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Abstract: We report micro-Raman spectroscopic studies of FeS2 pyrite in the diamond-anvil cell under hydrostatic and non-hydrostatic conditions to 55 GPa at room temperature. Four out of five Raman-active modes are resolved with helium as a pressure-transmitting medium to highest pressures. The fifth mode, T,(2) [377 cm(-1)], is weak and unresolved lying similar to2 cm(-1) from the intense A. mode [379 cm(-1)] at I bar. We observe an increase in the separation of the E, [344 cm(-1)] and T-g(1) [350 cm(-1)] modes under compression. All observed frequencies increase continuously with increasing pressure showing no evidence for a structural phase transition in accord with both X-ray diffraction and shock-wave studies. The A(g) and T-g(1) modes gain significantly in intensity relative to the E-g mode with increasing pressure probably resulting from Raman resonance effects. The T.(3) mode [430 cm(-1)] broadens unusually compared to the other pyrite modes with pressure. The Raman data are consistent with a contraction of the S-S and Fe-S bonds under pressure. The main effect of non-hydrostatic conditions on the Raman modes is a strong pressure-induced broadening; the pressure-dependence of the frequencies and relative intensities are not affected within the error of the measurements.
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Jun 2004
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Theoretical Physics
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Abstract: Allegations in a Comment (Fillaux and Cousson 2004 J. Phys.: Condens. Matter 16 1007) that our calculation of the intensity of neutrons diffracted by potassium bicarbonate is incorrect are shown to be ill-founded. The downfall of the Comment is not to apply quantum mechanics to the calculation of scattering by indistinguishable nuclei with overlapping degrees of freedom (protons or deutrons).
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Jul 2004
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RF
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Jul 2004
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Theoretical Physics
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Abstract: Allegations that our theoretical description of neutron scattering by entangled spin and spatial degrees of freedom is incorrect are shown to be misplaced for the allegations are derived from a naively incomplete, quantum mechanical calculation of neutron scattering by identical nuclei.
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Jul 2004
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Accelerator Physics
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Abstract: Diamond is a state of the art 3 GeV synchrotron light source that will be available to users in 2007. Considerable further progress has been made on the accelerator physics design of the storage ring, booster and other associated injector systems. Detailed analysis of injection processes, lifetime, coupling, instabilities, feedback systems and dynamic aperture have been undertaken driven by the procurement activity and the desire to fully understand all aspects of the accelerator's performance.
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Jul 2004
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Diagnostics
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Abstract: We present an overview of the diagnostics systems that will be implemented at the Diamond synchrotron light source. The aim of this paper is to give a complete picture of the systems to measure the quality of the electron beam from the injector through to the storage ring. We will show how we intend to measure the dimensions, the position and the time structure of the electron bunches. In addition, the instrumentation to measure the charge, the current and the emittance of the electron beam will be described. Finally, systems to provide accurate measurement of electron losses and the injection efficiency will be detailed.
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Jul 2004
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Controls
Diagnostics
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Abstract: The Diamond Light Source (DLS) is a new medium energy high brightness synchrotron light facility which is under construction on the Rutherford Appleton Laboratory site in the U.K. The accelerator facility can be divided into three major components; a 3 GeV 561 m circumference storage ring, a 158.4 m circumference full energy booster synchrotron and a 100 MeV pre-injector linac. This paper describes the linac design and plans for operation.
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Jul 2004
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Accelerator Physics
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Abstract: In synchrotron light sources correction of the linear coupling is an important issue related to the brightness of the photon beam and to the beam lifetime. The vertical emittance of the electron beam in the DIAMOND storage ring can be controlled using 168 skew quadrupoles embedded in the sextupoles of the ring. In this paper we report the linear coupling estimates for the expected misalignment errors and the results of coupling correction based on the analysis of the cross response matrix. Touschek lifetime estimates are also discussed.
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Jul 2004
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Accelerator Physics
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Abstract: The current status of design and construction of the UK's new 3rd generation light source, Diamond, is described.
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Jul 2004
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Abstract: Illuminating complexity: Time-resolved, microreactor-based, EDE/mass spectrometry (EDE=energy dispersive extended X-ray absorption fine structure) was used to probe the behaviour of both Rh and Pd components of alloyed nanoparticles during NO reduction by H2. The picture shows the NO conversion as a function of temperature. This surface enrichment in Pd is shown to curtail rapid oxidation of the Rh component by NO and leads to a promotion of NO reduction.
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Jul 2004
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