Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userComplete Set of Polarization Transfer Observables for the $^{12}{rm C}(p,n)$ Reaction at 296 MeV and 0$^{circ}$
377
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
A complete set of polarization transfer observables has been measured for the $^{12}{rm C}(p,n)$ reaction at $T_p=296 {rm MeV}$ and $theta_{rm lab}=0^{circ}$. The total spin transfer $Sigma(0^{circ})$ and the observable $f_1$ deduced from the measured polarization transfer observables indicate that the spin--dipole resonance at $E_x simeq 7 {rm MeV}$ has greater $2^-$ strength than $1^-$ strength, which is consistent with recent experimental and theoretical studies. The results also indicate a predominance of the spin-flip and unnatural-parity transition strength in the continuum. The exchange tensor interaction at a large momentum transfer of $Q simeq 3.6 {rm fm}^{-1}$ is discussed.
rate research
Read More
We report measurements of the cross section and a complete set of polarization transfer observables for the ${}^{16}{rm O}(vec{p},vec{n}){}^{16}{rm F}$ reaction at a bombarding energy of $T_p$ = 296 MeV and a reaction angle of $theta_{rm lab}$ = $0^{circ}$. The data are compared with distorted-wave impulse approximation calculations employing the large configuration-space shell-model (SM) wave functions. The well-known Gamow-Teller and spin-dipole (SD) states at excitation energies of $E_x$ $lesssim$ 8 MeV have been reasonably reproduced by the calculations except for the spin--parity $J^{pi}$ = $2^-$ state at $E_x$ = 5.86 MeV. The SD resonance at $E_x$ $simeq$ 9.5 MeV appears to have more $J^{pi}$ = $2^-$ strength than $J^{pi}$ = $1^-$ strength, consistent with the calculations. The data show significant strength in the spin-longitudinal polarized cross section $ID_L(0^{circ})$ at $E_x$ $simeq$ 15 MeV, which indicates existence of the $J^{pi}$ = $0^-$ SD resonance as predicted in the SM calculations.
Differential cross sections and complete sets of polarization observables are presented for the Gamow-Teller $^{12}{rm C}(vec{p},vec{n})^{12}{rm N}({rm g.s.},1^+)$ reaction at a bombarding energy of 296 MeV with momentum transfers $q$ of 0.1 to $2.2{rm fm}^{-1}$. The polarization transfer observables are used to deduce the spin-longitudinal cross section, $ID_q$, and spin-transverse cross sections, $ID_p$ and $ID_n$. The data are compared with calculations based on the distorted wave impulse approximation (DWIA) using shell-model wave functions. Significant differences between the experimental and theoretical results are observed for all three spin-dependent $ID_i$ at momentum transfers of $q gtrsim 0.5{rm fm}^{-1}$, suggesting the existence of nuclear correlations beyond the shell model. We also performed DWIA calculations employing random phase approximation (RPA) response functions and found that the observed discrepancy is partly resolved by the pionic and rho-mesonic correlation effects.
We report measurements of the cross-section and a complete set of polarization transfer coefficients for the ${}^{3}{rm He}(p,n)$ reaction at a bombarding energy $T_p$ = 346 MeV and a reaction angle $theta_{rm lab}$ = $0^{circ}$. The data are compared with the corresponding free nucleon-nucleon values on the basis of the predominance of quasi-elastic scattering processes. Significant discrepancies have been observed in the polarization transfer $D_{LL}(0^{circ})$, which are presumably the result of the three-proton $T$ = 3/2 resonance. The spin--parity of the resonance is estimated to be $1/2^-$, and the distribution is consistent with previous results obtained for the same reaction at $T_p$ = 48.8 MeV.
We measured both the differential cross section ($sigma_{p,p^prime}$ $=d^2sigma/dOmega dE_{x}$) and the $gamma$-ray emission probability ($R_gamma(E_x)$ $=sigma_{p,p^primegamma}$/$sigma_{p,p^prime}$) from the giant resonances excited by $rm^{12}C$(textit{p,p}$^prime$) reaction at 392 MeV and 0$^circ$, using a magnetic spectrometer and an array of NaI(Tl) counters. The absolute value of $R_gamma(E_x)$ was calibrated by using the well-known $gamma$-ray emission probability from $rm^{12}C^* ( 15.11$ MeV, $ 1^+$, $T=1$) and $rm^{16}O^* ( 6.9$ MeV, $2^+$, $T=0$) states within 5% uncertainty. We found that $R_gamma(E_x)$ starts from zero at $E_x=16$ MeV, increases to a maximum of 53.3$pm$0.4$pm$3.9% at $E_x=27$ MeV and then decreases. We also compared the measured values of $R_gamma(E_x)$ with statistical model calculation based on the Hauser-Feshbach formalism in the energy region $E_x=$ 16-32 MeV and discussed the features of $gamma$-ray emission probability quantitatively.
Passive detection of special nuclear material (SNM) is challenging due to its inherently low rate of spontaneous emission of penetrating radiation, the relative ease of shielding, and the fluctuating and frequently overwhelming background. Active interrogation (AI), the use of external radiation to increase the emission rate of characteristic radiation from SNM, has long been considered to be a promising method to overcome those challenges. Current AI systems that incorporate radiography tend to use bremsstrahlung beams, which can deliver high radiation doses. Low-energy ion-driven nuclear reactions that produce multiple monoenergetic photons may be used as an alternative. The $^{12}$C(p,p)$^{12}$C is one such reaction that could produce large gamma-ray yields of highly penetrating 4.4- and 15.1-MeV gamma rays. This reaction does not directly produce neutrons below the $sim$19.7-MeV threshold, and the 15.1-MeV gamma-ray line is well matched to the photofission cross-section of $^{235}$U and $^{238}$U. We report the measurements of thick-target gamma-ray yields at 4.4 and 15.1 MeV from the $^{12}$C(p,p)$^{12}$C at proton energies of 19.5, 25, and 30 MeV. Measurements were made with two 3 EJ309 cylindrical liquid scintillation detectors and thermoluminescent dosimeters placed at 0 and 90 degrees. We estimate the highest yields of the 4.4- and 15.1-MeV gamma rays of 1.65$times10^{10}$ sr$^{-1}mu$ C$^{-1}$ and 4.47$times10^8$ sr$^{-1}mu$ C$^{-1}$ at a proton energy of 30 MeV, respectively. The yield of 4.4 and 15.1 MeV gamma rays in all experimental configurations is greater than a comparable deuteron-driven reaction that produces the same gamma-ray energies- $^{11}$B(d,n$gamma$)$^{12}$C. However, a two orders of magnitude increase of the neutron radiation dose is observed when the proton energy increases from 19.5 to 30 MeV.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
