Development and performance of the Fast Neutron Imaging Telescope for SNM detection

FNIT (the Fast Neutron Imaging Telescope), a detector with both imaging and energy measurement capabilities, sensitive to neutrons in the range 0.8-20 MeV, was initially conceived to study solar neutrons as a candidate design for the Inner Heliosphere Sentinel (IHS) spacecraft of NASA\u27s Solar Sentinels program and successively reconfigured to locate fission neutron sources. By accurately identifying the position of the source with imaging techniques and reconstructing the Watt spectrum of fission neutrons, FNIT can detect samples of special nuclear material (SNM), including heavily shielded and masked ones. The detection principle is based on multiple elastic neutron-proton scatterings in organic scintillators. By reconstructing n-p event locations and sequence and measuring the recoil proton energies, the direction and energy spectrum of the primary neutron flux can be determined and neutron sources identified. We describe the design of the FNIT prototype and present its energy reconstruction and imaging performance, assessed by exposing FNIT to a neutron beam and to a Pu fission neutron source

Variability in the extreme helium star LSS 5121

We report a photometric and spectroscopic study of the hot extreme helium star LSS 5121. We found photometric variability, but no period was evident in its periodogram. This is consistent with the previous proposal, based on spectral line variations, that LSS 5121 is a non-radial pulsator similar to other hot extreme helium stars.Comment: 5 pages, 6 figure

Tidal resource and interactions between multiple channels in the Goto Islands, Japan

The Goto Islands in Nagasaki Prefecture, Japan, contain three parallel channels that are suitable for tidal energy development and are the planned location for a tidal energy test centre. Energy extraction is added to a 3D numerical hydrodynamic model of the region, using a sub-grid momentum sink approach, to predict the effects of tidal development. The available resource with first-generation turbines is estimated at 50-107MW peak output. Spreading turbine thrust across the whole cross-section to prevent bypass flow results in a 64% increase in peak power in one channel, highlighting the importance of 3D over 2D modelling. The energy available for extraction in each strait appears to be independent of the level of extraction in other straits. This contrasts with theoretical and numerical studies of other multi-channel systems. The weak interactions found in this study can be traced to the hydraulic effects of energy extraction not extending to neighbouring channels due to their geometry

Development of the fast neutron imaging telescope

We report on the development of a next generation neutron telescope, with imaging and energy measurement capabilities, sensitive to neutrons in the 2-20 MeV energy range. The Fast Neutron Imaging Telescope (FNIT) was initially conceived to study solar neutrons as a candidate instrument for the Inner Heliosphere Sentinels (IHS) program under formulation at NASA. This detector is now being adapted to locate Special Nuclear Material (SNM) for homeland security purposes by detecting fission neutrons and reconstructing the image of their source. In either case, the detection principle is based on multiple elastic neutron-proton scatterings in organic scintillator. By reconstructing the scattering coordinates and measuring the recoil proton energy, the direction and energy of each neutron can be determined and discrete neutron sources identified. We describe the performance of the FNIT prototype, report on the current status of R&D efforts and present the results of recent laboratory measurements

Perceived causes of differential attainment in UK postgraduate medical training: a national qualitative study

Objectives: Explore trainee doctors’ experiences of postgraduate training and perceptions of fairness in relation to ethnicity and country of primary medical qualification. Design: Qualitative semistructured focus group and interview study. Setting: Postgraduate training in England (London, Yorkshire and Humber, Kent Surrey and Sussex) and Wales. Participants: 137 participants (96 trainees, 41 trainers) were purposively sampled from a framework comprising: doctors from all stages of training in general practice, medicine, obstetrics and gynaecology, psychiatry, radiology, surgery or foundation, in 4 geographical areas, from white and black and minority ethnic (BME) backgrounds, who qualified in the UK and abroad. Results: Most trainees described difficult experiences, but BME UK graduates (UKGs) and international medical graduates (IMGs) could face additional difficulties that affected their learning and performance. Relationships with senior doctors were crucial to learning but bias was perceived to make these relationships more problematic for BME UKGs and IMGs. IMGs also had to deal with cultural differences and lack of trust from seniors, often looking to IMG peers for support instead. Workplace-based assessment and recruitment were considered vulnerable to bias whereas examinations were typically considered more rigorous. In a system where success in recruitment and assessments determines where in the country you can get a job, and where work–life balance is often poor, UK BME and international graduates in our sample were more likely to face separation from family and support outside of work, and reported more stress, anxiety or burnout that hindered their learning and performance. A culture in which difficulties are a sign of weakness made seeking support and additional training stigmatising. Conclusions: BME UKGs and IMGs can face additional difficulties in training which may impede learning and performance. Non-stigmatising interventions should focus on trainee–trainer relationships at work and organisational changes to improve trainees’ ability to seek social support outside work

“You can’t be a person and a doctor”. The work-life balance of doctors in training: a qualitative study

Objectives Investigate the work–life balance of doctors in training in the UK from the perspectives of trainers and trainees. Design Qualitative semistructured focus groups and interviews with trainees and trainers. Setting Postgraduate medical training in London, Yorkshire and Humber, Kent, Surrey and Sussex, and Wales during the junior doctor contract dispute at the end of 2015. Part of a larger General Medical Council study about the fairness of postgraduate medical training. Participants 96 trainees and 41 trainers. Trainees comprised UK graduates and International Medical Graduates, across all stages of training in 6 specialties (General Practice, Medicine, Obstetrics and Gynaecology, Psychiatry, Radiology, Surgery) and Foundation. Results Postgraduate training was characterised by work–life imbalance. Long hours at work were typically supplemented with revision and completion of the e-portfolio. Trainees regularly moved workplaces which could disrupt their personal lives and sometimes led to separation from friends and family. This made it challenging to cope with personal pressures, the stresses of which could then impinge on learning and training, while also leaving trainees with a lack of social support outside work to buffer against the considerable stresses of training. Low morale and harm to well-being resulted in some trainees feeling dehumanised. Work–life imbalance was particularly severe for those with children and especially women who faced a lack of less-than-full-time positions and discriminatory attitudes. Female trainees frequently talked about having to choose a specialty they felt was more conducive to a work–life balance such as General Practice. The proposed junior doctor contract was felt to exacerbate existing problems. Conclusions A lack of work–life balance in postgraduate medical training negatively impacted on trainees' learning and well-being. Women with children were particularly affected, suggesting this group would benefit the greatest from changes to improve the work–life balance of trainees

Future policy implications of tidal energy array interactions

Tidal stream energy technology has progressed to a point where commercial exploitation of this sustainable resource is practical, but tidal physics dictates interactions between tidal farms that raise political, legal and managerial challenges that are yet to be met. Fully optimising the design of a turbine array requires its developer to know about other farms that will be built nearby in the future. Consequently future developments, even those in adjacent channels, have the potential to impact on project efficiency. Here we review the relevant physics, consider the implications for marine policy, and discuss potential solutions. Possible management paths range from minimal regulation to prioritise a free market, to strongly interventionist approaches that prioritise efficient resource use. An attractive exemplar of the latter is unitization, an approach to resource allocation widely used in the oil and gas industry. We argue that an interventionist approach is necessary if the greatest possible energy yield is to be produced for a given level of environmental impact

Design optimization and performance capabilities of the fast neutron imaging telescope (FNIT)

We describe the design optimization process and performance characterization of a next generation neutron telescope, with imaging and energy measurement capabilities, sensitive to neutrons in the 1-20 MeV energy range. The response of the Fast Neutron Imaging Telescope (FNIT), its efficiency in neutron detection, energy resolution and imaging capabilities were characterized through a combination of lab tests and Monte Carlo simulations. Monte Carlo simulations, together with experimental data, are also being used in the development and testing of the image reconstruction algorithm. FNIT was initially conceived to study solar neutrons as a candidate instrument for the Inner Heliosphere Sentinel (IHS) spacecraft. However, the design of this detector was eventually adapted to locate Special Nuclear Material (SNM) sources for homeland security purposes, by detecting fission neutrons. In either case, the detection principle is based on multiple elastic neutron-proton scatterings in organic scintillator. By reconstructing event locations and measuring the recoil proton energies, the direction and energy spectrum of the primary neutron flux can be determined and neutron sources identified. This paper presents the most recent results arising from our efforts and outlines the performance of the FNIT detector

Fast Monte Carlo simulations and singularities in the probability distributions of non-equilibrium systems

A numerical technique is introduced that reduces exponentially the time required for Monte Carlo simulations of non-equilibrium systems. Results for the quasi-stationary probability distribution in two model systems are compared with the asymptotically exact theory in the limit of extremely small noise intensity. Singularities of the non-equilibrium distributions are revealed by the simulations.Comment: 4 pages, 4 figure