Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userStudy of $boldsymbol{(alpha,p)}$ and $boldsymbol{(alpha,n)}$ reactions with a Multi-Sampling Ionization Chamber
58
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
A large number of $(alpha,p)$ and $(alpha,n)$ reactions are known to play a fundamental role in nuclear astrophysics. This work presents a novel technique to study these reactions with the active target system MUSIC whose segmented anode allows the investigation of a large energy range of the excitation function with a single beam energy. In order to verify the method, we performed a direct measurements of the previously measured reactions $^{17}$O$(alpha,n)^{20}$Ne, $^{23}$Na$(alpha,p)^{26}$Mg, and $^{23}$Na$(alpha,n)^{26}$Al. These reactions were investigated in inverse kinematics using $^{4}$He gas in the detector to study the excitation function in the range of about 2 to 6 MeV in the center of mass. We found good agreement between the cross sections of the $^{17}$O$(alpha,n)^{20}$Ne reaction measured in this work and previous measurements. Furthermore we have successfully performed a simultaneous measurement of the $^{23}$Na$(alpha,p)^{26}$Mg and $^{23}$Na$(alpha,n)^{26}$Al reactions.
rate research
Read More
The $^{23}$Na$(alpha,p)^{26}$Mg and $^{23}$Na$(alpha,n)^{26}$Al reactions are important for our understanding of the $^{26}$Al abundance in massive stars. The aim of this work is to report on a direct and simultaneous measurement of these astrophysically important reactions using an active target system. The reactions were investigated in inverse kinematics using $^{4}$He as the active target gas in the detector. We measured the excitation functions in the energy range of about 2 to 6 MeV in the center of mass. We have found that the cross sections of the $^{23}$Na$(alpha,p)^{26}$Mg and the $^{23}$Na$(alpha,n)^{26}$Al reactions are in good agreement with previous experiments, and with statistical model calculations.
In this work, we systematically study the $alpha$ decay preformation factors $P_{alpha}$ and $alpha$ decay half-lives of 152 nuclei around $Z$ = 82, $N$ = 126 closed shells based on a generalized liquid drop model while $P_{alpha}$ is extracted from the ratio of the calculated $alpha$ decay half-life to the experimental one. The results show that there is an obvious linear relationship between $P_{alpha}$ and the product of valance protons (holes) $N_p$ and valance neutrons (holes) $N_n$. At the same time, we extract the $$P_{alpha}$ values of even-even nuclei around $emph{Z}$ = 82, $emph{N}$ = 126 closed shells from the work of Sun textit{et al.} [href {https://doi.org/10.1088/1361-6471/aac981} {J. Phys. G: Nucl. Part. Phys. $bm{45}$, 075106 (2018)}], in which the $P_{alpha}$ can be calculated by two different microscopic formulas. We find that the $P_{alpha}$ are also related to $N_pN_n$. Combining with our previous works [Sun textit{et al.}, href {https://doi.org/10.1103/PhysRevC.94.024338} {Phys. Rev. C $bm{94}$, 024338 (2016)}; Deng textit{et al.}, href {https://doi.org/10.1103/ PhysRevC 96.024318} {ibid. $bm{96}$, 024318 (2017)}; Deng textit{et al.}, href {https://doi.org/10.1103/PhysRevC.97.044322} {ibid. $bm{97}$, 044322 (2018)}] and the work of Seif textit{et al.} [href {http://dx.doi.org/10.1103/PhysRevC.84.064608}{Phys. Rev. C $bm{84}$, 064608 (2011)}], we suspect that this phenomenon of linear relationship for the nuclei around those closed shells is model independent. It may be caused by the effect of the valence protons (holes) and valence neutrons (holes) around the shell closures. Finally, using the formula obtained by fitting the $P_{alpha}$ calculated by the generalized liquid drop model (GLDM), we calculate the $alpha$ decay half-lives of these nuclei. The calculated results are agree with the experimental data well.
Form factors for $alpha+{^{12}}$C inelastic scattering are obtained within two theoretical ($alpha+alpha+alpha$) approaches: The hyperspherical framework for three identical bosons, and the algebraic cluster model assuming the $D_{3h}$ symmetry of an equilateral triangle subject to rotations and vibrations. Results show a good agreement, with form factors involving the Hoyle state having a slightly larger extension within the hyperspherical approach. Coupled-channel calculations using these form factors are ongoing.
Photoactivation measurements on 144Sm have been performed with bremsstrahlung endpoint energies from 10.0 to 15.5 MeV at the bremsstrahlung facility of the superconducting electron accelerator ELBE of Forschungszentrum Dresden-Rossendorf. The measured activation yield for the 144Sm(gamma,n) reaction is compared with the calculated yield using cross sections from previous photoneutron experiments. The activation yields measured for all disintegration channels 144Sm(gamma,n), (gamma,p) and (gamma,alpha) are compared to the yield calculated by using Hauser-Feshbach statistical models. A new parametrization of the photon strength function is presented and the yield simulated by using the modified photon strength parameters are compared to the experimental data.
One of the few p nuclei with an odd number of protons is 113In. Reaction cross sections of 113In(alpha,gamma)117Sb and 113In(alpha,n)116Sb have been measured with the activation method at center-of-mass energies between 8.66 and 13.64 MeV, close to the astrophysically relevant energy range. The experiments were carried out at the cyclotron accelerator of ATOMKI. The activities were determined by off-line detection of the decay gamma rays with a HPGe detector. Measured cross sections and astrophysical S factor results are presented and compared with statistical model calculations using three different alpha+nucleus potentials. The comparison indicates that the standard rates used in the majority of network calculations for these reactions were too fast due to the energy dependence of the optical alpha potential at low energy.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
