atom counting for nuclear astrophysics

Hui, SK; Paul, M.; Berkovits, D.; Ghelberg, S.; Hass, M.; Hershkowitz, A.; Navon, E.

doi:10.1016/s0168-583x(00)00101-4

Cited by 14 publications

(6 citation statements)

References 20 publications

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“…Importantly, this result, based on the 44 Ti/Ti isotopic ratio, is independent of chemical or counting efficiencies [15]. The experimental scheme was tested by producing a copious number of 44 Ti nuclei (∼ 2.7 × 10 9 ) via the reaction 34 S( 12 C,2n) 44 Ti [18]. The 44 Ti yield measured by AMS analysis and the derived cross section are consistent with those calculated by the evaporation code PACE2 [19].…”

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confidence: 89%

“…1) and the 46 Ti 10+ charge current was measured, leading to the 44 Ti/Ti ratio. In order to reduce systematic errors in the final r 44 values, the ratios were normalized to those measured for a calibration sample (Table 1; see [18,22] for information on the 44 Ti source material). Blank samples (having gone through the same chemical procedures, but containing no 44 Ti) were used to ensure that no background is present in the measurements.…”

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confidence: 99%

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Ca40(α,γ)Ti44Reaction in the Energy Regime of Supernova Nucleosynthesis

et al. 2006

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The 44 Ti(t 1/2 = 59 y) nuclide, an important signature of supernova nucleosynthesis, has recently been observed as live radioactivity by γ-ray astronomy from the Cas A remnant. We investigate in the laboratory the major 44 Ti production reaction, 40 Ca(α, γ) 44 Ti (Ecm ∼ 0.6-1.2 MeV/u), by direct off-line counting of 44 Ti nuclei. The yield, significantly higher than inferred from previous experiments, is analyzed in terms of a statistical model using microscopic nuclear inputs. The associated stellar rate has important astrophysical consequences, increasing the calculated supernova 44 Ti yield by a factor ∼ 2 over previous estimates and bringing it closer to Cas A observations. PACS numbers: 26.30.+k,97.60.Bw,95.85.Pw,24.60Dr The radionuclide 44 Ti(t 1/2 = 59 y) is considered an important signature of explosive nucleosynthesis in corecollapse supernovae (SN) [1], where multiple α capture is the path for SN nucleosynthesis from 28 Si to 56 Ni(Fe). 44 Ti is mainly produced during an α-rich freeze-out phase, the ratio 44 Ti/ 56 Ni being sensitive to the explosion conditions. Stellar production of 44 Ti determines the abundance of stable 44 Ca and contributes to that of 48 Ti (fed by 48 Cr on the α-chain). Live 44 Ti has been directly observed from a point source identified as Cassiopeia A (Cas A) by γ-and X-ray telescopes (CGRO, RXTE, BeppoSAX) and very recently by the INTEGRAL mission (see [2,3]). Cas A is believed to be the remnant of a core-collapse SN whose progenitor mass was in the range 22-25 M ⊙ (M ⊙ denotes a solar mass) [4]. Using known values of the distance and age of the remnant, half-life of 44 Ti and the combined γ flux from all observations, an initial 44 Ti yield of 160± 60 µM ⊙ is implied [3]. This value is larger by a factor of 2-10 than 44 Ti yields calculated in current models (e.g. [5,6]) and various explanations have been proposed [4,7,8,9]. 44 Ti γ-ray emission from SN1987A in the near Large Magellanic Cloud galaxy, the closest known SN remnant in the last two centuries, is below detection limits. But its present lightcurve is believed to be powered by 44 Ti radioactivity and the inferred initial 44 Ti yield is estimated to be 100-200 µM ⊙ (see [2]), similar to that of Cas A. Using the 56 Ni yield of SN1987A directly measured by γ-ray astronomy, the implied 44 Ti/ 56 Ni ratio is larger by * To whom correspondence should be addressed, email address: paul@vms.huji.ac.il a factor ∼3 than estimated by stellar calculations [2]. No other source of 44 Ti activity has been confirmed so far, despite a number of candidates and the improved sensitivity of the INTEGRAL γ-ray telescope [2]. Although many nuclear reactions play roles in determining the SN yield of 44 Ti [9, 10], the major production reaction is 40 Ca(α, γ) 44 Ti and its importance has been emphasized [11]. Experimental information about this reaction is incomplete and theoretical estimates are made less reliable by the suppression of dipolar T = 0 → 0 transitions in selfconjugate (N =Z) nuclei. The reaction was studied in the 70's b...

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confidence: 89%

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Ca40(α,γ)Ti44Reaction in the Energy Regime of Supernova Nucleosynthesis

et al. 2006

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“…A more recent off-line approach using AMS performed an integrated cross-section measurement over an extended energy range [12,[22][23][24]. The experiment consisted of a helium gas-cell under 40 Ca bombardment, with subsequent 44 Ti recoils implanted in a cooled copper catcher.…”

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confidence: 99%

New measurement of the astrophysically important40Ca(α,γ)44Ti reaction

et al. 2012

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The relatively short-lived radionuclide 44 Ti is of considerable importance for the interpretation of nucleosynthesis in core collapse supernova environments. Production is predominantly through the 40 Ca(α,γ)44 Ti reaction, which has been studied in this work over the energy range Ecm = 2.73 -4.18 MeV, via direct γ counting and the 4π-summing technique, utilizing a previously characterized 12 inch × 12 inch single NaI crystal. The inferred reaction rate is compared here to both current experimental measurements and theoretical model calculations.

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“…In this regard, AMS has been used to measure such production rates, e.g. of 44 Ti dominated by the 40 Ca(a, c) reaction [4], and of 26 Al through the 25 Mg(p, c) reaction [5].…”

Section: Introductionmentioning

confidence: 99%

Nuclear astrophysics and AMS – Probing nucleosynthesis in the lab

Wallner

2010

Nuclear Instruments and Methods in Physics Research Section B:

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atom counting for nuclear astrophysics

Cited by 14 publications

References 20 publications

Ca40(α,γ)Ti44Reaction in the Energy Regime of Supernova Nucleosynthesis

Ca40(α,γ)Ti44Reaction in the Energy Regime of Supernova Nucleosynthesis

New measurement of the astrophysically important40Ca(α,γ)44Ti reaction

Nuclear astrophysics and AMS – Probing nucleosynthesis in the lab

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