Optimisation and control of ion acceleration in intense laser-foil interactions

This thesis reports on experimental and numerical investigations of ion acceleration driven by the interaction of short, ultra-intense (> 1020 Wcm-2), linearly polarised pulses of laser light with thin foil targets. Four investigations were performed to explore various aspects of the acceleration and the physics underpinning potential applications of these sources.;The first investigation explores a hybrid scheme of radiation pressure-sheath acceleration, enhanced by relativistic transparency at an optimum foil thickness. Efficient proton acceleration with energies exceeding 94 MeV is achieved. The range of parameters over which this hybrid scenario occurs is discussed, and implications for ion acceleration driven by next-generation, multi-PW laser facilities are explored.;The second investigation concerns the diagnosis of the highly transient electric field responsible for ion acceleration in the target normal sheath acceleration (TNSA) regime. High resolution, temporally-resolved measurements of the field evolution are obtained using proton deectometry.;In the third investigation, a laser generated proton beam is used to heat and preexpand the rear-surface of a secondary foil. This target is then irradiated by a second laser pulse, with the resultant proton beam spatial-intensity distribution measured. For an increasingly expanded target the maximum proton energy, overall number of accelerated protons and the size of the proton beam consistently decreases. A simple analytical model describing the expansion behaviour is developed.;In the final investigation, initial steps towards proton focusing for the purposes of proton fast ignition (PFI) using novel conical targets are addressed. Clear focusing is observed for an open-tipped conical target. These beams are used to isochorically heat copper, with the X-ray emission imaged. Finally, in order to close in on a realistic PFI scenario, the effects of an external plasma surrounding the cone is explored.This thesis reports on experimental and numerical investigations of ion acceleration driven by the interaction of short, ultra-intense (> 1020 Wcm-2), linearly polarised pulses of laser light with thin foil targets. Four investigations were performed to explore various aspects of the acceleration and the physics underpinning potential applications of these sources.;The first investigation explores a hybrid scheme of radiation pressure-sheath acceleration, enhanced by relativistic transparency at an optimum foil thickness. Efficient proton acceleration with energies exceeding 94 MeV is achieved. The range of parameters over which this hybrid scenario occurs is discussed, and implications for ion acceleration driven by next-generation, multi-PW laser facilities are explored.;The second investigation concerns the diagnosis of the highly transient electric field responsible for ion acceleration in the target normal sheath acceleration (TNSA) regime. High resolution, temporally-resolved measurements of the field evolution are obtained using proton deectometry.;In the third investigation, a laser generated proton beam is used to heat and preexpand the rear-surface of a secondary foil. This target is then irradiated by a second laser pulse, with the resultant proton beam spatial-intensity distribution measured. For an increasingly expanded target the maximum proton energy, overall number of accelerated protons and the size of the proton beam consistently decreases. A simple analytical model describing the expansion behaviour is developed.;In the final investigation, initial steps towards proton focusing for the purposes of proton fast ignition (PFI) using novel conical targets are addressed. Clear focusing is observed for an open-tipped conical target. These beams are used to isochorically heat copper, with the X-ray emission imaged. Finally, in order to close in on a realistic PFI scenario, the effects of an external plasma surrounding the cone is explored

Patients report improvements in continuity of care when quality of life assessments are used routinely in oncology practice: Secondary outcomes of a randomised controlled trial.

INTRODUCTION AND AIM: In a randomised trial investigating the effects of regular use of health-related quality of life (HRQOL) in oncology practice, we previously reported an improvement in communication (objective analysis of recorded encounters) and patient well-being. The secondary aims of the trial were to measure any impact on patient satisfaction and patients' perspectives on continuity and coordination of their care. METHODS: In a prospective trial involving 28 oncologists, 286 cancer patients were randomised to: (1) intervention arm: regular touch-screen completion of HRQOL with feedback to physicians; (2) attention-control arm: completion of HRQOL without feedback; and (3) control arm: no HRQOL assessment. Secondary outcomes were patients' experience of continuity of care (Medical Care Questionnaire, MCQ) including 'Communication', 'Coordination' and 'Preferences to see usual doctor' subscales, patients' satisfaction, and patients' and physicians' evaluation of the intervention. Analysis employed mixed-effects modelling, multiple regression and descriptive statistics. RESULTS: Patients in the intervention arm rated their continuity of care as better than the control group for 'Communication' subscale (p=0.03). No significant effects were found for 'Coordination' or 'Preferences to see usual doctor'. Patients' evaluation of the intervention was positive. More patients in the intervention group rated the HRQOL assessment as useful compared to the attention-control group (86% versus 29%), and reported their doctors considered daily activities, emotions and quality of life. CONCLUSION: Regular use of HRQOL measures in oncology practice brought changes to doctor-patient communication of sufficient magnitude and importance to be reported by patients. HRQOL data may improve care through facilitating rapport and building inter-personal relationships

An optically multiplexed single-shot time-resolved probe of laser–plasma dynamics

We introduce a new approach to temporally resolve ultrafast micron-scale processes via the use of a multi-channel optical probe. We demonstrate that this technique enables highly precise time-resolved, two-dimensional spatial imaging of intense laser pulse propagation dynamics, plasma formation and laser beam filamentation within a single pulse over four distinct time frames. The design, development and optimization of the optical probe system is presented, as are representative experimental results from the first implementation of the multi-channel probe with a high-power laser pulse interaction with a helium gas jet target

Evaluating laser-driven Bremsstrahlung radiation sources for imaging and analysis of nuclear waste packages

A small scale sample nuclear waste package, consisting of a 28 mm diameter uranium penny encased in grout, was imaged by absorption contrast radiography using a single pulse exposure from an X-ray source driven by a high-power laser. The Vulcan laser was used to deliver a focused pulse of photons to a tantalum foil, in order to generate a bright burst of highly penetrating X-rays (with energy >500 keV), with a source size of <0.5 mm. BAS-TR and BAS-SR image plates were used for image capture, alongside a newly developed Thalium doped Caesium Iodide scintillator-based detector coupled to CCD chips. The uranium penny was clearly resolved to sub-mm accuracy over a 30 cm2 scan area from a single shot acquisition. In addition, neutron generation was demonstrated in situ with the X-ray beam, with a single shot, thus demonstrating the potential for multi-modal criticality testing of waste materials. This feasibility study successfully demonstrated non-destructive radiography of encapsulated, high density, nuclear material. With recent developments of high-power laser systems, to 10 Hz operation, a laser-driven multi-modal beamline for waste monitoring applications is envisioned

Defining the Middle Corona

International audienceAbstract The middle corona, the region roughly spanning heliocentric distances from 1.5 to 6 solar radii, encompasses almost all of the influential physical transitions and processes that govern the behavior of coronal outflow into the heliosphere. The solar wind, eruptions, and flows pass through the region, and they are shaped by it. Importantly, the region also modulates inflow from above that can drive dynamic changes at lower heights in the inner corona. Consequently, the middle corona is essential for comprehensively connecting the corona to the heliosphere and for developing corresponding global models. Nonetheless, because it is challenging to observe, the region has been poorly studied by both major solar remote-sensing and in-situ missions and instruments, extending back to the Solar and Heliospheric Observatory (SOHO) era. Thanks to recent advances in instrumentation, observational processing techniques, and a realization of the importance of the region, interest in the middle corona has increased. Although the region cannot be intrinsically separated from other regions of the solar atmosphere, there has emerged a need to define the region in terms of its location and extension in the solar atmosphere, its composition, the physical transitions that it covers, and the underlying physics believed to shape the region. This article aims to define the middle corona, its physical characteristics, and give an overview of the processes that occur there

Moving towards an enhanced community palliative support service (EnComPaSS): protocol for a mixed method study

BACKGROUND: The challenge of an ageing population and consequential increase of long term conditions means that the number of people requiring palliative care services is set to increase. One UK hospice is introducing new information and communication technologies to support the redesign of their community services; improve experiences of existing patients; and allow efficient and effective provision of their service to more people. Community Palliative Care Nurses employed by the hospice will be equipped with a mobile platform to improve communication, enable accurate and efficient collection of clinical data at the bedside, and provide access to clinical records at the point of care through an online digital nursing dashboard. It is believed that this will ensure safer clinical interventions, enable delegated specialist care deployment, support the clinical audit of patient care and improve patient safety and patient/carer experience. Despite current attempts to evaluate the implementation of such technology into end of life care pathways, there is still limited evidence supporting the notion that this can be sustained within services and implemented to scale. This study presents an opportunity to carry out a longitudinal evaluation of the implementation of innovative technology to provide evidence for designing more efficient and effective community palliative care services. METHODS: A mixed methods approach will be used to understand a wide range of organisational, economic, and patient-level factors. The first stage of the project will involve the development of an organisational model incorporating proposed changes resulting from the introduction of new novel mobile technologies. This model will guide stage two, which will consist of gathering and analysing primary evidence. Data will be collected using interviews, focus groups, observation, routinely collected data and documents. DISCUSSION: The implementation of this new approach to community-based palliative care delivery will require significant changes to established working patterns. This new service delivery model is being developed by the Hospice in collaboration with a team of international academic, industry, and clinical commissioning service improvement specialists. The findings from this initial evaluation will provide valuable baseline evidence regarding the delivery of palliative and end-of-life care services

REQUITE: A prospective multicentre cohort study of patients undergoing radiotherapy for breast, lung or prostate cancer

Purpose: REQUITE aimed to establish a resource for multi-national validation of models and biomarkers that predict risk of late toxicity following radiotherapy. The purpose of this article is to provide summary descriptive data. Methods: An international, prospective cohort study recruited cancer patients in 26 hospitals in eight countries between April 2014 and March 2017. Target recruitment was 5300 patients. Eligible patients had breast, prostate or lung cancer and planned potentially curable radiotherapy. Radiotherapy was prescribed according to local regimens, but centres used standardised data collection forms. Pre-treatment blood samples were collected. Patients were followed for a minimum of 12 (lung) or 24 (breast/prostate) months and summary descriptive statistics were generated. Results: The study recruited 2069 breast (99% of target), 1808 prostate (86%) and 561 lung (51%) cancer patients. The centralised, accessible database includes: physician-(47,025 forms) and patient-(54,901) reported outcomes; 11,563 breast photos; 17,107 DICOMs and 12,684 DVHs. Imputed genotype data are available for 4223 patients with European ancestry (1948 breast, 1728 prostate, 547 lung). Radiation-induced lymphocyte apoptosis (RILA) assay data are available for 1319 patients. DNA (n = 4409) and PAXgene tubes (n = 3039) are stored in the centralised biobank. Example prevalences of 2-year (1-year for lung) grade >= 2 CTCAE toxicities are 13% atrophy (breast), 3% rectal bleeding (prostate) and 27% dyspnoea (lung). Conclusion: The comprehensive centralised database and linked biobank is a valuable resource for the radiotherapy community for validating predictive models and biomarkers. Patient summary: Up to half of cancer patients undergo radiation therapy and irradiation of surrounding healthy tissue is unavoidable. Damage to healthy tissue can affect short-and long-term quality-of-life. Not all patients are equally sensitive to radiation "damage" but it is not possible at the moment to identify those who are. REQUITE was established with the aim of trying to understand more about how we could predict radiation sensitivity. The purpose of this paper is to provide an overview and summary of the data and material available. In the REQUITE study 4400 breast, prostate and lung cancer patients filled out questionnaires and donated blood. A large amount of data was collected in the same way. With all these data and samples a database and biobank were created that showed it is possible to collect this kind of information in a standardised way across countries. In the future, our database and linked biobank will be a resource for research and validation of clinical predictors and models of radiation sensitivity. REQUITE will also enable a better understanding of how many people suffer with radiotherapy toxicity

Evaluating the Effects of SARS-CoV-2 Spike Mutation D614G on Transmissibility and Pathogenicity.

Global dispersal and increasing frequency of the SARS-CoV-2 spike protein variant D614G are suggestive of a selective advantage but may also be due to a random founder effect. We investigate the hypothesis for positive selection of spike D614G in the United Kingdom using more than 25,000 whole genome SARS-CoV-2 sequences. Despite the availability of a large dataset, well represented by both spike 614 variants, not all approaches showed a conclusive signal of positive selection. Population genetic analysis indicates that 614G increases in frequency relative to 614D in a manner consistent with a selective advantage. We do not find any indication that patients infected with the spike 614G variant have higher COVID-19 mortality or clinical severity, but 614G is associated with higher viral load and younger age of patients. Significant differences in growth and size of 614G phylogenetic clusters indicate a need for continued study of this variant