Monoenergetic ion beam generation by driving ion solitary waves with circularly polarized laser light

Experimental data from the Trident Laser facility is presented showing quasimonoenergetic carbon ions from nm-scaled foil targets with an energy spread of as low as ±15% at 35?MeV. These results and high-resolution kinetic simulations show laser acceleration of quasimonoenergetic ion beams by the generation of ion solitons with circularly polarized laser pulses (500?fs, λ=1054 nm). The conversion efficiency into monoenergetic ions is increased by an order of magnitude compared with previous experimental results, representing an important step towards applications such as ion fast ignition.     

Cole-Cole Analysis of the Superspin Glass System Co 80 Fe 20 /Al 2 O 3

Ac susceptibility measurements were performed on discontinuous magnetic multilayers [Co 80 Fe 20 ( t )/Al 2 O 3 (3 nm)] 10 , t = 0.9 and 1.0 nm, by Superconducting Quantum Interference Device (SQUID) magnetometry. The CoFe forms nearly spherical ferromagnetic single-domain nanoparticles in the diamagnetic Al 2 O 3 matrix. Due to dipolar interactions and random distribution of anisotropy axes the system exhibits a spin-glass phase. We measured the ac susceptibility as a function of temperature 20 h T h 100 K at different dc fields and as a function of frequency 0.01 h f h 1000 Hz. The spectral data were successfully analyzed by use of the phenomenological Cole-Cole model, giving a power-law temperature dependence of the characteristic relaxation time c and a high value for the polydispersivity exponent, f , 0.8, typical of spin glass systems.     

Observation of the Debye-Waller factor in a colloidal single crystal

Bragg diffraction spot intensities of a colloidal single crystal were found to exhibit a DebyeWaller factor-like decay. The Lindemann parameter and the mean-square displacement after infinite times of the colloidal particles could be obtained.     

Measurement of charge distributions for 229Th(nth,f) and 232U(nth,f)

A gas ΔE ? E_R telescope has been used to measure charge yields and their correlations with kinetic energies for ²²⁹Th and ²³²U. Even-charge yields are enhanced compared with odd-charge yields for both fissioning systems; this enhancement increases for events with higher kinetic energy. The mean odd-even effect $\text{δ}{}_{\mathrm{<mtext>p</mtext>}}\text{is}\text{= (40±4)\%}\text{for}{}^{229}\text{Th}$; it is $\text{(21 ± 3)\%}\text{for}{}^{232}\text{U-the same as for}{}^{233}\text{U}\text{((22.1±2.1)\%)}\text{and}{}^{235}\text{U}\text{((23.7±0.7)\%)}$. The energy-integrated δ_p and δ_p for different energy windows, vary strongly as a function of charge (Z) due to the underlying shells. The δ_p averaged over Z increases fast with kinetic energy, contrary to the existing results for ²³³U and ²³⁵U, where δ_p flattens off at low energies. For both systems, the most probable kinetic energy ē shows a strong odd-even stagger; the mean odd-even effect on energy, $\text{δE}{}_{\mathrm{<mtext>K</mtext>}}{}^{\mathrm{<mtext>o?e</mtext>}}\text{,}\text{is}\text{1.4 ± 0.3}\text{MeV for}{}^{229}\text{Th, and}\text{1.7±0.4}\text{MeV for}{}^{232}\text{U}\text{—}$ the latter is about twice the value for ${}^{233}\text{U}\text{(0.95 ± 0.09}\text{MeV}\text{)}\text{and}{}^{235}\text{U}\text{(0.7}\text{MeV}\text{)}$. These results are discussed in terms of the existing models.     

Measurement of isothermal diffusion coefficients at 37°C in the systems glycine−NaCl−H2O,dl-α alanine−NaCl−H2O,anddl-α-aminobutyric acid−NaCl−H2O

Isothermal diffusion coefficients have been measured at 37°C in the systems glycine–NaCl–H₂O,dl--alanine–NaCl–H₂O, anddl--aminobytyric acid–NaCl–H₂O. Experiments were performed at 0.5 and 1.0M in both solutes. It was found that the cross-term diffusion coefficientsD ₁₂ andD ₂₁ increased and the main-term diffusion coefficientsD ₁₁ andD ₂₂ decreased as the length of the hydrocarbon chain of the amino acid increased. The cross-term diffusion coefficients for the system with glycine were only 2% of the values of the mainterm diffusion coefficients while those for the system withdl--aminobutyric acid approached 10% of the main-term diffusion coefficients at 1.0M.     

Formation of sulfur surface species on a commercial NO<Subscript>x</Subscript>-storage reduction catalyst

The influence of SO₂ exposure under lean (oxidizing) and rich (reducing) reaction conditions on the storage and oxidation/reduction function of a commercial NO_x storage-reduction catalyst was investigated by temperature-programmed uptake experiments and high temperature XRD. Both the storage capacity and the oxidation/reduction function of the catalyst were deactivated by SO₂ exposure under lean and rich reaction conditions. The deactivation of the storage component, i.e. the loss of the NO_x storage capacity, resulted mainly from the formation of Ba-sulfates accumulating in the bulk phase, which have a high thermal stability (>800°C) and, therefore, cannot be removed under the typical operation conditions of a NSR catalyst. For the oxidation function only a temporarily deactivation during lean reaction conditions was observed. Besides the formation of SO^2- ₄ species on the storage component at the beginning of the SO₂ exposure under rich conditions, an adsorption of SO₂ on the noble metal component was observed resulting in the formation of sulfur deposits. The oxidation of these sulfur species with a subsequent spillover of SO^2- ₄ species to the storage component during lean conditions could accelerate the deactivation of the storage capacity.     

High pressure X-ray diffraction studies on UAI2, UAI2, and UAI4 systems

Abstract

The UAI₂, UAI₂, AND UAI₄ compounds have been studied by high pressure X-ray diffraction up to a maximum pressure of ～ 35 GPa. The compressibility behaviour of UAI₂ has been found to be consistent with the itinerant 5f states, whereas that of UAI₂ and UAI₄, indicate a more localized nature. Further, UAI₂ has been found to undergo a structural transition at ～ 11 GPa and the structure of the high pressure phase has been identified to be of MgNi₂ type with space group P6₃/mmc. The structure of UAI₂ at ambient pressure is of MgCu₂ type with space group Fd3m. From the electronic considerations, for instance, free electrons per atom ratio e/a, it is anticipated that it may transform back to MgCu₂ type structure at still higher pressures. On similar considerations, it is expected that most of the AB₂ type Laves phase compounds of the ‘f’ electron systems may undergo the structural sequence: MgCu₂ – MgZn₂ (or MgNi₂) – MgCu₂ due to increased delocalization of their ‘f’ electron states.