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Didcot, United Kingdom

Diamond Light Source is the UK's national synchrotron science facility located in Oxfordshire, United Kingdom. Its purpose is to produce intense beams of light whose special characteristics are useful in many areas of scientific research. In particular it can be used to investigate the structure and properties of a wide range of materials from proteins , and engineering components to conservation of archeological artifacts . The facility's name is abbreviated to Diamond throughout this article. Wikipedia.

A detector cascaded model is proposed to describe charge-sharing effect in single-photon counting segmented silicon detectors. Linear system theory is applied to this cascaded model in order to derive detector performance parameters such as large-area gain, presampling Modulation Transfer Function (MTF), Noise Power Spectrum (NPS) and Detective Quantum Efficiency (DQE) as a function of energy detection threshold. This theory is used to model one-dimensional detectors (i.e. strip detectors) where X-ray-generated charge can be shared between two sampling elements, but the concepts developed in this article can be generalized to two-dimensional arrays of detecting elements (i.e. pixels detectors). The zero-frequency DQE derived from this model is consistent with expressions reported in the literature using a different method. The ability of this model to simulate the effect of charge sharing on image quality in the spatial frequency domain is demonstrated by applying it to a hypothetical one-dimensional single-photon counting detector illuminated with a typical mammography spectrum. © 2010 IOP Publishing Ltd and SISSA. Source

Nave C.,Diamond Light Source
Journal of Synchrotron Radiation

An analysis is given of the effect of different beam and detector parameters on the sharpness of recorded diffraction features for macromolecular crystals of different quality. The crystal quality parameters include crystal strain, crystal or mosaic block size and mosaic block misorientation. Calculations are given for instrument parameters such as angular resolution of the detector, beam divergence and wavelength bandpass to be matched to the intrinsic diffraction properties from these crystals with the aim of obtaining the best possible data out of each crystal. Examples are given using typical crystal imperfections obtained from the literature for both room-temperature and cryo-cooled crystals. Possible implications for the choice of X-ray source, beamline design, detector specifications, instrument set-up and data processing are discussed, together with the limitations of the approach. © 2014 International Union of Crystallography. Source

Han J.-H.,Diamond Light Source
Physical Review Special Topics - Accelerators and Beams

We study the possibility to produce a 1.6 pC electron beam (107 electrons) with a bunch length of less than 10 fs and a beam energy of a few MeV. Such a short, relativistic beam will be useful for an electron diffraction experiment with a 10 fs time resolution. An electron beam with 107 electrons will allow a single-shot experiment with a laser pulse pump and an electron beam probe. In this design, an S-band photocathode gun is used for generating and accelerating a beam and a buncher consisting of two S-band four-cell cavities is used for temporally compressing the beam. Focusing solenoids control the beam transverse divergence and size at the sample. Numerical optimization is carried out to achieve a beam with a 4 fs full-width-at-half-maximum length, a 26 microradian root-mean-square divergence, and a 2 nm transverse coherence length at a 3.24 MeV beam energy. When state-of-the-art rf stability is considered, beam arrival time jitter at the sample is calculated to be about 10 fs. © 2011 American Physical Society. Source

Christensen K.E.,Diamond Light Source
Crystallography Reviews

For zeolite-type frameworks the focus has for a long time been put on producing new structures that can give optimized properties for a variety of different purposes. Many new structures have been produced on a trial and error basis. Open-framework germanates have played the role of forming many new structures as it is easier to form certain building units within the germanate system. It is time to start comparing synthesis mechanisms and building units to determine how we can control the synthesis. Here we will give an overview of some of the structures found within the open-framework germanate system and demonstrate that in order for more optimized systems to be synthesized there is a clear need for the more detailed comparison of the structural systematics of existing materials. © 2010 Taylor & Francis. Source

Jephcoat A.P.,Diamond Light Source
Nature Materials

Eremets and Troyan achieved room-temperature compression and also sputtered electrodes into the diamond-anvil cell that allowed the conductivity of the sample to be measured, hence going directly to the heart of the process needed to confirm metallization. The authors passivated the diamond surface with a thin layer of sputtered gold or copper, which, while maintaining high transparency for visible light, prevented pressurized hydrogen from contacting bare diamond, a notoriously ill-suited combination in this type of set-up. Eremets and Troyan extrapolate a zero-bandgap state to 260-270 GPa. As pressure increases above 200GPa, they observe a rapid decrease in Raman vibron frequency ascribed to molecular hydrogen, in stark contrast with studies at lower temperature. A pronounced hysteresis is also observed on decreasing the pressure, the molecular Raman activity returns only at around 200 GPa indicating a first order transformation, as would be expected across a melting transition. Source

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