Production of Highly Polarized Positrons Using Polarized Electrons at MeV Energies

The Polarized Electrons for Polarized Positrons experiment at the injector of the Continuous Electron Beam Accelerator Facility has demonstrated for the first time the efficient transfer of polarization from electrons to positrons produced by the polarized bremsstrahlung radiation induced by a polarized electron beam in a high-Z target. Positron polarization up to 82% have been measured for an initial electron beam momentum of 8.19 MeV/c, limited only by the electron beam polarization. This technique extends polarized positron capabilities from GeV to MeV electron beams, and opens access to polarized positron beam physics to a wide community

How analysts think: sense-making strategies in the analysis of temporal evolution and criminal network structures and activities

Analysis of criminal activity based on offenders’ social networks is an established procedure in intelligence analysis. The complexity of the data poses an obstacle for analysts to gauge network developments, e.g. detect emerging problems. Visualization is a powerful tool to achieve this, but it is essential to know how the analysts’ sense-making strategies can be supported most efficiently. Based on a think aloud study we identified ten cognitive strategies on a general level to be useful for designers. We also provide some examples how these strategies can be supported through appropriate visualizations

Wound care in older adults

Wound care in older adults is complex. A logical, structured approach should be taken, using a nursing process such as assessing, planning, implementing and evaluating. This clinical focus paper outlines the nursing process to support wound care in this patient group. It recommends considering dressing selection as a cost-effective, prescribing decision because of the risks and comorbidities associated with these patient

Charge and fluence lifetime measurements of a dc high voltage GaAs photogun at high average current

GaAs-based dc high voltage photoguns used at accelerators with extensive user programs must exhibit long photocathode operating lifetime. Achieving this goal represents a significant challenge for proposed high average current facilities that must operate at tens of milliamperes or more. This paper describes techniques to maintain good vacuum while delivering beam, and techniques that minimize the ill effects of ion bombardment, the dominant mechanism that reduces photocathode yield of a GaAs-based dc high voltage photogun. Experimental results presented here demonstrate enhanced lifetime at high beam currents by: (a) operating with the drive laser beam positioned away from the electrostatic center of the photocathode, (b) limiting the photocathode active area to eliminate photoemission from regions of the photocathode that do not support efficient beam delivery, (c) using a large drive laser beam to distribute ion damage over a larger area, and (d) by applying a relatively low bias voltage to the anode to repel ions created within the downstream beam line. A combination of these techniques provided the best total charge extracted lifetimes in excess of 1000 C at dc beam currents up to 9.5 mA, using green light illumination of bulk GaAs inside a 100 kV photogun

Post-combustion carbon dioxide capture cost reduction to 2030 and beyond

Post-combustion CO2 capture (PCC) can be achieved using a variety of technologies. Importantly it is applicable to a wide range of processes and may also be retrofitted in certain cases. This paper covers the use of PCC for low carbon power generation from new natural gas combined cycle (NGCC) plants that are expected to be built in the UK in the 2020s and 2030s and that will run into the 2050s. Costs appear potentially comparable with other low carbon and controllable generation sources such as nuclear or renewables plus storage, especially with the lower gas prices that can be expected in a carbon-constrained world. Non-fuel cost reduction is still, however, desirable and, since CO2 capture is a new application, significant potential is likely to exist. For the NGCC+PCC examples shown in this paper, moving from ‘first of a kind’ (FOAK) to ‘nth of a kind’ (NOAK) gives significant improvements through both reduced financing costs and capital cost reductions. To achieve this the main emphasis needs to be on ‘commercial readiness’, rather than on system-level ‘technical readiness’, and on improvements through innovation activities, supported by underpinning research, that develop novel sub-processes; this will also maintain NOAK status for cost-effective financing. Feasible reductions in the energy penalty for PCC capture have much less impact, reflecting the inherently high levels of efficiency for modern NGCC+PCC plants

Photoinjector improvements at CEBAF in support of parity violation experiments

Three photoinjector modifications were undertaken at CEBAF to help ensure successful completion of the PREx and Qweak parity violation experiments: the development of a pockels cell high voltage switch that provides stable voltages at 960 Hz helicity flip rate with 60 μs rise/fall time, the installation of a two-Wien-filter spin flipper for slow spin reversal, and the installation of a new photogun with inverted insulator geometry that operates at higher bias voltage

Developing CCS in the UK and beyond: insights from the UK CCS Research Centre

The UK Carbon Capture and Storage Research Centre co-ordinates a programme of research covering all aspects of CCS in support of basic science and UK government efforts on energy and climate change. This paper will present progress and ‘lessons learned’ from the Centre’s activities, with a particular focus on the development and use of pilot scale facilities and encouraging industrial and other stakeholder engagement in research. It will also highlight key features of an extensive programme of international engagement activities undertaken by the Centre, identifying added value for both the UK CCS community and global development of CCS