Search results for "electromagnetic"
showing 10 items of 1595 documents
The 16O(γ, 2N) reaction measured with tagged photons
1991
The results of tagged-photon measurements of the 4He(γ, pn)d, 4He(γ, pn)pn and 4He(γ, pp)nn reactions, carried out with photons of energies 80–131 MeV, are presented. The (γ, pn)d three-body-breakup cross section dominates the four-body-breakup cross section. The three-body-breakup cross section and the corresponding deuteron recoil-momentum spectrum are reasonably accounted for by a mechanism of photon absorption on correlated proton-neutron pairs. In contrast the four-body-breakup mechanism appears to have two components: absorption on correlated proton-neutron pairs and a more complex additional component which has a distribution similar to phase space. The data rule out substantial phot…
The (γ, n) reaction on 16O between giant resonance and pion threshold
1982
Abstract A new TOF facility has been built for measurements of differential (γ, n) cross sections to discrete final states of light nuclei in the photon energy range between giant resonance and pion threshold. The observed neutron angle θn can continuously be varied between 0° and 150°, and additionally measurements at 175° and 180° are possible. Differential cross sections for the reaction 16O(γ, n0)15O are presented for Eγ = 60 MeV (40° ⩽ θn ⩽ 149°) and for θn = 90° (60 MeV ⩽ Eγ ⩽ 160 MeV). The results, combined with the corresponding (γ, p0) cross sections, indicate an absorption mechanism of high energy photons by neutron-proton pairs.
Total cross sections of reactions induced by neutron-rich light nuclei
1989
Total nuclear reaction cross-sections are determined by means of a 4π-γ method. The results cover a wide span of targets for various stable beams. The validity of the method is shown in a combined systematics including also the results of transmission-type experiments. The data are very well described by the formula developed by Kox et al. The same method is applied to secondary fragment beams produced from a 44 MeV/u22Ne beam on a 332mg/cm2 181Ta target. Using the LISE spectrometer the fragments4, 6He,6–9, 11Li,7, 9–12, 14Be,10–15, 17B11–19C,13–19N,15–21O,18– 21F and20,21 Ne are analyzed and transported to interact with a 199.4 mg/cm2 Cu target surrounded by a 4π-γ counter. The measured to…
The 236U neutron capture cross-section measured at the n TOF CERN facility
2016
International audience; The $^{236}$U isotope plays an important role in nuclear systems, both for future and currently operating ones. The actual knowledge of the capture reaction of this isotope is satisfactory in the thermal region, but it is considered insufficient for Fast Reactor and ADS applications. For this reason the $^{236} \text{U}(n, \gamma)$ reaction cross-section has been measured for the first time in the whole energy region from thermal energy up to 1 MeV at the n_TOF facility with two different detection systems: an array of C$_6$D$_6$ detectors, employing the total energy deposited method, and a 4$\pi$ total absorption calorimeter (TAC), made of 40 BaF$_2$ crystals. The t…
Numerical Investigations of an Implicit Leapfrog Time-Domain Meshless Method
2014
Numerical solution of partial differential equations governing time domain simulations in computational electromagnetics, is usually based on grid methods in space and on explicit schemes in time. A predefined grid in the problem domain and a stability step size restriction need. Recently, the authors have reformulated the meshless framework based on smoothed particle hydrodynamics, in order to be applied for time domain electromagnetic simulation. Despite the good spatial properties, the numerical explicit time integration introduces, also in a meshless context, a severe constraint. In this paper, at first, the stability condition is addressed in a general way by allowing the time step inc…
A Pooled Analysis of Extremely Low-Frequency Magnetic Fields and Childhood Brain Tumors
2010
Pooled analyses may provide etiologic insight about associations between exposure and disease. In contrast to childhood leukemia, no pooled analyses of childhood brain tumors and exposure to extremely low-frequency magnetic fields (ELF-MFs) have been conducted. The authors carried out a pooled analysis based on primary data (1960–2001) from 10 studies of ELF-MF exposure and childhood brain tumors to assess whether the combined results, adjusted for potential confounding, indicated an association. The odds ratios for childhood brain tumors in ELF-MF exposure categories of 0.1–<0.2 μT, 0.2–<0.4 μT, and ≥0.4 μT were 0.95 (95% confidence interval: 0.65, 1.41), 0.70 (95% CI: 0.40, 1.22), and 1.1…
Microwave experiments on electromagnetic evanescent waves and tunneling effect
1993
A set of experiments is described to measure the decay of electromagnetic evanescent waves and the tunneling effect through an airgap. The experiments are performed using microwaves and have been designed to be carried out by third year students of physics. The proposed experimental setup can be regarded as a quantum mechanical simulator for the one‐dimensional motion of a particle.
Kinetic Interaction of Cold and Hot Protons With an Oblique EMIC Wave Near the Dayside Reconnecting Magnetopause
2021
STR acknowledges support from the ISSI international team Cold plasma of ionospheric origin in the Earth's magnetosphere and of the Ministry of Economy and Competitiveness (MINECO) of Spain (grant FIS2017-90102-R). Research at IRAP was supported by CNRS, CNES and the University of Toulouse. JHL and DLT acknowledge support from NASA Grant 80NSSC18K1378. RED was supported by NASA grants 80NSSC19K070 and 80NSSC19K0254. MA was supported by SNSA Grant 56/18. SKV and RCA acknowledge support from NASA Grant 80NSSC19K0270. Work performed by MMS team members is supported by NASA contract NNG04EB99C.
Light absorption and conversion in solar cell based on Si:O alloy
2013
Thin film Si:O alloys have been grown by plasma enhanced chemical vapor deposition, as intrinsic or highly doped (1 to 5 at. % of B or P dopant) layers. UV-visible/near-infrared spectroscopy revealed a great dependence of the absorption coefficient and of the optical gap (Eg) on the dopant type and concentration, as Eg decreases from 2.1 to 1.9 eV, for the intrinsic or highly p-doped sample, respectively. Thermal annealing up to 400 °C induces a huge H out-diffusion which causes a dramatic absorption increase and a reduction of Eg, down to less than 1.8 eV. A prototypal solar cell has been fabricated using a 400 nm thick, p-i-n structure made of Si:O alloy embedded within flat transparent c…
Comparison of asymmetric and symmetric cavity configurations of erbium-doped fiber laser in active Q-switched regime
2012
We present a comparative analysis of the dynamics of an actively Q-switched erbium-doped fiber laser assembled in two configurations of Fabry–Perot cavity, asymmetric and symmetric, specified by the location of an acousto-optic Q-switch modulator relative to the output couplers. In both configurations, the length of an active (Er3+-doped) fiber is chosen such that the laser does not spuriously emit at the moments when the modulator is blocked, which is important for the pulse-on-demand operation. We show experimentally that the symmetric cavity configuration permits enlarging of the active fiber length twice as compared to the asymmetric one, thereby increasing the energy and decreasing the…