Magnetron deposition of metal-ceramic protective coatings on glasses of windows of space vehicles

Transparent refractory metal-ceramic nanocomposite coatings with a high coefficient of elasticrecovery and microhardness on the basis of Ni/Si-Al-N are formed on a glass substrate by the pulse magnetron deposition method. The structure-phase states were investigated by TEM, SEM. It was established that the first layer consists of Ni nanograins with a fcc crystalline lattice, the second layer is two-phase: 5-10 nm nanocrystallites of the AlN phase with the hcp crystalline lattice in amorphous matrix of the Si3N4 phase

Magnetron deposition of metal-ceramic protective coatings on glasses of windows of space vehicles

Transparent refractory metal-ceramic nanocomposite coatings with a high coefficient of elasticrecovery and microhardness on the basis of Ni/Si-Al-N are formed on a glass substrate by the pulse magnetron deposition method. The structure-phase states were investigated by TEM, SEM. It was established that the first layer consists of Ni nanograins with a fcc crystalline lattice, the second layer is two-phase: 5-10 nm nanocrystallites of the AlN phase with the hcp crystalline lattice in amorphous matrix of the Si3N4 phase

Coulomb dissociation of N 20,21

Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on N20,21 are reported. Relativistic N20,21 ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the N19(n,γ)N20 and N20(n,γ)N21 excitation functions and thermonuclear reaction rates have been determined. The N19(n,γ)N20 rate is up to a factor of 5 higher at

Coulomb dissociation of O-16 into He-4 and C-12

We measured the Coulomb dissociation of O-16 into He-4 and C-12 within the FAIR Phase-0 program at GSI Helmholtzzentrum fur Schwerionenforschung Darmstadt, Germany. From this we will extract the photon dissociation cross section O-16(alpha,gamma)C-12, which is the time reversed reaction to C-12(alpha,gamma)O-16. With this indirect method, we aim to improve on the accuracy of the experimental data at lower energies than measured so far. The expected low cross section for the Coulomb dissociation reaction and close magnetic rigidity of beam and fragments demand a high precision measurement. Hence, new detector systems were built and radical changes to the (RB)-B-3 setup were necessary to cope with the high-intensity O-16 beam. All tracking detectors were designed to let the unreacted O-16 ions pass, while detecting the C-12 and He-4

Fully exclusive measurements of quasi-free single-nucleon knockout reactions in inverse kinematics.

This thesis will present a novel experimental method for investigating proton-induced single-nucleon knockout reactions at relativistic energies. For the first time this type of reactions is studied in complete and inverse kinematics, using a 12C beam at an energy of 400 MeV/u impinged on a plastic CH2 target, where the reactions on hydrogen take place. It is shown that the reaction mechanism is dominated by quasi-free proton-nucleon scattering process of a type (p,2p) or (p,pn) within the nucleus, that is reflected in a strong spatial correlation between the two outgoing nucleons. The reactions are foreseen as an ideal way to explore single-particle and cluster structure of nuclei and will become an important part of the physics program at the future R3B (Reactions with Relativistic Radioactive Beams) experiment at FAIR, which will be based on kinematically complete measurements of the reactions with neutron-proton asymmetric nuclei. The benchmark experiment, which is discussed in this work, was performed at a prototype LAND-R3B setup at GSI, Germany. The total cross section of 30.5±2.3 mb has been measured for the 12C(p,2p)11B reaction in inverse kinematics, and the cross section of 18.1±2 mb has been extracted for the removal of a proton from the p-shell in 12C. Employing the in-flight γ-ray spectroscopy, the following exclusive (p,2p) cross sections are determined for individual low-lying p-hole states in the residual 11 B nucleus: 12.7±1.5 mb for the ground state, 3.1±0.4 mb for the first excited state 2.125 MeV (1/2− ) and 2.2±0.3 mb for the excited state 5.02 MeV (3/2− ). The excitation energy of deep-hole particle-unstable states is reconstructed via invariant-mass measurements of mainly two-body decays of the 11B residue. A broad peak at around 15 MeV in the excitation spectrum of 11B is observed and interpreted as a proton knockout from strongly bound s-shell in 12C. The internal momentum distribution of protons, which are removed from the p-shell in 12C, is measured redundantly using two methods: the detection of residual 11B fragments and the angular and energy measurements of scattered proton pairs. The momentum width of 105 MeV/c is extracted using both methods. A similar value of 106 MeV/c is obtained for the internal momentum width of p-state neutrons probed through the 12C(p,pn)11C reaction. The momentum width of 132 MeV/c is determined for deeply bound s-shell protons via the measurements of scattered protons. Detailed simulations of the experimental response have been developed as a part of the analysis

α\alpha-clustering at the Surface of Tin Isotopes 112−124^{112−124}Sn Studied with (p,pα)(p, p\alpha) Reaction

International audienceα-clustering strength at the surface of tin isotopes ^112,116,120,124Sn was measured by using quasi-free (p, pα) reaction at RCNP. By measuring the scattered protons and α particles in coincidence, formation of α clusters at the surface of tin isotopes was clearly evidenced. Surface α-clustering in heavy nuclei provides a natural explanation for the origin of α particles in α decay, and may also impact the neutron-skin thickness which plays an important role in constraining the nuclear symmetry energy

α\alpha-clustering in Heavy Nuclei 112–124^{112–124}Sn Probed with (p,pα)(p,p\alpha ) Reaction

International audienceWe measured the α-clustering strength at the surface of tin isotopes ^112,116,120,124Sn by using quasi-free $(p,p\alpha )$ reaction at RCNP. Formation of α clusters at the surface of tin isotopes was clearly evidenced from our results. Surface α-clustering in heavy nuclei provides a natural explanation for the origin of α particles in α decay, and may also impact the neutron-skin thickness which plays a critical role in constraining the nuclear symmetry energy

Formation of α clusters in dilute neutron-rich matter

International audienceThe surface of neutron-rich heavy nuclei, with a neutron skin created by excess neutrons, provides an important terrestrial model system to study dilute neutron-rich matter. By using quasi-free α cluster–knockout reactions, we obtained direct experimental evidence for the formation of α clusters at the surface of neutron-rich tin isotopes. The observed monotonous decrease of the reaction cross sections with increasing mass number, in excellent agreement with the theoretical prediction, implies a tight interplay between α-cluster formation and the neutron skin. This result, in turn, calls for a revision of the correlation between the neutron-skin thickness and the density dependence of the symmetry energy, which is essential for understanding neutron stars. Our result also provides a natural explanation for the origin of α particles in α decay.</jats:p

Exclusive measurements of quasi-free proton scattering reactions in inverse and complete kinematics

Quasi-free scattering reactions of the type (p, 2p) were measured for the first time exclusively in complete and inverse kinematics, using a 12C beam at an energy of ∼400 MeV/u as a benchmark. This new technique has been developed to study the single-particle structure of exotic nuclei in experiments with radioactive-ion beams. The outgoing pair of protons and the fragments were measured simultaneously, enabling an unambiguous identification of the reaction channels and a redundant measurement of the kinematic observables. Both valence and deeply-bound nucleon orbits are probed, including those leading to unbound states of the daughter nucleus. Exclusive (p, 2p) cross sections of 15.8(18) mb, 1.9(2) mb and 1.5(2) mb to the low-lying 0p-hole states overlapping with the ground state (3/2−) and with the bound excited states of 11B at 2.125 MeV (1/2−) and 5.02 MeV (3/2−), respectively, were determined via γ -ray spectroscopy. Particle-unstable deep-hole states, corresponding to proton removal from the 0s-orbital, were studied via the invariant-mass technique. Cross sections and momentum distributions were extracted and compared to theoretical calculations employing the eikonal formalism. The obtained results are in a good agreement with this theory and with direct-kinematics experiments. The dependence of the proton–proton scattering kinematics on the internal momentum of the struck proton and on its separation energy was investigated for the first time in inverse kinematics employing a large-acceptance measurement

Quasi-free (p,2p) reactions in inverse kinematics for studying the fission yield dependence on temperature

Despite the recent experimental and theoretical progress in the investigation of the nuclear fission process, a complete description still represents a challenge in nuclear physics because it is a very complex dynamical process, whose description involves the coupling between intrinsic and collective degrees of freedom, as well as different quantum-mechanical phenomena. To improve on the existing data on nuclear fission, we produce fission reactions of heavy nuclei in inverse kinematics by using quasi-free (p,2p) scattering, which induce fission through particle-hole excitations that can range from few to ten's of MeV. The measurement of the four-momenta of the two outgoing protons allows to reconstruct the excitation energy of the fissioning compound nucleus and therefore to study the evolution of the fission yields with temperature. The realization of this kind of experiment requires a complex experimental setup, providing full isotopic identification of both fission fragments and an accurate measurement of the momenta of the two outgoing protons. This was realized recently at the GSI/FAIR facility and here some preliminary results are presented