Opportunity or necessity? Conceptualizing entrepreneurship at African small-scale mines

This article critically examines the policy environment in place for artisanal and small-scale mining (ASM) – low-tech, labour-intensive mineral extraction and processing – in sub-Saharan Africa, with a view to determining whether there is adequate ‘space’ for the sector's operators to flourish as entrepreneurs. In recent years, there has been growing attention paid to ASM in the region, particularly as a vehicle for stimulating local economic development. The work being planned under the Africa Mining Vision (AMV), a comprehensive policy agenda adopted by African heads of state in February 2009, could have an enormous impact on this front. One of its core objectives is to pressure host governments into Boosting Artisanal and Small-Scale Mining by following a series of streamlined recommendations. It is concluded, however, that there is a disconnect between how entrepreneurship in ASM has been interpreted and projected by proponents of the AMV on the one hand, and the form it has mostly taken in practice on the other hand. This gulf must be rapidly bridged if ASM is to have a transformative impact, economically, in the region. © 2017 Elsevier Inc

The LUX-ZEPLIN (LZ) Experiment

We describe the design and assembly of the LUX-ZEPLIN experiment, a direct detection search for cosmic WIMP dark matter particles. The centerpiece of the experiment is a large liquid xenon time projection chamber sensitive to low energy nuclear recoils. Rejection of backgrounds is enhanced by a Xe skin veto detector and by a liquid scintillator Outer Detector loaded with gadolinium for efficient neutron capture and tagging. LZ is located in the Davis Cavern at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. We describe the major subsystems of the experiment and its key design features and requirements

The LUX-ZEPLIN (LZ) radioactivity and cleanliness control programs

LUX-ZEPLIN (LZ) is a second-generation direct dark matter experiment with spin-independent WIMP-nucleon scattering sensitivity above 1.4×10−48cm2 for a WIMP mass of 40GeV/c2 and a 1000days exposure. LZ achieves this sensitivity through a combination of a large 5.6t fiducial volume, active inner and outer veto systems, and radio-pure construction using materials with inherently low radioactivity content. The LZ collaboration performed an extensive radioassay campaign over a period of six years to inform material selection for construction and provide an input to the experimental background model against which any possible signal excess may be evaluated. The campaign and its results are described in this paper. We present assays of dust and radon daughters depositing on the surface of components as well as cleanliness controls necessary to maintain background expectations through detector construction and assembly. Finally, examples from the campaign to highlight fixed contaminant radioassays for the LZ photomultiplier tubes, quality control and quality assurance procedures through fabrication, radon emanation measurements of major sub-systems, and bespoke detector systems to assay scintillator are presented