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Jungmann J.H.,FOM Institute for Atomic and Molecular Physics | Smith D.F.,FOM Institute for Atomic and Molecular Physics | MacAleese L.,FOM Institute for Atomic and Molecular Physics | MacAleese L.,University Claude Bernard Lyon 1 | And 3 more authors.
Journal of the American Society for Mass Spectrometry | Year: 2012

We demonstrate the capabilities of a highly parallel, active pixel detector for large-area, mass spectrometric imaging of biological tissue sections. A bare Timepix assembly (512×512 pixels) is combined with chevron microchannel plates on an ion microscope matrix-assisted laser desorption time-of-flight mass spectrometer (MALDI TOF-MS). The detector assembly registers position- and time-resolved images of multiple m/z species in every measurement frame. We prove the applicability of the detection system to biomolecular mass spectrometry imaging on biologically relevant samples by mass-resolved images from Timepix measurements of a peptide-grid benchmark sample and mouse testis tissue slices. Mass-spectral and localization information of analytes at physiologic concentrations are measured in MALDI-TOF-MS imaging experiments. We show a high spatial resolution (pixel size down to 740×740 nm2 on the sample surface) and a spatial resolving power of 6 μm with a microscope mode laser field of view of 100-335 μm. Automated, large-area imaging is demonstrated and the Timepix' potential for fast, large-area image acquisition is highlighted. © American Society for Mass Spectrometry, 2012.

Van Lysebetten A.,National Institute for Subatomic Physics Nikhef
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2010

The Vertex Locator (VELO) of the LHCb experiment consists of two halves each equipped with 23 silicon modules along the beam direction. The detector is mounted in a setup similar to Roman pots. The VELO will offer a powerful tool for primary and secondary vertex reconstruction. In order to achieve this, the detector went through a complete and thorough commissioning phase. This process spans a range of activities: individual module characterization in testbeams, detector integration, system tests and offline alignment procedures. After this extensive commissioning period the LHCb experiment entered a new exciting phase during the year 2008. The experiment saw the first beam! Moreover with data taken in the VELO detector the first LHC induced tracks could be reconstructed. © 2009 Elsevier B.V.

Jungmann J.H.,FOM Institute for Atomic and Molecular Physics | MacAleese L.,FOM Institute for Atomic and Molecular Physics | Visser J.,National Institute for Subatomic Physics Nikhef | Vrakking M.J.J.,FOM Institute for Atomic and Molecular Physics | And 2 more authors.
Analytical Chemistry | Year: 2011

Highly parallel, active pixel detectors enable novel detection capabilities for large biomolecules in time-of-flight (TOF) based mass spectrometry imaging (MSI). In this work, a 512 × 512 pixel, bare Timepix assembly combined with chevron microchannel plates (MCP) captures time-resolved images of several m/z species in a single measurement. Mass-resolved ion images from Timepix measurements of peptide and protein standards demonstrate the capability to return both mass-spectral and localization information of biologically relevant analytes from matrix-assisted laser desorption ionization (MALDI) on a commercial ion microscope. The use of a MCP-Timepix assembly delivers an increased dynamic range of several orders of magnitude. The Timepix returns defined mass spectra already at subsaturation MCP gains, which prolongs the MCP lifetime and allows the gain to be optimized for image quality. The Timepix peak resolution is only limited by the resolution of the in-pixel measurement clock. Oligomers of the protein ubiquitin were measured up to 78 kDa. © 2011 American Chemical Society.

Koekoek G.,National Institute for Subatomic Physics Nikhef | Van Holten J.W.,National Institute for Subatomic Physics Nikhef
Classical and Quantum Gravity | Year: 2011

The method of geodesic deviations has been applied to derive accurate analytic approximations to geodesics in Schwarzschild spacetime. The results are used to construct analytic expressions for the source terms in the ReggeWheeler and ZerilliMoncrief equations, which describe the propagation of gravitational waves emitted by a compact massive object moving in the Schwarzschild background spacetime. The wave equations are solved numerically to provide the asymptotic form of the wave at large distances for a series of non-circular bound orbits with periastron distances up to the ISCO radius, and the power emitted in gravitational waves by the extreme mass-ratio binary system is computed. The results compare well with those of purely numerical approaches. © 2011 IOP Publishing Ltd.

Snippe Q.H.C.,National Institute for Subatomic Physics Nikhef | Meinders T.,National Institute for Subatomic Physics Nikhef
Materials Science and Engineering A | Year: 2011

In subatomic particle physics, unstable particles can be detected with a so-called vertex detector, placed inside a particle accelerator. A detecting unit close to the accelerator bunch of charged particles must be separated from the accelerator vacuum. A thin sheet with a complex 3D shape prevents the detector vacuum from polluting the accelerator vacuum. Therefore, this sheet has to be completely leak tight. However, this can conflict with restrictions concerning maximum sheet thickness of the product. To produce such a complex thin sheet, superplastic forming can be very attractive in cases where a small number of products is needed. In order to predict gas permeability of these formed sheets, many mechanical experiments are necessary, where the gas leak has to be measured. To obtain insight in the mechanical behaviour of the used material, ALNOVI-1, tensile experiments were performed to describe the uniaxial stress-strain behaviour. From these experiments, a high strain rate sensitivity was measured. The flow stress of this material under superplastic conditions was low and the material behaved in an isotropic manner upon large plastic strains. The results of these experiments were used to predict the forming pressure as a function of time in a free bulge experiment, such that a predefined target strain rate will not be exceeded in the material. An extra parameter within these bulging experiments is the application of a hydrostatic pressure during the forming process. Such a pressure postpones the nucleation and growth of internal cavities, which means that higher plastic strains can be reached before failure. Results from these experiments showed that at higher hydrostatic pressures, higher bulges were made. All these bulges were leak tested, showing also that higher hydrostatic pressures lead to a lower void volume fraction at higher hydrostatic pressures, since these bulges were more leak tight at the same bulge height than bulges made without the application of this pressure. This article describes the setup and results of the uniaxial (tensile) and biaxial (bulging) experiments on the superplastic aluminium ALNOVI-1. © 2010 Elsevier B.V.

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