296 Works

The FastGas detector

JE Bateman, R M Dalgliesh, DM Duxbury, S A Holt, David McPhail, AS Marsh, N J Rhodes, E M Schooneveld, EJ Spill & R Stephenson
The development and testing of the FastGas neutron detector is described. Based on a Microstrip Gas Chamber the aim of the project was to produce a high counting rate detector capable of replacing the existing (superscript)3He tubes for specular reflectometry, currently in use on the ISIS reflectometer instruments. The detector system is descrbed together with results of neutron beam tests carried out at the ISIS spallation neutron source.

A revised equation of state for in situ pressure determination using fcc-Pb (0 < P < 13 GPa, T> 100 K)

Dominic Fortes
A pressure- and temperature-dependent equation of state (PVT EoS) parameterisation for the low-pressure face-centred-cubic polymorph of Pb metal has been derived from literature data. This PVT EoS enables the use of Pb as a pressure marker in high-pressure neutron diffraction studies on the PEARL beamline at ISIS, for example. The new equation of state supersedes the previously used version [Fortes et al., 2007: High Press. Res., 27, 201-212], being developed from a wider range of...

Proceedings of the molecular spectroscopy science meeting 2018

Indri Adilina, C Andreani, Robert Applin, Laura Arcidiacono, Jeffery Armstrong, Ana Batista De Carvalho, Alex De Bruin, Keith Butler, Hamish Cavaye, Alisha Davidson, F Demmel, Huan Doan, S Dixon, F Fernandez-Alonso, Giulia Festa, V Garcia Sakai, SO Halukeerthi, Brandon Hewer, S Imberti, Aleksandar Ivanov, Maciej Krzystyniak, S Sukran, Adriana Mamede, Maria Paula Marques, J Martinez-Gonzalez … & Andrea Zachariou

FLAME-II : a redesign of the flexible large-scale agent-based modelling environment

LS Chin, DJ Worth, C Greenough, S Coakley, M Holcombe & M Gheorghe
This report reviews the current design of FLAME and highlights its limitations. This is followed by the description of a proposed re-design which will overcome the current limitations and enable the exploration of various optimisation and parallelisation strategies. Some of these strategies are briefly discussed, along with other concerns such as backward compatibility and agent topology management.

Summary of space weather worst-case environments

M.A Hapgood, R Horne, D Kerridge, B Jones, P Cannon, K Ryden, M Gibbs, D Jackson, A Rodger, A Thomson, C Dyer, L Candler & A Senior

Monte-Carlo simulations for the development of TOSCA's guide at ISIS

J Fernandez Castanon
McStas software package offers the possibility to determine accurate estimates for flux, resolution and optimization parameters with the aim to achieve the best guide for TOSCA instrument, sited at ISIS. Different simulations are compared, defining new perspectives for instruments similar to TOSCA, pursuing optimize the resolution with the minimum costs. Most of the instruments which have at their disposal a neutron guide have lengths greater than 50 or 60 m, as for example the instrument...

Monte Carlo modelling of the OSIRIS neutron backscattering spectrometer

K Pokhilchuk
This report focuses on modelling the OSIRIS neutron-backscattering instrument using Monte Carlo methods with the use of the McStas software package. The aim is to match the experimental energy resolution of OSIRIS and thus be able to simulate the instrument in order to investigate its various properties and performance characteristics. Furthermore, understanding quantitatively how different components of OSIRIS contribute towards its resolution function will provide insight into potential upgrade possibilities of the instrument. The simulated...

Neutrons at ESS-Bilbao: From Production to Utilisation

JP De Vicente, F Fernandez-Alonso, F Sordo & F J Bermejo
Collaborative efforts between the Neutronics and Target Design Group at the Instituto de Fusión Nuclear and the Molecular Spectroscopy Group at the ISIS Pulsed Neutron and Muon Source date back to 2012 in the context of the ESS-Bilbao project. The rationale for these joint activities was twofold, namely: to assess the realm of applicability of the low-energy neutron source proposed by ESS-Bilbao; and to explore instrument capabilities for pulsed-neutron techniques in the range 0.05-3 ms,...

IRIS & OSIRIS International Beamline Review - Report Presented to the Panel

F Demmel, V Garcia-Sakai, Sanghamitra Mukhopadhyay, S F Parker, F Fernandez-Alonso, J Armstrong, Fernando Bresme, JP De Vicente, F Sordo, F J Bermejo, C G Salzmann & S E McLain
The ISIS Facility at the STFC Rutherford Appleton Laboratory is a major international centre for neutron scattering and muon spectroscopy. To ensure that the instrumentation suite is kept at the forefront of capability, the ISIS Director has instituted a series of rolling reviews across the instrument suite, such that every instrument will be reviewed by an international panel every 10 years or when a major upgrade is required. Following an earlier review of the TOSCA...

FLAME Tutorial Examples : Predation - a simple predator-prey model

Gemma Poulter & C Greenough
FLAME - the Flexible Large-scale Agent Modelling Environment - is a framework for developing agent-based models. FLAME has been developed in a collaboration between the Computer Science Department of the University of Sheffield and the Software Engineering Group of the STFC Rutherford Appleton Laboratory. This report documents the FLAME implementation of a simple predator-prey model. Within a fixed domain sheep and wolves move randomly, and this costs a wolf 1 unit of energy. If, after...

TOSCA International Beamline Review

Svemir Rudic, A J Ramirez-Cuesta, S F Parker, F Fernandez-Alonso, Roberto Pinna, G Gorini, C G Salzmann, S E McLain & N T Skipper
The ISIS Facilty at the STFC Rutherford Appleton Laboratory is a major international centre for neutron and muon scattering. To ensure that the instrumentation suite is kept at the forefront of capability, the ISIS Director has instituted a series of rolling reviews for all the instruments, such that every instrument will be reviewed by an international panel every 10 years or when a major upgrade is required. For one of the first reviews the inelastic...

SCARF Annual Report 2012-2013

Derek Ross

VESUVIO Data Reduction and Analysis in Mantid

Samuel Jackson
VESUVIO is a neutron spectrometer at the ISIS pulsed neutron source operating at high energies in the 1 eV range and uses the experimental technique known as neutron Compton scattering to measure the momentum distributions of condensed matter systems [1]. Mantid [2] is a data analysis application for neutron and muon scattering data used by multiple facilities across the world. Recently, extensive work has been carried out to integrate the bespoke data reduction and analysis...

On computing inverse entries of a sparse matrix in an out-of-core environment

, IS Duff, Y Robert, F-H Rouet & B Ucar
The inverse of an irreducible sparse matrix is structurally full, so that it is impractical to think of computing or storing it. However, there are several applications where a subset of the entries of the inverse is required. Given a factorization of the sparse matrix held in outof- core storage, we show how to compute such a subset efficiently, by accessing only parts of the factors. When there are many inverse entries to compute, we...

A fast method for binary programming using first-order derivatives, with application to topology optimization with buckling constants

PA Browne, CJ Budd, N I M Gould, HA Kim & JA Scott
We present a method for fnding solutions of large-scale binary programming problems where the calculation of derivatives is very expensive. We then apply this method to a topology optimization problem of weight minimisation subject to compliance and buckling constraints. We derive an analytic expression for the derivative of the stress stiffness matrix with respect to the density of an element in the finite-element setting. Results are presented for a number of two-dimensional test problems.

Trajectory-following methods for large-scale degenerate convex quadratic programming

N I M Gould, D Orban & DP Robinson
We consider a class of infeasible, path-following methods for convex quadratric programming.Our methods are designed to be effective for solving both nondegerate and degenerate problems, where degeneracy is understood to mean the failure of strict complementarity at a solution. Global convergence and a polynomial bound on the number of iterations required is given. An implementation, CQP, is available as part of GALAHAD. We illustrate the advantages of our approach on the CUTEr and Maros-Meszaros test...

Level-based heuristics and hill climbing for the antibandwidth maximization problem

J Scott & Y Hu
The antibandwidth maximization problem is the dual of the well-known bandwidth minimization problem. In this paper, we consider the feasibility of adapting heuristic algorithms for the bandwidth minimization problem to the antibandwidth maximization problem. In particular, using an inexpensive level-based heuristic we obtain an initial ordering that we re ne using a hill-climbing algorithm. This approach performs well on matrices coming from a range of practical problems with an underlying mesh. Comparisons with existing approaches...

CLF 2010 - 2011 : Central Laser Facility Annual Report

B E Wyborn

Adapting Open Source tools to cater for a diverse computing infrastructure

A Horwich
The Scientific Computing Technology Group (SCT) computing infrastructure consists of many different functional services, ranging from high performance compute clusters such as SCARF (a facility run for all of STFC) and the National Service for Computational Chemistry Software (NSCCS), to e-Infrastructure like the UK National Grid Service (NGS), and VMware ESX virtualisation technologies. Alongside site wide STFC policies on security, SCT must also provision mechanisms to effectively manage and monitor the security of these services,...

The MODES user guide v3

Spencer Howells, V Garcia Sakai, F Demmel, M T F Telling & F Fernandez-Alonso

SCARF annual report 2016-2017

Derek Ross

SCARF Annual Report 2015-2016

Derek Ross

Proceedings of the Molecular Spectroscopy Science Meeting 2015

J Armstrong, H Bordallo, Fernando Bresme, Carlos Cabrillo, L Chi, Gianfelice Cinque, F Demmel, JP De Vicente, Pedro Duarte Vaz, F Fernandez-Alonso, Ricardo Fernandez-Perea, Sara Fletcher, V Garcia Sakai, Anne Guilbert, MA Gonzalez Gonzalez, H Hedgeland, Spencer Howells, I Iriarte-Carretero, Zheng Jiang, M Jura, Maths Karlsson, P J C King, Maciej Krzystyniak, A Lazzarini, P Li … & I Vázquez-Fernández

Simulation support within MANTID for molecular spectroscopy

Daniel Nixon
This document aims to describe the current state of the support for loading and manipulating data created with an external simulation package within Manipulation and Analysis Toolkit for Instrument Data (MANTID) as well as the means in which this data can be visualised and compared with experimental data.

Simulating hyperfine coupling constants of muoniated radicals using density functional theory calculations

Jamie Peck, F L Pratt & S P Cottrell
In this work we consider potential benefits, and limitations of linking ab initio Density Functional Theory (DFT) methods with existing ?SR data analysis codes. This is motivated by the desire to provide users of the ?SR technique with additional tools to help them better understand and interpret their data. The DFT method may be considered as complementary to the ?SR technique. It is essential for interpreting muonium chemistry type experiments, where it provides the experimenter...

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Affiliations

  • University College London
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