scholarly journals Transfer reactions for nuclear astrophysics

2018 ◽  
Vol 184 ◽  
pp. 01009
Author(s):  
Fairouz Hammache
Keyword(s):  
Cross Sections ◽  
Charged Particles ◽  
Nuclear Astrophysics ◽  
Theoretical Models ◽  
Theoretical Concept ◽  
Transfer Reactions ◽  
Indirect Methods ◽  
R Matrix ◽  
Direct Measurements ◽  
Threshold Resonances

Direct measurements of cross sections at stellar energies are very challenging - if at all possible. This is essentially due to the very low cross-sections of the reactions of interest (especially when it involves charged particles), and/or to the radioactive nature of many key nuclei. Direct measurements with charged particles are often performed at higher energies and then extrapolated down to stellar energies using R-matrix calculations. However, these extrapolations are delicate because of the possible existence of unobserved low-energy or sub-threshold resonances. In order to bypass the difficulties related to direct measurements, indirect methods such as transfer reactions are used. These experiments are usually performed at higher energies and their conditions are relatively less stringent than in direct measurements. However, these methods rely on theoretical models for which the input parameters may be an important source of systematic uncer-tainties and thus need to be determined carefully. In this manuscript, a short overview on the difficulties related to direct measurements will be given as well as a description of thetransfer reaction method and the theoretical concept behind. Finally, the method will be illustrated through two recent performed studies.

scholarly journals Continuous spectra of light charged particles from interaction of 30 MeV energy protons with cooper

2020 ◽  
Vol 239 ◽  
pp. 01033
Author(s):  
Timur Zholdybayev ◽  
Zhuldyz Mukan ◽  
Bakhtiyar Sadykov ◽  
Bek Duisebayev ◽  
Maulen Nassurlla ◽  
...  
Keyword(s):  
Experimental Data ◽  
Cross Sections ◽  
Nuclear Physics ◽  
Charged Particles ◽  
Theoretical Models ◽  
Isochronous Cyclotron ◽  
The Cross ◽  
Light Charged Particles

This paper presents the experimental double-differential and integral cross sections of reactions (p,xp), and (p,xα) on natCu nucleus. The experiment with the protons, accelerated to energy of 30.0 MeV was performed at the isochronous cyclotron of Institute of Nuclear Physics (Kazakhstan). We investigated the adequacy of the theoretical models in explaining the measured experimental data and contributions of direct, preequilibrium and compound processes in the formation of the cross sections were determined. We assert that the traditional frameworks are valid for the description of the experimental data.

scholarly journals Asymptotic theory of charged particle transfer reactions at low energies and nuclear astrophysics

2019 ◽  
Vol 49 ◽  
pp. 1960016
Author(s):  
R. Yarmukhamedov ◽  
K. I. Tursunmakhatov ◽  
N. Burtebayev
Keyword(s):  
Cross Sections ◽  
Asymptotic Theory ◽  
Nuclear Astrophysics ◽  
Transfer Reactions ◽  
Dispersion Theory ◽  
Low Energies ◽  
Proton Transfer Reactions ◽  
Stellar Energy ◽  
Text Model ◽  
Three Body

An asymptotic theory is proposed for the peripheral transfer [Formula: see text] reaction at low energies within the three-body ([Formula: see text], [Formula: see text] and [Formula: see text]) model by combining the dispersion theory and DWBA, where [Formula: see text], [Formula: see text] and [Formula: see text] is a transferred particle. The contribution of the three-body ([Formula: see text], [Formula: see text] and [Formula: see text]) Coulomb dynamics of the transfer mechanism both to the peripheral partial amplitudes for the partial wave [Formula: see text] and to the DWBA amplitude is investigated. The results of the analysis of the differential cross sections of the specific proton transfer reactions at above-barrier energies are presented. New estimates and their uncertainties are obtained for values of the asymptotic normalization coefficients for [Formula: see text] and [Formula: see text] as well as for the direct astrophysical [Formula: see text] factors at stellar energy of the radiative capture [Formula: see text] and [Formula: see text] reactions.

On threshold resonances

1970 ◽  
Vol 48 (15) ◽  
pp. 1747-1758 ◽  
Author(s):  
C. T. Tindle
Keyword(s):  
Cross Sections ◽  
Matrix Theory ◽  
Threshold Level ◽  
R Matrix ◽  
Neutral Particles ◽  
S Matrix ◽  
Energy Neutron ◽  
Square Well ◽  
Neutron Cross Sections ◽  
Threshold Resonances

A comparison is made of the way R-matrix and S-matrix theories analyze the threshold resonances which occur in the scattering of neutral particles by a square well. Both approaches are found to provide very good approximate formulas. However, modifications of the usual S-matrix expansions must first be made. The behavior of the energy of the threshold level is quite different in the two alternatives. By comparing the two theories in their interpretation of the low-energy neutron cross sections of 1H, 16O, and 208Pb it is concluded that.R-matrix theory provides a better interpretation for unbound levels and S-matrix theory is preferable when the threshold level is bound.

scholarly journals OPTICAL DEPTH FOR VHE γ-RAYS FROM DISTANT SOURCES FROM A GENERIC EBL DENSITY

2008 ◽  
Vol 17 (09) ◽  
pp. 1515-1520 ◽  
Author(s):  
M. RAUE ◽  
D. MAZIN
Keyword(s):  
Ad Hoc ◽  
Far Infrared ◽  
Theoretical Models ◽  
High Energy ◽  
Indirect Methods ◽  
Extragalactic Background Light ◽  
Direct Measurements ◽  
Very High Energy ◽  
Γ Rays ◽  
Direct And Indirect Methods

Very-high-energy (VHE; E > 100 GeV ) γ-rays from distant sources suffer attenuation through pair-production with low energy photons from the diffuse extragalactic photon fields in the ultraviolet (UV) to far-infrared (FIR) (commonly referred to as extragalactic background light; EBL). When modeling the intrinsic spectra of the VHE γ-ray sources it is crucial to correctly account for the attenuation. Unfortunately, direct measurements of the EBL are difficult and the knowledge about the EBL over certain wavelength ranges is poor. To calculate the EBL attenuation, usually predictions from theoretical models are used. Recently, the limits on the EBL from direct and indirect methods have narrowed down the possible EBL range and many of the previous models are in conflict with these limits. We propose a new generic EBL density (not a complete model), which is in compliance with the new EBL limits. EBL evolution with redshift is included in the calculation in a very simple but effective ad hoc way. Properties of this generic EBL are discussed.

INDIRECT MEASUREMENTS OF NUCLEAR ASTROPHYSICS REACTIONS USING UNSTABLE NUCLEAR BEAMS

2006 ◽  
Vol 15 (08) ◽  
pp. 1899-1907 ◽  
Author(s):  
WEI-PING LIU ◽  
ZHI-HONG LI ◽  
XI-XIANG BAI ◽  
YOU-BAO WANG ◽  
GANG LIAN ◽  
...  
Keyword(s):  
Inverse Kinematics ◽  
Spectroscopic Factor ◽  
Ion Beam ◽  
Nuclear Astrophysics ◽  
Reaction Rates ◽  
Transfer Reactions ◽  
Angular Distributions ◽  
Indirect Measurements ◽  
R Matrix ◽  
Asymptotic Normalization Coefficient

This paper described the nuclear astrophysical studies using the unstable ion beam facility GIRAFFE, by indirect measurements. We measured the angular distributions for some single proton or neutron transfer reactions, such as 7 Be ( d,n )8 B , 11 C ( d,n )12 N , 8 Li ( d,n )9 Be , 8 Li ( d,p )9 Li and 13 N ( d,n )14 O in inverse kinematics, and derived the astrophysical S-factors or reaction rates of 7 Be ( p ,γ)8 B , 11 C ( p ,γ)12 N , 8 Li ( n ,γ)9 Li , 13 N ( p ,γ)14 O by asymptotic normalization coefficient, spectroscopic factor, and R-matrix approach at astrophysically relevant energies.

scholarly journals Transfer Reactions As a Tool in Nuclear Astrophysics

2021 ◽  
Vol 8 ◽  
Author(s):  
Faïrouz Hammache ◽  
Nicolas de Séréville
Keyword(s):  
Cross Sections ◽  
Transfer Reaction ◽  
Nuclear Reactions ◽  
Experimental Studies ◽  
Nuclear Astrophysics ◽  
Spectroscopic Properties ◽  
Reaction Rates ◽  
Theoretical Concept ◽  
Reaction Method ◽  
Basic Features

Nuclear reaction rates are one of the most important ingredients in describing how stars evolve. The study of the nuclear reactions involved in different astrophysical sites is thus mandatory to address most questions in nuclear astrophysics. Direct measurements of the cross-sections at stellar energies are very challenging–if at all possible. This is essentially due to the very low cross-sections of the reactions of interest (especially when it involves charged particles), and/or to the radioactive nature of many key nuclei. In order to overcome these difficulties, various indirect methods such as the transfer reaction method at energies above or near the Coulomb barrier are used to measure the spectroscopic properties of the involved compound nucleus that are needed to calculate cross-sections or reaction rates of astrophysical interest. In this review, the basic features of the transfer reaction method and the theoretical concept behind are first discussed, then the method is illustrated with recent performed experimental studies of key reactions in nuclear astrophysics.

CROSS SECTIONS FOR NUCLEAR ASTROPHYSICS

2008 ◽  
Vol 17 (10) ◽  
pp. 2165-2170
Author(s):  
PIERRE DESCOUVEMONT
Keyword(s):  
Cross Sections ◽  
Matrix Method ◽  
Potential Model ◽  
Nuclear Astrophysics ◽  
Reaction Rates ◽  
Low Energy ◽  
R Matrix ◽  
General Properties ◽  
Microscopic Models

General properties of low-energy cross sections and of reaction rates are presented. We describe different models used in nuclear astrophysics: microscopic models, the potential model, and the R-matrix method. Two important reactions, 7 Be ( p ,γ)8 B and 12 C (α,γ)16 O , are then briefly discussed.

scholarly journals Experimental Investigation of radiative proton-capture reactions relevant to Nucleosynthesis

2019 ◽  
Vol 24 ◽  
pp. 168
Author(s):  
A. Khaliel ◽  
T. J. Mertzimekis ◽  
A. Psaltis ◽  
I. Psyrra ◽  
A. Kanellakopoulos ◽  
...  
Keyword(s):  
Cross Sections ◽  
Nuclear Reactions ◽  
Nuclear Astrophysics ◽  
Theoretical Models ◽  
Reaction Cross ◽  
Tandem Accelerator ◽  
Proton Capture ◽  
Isotopic Abundances ◽  
Vast Network ◽  
Reaction Cross Sections

One of the primary objectives of the field of Nuclear Astrophysics is the study of the elemental and isotopic abundances in our solar system. Although a lot of progress has been made regarding a large number of nuclides, there is still a number of neutron-deficient nuclei, ie the p nuclei, which cannot be created via the s and r processes. These processes are responsible for the production of the bulk of heavy nuclides. The pre-explosive or explosive phases of massive stars are considered potential loci for p nuclides production via various combinations of photodisintegrations and nucleon captures, along with β+ decays and electron captures. For the study of the vast network of nuclear reactions (over 20'000) that are responsible for observed isotopic abundances, the statistical model of Hauser-Feshbach is employed. The model requires the knowledge of nuclear reaction cross sections, quantities that can be measured in the laboratory. In this work, we report on recent experimental attempts to measure such cross sections in radiative proton-capture reactions involving 107,109Ag near the astrophysically relevant energy window. Measurements have been performed at the Tandem Accelerator Laboratory of the N.S.C.R. “Demokritos”. The results are compared to various theoretical models, using the TALYS and EMPIRE codes, in an attempt to provide experimental input to astrophysical models.

scholarly journals A review of the fission programme at the CERN n_TOF facility

2019 ◽  
Vol 23 ◽  
pp. 16
Author(s):  
A. Tsinganis ◽  
For the N_TOF Collaboration
Keyword(s):  
Cross Sections ◽  
High Performance ◽  
Nuclear Astrophysics ◽  
Theoretical Models ◽  
High Energy ◽  
High Energy Resolution ◽  
Scientific Programme ◽  
Fuel Cycles ◽  
Accelerator Driven Systems ◽  
Radiative Neutron Capture

Since 2001, the scientific programme of the CERN n_TOF facility has focused mainly on the study of radiative neutron capture reactions, which are of great interest to nuclear astrophysics and on neutron-induced fission reactions, which are of relevance for nuclear technology, as well as essential for the development of theoretical models of fission. Taking advantage of the high instantaneous neutron flux and high energy resolution of the facility, as well as of high-performance detection and acquisition systems, accurate new measurements on several long-lived actinides, from 232Th to 245Cm, have been performed so far. Data on these isotopes are needed in order to improve the safety and efficiency of conventional reactors, as well as to develop new systems for nuclear energy production and treatment of nuclear waste, such as Generation IV reactors, Accelerator Driven Systems and reactors based on innovative fuel cycles. A review of the most important results on fission cross-sections and fragment properties obtained at n_TOF for a variety of isotopes is presented along with the perspectives arising from the newly added 19 m flight-path, which will expand the measurement capabilities to even more rare or short-lived isotopes, such as 230Th, 232U, 238Pu and 244Cm.

scholarly journals Dispersion (asymptotic) theory of charged-particle transfer reactions and nuclear astrophysics

2020 ◽  
Vol 227 ◽  
pp. 01019
Author(s):  
R. Yarmukhamedov ◽  
K.I. Tursunmakhatov ◽  
S.B. Igamov
Keyword(s):  
Cross Sections ◽  
Asymptotic Theory ◽  
Residual Nucleus ◽  
Nuclear Astrophysics ◽  
Transfer Reactions ◽  
Projectile Energy ◽  
Dispersion Theory ◽  
Low Energies ◽  
Stellar Energy ◽  
Three Body

A new asymptotic theory is proposed for the peripheral transfer A(x, y)B reaction at low energies within the three-body (A, a and y) model by com bining the dispersion theory and DWBA, where x= y + a, B= A + a, and a is a transferred particle. The results of the analysis of the differential cross sections of the proton transfer 9Be(1°B, 9Be)1°B reaction at the 1°B projectile energy of 100 MeV populating the ground and excited states of the residual nucleus are presented. New estimates and their uncertainties are obtained for values of the asymptotic normalization coefficients for 9Be + p ^ 1°B and for the astrophys- ical S factors at stellar energy of the radiative capture 9Be(ρ, γ)1°B reaction.

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