Calibrated in-vacuum quantum efficiency system for metallic and III-V thin-film photocathodes

The construction and calibration of a high vacuum system for thin film growth and in situ quantum efficiency (QE) measurement are described. Surface cleaning by in situ argon ion sputtering and annealing is supported. The QE measurement is based on an external 265 nm LED and in situ positively biased collector grid. The system is applied to two metallic and two semiconducting photocathodes: polycrystalline silver and copper, and single crystal InP and InSb. Surface cleaning protocols are shown to have a dramatic effect on the QE for all of these materials. The maximum QE values achieved for clean InSb and InP are around 8 × 10−5, for Cu 9 × 10−5 and for Ag 2 × 10−4

A New Model-Independent Method for Extracting Spin-Dependent Cross Section Limits from Dark Matter Searches

A new method is proposed for extracting limits on spin-dependent WIMP-nucleon interaction cross sections from direct detection dark matter experiments. The new method has the advantage that the limits on individual WIMP-proton and WIMP-neutron cross sections for a given WIMP mass can be combined in a simple way to give a model-independent limit on the properties of WIMPs scattering from both protons and neutrons in the target nucleus. Extension of the technique to the case of a target material consisting of several different species of nuclei is discussed.Comment: 15 pages, 6 Encapsulated Postscript figure

Implementation of a local principal curves algorithm for neutrino interaction reconstruction in a liquid argon volume

A local principal curve algorithm has been implemented in three dimensions for automated track and shower reconstruction of neutrino interactions in a liquid argon time projection chamber. We present details of the algorithm and characterise its performance on simulated data sets.Comment: 14 pages, 17 figures; typing correction to Eq 5, the definition of the local covariance matri

Moving away from flat solar panels to PVtrees : exploring ideas and people's perceptions

Photovoltaic Trees (PVTrees) are artificial solar structures that look like sculptural trees and exist from small scale (size of a bonsai tree) to large scale (about the size of a wind turbine). The aesthetics of solar trees differ and they have been designed to provide different means of power to different urban and built environments. These range from powering mobile phones, electric cars, buildings and street lights covering small and large scale areas (one or a forest of PVTrees). This study brought together a research team of physicists and designers and to conduct focus groups with design based methods and prototyping (clustering of ideas, sketching and modelling) along with a computational 3D PVTree design tool. The focus groups consisted of capturing a) people's perception on PVTrees, idea generations and development of the 3D model and b) further discussion and evaluation of insights. A public exhibition followed to capture public perception on design concepts using 3D models, and a voting exercise. Overall it was found that PVTrees were received positively by the public with desires for them to be multifunctional by providing power yet also having a secondary function e.g. a shelter or seat. The paper details this, considerations for concept development, and the future direction of research in the area

WIMP direct detection overview

This review on weakly interacting massive particle (WIMP) dark matter direct detection focuses on experimental approaches and the corresponding physics basics. The presentation is intended to provide a quick and concise introduction for non-specialists to this fast evolving topic of astroparticle physics.Comment: 13 pages, 6 figures, invited review for the Proc. XXth Int. Conf. Neutrino Physics and Astrophysics, May 25-30, 2002, Munich, Germany; version includes correction of typo in eqn.2; to appear in Nucl. Phys. B Proc. Supp

Calibrated in-vacuum quantum efficiency system for metallic and III-V thin-film photocathodes

The construction and calibration of a high vacuum system for thin film growth and in situ quantum efficiency (QE) measurement are described. Surface cleaning by in situ argon ion sputtering and annealing is supported. The QE measurement is based on an external 265 nm LED and in situ positively biased collector grid. The system is applied to two metallic and two semiconducting photocathodes: polycrystalline silver and copper, and single crystal InP and InSb. Surface cleaning protocols are shown to have a dramatic effect on the QE for all of these materials. The maximum QE values achieved for clean InSb and InP are around 8 × 10−5, for Cu 9 × 10−5 and for Ag 2 × 10−4

Electron-hadron shower discrimination in a liquid argon time projection chamber

By exploiting structural differences between electromagnetic and hadronic showers in a multivariate analysis we present an efficient Electron-Hadron discrimination algorithm for liquid argon time projection chambers, validated using Geant4 simulated data