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Study of the 40 Ca( ) 44 Ti reaction at stellar temperatures with DRAGON Christof Vockenhuber for the DRAGON collaboration Vancouver, B.C., Canada
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 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 McMaster University, Hamilton, ON, Canada M. Paul Hebrew University / Weizmann Institute, Israel W. Kutschera, A. Wallner University of Vienna, Austria D. Frekers University of Münster, Germany A.M. Laird, R. Lewis University of York, England H. Crawford, L. Fogarty, E. Ó’Conner, B. Wales, Summer students from Canada and Ireland poster – No Number B. Laxdal, M. Marchetto, K. Jayamana, ISAC operators TRIUMF staff, Vancouver, BC, Canada
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Role of 44 Ti in Astrophysics laboratory half-life of 60.0 +/- 1.0 years decay through electron capture, if ionized half-life becomes longer detected in space by -ray satellites and in pre-solar grains produced in supernova detection of relatively recent supernovae alpha-rich freeze-out just above the collapsing core observed quantity of 44 Ti depends critically on ‘mass-cut’ understanding of production requires reliable reaction rates dominated by 4 reactions: 3 process 44 Ti( ,p) 47 V 45 V(p ) 46 Cr 40 Ca( ) 44 Ti
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Previous measurements of 40 Ca( ) 44 Ti prompt ray measurements in the 1970s 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 resonance strength of a few isolated resonances recent AMS measurement H. Nassar et al., PRL 96 (2006) 041102 integral measurement of a large energy range discrepancy by a factor of ~5
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Level scheme H. Nassar et al., Nucl. Phys. A 758 (2005) 411c
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Astrophysical Reaction Rate Reaction rate: Resonance strength: Measured Yield ( 44 Ti / 40 Ca ): Y( = 1 eV ) ~ 10 –11
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Experiment at DRAGON alpha-rich freeze-out takes place at a large temperature regime cover a large energy range ( E cm ~ 2.0 – 4.2 MeV ) 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 E cm ~ 10 keV / Torr 1 Torr: 220 energy steps 8 Torr: 30 energy steps
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Experiment at DRAGON Advantage: direct detection of recoils ( 44 Ti) and rays measurement of single resonances high efficiency windowless He gas target + BGO detector array acceptance: < 20 mrad ( 44 Ti recoils ~ 6 mrad) high suppression of beam recoil separator~10 7 detector ~10 4 coincidence ~10 3 measurements of < meV possible
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Experiment at DRAGON Challenges: 40 Ca 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) suppression of 40 Ca depends on selected charge state ( ~10 6 – 10 11 ) A/q ambiguities 44 Ti 11+ ↔ 40 Ca 10+ charge state distribution after the gas target acceptance of recoil spectrometer identification of 44 Ti ion chamber, TOF
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 What we measure 40 Ca beam on target elastically scattered He atoms with collimated SB detectors beam contamination with ion chamber produced 44 Ti recoils 44 Ti detected at the ion chamber charge state fraction after the target detection efficiencies rays in coincidence with 44 Ti energies and multiplicity z-position along the gas target
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 DRAGON windowless Gas Target Target thickness 1 – 10 Torr H 2 or He gas ~10 18 atoms / cm 2 Elastic monitor detectors: detect scattered gas particles Charge State Booster (CSB): 100 nm SiN foil (30 g/cm 2 ) increase mean charge state by ~2 charge state distribution independent of position along the path in the target CSB gas foil
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 30 BGO Gamma detectors surrounding gas target geometrical efficiency of ~ 90 % effective efficiency depends on energy and multiplicity determined from GEANT simulations and point source studies DRAGON detector Array
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Christof Vockenhuber 40 Ca( ) 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
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Particle Identification entrance window 130 µg/cm² Mylar, 50 µg/cm² PP, 15-30 µg/cm² SiN diameter 5 cm energy resolution: ~ 1 % for 1 MeV/u 40 Ca Cathode Frisch Grid Anode 1Anode 2Anode 3 Ionization chamber
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Beam Contamination Hybrid-surface ion source 14 IC Anode 2 IC Anode 1 +
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 44 Ti identification Ionization chamber singles
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 44 Ti identification Ionization chamber – ray coincidence coincidencesY ~ 1 x 10 -10
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 44 Ti identification Time-of-Flight through Spectrometer
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Beam Suppression
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Charge State Distribution of 44 Ti
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Charge State Distribution of 44 Ti
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Charge State Distribution of 44 Ti
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Charge State Distribution of 44 Ti
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Charge State Distribution of 44 Ti
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Charge State Distribution of 44 Ti
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Excitation function 40 Ca( ) 44 Ti 1.0 T 9 temperature regime 2.8 T 9 preliminary !
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 BGO ray spectrum 1.130 MeV 40 Ca
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 coincidence measured ray data will be used to estimate BGO efficiency
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Summary We measured the 40 Ca( ) 44 Ti reaction at the recoil mass spectrometer DRAGON in the energy regime of supernova nucleosynthesis (T 9 ~ 1 – 2.8) A first preliminary analysis gives a total 44 Ti yield between prompt ray and AMS data, a detailed analysis including ray data and GEANT simulation for BGO efficiency will follow Additionally, we learned a lot: could demonstrate to measure resonance strength for astrophysics in mass 40 region measure an excitation function over a large energy range important for reactions with radioactive beams
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006
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R. Diehl et al. (2005)
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 IC spectra 44 Ti 10+ singles 44 Ti 10+ 40 Ca 7+ 850 keV/u 8 Torr He Y ~ 4 x 10 -12
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 IC spectra 44 Ti 10+ 44 Ti 10+ coincidences 40 Ca 7+ 850 keV/u 8 Torr He Y ~ 4 x 10 -12
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 IC spectra 44 Ti 9+ 44 Ti 9+ singles 40 Ca 7+ 716 keV/u 8 Torr He Y ~ 2 x 10 -13
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 IC spectra 44 Ti 9+ 44 Ti 9+ coincidences 40 Ca 7+ 716 keV/u 8 Torr He Y ~ 2 x 10 -13
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Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 27 2006 Charge State Distribution of 44 Ti without charge state booster foil
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