Nuclear fusion induced by x rays in a crystal

Fission and evaporation cross sections were measured in a broad range of energies near the Coulomb barrier and up to 180 MeV in the reactions 46He+U'9Bi and 'Li+2"8Pb. The secondary 4.hHe beams were produced using the beam-transport line of the U400M accelerator at FLNR, JINR. The experimental fusion and fission excitation functions obtained for the different reactions 4He+2"9Bi, 'He+*"'Bi and 7Li+Z'1XPb and leading to the same composite nuclei 2".2'5At were analyzed using the PACE-4 and CC codes from the point of view of the fusion reaction mechanism induced by weakly bound nuclei. The comparison between the fission and fusion excitation functions for the three reactions 46He+211yBi and 7Li+2"8Pb has shown that they are the same within the experimental error for a broad range of energy.

Phys Rev C, 2020

Nuclear fusion reactions of D-D are examined in an environment comprised of high density cold fuel embedded in metal lattices in which a small fuel portion is activated by hot neutrons. Such an environment provides for enhanced screening of the Coulomb barrier due to conduction and shell electrons of the metal lattice, or by plasma induced by ionizing radiation (γ quanta). We show that neutrons are far more efficient than energetic charged particles, such as light particles (e−, e+) or heavy particles (p, d, α) in transferring kinetic energy to fuel nuclei (D) to initiate fusion processes. It is well-known that screening increases the probability of tunneling through the Coulomb barrier. Electron screening also significantly increases the probability of large- versus small-angle Coulomb scattering of the reacting nuclei to enable subsequent nuclear reactions via tunneling. This probability is incorporated into the astrophysical factor S(E). Aspects of screening effects to enable calculation of nuclear reaction rates are also evaluated, including Coulomb scattering and localized heating of the cold fuel, primary D-D reactions, and subsequent reactions with both the fuel and the lattice nuclei. The effect of screening for enhancement of the total nuclear reaction rate is a function of multiple parameters including fuel temperature and the relative scattering probability between the fuel and lattice metal nuclei. Screening also significantly increases the probability of interaction between hot fuel and lattice nuclei increasing the likelilhood of Oppenheimer-Phillips processes opening a potential route to reaction multiplication. We demonstrate that the screened Coulomb potential of the target ion is determined by the nonlinear Vlasov potential and not by the Debye potential. In general, the effect of screening becomes important at low kinetic energy of the projectile. We examine the range of applicability of both the analytical and asymptotic expressions for the well-known electron screening lattice potential energy Ue, which is valid only for E >> Ue (E is the energy in the center of mass reference frame). We demonstrate that for E ≤ Ue, a direct calculation of Gamow factor for screened Coulomb potential is required to avoid unreasonably high values of the enhancement factor f (E) by the analytical—and more so by the asymptotic—formulas.

Physical Review C, 2011

Complete and incomplete fusion cross sections for $^{6}$Li+$^{159}$Tb have been measured at energies around the Coulomb barrier by the $\gamma$-ray method. The measurements show that the complete fusion cross sections at above-barrier energies are suppressed by $\sim$34% compared to the coupled channels calculations. A comparison of the complete fusion cross sections at above-barrier energies with the existing data of $^{11,10}$B+$^{159}$Tb and $^{7}$Li+$^{159}$Tb shows that the extent of suppression is correlated with the $\alpha$-separation energies of the projectiles. It has been argued that the Dy isotopes produced in the reaction $^{6}$Li+$^{159}$Tb, at below-barrier energies are primarily due to the $d$-transfer to unbound states of $^{159}$Tb, while both transfer and incomplete fusion processes contribute at above-barrier energies.

Condensed Matter Nuclear Science, 2005

Nucleus, 2018

The study of heavy ion nuclear reactionis an important tool to observe and disentangle different and competing mechanisms, which may arise in the different energy regimes. In particular, at relatively low bombarding energy, it is quite interesting the comparison between pre-equilibrium and thermal emission of light charged particles from hot nuclear systems [ 1 - 6 ]. Indeed, the nuclear structure of the interacting partners can be strongly correlated to the dynamics, especially at energies close to the Coulomb barrier, and this effect emerges when some nucleons or clusters of nucleons are either emitted or captured. In particular, a major attention has been devoted, in the last years, to the possible observation of cluster structure effects in the competing nuclear reaction mechanisms, especially when fast processes are involved. At this purpose, the four reactions 16 O+ 30 Si at 111 MeV, 16 O+ 30 Si at 128 MeV, 18 O+ 28 Si at 126 MeV, 19 F+ 27 Al at 133 MeV have been measured to s...

2015

The effect of the absorption of hard X-ray photons on the solid-state dynamics, at energies below the defect creation threshold, is considered. First, it is shown that due to the sensitivity to parameter choices, the present state of the theoretical description of photon-electron-lattice coupling cannot decide on whether the local energy deposition due to the absorption of single photons leads to an acceleration of atomic dynamics at fluences before macroscopic effects due to sample heating set in. Second, a direct study of the dynamics under different incident photon fluxes by atomic-scale X-ray Photon Correlation Spectroscopy (aXPCS) is reported, which provides an upper bound of 0.005 additional atomic jumps per absorbed photon of 8 keV. The relevance of such considerations for emergent experimental methods, such as studying atomic dynamics using X-rays as probes, is pointed out.

Based on the concept of "damp matching" [1] and the famous d ϩ t fusion data, a conventional quantum mechanics calculation shows that the plasma fusion, muon-catalyzed fusion, and the lowenergy nuclear reaction are essentially same in the sense of resonant tunneling through the Coulomb barrier. The good agreement between theory and experimental data justifies the selectivity in resonant tunneling, which implies the possibility of having fusion energy with no strong neutron and gamma radiation. KEY WORDS: d ϩ t fusion cross section; selective resonant tunneling; Coulomb barrier; muon-catalyzed fusion.

EPJ Web of Conferences, 2011

Excitation functions are measured for complete fusion and transfer reactions of 6 Li and 7 Li with 197 Au at energies around the Coulomb barrier. Coupled channel calculations including the couplings to both target and projectile excited states have been performed and are found to explain the data at energies below the barrier. At above barrier energies the complete fusion cross sections are found to be suppressed compared to the coupled channel calculations for both the systems. A systematic comparison of fusion cross-section for halo nuclei 6,8 He and weakly bound stable nuclei 6,7 Li on 197 Au target is also presented. Large neutron transfer cross-sections are observed for 6,7 Li as compared to tightly bound projectiles 12 C, 16 O.

Physics Letters A, 1990

We propose a model which accounts for cold fusion processes on the basis of a lattice collapse, induced in a deuterated metal by a thermodynamic instability. A deuteron drag phenomenon enhances the nuclear reaction yield. Neutron emission is given as a function of thermodynamic parameters of the metal--deuterium system. 0375-9601/90/$ 03.50

Physical Review C, 2018

We report the first measurement of the fusion excitation functions for 39,47 K + 28 Si at nearbarrier energies. Evaporation residues resulting from the fusion process were identified by direct measurement of their energy and time-of-flight with high geometric efficiency. At the lowest incident energy, the cross-section measured for the neutron-rich 47 K induced reaction is ∼6 times larger than that of the β-stable system. This experimental approach, both in measurement and analysis, demonstrates how to efficiently measure fusion with low-intensity, re-accelerated radioactive beams, establishing the framework for future studies.