[en] The resonant electron tunnelling (RET) model for the sputtering of atoms in excited electronic states has been tested for Ni atoms sputtered from Ni, Ni₃Al and NiAl. Laser sputter neutral mass spectrometry using one-colour two-photon ionisation schemes has been used to measure the relative yields of atoms sputtered into the ³F ground atomic state and the ³D metastable state. It is found that more Ni atoms are sputtered into the excited state than the ground state, and that the energy distribution of sputtered atoms peaks at a higher energy for the excited state compared to the ground state, as found previously. In addition the relative population of the ³D state is more pronounced for NiAl than for Ni₃Al or Ni. This is due to the increased interaction strength in NiAl, due to greater overlapping between the surface and atomic electronic structures

[en] Using one-color two step ionisation schemes, we have measured using resonant ionisation spectroscopy (RIS) the number of Ni atoms ejected in the ground state (a³F₄) and an electronically excited state (a³D₃) state from both Ni₃Al and pure Ni surfaces. The ratio of the RIS signal from the a³D₃ state to that from the a³F₄ state is 1.07±0.03 for Ni₃Al and 1.05±0.08 for pure Ni. To within experimental error, we saw no difference between pure Ni and the alloy in the relative sputter yield of Ni atoms in the excited a³D₃ state compared to ground a³F₄ state. There is a difference in the electronic band structure between pure Ni and Ni₃Al. The above result indicates the different band structure does not influence the relative sputter yields of excited states

No abstract available

No abstract available

[en] In this paper, we study the perturbative aspects of a 'B-twisted' two-dimensional (0,2) heterotic sigma model on a holomorphic gauge bundle E over a complex, hermitian manifold X. We show that the model can be naturally described in terms of the mathematical theory of 'Chiral Differential Operators'. In particular, the physical anomalies of the sigma model can be reinterpreted as an obstruction to a global definition of the associated sheaf of vertex superalgebras derived from the free conformal field theory describing the model locally on X. In addition, one can also obtain a novel understanding of the sigma model one-loop beta function solely in terms of holomorphic data. At the (2,2) locus, one can describe the resulting half-twisted variant of the topological B-model in terms of a mirror 'Chiral de Rham complex' (or CDR) defined by Malikov et al. Via mirror symmetry, one can also derive various conjectural expressions relating the sheaf cohomology of the mirror CDR to that of the original CDR on pairs of Calabi-Yau mirror manifolds. An analysis of the half-twisted model on a non-Kaehler group manifold with torsion also allows one to draw conclusions about the corresponding sheaves of CDR (and its mirror) that are consistent with mathematically established results by Ben-Bassat on the mirror symmetry of generalised complex manifolds. These conclusions therefore suggest an interesting relevance of the sheaf of CDR in the recent study of generalised mirror symmetry

[en] Poster presentation

[en] The Harwell type 95/0075 survey meter developed by Leake is widely used in neutron area monitoring. Since the neutron directional distribution for a stray field often remains unknown, it is important to determine the angular response and the collimated beam response of the detector. It is also important to clarify the relationship between these responses and the detector structures. This study aims to determine the angular response and the collimated beam response of a detector based on Leake's design. The results suggest that the detector angular response is isotropic for fast neutrons; and local dependence of the response to collimated beams of thermal and intermediate energy neutrons was found to be independent of the absorber layer variations. (Author)

[en] Monitoring of corrosion is in most cases based on simulation of environmental conditions on a large and complex structure such as a buried pipeline using a small probe, and the measurement of thermodynamics and kinetics of corrosion processes occurring on the probe surface. This paper presents a hybrid corrosion monitoring probe designed for simulating deteriorating conditions wrought by disbonded coatings and for measuring current densities and distribution of such densities on a simulated pipeline surface. The concept of the probe was experimentally evaluated using immersion tests under cathodic protection (CP) in high resistivity aqueous solution. Underneath the disbonded area, anodic currents and cathodic currents were carefully measured. Anodic current densities were used to calculate metal loss according to Faraday’s law. Calculated corrosion patterns were compared with corrosion damage observed at the surface of the probe after a series of stringent tests. The capability of the probe to measure anodic current densities under CP, without requiring interruption, was demonstrated in high resistivity aqueous solution. The pattern of calculated metal loss correlated well with corrosion products distribution observed at the array surface. Working principles of the probe are explained in terms of electrochemistry.

[en] In this study, L_l, Lα, L_β, and L_γ X-ray fluorescence cross sections have been measured for ₆9Tm using characteristic X-ray radiated from secondary sources at three different energy values (11.372 keV for L₁, 9.657 keV for L₂ and 8.907 keV for L₃). To excite secondary sources, ²41Am radioisotope point source were used. Experimental measurements have been performed using a Si(Li) solid-state detector with 160 keV resolution at 5.9 keV X-ray energy. As a result of measurements, fluorescence (ω₁, ω₂, ω₃) and Auger yields (α₁, α₂, α₃) of L subshells of Tm were determined semi-empirically. The measured L subshell fluorescence and Auger yields were compared with the previous theoretical, fitted and semi-empirical values.

[en] A ³He gas proportional counter is an ideal detector for thermal and epithermal neutron detection because of its high sensitivity. This kind of detector has been widely used in moderator-type neutron area monitors such as a Neutron Survey Meter or a Neutron Multisphere Spectrometer. The characteristics of two spherical ³He gas proportional counters with different gas pressures, have been determined in terms of their energy responses, their angular responses and their collimated beam responses. The results confirm that the ³He proportional counters have approximate 1/E_n^1/2 energy responses and isotropic responses. (Author)