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Jacobs P.,RWTH Aachen | Houben A.,RWTH Aachen | Schweika W.,European Spallation Source ESS | Schweika W.,Julich Research Center | And 3 more authors.
Journal of Applied Crystallography | Year: 2015

This paper introduces a two-dimensional extension of the well established Rietveld refinement method for modeling neutron time-of-flight powder diffraction data. The novel approach takes into account the variation of two parameters, diffraction angle 2θ and wavelength λ, to optimally adapt to the varying resolution function in diffraction experiments. By doing so, the refinement against angular-and wavelength-dispersive data gets rid of common data-reduction steps and also avoids the loss of high-resolution information typically introduced by integration. In a case study using a numerically simulated diffraction pattern of Rh0.81Fe3.19N taking into account the layout of the future POWTEX instrument, the profile function as parameterized in 2θ and λ is extracted. As a proof-of-concept, the resulting instrument parameterization is then utilized to perform a typical refinement of the angular-and wavelength-dispersive diffraction pattern of CuNCN, yielding excellent residuals within feasible computational efforts. Another proof-of-concept is carried out by applying the same approach to a real neutron diffraction data set of CuNCN obtained from the POWGEN instrument at the Spallation Neutron Source in Oak Ridge. The paper highlights the general importance of the novel approach for data analysis at neutron time-of-flight diffractometers and its possible inclusion within existing Rietveld software packages. © 2015 Philipp Jacobs et al.


Magallanes F.C.,CERN | Magallanes F.C.,Laval University | Aguglia D.,CERN | Viarouge P.,Laval University | And 2 more authors.
Digest of Technical Papers-IEEE International Pulsed Power Conference | Year: 2013

This paper presents the principles and design methodologies of a novel active bouncer system, to be implemented in a transformer-based klystron modulator, which is able to meet two different objectives : 1. Regulate the output pulse voltage flattop, and 2. Attenuate the power fluctuation withdrawn from the AC network. This solution allows the utilization of a standard constant voltage/constant current power supply as a capacitor charger. The solution consists of a 4-quadrant switching converter placed in series with the main capacitor bank (forming a unique element in parallel with the capacitor charger), controlled with specific feedback loops to achieve the two objectives. The complete design method, including a numerical optimization, of the whole system, is presented in the paper. Analyses of the compromises between the active bouncer specifications and the other modulator sub-components design is presented as well. © 2013 IEEE.


Stadlmann J.,Helmholtz Center for Heavy Ion Research | Spiller P.,Helmholtz Center for Heavy Ion Research | Gehring R.,Karlsruhe Institute of Technology | Jensen E.,CERN | And 2 more authors.
IPAC 2014: Proceedings of the 5th International Particle Accelerator Conference | Year: 2014

EuCARD2 is an Integrating Activity Project for coordinated Research and Development on Particle Accelerators, co-funded by the European Commission under the FP7 Capacities Programme. Within the network EnEfficient [1] we address topics around energy efficiency of research accelerators. The ambitious scientific research goals of modern accelerator facilities lead to high requirements in beam power and beam quality for those research accelerators. In conjunction with the users' needs the power consumption and environmental impact of the research facilities becomes a major factor in the perception of both funding agencies and the general public. In this network we combine and focus the R&D done individually at different research centers into a series of workshops. We cover the topics "Energy recovery from cooling circuits", "Higher electronic efficiency RF power generation", "Short term energy storage systems", "Virtual power plants" and "Beam transfer channels with low power consumption". Our network activities are naturally open to external participants. With this work we will introduce our energy efficiency topics to interested participants and contributors from the whole community. Copyright © 2014 CC-BY-3.0 and by the respective authors.


Buffet J.C.,Laue Langevin Institute | Correa J.,Laue Langevin Institute | Van Esch P.,Laue Langevin Institute | Guerard B.,Laue Langevin Institute | And 2 more authors.
IEEE Nuclear Science Symposium Conference Record | Year: 2012

The main goal in neutron reflectometry instruments is to achieve a high angular resolution and high counting rates. Although 3He shortage affects scientific research in neutron scattering science due to its wide use in detectors as neutron converter; this is not the main issue for neutron reflectometry application where detector sizes are generally moderate. Indeed 3He detectors are instead limited in spatial resolution. To reduce the particles traces and thereby increase the spatial resolution those detectors are operated at high quencher gas pressure, resulting in mechanical constraints. A promising alternative, to accomplish these goals, is to exploit solid 10B-films employed in a proportional gas chamber. The challenge with this technique is to attain a suitable detection efficiency. This can be achieved by operating the 10B conversion layer at grazing angle relative to the incoming neutron direction. The Multi-Blade design is based on this operational principle and it is conceived to be modular in order to be adaptable to different applications. A prototype has been developed at ILL and the results obtained on our monochromatic test beam line are presented here. A significant concern in a modular design is the uniformity of detector response: several effects might contribute to degrade the uniformity and they have to be taken into account in the detector concept: overlap between different substrates, coating uniformity, substrate flatness, parallax errors, etc. A simulation has been developed to address these problems. © 2012 IEEE.


Arnold P.,European Spallation Source ESS | Fydrych J.,European Spallation Source ESS | Hees W.,European Spallation Source ESS | Jurns J.,European Spallation Source ESS | And 2 more authors.
IPAC 2014: Proceedings of the 5th International Particle Accelerator Conference | Year: 2014

The European Spallation Source (ESS) is a neutron science facility funded by a collaboration of 17 European countries currently under design and construction in Lund, Sweden. Cryogenic cooling is vital for large sections at ESS. Mainly there is a 2.0 GeV proton linac using superconducting RF cavities operating at 2 K. In addition to cooling the SRF cavities, cryogenics is also used for the cold hydrogen moderator surrounding the target. ESS furthermore uses both liquid helium and liquid nitrogen in a number of the neutron instruments. There is also a cryogenic installation associated with the site acceptance testing of the ESS cryomodules [1]. This paper describes the conceptual design of the ESS cryogenic system including the expected heat loads and cryoplant features. Challenges associated with the required high reliability and turn-down capability will also be discussed. Copyright © 2014 CC-BY-3.0 and by the respective authors.

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