Study of the 40 Ca( ) 44 Ti reaction at stellar temperatures with DRAGON Christof Vockenhuber for the DRAGON collaboration Vancouver, B.C., Canada
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 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
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Role of 44 Ti in Astrophysics laboratory half-life of /- 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
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 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) integral measurement of a large energy range discrepancy by a factor of ~5
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Level scheme H. Nassar et al., Nucl. Phys. A 758 (2005) 411c
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Astrophysical Reaction Rate Reaction rate: Resonance strength: Measured Yield ( 44 Ti / 40 Ca ): Y( = 1 eV ) ~ 10 –11
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 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
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 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
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 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 – ) 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
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 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
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 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
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 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
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 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( ) 44 Ti at DRAGON NIC-IX June Particle Identification entrance window 130 µg/cm² Mylar, 50 µg/cm² PP, µg/cm² SiN diameter 5 cm energy resolution: ~ 1 % for 1 MeV/u 40 Ca Cathode Frisch Grid Anode 1Anode 2Anode 3 Ionization chamber
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Beam Contamination Hybrid-surface ion source 14 IC Anode 2 IC Anode 1 +
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Ti identification Ionization chamber singles
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Ti identification Ionization chamber – ray coincidence coincidencesY ~ 1 x
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Ti identification Time-of-Flight through Spectrometer
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Beam Suppression
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Charge State Distribution of 44 Ti
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Charge State Distribution of 44 Ti
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Charge State Distribution of 44 Ti
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Charge State Distribution of 44 Ti
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Charge State Distribution of 44 Ti
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Charge State Distribution of 44 Ti
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Excitation function 40 Ca( ) 44 Ti 1.0 T 9 temperature regime 2.8 T 9 preliminary !
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June BGO ray spectrum MeV 40 Ca
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June coincidence measured ray data will be used to estimate BGO efficiency
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June 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
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June
R. Diehl et al. (2005)
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June IC spectra 44 Ti 10+ singles 44 Ti Ca keV/u 8 Torr He Y ~ 4 x
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June IC spectra 44 Ti Ti 10+ coincidences 40 Ca keV/u 8 Torr He Y ~ 4 x
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June IC spectra 44 Ti Ti 9+ singles 40 Ca keV/u 8 Torr He Y ~ 2 x
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June IC spectra 44 Ti Ti 9+ coincidences 40 Ca keV/u 8 Torr He Y ~ 2 x
Christof Vockenhuber 40 Ca( ) 44 Ti at DRAGON NIC-IX June Charge State Distribution of 44 Ti without charge state booster foil