Search results for "NUCLEOSYNTHESIS"

Nuclear Data for the Thorium Fuel Cycle and the Transmutation of Nuclear Waste

2016

Neutron-induced reaction cross sections play an important role in a wide variety of research fields, ranging from stellar nucleosynthesis, the investigation of nuclear level density studies, to applications of nuclear technology, including the transmutation of nuclear waste, accelerator-driven systems, and nuclear fuel cycle investigations. Simulations of nuclear technology applications largely rely on evaluated nuclear data libraries. These libraries are based both on experimental data and theoretical models. An outline of experimental nuclear data activities at CERN’s neutron time-of-flight facility, n_TOF, will be presented.

Stellar(n,γ)Cross Section ofNi62

2005

The 62Ni(n,gamma)63Ni(t(1/2)=100+/-2 yr) reaction plays an important role in the control of the flow path of the slow neutron-capture (s) nucleosynthesis process. We have measured for the first time the total cross section of this reaction for a quasi-Maxwellian (kT=25 keV) neutron flux. The measurement was performed by fast-neutron activation, combined with accelerator mass spectrometry to detect directly the 63Ni product nuclei. The experimental value of 28.4+/-2.8 mb, fairly consistent with a recent calculation, affects the calculated net yield of 62Ni itself and the whole distribution of nuclei with 62<A<90 produced by the weak s process in massive stars.

Study of excited states of [sup 31]S through beta-decay of [sup 31]Cl for nucleosynthesis in ONe novae

2011

We have produced an intense and pure beam of 31Cl with the MARS Separator at the Texas A&M University and studied β‐decay of 31Cl by implanting the beam into a novel detector setup, capable of measuring β‐delayed protons and γ‐rays simultaneously. From our data, we have established decay scheme of 31Cl, found resonance energies with 1 keV precision, have measured its half‐life with under 1% accuracy, found its Isobar Analog State decay and by using the IMME obtained an improved mass excess for its ground state. In this contribution, a description of the used method along with selected preliminary experimental results are given and their relevance for novae nucleosynthesis discussed.

Novel Techniques for Constraining Neutron-capture Rates relevant to Heavy-element Nucleosynthesis

2017

In this contribution we discuss new experimental approaches to indirectly provide information on neutron-capture rates relevant to the $r$-process. In particular, we focus on applications of the Oslo method to extract fundamental nuclear properties for reaction-rate calculations: the nuclear level density and the $\gamma$ strength function. Two methods are discussed in detail, the Oslo method in inverse kinematics and the beta-Oslo method. These methods present a first step towards constraining neutron-capture rates of importance to the $r$-process.

Nuclear Physics Constraints to Bring the Astrophysical R-Process to the “Waiting Point”

1988

Rapid neutron-capture (r-process) nucleosynthesis of heavy elements generally involves the participation of large numbers of stable to highly unstable nuclear species. Most of these properties are experimentally unknown and have to be predicted from nuclear models. So far, the uncertainties of such predictions have not allowed putting substantial constraints on astrophysical scenarios. For the classical r-process it is shown that the s-decay properties of only a few key-nuclei, i.e. the recently measured “waiting-point” nuclei 130Cd82 and 80Zn50 together with new shell-model predictions for their N ≈ 82 and 50 neighbours, may be sufficient to explain the observed r-abundances in the A ≈ 130…

Production and isobaric separation of 63Ni ions for determination of the 62Ni(n,γ)63Ni reaction cross section at stellar temperatures

2004

Cosmological promising parameters of stau in the minimal supersymmetric standard model

2009

We find that we can account for the possible descrepancy of the primordial abundance of 7 Li between the observation and the prediction of the Big-Bang Nucleosynthesis in a scenario of the Big-Bang Nucleosynthesis with the Minimal Supersymmetric Standard Model. This scenario is consistent with a stau-neutralino coannihilation scenario to explain the relic abundance of dark matter. The solution to the discrepancy is given by taking the values of parameters; the mass of the neutralino as 300 GeV and the mass difference between the stau and the neutralino as (100 – 120) MeV.

Operation of the r-process and cosmochronology

1993

Abstract The rapid neutron capture process produced about half of the heavy elements in nature beyond the Fe-peak. In the past quite a number of astrophysical sites have been suggested, but none of them has yet been uniquely identified. Without assuming a particular site or model, we deduce the conditions responsible for the production of r-process nuclei by making use of the following information: (1) the solar r-process abundances and (2) nuclear masses and beta decay half lives for nuclei far from stability - in particular experimental information near magic neutron numbers, which determines the shape of the r-process peaks. In addition, we review briefly galactic age determinations base…

Gamow-Teller Transitions Studied in ([sup 3]He, t) Reaction and Analogous β decay

2010

Due to the simplicity of the στ operator that causes Gamow‐Teller (GT) transitions, they are the most popular nuclear weak process in the Universe. The GT transitions in pf‐shell nuclei, for example, starting from stable Tz = +1 and proton‐rich Tz = +1 nuclei, where Tz = (N−Z)/2, play important roles in the supernova‐explosion or rp‐process nucleosynthesis. In the β‐decay study of pf‐shell nuclei, half‐lives can be measured rather accurately. On the other hand, in a high‐resolution (3He, t) charge‐exchange reaction at 0°, individual GT transitions up to high excitations can be studied. In order to derive reliable GT transition strengths B(GT), we present a unique analysis that combines the …

Mass Spectrometry Using Paul Traps

2009

Mass is one of the basic quantities to characterize any material object, whether an atom, molecule, nucleus, or elementary particle. The measurement of mass therefore serves to detect and identify atomic, molecular, and nuclear species, and can help determine their structure and binding energy. For example, a precise determination of the mass of a nucleus is of importance through its binding energy, not only for various aspects of nuclear physics but also for other branches of physics, e.g. tests of the weak interaction, of quantum electrodynamics, and of the standard model [46]. Also in astrophysics the masses of unstable isotopes involved in stellar nucleosynthesis, especially the r proce…