| 1. |
- Reifarth, R., et al.
(author)
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Nuclear astrophysics with radioactive ions at FAIR
- 2016
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In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 665:1
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Conference paper (peer-reviewed)abstract
- The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process beta-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes.
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| 2. |
- Indriolo, N., et al.
(author)
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Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
- 2015
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In: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 800:1, s. 40-
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Journal article (peer-reviewed)abstract
- In diffuse interstellar clouds the chemistry that leads to the formation of the oxygen-bearing ions OH+, H2O+, and H3O+ begins with the ionization of atomic hydrogen by cosmic rays, and continues through subsequent hydrogen abstraction reactions involving H2. Given these reaction pathways, the observed abundances of these molecules are useful in constraining both the total cosmic-ray ionization rate of atomic hydrogen (ζH) and molecular hydrogen fraction (f_H_2). We present observations targeting transitions of OH+, H2O+, and H3O+ made with the Herschel Space Observatory along 20 Galactic sight lines toward bright submillimeter continuum sources. Both OH+ and H2O+ are detected in absorption in multiple velocity components along every sight line, but H3O+ is only detected along 7 sight lines. From the molecular abundances we compute f_H_2 in multiple distinct components along each line of sight, and find a Gaussian distribution with mean and standard deviation 0.042 ± 0.018. This confirms previous findings that OH+ and H2O+ primarily reside in gas with low H2 fractions. We also infer ζH throughout our sample, and find a lognormal distribution with mean log (ζH) = –15.75 (ζH = 1.78 × 10–16 s–1) and standard deviation 0.29 for gas within the Galactic disk, but outside of the Galactic center. This is in good agreement with the mean and distribution of cosmic-ray ionization rates previously inferred from H_3^+ observations. Ionization rates in the Galactic center tend to be 10-100 times larger than found in the Galactic disk, also in accord with prior studies.
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| 3. |
- Nacher, E., et al.
(author)
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Proton response of CEPA4: A novel LaBr3(Ce)-LaCl3(Ce) phoswich array for high-energy gamma and proton spectroscopy
- 2015
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In: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 769, s. 105-111
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Journal article (peer-reviewed)abstract
- A new phoswich array, for the detection of high-energy protons and gamma rays from nuclear reactions, has been built. This new detector consists of four individual closely packed scintillator detectors, each of them made of 4 cm of LaBr3(Ce) and G cm of LaCl3(Ce) in phoswich configuration (optically coupled and with a common readout). In this paper we report on the results of a beam test performed at the Bronowice Cyclotron Centre (CCB) in Krakow, showing the response of this versatile instrument to high energy protons (70-230 MeV). Furthermore, for the first time we prove that we can reconstruct the original energy of fast protons (E > 200 MeV) which pass through the total length of the crystal while still retaining a good energy resolution.
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