produced in supernova n detection of relatively recent supernovae n alpha-rich freeze-out just above the collapsing core n observed quantity of 44 Ti depends critically on ‘mass-cut’ n understanding of production requires reliable reaction rates n dominated by 4 reactions: 44 Ti(a, p)47 V 3 a process 45 V(p, g)46 Cr 40 Ca(a, g)44 Ti Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Previous measurements of 40 Ca(a, g)44 Ti n prompt g ray measurements in the 1970 s E. L. Cooperman et al. , Nucl. Phys. A 284 (1977) 163 W. R. Dixon et al. , Phys. Rev. C 15 (1977) 1896; Can. J. Phys. 58 (1980) 1360 n resonance strength of a few isolated resonances discrepancy by a factor of ~5 n recent AMS measurement H. Nassar et al. , PRL 96 (2006) 041102 n integral measurement of a large energy range Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Level scheme H. Nassar et al. , Nucl. Phys. A 758 (2005) 411 c Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Astrophysical Reaction Rate Reaction rate: Resonance strength: Measured Yield ( 44 Ti / 40 Ca ): Y( wg = 1 e. V ) ~ 10 – 11 Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Experiment at DRAGON n alpha-rich freeze-out takes place at a large temperature regime cover a large energy range ( Ecm ~ 2. 0 – 4. 2 Me. V ) n several narrow resonances contribute to the yield ‘thin’ target for sufficient resolution ’thick’ target to apply thick target yield energy loss in the gas target DEcm ~ 10 ke. V / Torr 1 Torr: 220 energy steps 8 Torr: 30 energy steps Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Experiment at DRAGON n Advantage: n n n direct detection of recoils (44 Ti) and g rays measurement of single resonances high efficiency windowless He gas target + BGO g detector array acceptance: < 20 mrad (44 Ti recoils ~ 6 mrad) high suppression of beam n recoil separator ~107 n detector ~104 n g coincidence ~103 measurements of wg < me. V possible Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Experiment at DRAGON n Challenges: n 40 Ca n n beam from Off-line Ion Source 2+ required for acceptance at RFQ accelerator (A/q < 30) 40 Ar contamination (can be measured with ion chamber) n suppression of 40 Ca depends on selected charge state ( ~106 – 1011 ) 44 Ti 11+ ↔ 40 Ca 10+ n A/q ambiguities n charge state distribution after the gas target n acceptance of recoil spectrometer n identification of 44 Ti n ion chamber, TOF Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

What we measure n 40 Ca n n n elastically scattered He atoms with collimated SB detectors beam contamination with ion chamber produced 44 Ti recoils n n beam on target 44 Ti detected at the ion chamber charge state fraction after the target detection efficiencies g rays in coincidence with 44 Ti n n energies and multiplicity z-position along the gas target Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

DRAGON windowless Gas Target CSB Target thickness 1 – 10 Torr H 2 or He gas ~1018 atoms / cm 2 gas foil Elastic monitor detectors: detect scattered gas particles Charge State Booster (CSB): 100 nm Si. N foil (30 mg/cm 2) n increase mean charge state by ~2 n charge state distribution independent of position along the path in the target Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

DRAGON g detector Array n n n 30 BGO Gamma detectors surrounding gas target geometrical efficiency of ~ 90 % effective efficiency depends on g energy and multiplicity determined from GEANT simulations and point source studies Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Recoil Mass Separator Inverse Kinematics: Energy spread a few percent achromatic system Cone angle a few 10 mrad large gaps, large detectors Energy of recoils < beam energy problem of energy loss tails Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Particle Identification Ionization chamber Cathode Frisch Grid Anode 1 Anode 2 Anode 3 entrance window 130 µg/cm² Mylar, 50 µg/cm² PP, 15 -30 µg/cm² Si. N diameter 5 cm energy resolution: ~ 1 % for 1 Me. V/u 40 Ca Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

IC Anode 1 Beam Contamination 14 + Hybrid-surface ion source IC Anode 2 Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

44 Ti identification Ionization chamber singles Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

44 Ti identification Ionization chamber – g ray coincidences Christof Vockenhuber Y ~ 1 x 10 -10 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

44 Ti identification Time-of-Flight through Spectrometer Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Beam Suppression Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Charge State Distribution of 44 Ti Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Charge State Distribution of 44 Ti Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Charge State Distribution of 44 Ti Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Charge State Distribution of 44 Ti Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Charge State Distribution of 44 Ti Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Charge State Distribution of 44 Ti Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Excitation function 40 Ca(a, g)44 Ti preliminary ! 1. 0 T 9 Christof Vockenhuber temperature regime 40 Ca(a, g)44 Ti at DRAGON 2. 8 T 9 NIC-IX June 27 2006

BGO g ray spectrum 1. 130 Me. V Christof Vockenhuber 40 Ca(a, g)44 Ti 40 Ca at DRAGON NIC-IX June 27 2006

g-g coincidence measured g ray data will be used to estimate BGO efficiency Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Summary n We measured the 40 Ca(a, g)44 Ti reaction at the recoil mass spectrometer DRAGON in the energy regime of supernova nucleosynthesis (T 9 ~ 1 – 2. 8) n A first preliminary analysis gives a total 44 Ti yield between prompt g ray and AMS data, a detailed analysis including g ray data and GEANT simulation for BGO efficiency will follow n Additionally, we learned a lot: n could demonstrate to measure resonance strength for astrophysics in mass 40 region n measure an excitation function over a large energy range important for reactions with radioactive beams Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON R. Diehl et al. (2005) 2006 NIC-IX June 27

IC spectra 44 Ti 10+ 40 Ca 7+ 850 ke. V/u 8 Torr He singles Y ~ 4 x 10 -12 44 Ti 10+ Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

IC spectra 44 Ti 10+ 40 Ca 7+ 850 ke. V/u 8 Torr He coincidences Y ~ 4 x 10 -12 44 Ti 10+ Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

IC spectra 44 Ti 9+ 40 Ca 7+ 716 ke. V/u 8 Torr He singles Y ~ 2 x 10 -13 44 Ti 9+ Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

IC spectra 44 Ti 9+ 40 Ca 7+ 716 ke. V/u 8 Torr He coincidences Y ~ 2 x 10 -13 44 Ti 9+ Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006

Charge State Distribution of 44 Ti without charge state booster foil Christof Vockenhuber 40 Ca(a, g)44 Ti at DRAGON NIC-IX June 27 2006