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Laser-driven ion accelerators can deliver high-energy, high peak current beams from relativistic laser plasmas formed in solid-density materials [1, 2]. This innovative concept attracts a lot of attention for various multidisciplinary applications as a compact alternative to conventional accelerators [3]. However, achieving energy levels suitable for applications such as radiation therapy remains a challenge for laser-driven ion accelerators. Here, we report on experimental generation of plasma-accelerated proton beams with a spectrally separated high-energy component of up to 150MeV by irradiating solid-density plastic foil targets with ultrashort laser pulses from a repetitive Petawatt laser. Three-dimensional particle-in-cell simulations reveal that the observed beam parameters result from cascaded acceleration regimes that occur at the onset of relativistically induced transparency. The ultrashort pulse duration allows a rapid sequence of these regimes at highest intensity, enabling proton acceleration to unprecedented energy levels. Target transparency was identified to discriminate the high-performance domain of the acquired data set, making it a suitable feedback parameter for automated laser and target optimisation to enhance stability of plasma accelerators in the future. Ultimately, our results encourage further exploration and application of laser-driven plasmas as compact proton accelerators in the multi-100MeV range.

Background:Post-positivist critics of the linear-rational understanding of the role of knowledge in decision making have long argued the need for the construction of socially robust knowledge to illuminate policy problems from a variety of perspectives, including lived experiences. Aims and objectives:This article charts the attempts of researchers to employ a creative method, digital storytelling, alongside more traditional scientific data in stakeholder deliberations to inform local food governance in South Africa. Methods:Four storytellers from a marginalised group created and introduced their digital story about a ‘time when they had to make a difficult choice about what food to purchase or get’ to a public governance forum and the reactions of the audience self-reported. Findings:The digital stories were emotionally compelling and gave granular detail to the more top-down perspective of the scientific data. There were concerns, however, for the welfare of the storytellers when introducing their stories in the forum. Discussion and conclusion:Our findings highlight the multi-functionality of digital storytelling as a method of creativity within the process of co-production, not just as a technique to make visible knowledge from marginalised groups, but also as a mechanism (when used and viewed in a wider governance context) to promote knowledge mobilisation and alternative ways of knowing. The use of digital storytelling in these wider governance contexts, or social learning spaces, however, also surfaces ethical and other risks.

For high-intensity laser-solid interactions, the absolute density and surface density gradients of the target at the arrival of the ultra-relativistic laser peak are critical parameters. Accurate modeling of the leading edge-driven target pre-expansion is desired to strengthen the predictive power of associated computer simulations. The transition from an initial solid state to a plasma state, i.e., the breakdown of the solid, defines the starting point of the subsequent target pre-expansion. In this work, we report on the time-resolved observation of transient laser-induced breakdown (LIB) during the leading edge of high-intensity petawatt-class laser pulses with peak intensities of up to 5.7 × 10^21 W/cm^2 in interaction with dielectric cryogenic hydrogen jet targets. LIB occurs much earlier than what is typically expected following the concept of barrier suppression ionization. The observation is explained by comparing a characterization study of target specific LIB thresholds with laser contrast measurements. The results demonstrate the relevance of the laser pulse duration dependence of LIB for high-intensity laser-solid interactions. We provide an effective approach to determine the onset of LIB and thereby the starting point of target pre-expansion in other laser-target systems.

Small Island Developing States (SIDS) have high burdens of nutrition-related chronic diseases. This has been associated with lack of access to adequate and affordable nutritious foods and increasing reliance on imported foods. Our aim in this study was to investigate dietary patterns and food insecurity and assess their associations with socio-demographic characteristics and food sources. We recruited individuals aged 15 years and above from rural and urban areas in Fiji (n = 186) and St. Vincent and the Grenadines (SVG) (n = 147). Data collection included a 24 h diet recall, food source questionnaire and the Food Insecurity Experience Scale. We conducted latent class analysis to identify dietary patterns, and multivariable regression to investigate independent associations with dietary patterns. Three dietary patterns were identified: (1) low pulses, and milk and milk products, (2) intermediate pulses, and milk and milk products and (3) most diverse. In both SIDS, dietary pattern 3 was associated with older age, regularly sourcing food from supermarkets and borrowing, exchanging, bartering or gifting (BEB). Prevalence of food insecurity was not statistically different across dietary patterns. In both SIDS, food insecurity was higher in those regularly sourcing food from small shops, and in SVG, lower in those regularly using BEB. These results complement previous findings and provide a basis for further investigation into the determinants of dietary patterns, dietary diversity and food insecurity in these settings.

The objectives of the study were to determine the prevalence of food insecurity in greater Johannesburg metropole (South Africa). A total of 1000 households were interviewed using standardised food insecurity scaling and scoring metrics. Findings revealed that 34% of households experienced food insecurity and almost 60% spent R1000($57) or less on food per month. Only half of respondents reported adequate food provisioning throughout the year. Many households frequently bought less preferred foods or only what was necessary and almost 50% borrowed food or money to cope with food insecurity. Appropriate interventions to alleviate food and nutrition security are essential.

Due to the non-linear nature of relativistic laser induced plasma processes, the development of laser-plasma accelerators requires precise numerical modeling. Especially high intensity laser-solid interactions are sensitive to the temporal laser rising edge and the predictive capability of simulations suffers from incomplete information on the plasma state at the onset of the relativistic interaction. Experimental diagnostics utilizing ultra-fast optical backlighters can help to ease this challenge by providing temporally resolved inside into the plasma density evolution. We present the successful implementation of an off-harmonic optical probe laser setup to investigate the interaction of a high-intensity laser at $$5.4\times 10^{21}\,\hbox {W/cm}^{2}$$ 5.4 × 10 21 W/cm 2 peak intensity with a solid-density cylindrical cryogenic hydrogen jet target of $${5}\,{\upmu }\mathrm{m}$$ 5 μ m diameter as a target test bed. The temporal synchronization of pump and probe laser, spectral filtering and spectrally resolved data of the parasitic plasma self-emission are discussed. The probing technique mitigates detector saturation by self-emission and allowed to record a temporal scan of shadowgraphy data revealing details of the target ionization and expansion dynamics that were so far not accessible for the given laser intensity. Plasma expansion speeds of up to $$(2.3 \pm 0.4)\times 10^{7}\,\hbox {m/s}$$ ( 2.3 ± 0.4 ) × 10 7 m/s followed by full target transparency at $${1.4}\,{\mathrm{ps}}$$ 1.4 ps after the high intensity laser peak are observed. A three dimensional particle-in-cell simulation initiated with the diagnosed target pre-expansion at $${-0.2}\,{\mathrm{ps}}$$ - 0.2 ps and post processed by ray tracing simulations supports the experimental observations and demonstrates the capability of time resolved optical diagnostics to provide quantitative input and feedback to the numerical treatment within the time frame of the relativistic laser-plasma interaction.

Well before the Covid-19 pandemic, rapidly growing cities of the global South were at the epicenter of multiple converging crises affecting food systems. Globally, government lockdown responses to the disease triggered shocks which cascaded unevenly through urban food systems, exacerbating food insecurity. Cities worldwide developed strategies to mitigate shocks, but research on statecraft enabling food systems resilience is sparse. Addressing this gap, we analyse the case of the African metropolis of Cape Town, where lockdown disrupted livelihoods, mobility and food provision, deepening food insecurity. Employing a vital systems security lens, we show how civil society and state networks mobilised to mitigate and adapt to lockdown impacts. Building on preceding institutional transformations, civil society and state collaborated to deliver emergency food aid, while advocacy networks raised food on the political agenda, formulated proposals, and navigated these through a widened policy window. Emergency statecraft assembled networks and regulatory instruments to secure food systems, enhance preparedness for future disruptions and present opportunities for transition towards more sustainable food systems. However, current food systems configuration enabled powerful actors to resist deeper transformation while devolving impacts to community networks. Despite resilient vested interests and power disparities, advocacy coalitions can anticipate and leverage crises to incrementally advance transformational, pro-poor statecraft.

Background The high burden of disease related to malnutrition in Small Island Developing States (SIDS) has been exacerbated by increasing levels of food insecurity (FI) and loss of food sovereignty. Internationally, household, or individual level FI is associated with poorer diets and nutritional status. Our study aimed to investigate whether there are distinct dietary patterns, and if so whether they are associated with socio-demographic characteristics (SDC), dietary diversity scores (DDS), food sources and experience of food insecurity in adults in two SIDS: Fiji and St. Vincent and the Grenadines (SVG). Methods A cross-sectional household survey was conducted, recruiting adults and adolescents (> 15 years) from 95 and 86 households in rural and urban Fiji (n=186) and SVG (n=147), respectively. Data were collected by trained interviewers using standard tools with a 24-hour recall component, adapted to the local food environments. Latent class analysis (LCA) was conducted using 13 food groups, and moderate to severe FI categories derived from the Food Insecurity Experience Scale (FIES). LCA was undertaken in R, and best fit solutions were based on the AIC results. Differences between the LCA derived classes were examined using one-way ANOVA and Pearson Chi-Squared tests. Results In both Fiji and SVG the best fit LCA derived 3 distinct dietary patterns, across which were differences in DDS (p weekly sourcing of food by borrowing/exchanging (p weekly sourcing food from a small shop varied by dietary pattern (p=0.002), being highest in that with the lowest DDS. In Fiji FI was associated with dietary patterns (p=0.011), ranging from 6.7% (95%CI 3.0, 14.1) to 26.5% (95%CI 14.3, 43.7). In SVG there was no apparent association between FI and dietary pattern (p=0.507), and FI in the whole sample was 35.4% (95%CI 27.6, 43.1). Conclusion Food environment and culture likely accounts for differences across settings. However, associations were found among dietary patterns and SDC, FI and food sources in at least one setting, with sourcing food through borrowing/bartering prominent among groups in both settings, with the highest DDS. This highlights the need for further research to inform policies.

Background Small Island Developing States (SIDS) often lack food and nutrition security and sovereignty due to historically poor infrastructure to support local food systems, reduced domestic food production and increased reliance on generally processed imported foods. We aimed to estimate the prevalence of food insecurity (FI) and to investigate associations between FI and socio-demographic factors, food sources and dietary diversity score (DDS) in two SIDS: Fiji and Saint Vincent and the Grenadines (SVG). Methods We conducted a cross-sectional survey with adults (≥15years) from 95 and 86 sampled households in Fiji and SVG, respectively. We recruited households from urban, rural, higher and lower income areas (n=184 individuals Fiji; n=144 SVG) and administered a context-relevant toolkit to collect individual-level information on FI, dietary intake to calculate DDS (scored out of 10, based on food groups consumed), food sources, socio-economic and health data. We administered the Food and Agriculture Organization’s (FAO) Food Insecurity Experience Scale, and as recommended by FAO scaled the data using Rasch modelling, and defined FI as those in the moderate or severe categories. We undertook bivariate analyses to assess associations followed by multivariable logistic regression with FI as the dependent variable, adjusted for household clustering. Results In Fiji and SVG respectively, 12.5% (95%CI 7.6, 17.9) and 35.4% (95%CI 27.6, 43.1) individuals experienced FI. A greater proportion of those experiencing FI were female and older adults, had less than secondary education, were urban residents and smaller ( weekly) sourcing food from small shops was associated with FI in both countries, particularly in Fiji (47.8% FI vs 18.4% not FI, 95%CI on diff: 8.2, 50.7). In the multivariable analysis, FI was associated with females and regularly sourcing food from small shops in both countries. In Fiji, but not SVG, FI was associated with older age (Fiji OR 1.05; 95%CI 1.02, 1.08). Regularly sourcing food through borrowing/exchanging was associated with lower FI in SVG but not Fiji (SVG OR 0.38; 95%CI 0.15, 0.97). Conclusion Policy action is needed to improve food security, particularly among women and older adults. Our findings indicate avenues for future research, such as the association between small shops and FI and the role that food borrowing/exchanging may play in improving food security and health in SIDS.

After the rediscovery of the normal tissue sparing effect of high dose rate radiation, i.e. the so-called FLASH effect, by Favaudon et al. in 2014, research activities on this topic have been revived and are flourishing ever since. Yet, the exact biological mechanism as well as the required boundary conditions and radiation qualities to reach said sparing remain mostly unclear. We present a laser-based irradiation platform at the Draco PW facility that enables systematic studies into the FLASH regime using proton peak dose rates of up to 10^9 Gy/s. Besides the PW class laser acceleration source, a key component is a pulsed high-field beamline to transport and shape the laser driven proton bunches spectrally and spatially in order to generate homogeneous dose distributions tailored to match the irradiation sample. Making use of the diverse capabilities of the laser driven irradiation platform a pilot experiment of highest complexity has been conducted – a systematic in-vivo tumor irradiation in a specifically developed mouse model. A plethora of online particle diagnostics, including Time-of-Flight, bulk scintillators and screens as well as ionization chambers, in conjunction with diagnostics for retrospective absolute dosimetry (radiochromic films) allowed for an unprecedented level of precision in mean dose delivery (±10 %) and dose homogeneity (±5 %) for the challenging beam qualities of a laser accelerator. The tailored detector suite is complemented by predictive simulations. The talk addresses how our interdisciplinary team overcame all hurdles from animal model development, over enhancing the laser and laser acceleration stability, to dose delivery and online dose monitoring. Results on radiation induced tumor growth delay by laser driven as well as conventionally accelerated proton beams are critically discussed.

Laser-driven proton pulse provide unique properties in terms of pulse structure (ns) and instantaneous dose rate (10^9 Gy/s) but - inherently broadband and highly divergent - pose a challenge to established beamline concepts on the path to application-adapted irradiation field formation, particularly for three-dimensional cases. We present the successful implementation and characterisation of a highly efficient and tuneable dual pulsed solenoid beamline at the Draco PW facility[1] to generate volumetric dose distribution tailored to specific applications[2]. The vast experimental scope and already successfully performed studies range from systematic volumetric in-vivo tumour irradiations in a dedicated mouse model (with a stable mean dose delivery of ±10 % and a spatial dose homogeneity of ±5 % over a cylindrical volume of 5 mm diameter and height) to high-dose-rate irradiations in the FLASH regime (using proton peak dose rates of up to 10^9 Gy/s with about 20 Gy/shot homogeneously over a cylindrical sample volume of 4.5 mm diameter and 3 mm height) as well as particle diagnostics commissioning (with a multitude of spatial and spectral dose distributions). The beamline setup is complemented by a complex beam monitoring and dosimetry detector suite adapted to the ultra-high dose rate pulses and is in its unique synergy and redundancy capable of %-level precision dose delivery to samples as required for systematic irradiation studies. In addition to established radiochromic film dosimetry, the detector suite includes saturation-corrected (transmission) ionisation chambers [3] as well as screen and bulk scintillator setups, partly with tomographic reconstruction capabilities for 3D dose distribution retrieval. Moreover, non-invasive, single-shot-capable online time-of-flight-based spectral characterisation of filtered proton pulses has proven a powerful tool for beam monitoring as well as dosimetric purposes. In this presentation the complex and versatile dose delivery system of laser-driven protons at the Draco PW using pulsed solenoids will be discussed. Its characterisation, technological development and improvement as well as the dosimetry suite as a vital part of the precise dose delivery will be addressed, while the presentation by U. Schramm covers recent experimental activities in detail. [1] T. Ziegler, et al., Proton beam quality enhancement by spectral phase control of a PW-class laser system, https://arxiv.org/abs/2007.11499 (2020) [2] Brack, et al., Spectral and spatial shaping of laser-driven proton beams using a pulsed high-field magnet beamline, SciRep, 10:9118, (2020) [3] Gotz M, et al., A new model for volume recombination in plane‐parallel chambers in pulsed fields of high dose‐per‐pulse. Phys Med Biol., 62: 8634, (2017)

International audience; Blast-wave-driven hydrodynamic instabilities are studied in the presence of a background B-field through experiments and simulations in the high-energy-density (HED) physics regime. In experiments conducted at the Laboratoire pour l’utilisation des lasers intenses (LULI), a laser driven shock-tube platform was used to generate a hydrodynamically unstable interface with a prescribed sinusoidal surface perturbation, and short-pulse x-ray radiography was used to characterize the instability growth with and without a 10-T B-field. The LULI experiments were modeled in FLASH using resistive and ideal magnetohydrodynamics (MHD), and comparing the experiments and simulations suggests that the Spitzer model implemented in FLASH is necessary and sufficient for modeling these planar systems. These results suggest insufficient amplification of the seed B-field, due to resistive diffusion, to alter the hydrodynamic behavior. Although the ideal-MHD simulations did not represent the experiments accurately, they suggest that similar HED systems with dynamic plasma-β(2μ0ρv2/B2) values of less than ∼100 can reduce the growth of blast-wave-driven Rayleigh–Taylor instabilities. These findings validate the resistive-MHD FLASH modeling that is being used to design future experiments for studying B-field effects in HED plasmas.

The highly concentrated formal agri‐food sector holds enormous power in the governance of the food system in South Africa. Yet the concept of food democracy holds that all people should have an equal opportunity to participate in (re)shaping their food system. To contribute to decision making, however, stakeholders not only need access to knowledge about the food system, but should also be able to inform what is considered relevant knowledge. Communities of practice—groups of people who share a common interest or concern and who deepen their knowledge and expertise in this area by interacting on an ongoing basis—provide novel spaces for stakeholder involvement in food governance. This article sets out the process of establishing and maintaining a community of (food) practice in the Western Cape province of South Africa. Through participant observation, analysis of unpublished documents, as well as in depth interviews, the core elements of the community of practice are charted over its 3 yr history. The article demonstrates the informal and evolving nature of communities of practice as social learning structures that can gain credibility and potentially develop into more formal democratic institutions over.

The interaction of supersonic laser-generated plasma jets with a secondary gas target was studied experimentally. The plasma parameters of the jet, and the resulting shock, were characterized using a combination of multi-frame interferometry/shadowgraphy, and x-ray diagnostics, allowing for a detailed study of their structure and evolution. The velocity was obtained with an x-ray streak camera, and filtered x-ray pinhole imaging was used to infer the electron temperature of the jet and shock. The topology of the ambient plasma density was found to have a significant effect on the jet and shock formation, as well as on their radiation characteristics. The experimental results were compared with radiation hydrodynamic simulations, thereby providing further insights into the underlying physical processes of the jet and shock formation and evolution.

Communities of Practice are sites of social learning for the co-production of knowledge. Building on recent literature on Transdisciplinary Communities of Practice, this article reflects on the experiences of an emergent ‘Food Governance Community of Practice’ in South Africa that brings together multiple stakeholders to co-produce knowledge to inform local food policy and governance. Our results show the following lessons for managers and participants engaged in establishing similar ‘third spaces’ for knowledge co-production: 1) make inevitable power asymmetries explicit; 2) the identity of the group should not be built on a particular normative position but emerge from discursive processes and 3) create a balance between supporting peripheral learning and maintaining the specialist cutting edge discussions needed for co-production. Furthermore, the most beneficial legacy of a Community of Practice may not be the outputs in terms of the co-produced knowledge but the development of a cohesive group of stakeholders with a new shared way of knowing.

Small Island Developing States (SIDS) have high and increasing rates of diet-related diseases. This situation is associated with a loss of food sovereignty and an increasing reliance on nutritionally poor food imports. A policy goal, therefore, is to improve local diets through improved local production of nutritious foods. Our aim in this study was to develop methods and collect preliminary data on the relationships between where people source their food, their socio-demographic characteristics and dietary quality in Fiji and Saint Vincent and the Grenadines (SVG) in order to inform further work towards this policy goal. We developed a toolkit of methods to collect individual-level data, including measures of dietary intake, food sources, socio-demographic and health indicators. Individuals aged ≥15 years were eligible to participate. From purposively sampled urban and rural areas, we recruited 186 individuals from 95 households in Fiji, and 147 individuals from 86 households in SVG. Descriptive statistics and multiple linear regression were used to investigate associations. The mean dietary diversity score, out of 10, was 3.7 (SD1.4) in Fiji and 3.8 (SD1.5) in SVG. In both settings, purchasing was the most common way of sourcing food. However, 68% (Fiji) and 45% (SVG) of participants regularly (&gt, weekly) consumed their own produce, and 5% (Fiji) and 33% (SVG) regularly consumed borrowed/exchanged/bartered food. In regression models, independent positive associations with dietary diversity (DD) were: borrowing/exchanging/bartering food (β = 0.73 (0.21, 1.25)), age (0.01 (0.00, 0.03)), and greater than primary education (0.44 (0.06, 0.82)). DD was negatively associated with small shop purchasing (−0.52 (95% CIs −0.91, −0.12)) and rural residence (−0.46 (−0.92, 0.00)). The findings highlight associations between dietary diversity and food sources and indicate avenues for further research to inform policy actions aimed at improving local food production and diet.

This study described food security status and explored coping mechanisms of students at times of food insecurity at the University of the Witwatersrand. The sample consisted of 387 undergraduate students from all faculties and a subsample of 30 students who received financial aid. The 30 subsample students were also assessed regarding their coping strategies. Action research approaches included key indicators such as the Household Food Insecurity Access Scale (HFIAS), and the Dietary Diversity Score (DDS). The HFIAS score showed that 1% of students was severely food insecure and 6% were identified as moderately food insecure. The DDS score amongst the sample was seven out of a possible 12 points. African male students originating from townships who were on financial aid and did not eat in university dining halls were the most vulnerable group to food insecurity. Almost all (97%) participants believed hunger could impact negatively on academic performance and 52% reported having personally experienced the impact of hunger on academic performance. Food security coping strategies used by students were avoiding expensive fast-food places; food pooling, shared meal preparation schedules; eating fewer meals and going home to get food. Wits should develop effective strategies to address pockets of hunger and food insecurity.

The township cash economy of fast food, takeaways, and prepared meals is collectively termed ‘informal foodservice’. An analysis of a five-township ∼3800 microenterprise census, and qualitative sup...

In sub-Saharan Africa, urbanisation and food systems change contribute to rapid dietary transitions promoting obesity. It is unclear to what extent these changes are mediated by neighbourhood food environments or other factors. This paper correlates neighbourhood food provision with household consumption and poverty in Khayelitsha, South Africa and Ahodwo, Ghana. Georeferenced survey data of food consumption and provision were classified by obesity risk and protection. Outlets were mapped, and density and distribution correlated with risk classes. In Khayelitsha, 71% of households exceeded dietary obesity risk thresholds while 16% consumed protective diets. Obesogenic profiles were less (26%) and protective more prevalent (23%) in Ahodwo despite greater income poverty in Khayelitsha. Here, income-deprived households consumed significantly (p &lt, 0.005) less obesogenic and protective diets. Small informal food outlets dominated numerically but supermarkets were key household food sources in Khayelitsha. Although density of food provision in Ahodwo was higher (76/km2), Khayelitsha outlets (61/km2) provided greater access to obesogenic (57% Khayelitsha, 39% Ahodwo) and protective (43% Khayelitsha, 16% Ahodwo) foods. Consumption and provision profiles correlate more strongly in Ahodwo than Khayelitsha (rKhayelitsha = 0.624, rAhodwo = 0.862). Higher obesogenic food consumption in Khayelitsha suggests that risky food environments and poverty together promote obesogenic diets.

Accretion processes play a crucial role in a wide variety of astrophysical systems. Of particular interest are magnetic cataclysmic variables, where, plasma flow is directed along the star’s magnetic field lines onto its poles. A stationary shock is formed, several hundred kilometres above the stellar surface; a distance far too small to be resolved with today’s telescopes. Here, we report the results of an analogous laboratory experiment which recreates this astrophysical system. The dynamics of the laboratory system are strongly influenced by the interplay of material, thermal, magnetic and radiative effects, allowing a steady shock to form at a constant distance from a stationary obstacle. Our results demonstrate that a significant amount of plasma is ejected in the lateral direction; a phenomenon that is under-estimated in typical magnetohydrodynamic simulations and often neglected in astrophysical models. This changes the properties of the post-shock region considerably and has important implications for many astrophysical studies.

Extreme field gradients intrinsic to relativistic laser plasma interactions enable compact MeV proton accelerators with unique bunch characteristics. Yet, direct control of the proton beam profile is usually not possible. So far, only complex micro-engineering of the relativistic plasma accelerator itself and limited adoption of conventional beam optics provided access to global beam parameters that define propagation. We present a novel, counter-intuitive all-optical approach to imprint detailed spatial information from the driving laser pulse to the proton bunch. The concept was motivated by an effect initially observed in an experiment dedicated to laser-driven proton acceleration from a renewable micrometer sized cryogenic Hydrogen jet target at the 150 TW Draco laser at HZDR. A compact, recollimating single plasma mirror was used to enhance the temporal laser contrast, which could be monitored on a single-shot base by means of self-referenced spectral interferometry with extended time excursion (SRSI-ETE) at unprecedented dynamic and temporal range. Unexpectedly, the accelerated proton beam profile showed in this experiment prominent features of the collimated laser beam, such as the shadow of obstacles inserted deliberately in the beam. In a series of further experiments, the spatial profile of the energetic proton bunch was found to exhibit identical features as the fraction of the laser pulse passing around a target of limited size. The formation of quasi-static electric fields in the beam path by ionization of residual gas in the experimental chamber results in asynchronous information transfer between the laser pulse and the naturally delayed proton bunch. Such information transfer between the laser pulse and the naturally delayed proton bunch is attributed to the formation of quasi-static electric fields in the beam path by ionization of residual gas. Essentially acting as a programmable memory, these fields provide access to a new level of proton beam manipulation.

The shape of a wave carries all information about the spatial and temporal structure of its source, given that the medium and its properties are known. Most modern imaging methods seek to utilize this nature of waves originating from Huygens’ principle. We discuss the retrieval of the complete kinetic energy distribution from the acoustic trace that is recorded when a short ion bunch deposits its energy in water. This novel method, which we refer to as Ion-Bunch Energy Acoustic Tracing (I-BEAT), is a refinement of the ionoacoustic approach. With its capability of completely monitoring a single, focused proton bunch with prompt readout and high repetition rate, I-BEAT is a promising approach to meet future requirements of experiments and applications in the field of laser-based ion acceleration. We demonstrate its functionality at two laser-driven ion sources for quantitative online determination of the kinetic energy distribution in the focus of single proton bunches.

We report on our latest transverse focusing results of subnanosecond proton bunches achieved with a laser-driven multi-MeV ion beamline. In the frame of the LIGHT collaboration, a target normal sheath acceleration (TNSA) source based 6 m long beamline was installed. In the past years, the laser-driven proton beam was transported and shaped by this beamline. The particle beam is collimated with a pulsed high-field solenoid and rotated in longitudinal phase space with a radio-frequency cavity which leads to an energy compression with an energy spread of $(2.7\ifmmode\pm\else\textpm\fi{}1.7)%$ ($\mathrm{\ensuremath{\Delta}}\mathrm{E}/{\mathrm{E}}_{0}$ at FWHM) or a time compression to the subnanosecond regime. Highest peak intensities in the subnanosecond regime open up an interesting field for several applications, e.g., proton imaging, as injectors in conventional accelerators or precise stopping power measurements in a plasma. We report on achieving highest peak intensities using an installed second solenoid as a final focusing system in our beamline to achieve small focal spot sizes. We measured a focal spot size of $1.1\ifmmode\times\else\texttimes\fi{}1.2\text{ }\mathrm{mm}$ leading to $5.8\ifmmode\times\else\texttimes\fi{}{10}^{19}\text{ }\mathrm{protons}\text{ }\mathrm{per}\text{ }\mathrm{s}\text{ }{\mathrm{cm}}^{2}$ at a central energy bin of $(9.55\ifmmode\pm\else\textpm\fi{}0.25)\text{ }\mathrm{MeV}$, which can be combined with a bunch duration below 500 ps at FWHM.

Author(s): Brack, Florian-Emanuel; Kroll, Florian; Gaus, Lennart; Bernert, Constantin; Beyreuther, Elke; Cowan, Thomas E; Karsch, Leonhard; Kraft, Stephan; Kunz-Schughart, Leoni A; Lessmann, Elisabeth; Metzkes-Ng, Josefine; Obst-Huebl, Lieselotte; Pawelke, Jorg; Rehwald, Martin; Schlenvoigt, Hans-Peter; Schramm, Ulrich; Sobiella, Manfred; Szabo, Emilia Rita; Ziegler, Tim; Zeil, Karl | Abstract: An amendment to this paper has been published and can be accessed via a link at the top of the paper.

International audience; Many supernova remnants (SNRs), such as G296.5 + 10.0, exhibit an axisymmetric or barrel shape. Such morphologies have previously been linked to the direction of the Galactic magnetic field (GMF) although this remains uncertain. These SNRs generate magnetohydrodynamic (MHD) shocks in the interstellar medium (ISM), modifying its physical and chemical properties. The ability to study these shocks through observations is difficult due to the small spatial scales involved. In order to answer these questions, we perform a scaled laboratory experiment in which a laser-generated blast wave expands under the influence of a uniform magnetic field. The blast wave exhibits a spheroidal shape, whose major axis is aligned with the magnetic field, in addition to a more continuous shock front. The implications of our results are discussed in the context of astrophysical systems.

Socio-economic disparities create conditions that contribute to poor population health. Poor health increases this socio-economic burden on the health care system and undermines society’s capacity to reduce disparities and develop resilience to converging challenges regarding global, regional and national food systems. Using a structured mixed literature review design as well as both primary and secondary data sources collected through a combination of qualitative and quantitative methods and studies, this paper reflects on some key socio-economic challenges facing South Africa and shows how the findings from the research can contribute to and address public health and agricultural development policies and challenges. These themes have been presented within the broader and contemporary discourse on the relationship between ecological health, food security and national development. The agriculture system in South Africa is one of the biggest governments supported systems with a wide community reach and is thus a key sector. The debilitating effects of unhealthy communities, poor environments and socio-economic disparities are inextricably linked to food and nutrition insecurity. The findings from the reviews of the various papers and reports clearly demonstrate on the one hand the high prevalence of food and nutrition security but on the other hand reports and studies emphasize the positive outcomes of an integrated approach to addressing nutrition and food security. Furthermore, agricultural extension highlights how multi and trans-disciplinary methods based on ecological health promotion can achieve systemic changes to improve food security, public health status and also contribute socio-economic development.

Input-intensive industrial-scale production systems are not sustainable means of addressing issues such as food security, nutrition security and sustainable livelihoods. Several literatures suggest that the solution to world hunger is to diversify agriculture and reorient it around ecological practices. There is considerable evidence that supports agro-ecological farming system ss a viable alternative that can improve food production especially for the most vulnerable farming households. In addition, literature shows that an agro-ecology food system holds the key to increasing dietary diversity at the local level, as well as reducing the multiple health risks from industrial agriculture. This paper is aimed at discussing the benefits of agro-ecology food system and how agricultural support systems can play a role. The emphasis of the paper is the application of the agro-ecology approach in an urban/ peri-urban setting. An evaluation report of City of Johannesburg (CoJ) Food Resilience Programme Evaluation unpublished report (2016), shows that very few households engage in gardening/ urban agriculture either in their backyards or nearby open spaces due to the following reasons; strict city by-laws, no access to land, no knowledge of innovative/alternative farming practices lack of interest and limited resources.

International audience; This article reports on the development of thin diamond detectors and their characterization for their application in temporal profile measurements of subnanosecond ion bunches. Two types of diamonds were used: a 20 μm thin polycrystalline chemical vapor deposited (CVD) diamond and a membrane with a thickness of (5 ± 1) μm etched out of a single crystal (sc) CVD diamond. The combination of a small detector electrode and an impedance matched signal outlet leads to excellent time response properties with a signal pulse resolution (FWHM) of τ = (113 ± 11) ps. Such a fast diamond detector is a perfect device for the time of flight measurements of MeV ions with bunch durations in the subnanosecond regime. The scCVD diamond membrane detector was successfully implemented within the framework of the laser ion generation handling and transport project, in which ion beams are accelerated via a laser-driven source and shaped with conventional accelerator technology. The detector was used to measure subnanosecond proton bunches with an intensity of 10⁸ protons per bunch.

In the last two decades, the generation of intense ion beams based on laser-driven sources has become an extensively investigated field. The LIGHT collaboration combines a laserdriven intense ion source with conventional accelerator technology based on the Expertise of laser, plasma and accelerator physicists. Our collaboration has installed a laser-driven multi-MeV ion beamline at the GSI Helmholtzzentrum fuer Schwerionenforschung delivering intense proton bunches in the subnanosecond regime. We investigate possible applications for this beamline, especially in this report we focus on the imaging capabilities. We report on our proton beam homogenization and on first imaging results of a solid target., 5 figures, 5 pages

Proton beams may provide superior dose-conformity in radiation therapy. However, the large sizes and costs limit the widespread use of proton therapy (PT). The recent progress in proton acceleration via high-power laser systems has made it a compelling alternative to conventional accelerators, as it could potentially reduce the overall size and cost of the PT facilities. However, the laser-accelerated beams exhibit different characteristics than conventionally accelerated beams, i.e. very intense proton bunches with large divergences and broad-energy spectra. For the application of laser-driven beams in PT, new solutions for beam transport, such as beam capture, integrated energy selection, beam shaping and delivery systems are required due to the specific beam parameters. The generation of these beams are limited by the low repetition rate of high-power lasers and this limitation would require alternative solutions for tumour irradiation which can efficiently utilize the available high proton fluence and broad-energy spectra per proton bunch to keep treatment times short. This demands new dose delivery system and irradiation field formation schemes. In this paper, we present a multi-functional light-weight and compact proton gantry design for laser-driven sources based on iron-less pulsed high-field magnets. This achromatic design includes improved beam capturing and energy selection systems, with a novel beam shaping and dose delivery system, so-called ELPIS. ELPIS system utilizes magnetic fields, instead of physical scatterers, for broadening the spot-size of broad-energetic beams while capable of simultaneously scanning them in lateral directions. To investigate the clinical feasibility of this gantry design, we conducted a treatment planning study with a 3D treatment planning system augmented for the pulsed beams with optimizable broad-energetic widths and selectable beam spot sizes. High quality treatment plans could be achieved with such unconventional beam parameters, deliverable via the presented gantry and ELPIS dose delivery system. The conventional PT gantries are huge and require large space for the gantry to rotate the beam around the patient, which could be reduced up to 4 times with the presented pulse powered gantry system. The further developments in the next generation petawatt laser systems and laser-targets are crucial to reach higher proton energies. However, if proton energies required for therapy applications are reached it could be possible in future to reduce the footprint of the PT facilities, without compromising on clinical standards.

The generation of intense ion beams from high-intensity laser-generated plasmas has been the focus of research for the last decade. In the LIGHT collaboration the expertise of heavy ion accelerator scientists and laser and plasma physicists has been combined to investigate the prospect of merging these ion beams with conventional accelerator technology and exploring the possibilities of future applications. We report about the goals and first results of the LIGHT collaboration to generate, handle and transport laser driven ion beams. This effort constitutes an important step in research for next generation accelerator technologies.

We have developed a new radiography setup with a short-pulse laser-driven x-ray source. Using a radiography axis perpendicular to both long- and short-pulse lasers allowed optimizing the incident angle of the short-pulse laser on the x-ray source target. The setup has been tested with various x-ray source target materials and different laser wavelengths. Signal to noise ratios are presented as well as achieved spatial resolutions. The high quality of our technique is illustrated on a plasma flow radiograph obtained during a laboratory astrophysics experiment on POLARs.

A laser-driven, multi-MeV-range ion beamline has been installed at the GSI Helmholtz center for heavy ion research. The high-power laser PHELIX drives the very short (picosecond) ion acceleration on μm scale, with energies ranging up to 28.4 MeV for protons in a continuous spectrum. The necessary beam shaping behind the source is accomplished by applying magnetic ion lenses like solenoids and quadrupoles and a radiofrequency cavity. Based on the unique beam properties from the laser-driven source, high-current single bunches could be produced and characterized in a recent experiment: At a central energy of 7.8 MeV, up to 5 × 108 protons could be re-focused in time to a FWHM bunch length of τ = (462 ± 40) ps via phase focusing. The bunches show a moderate energy spread between 10% and 15% (ΔE/E0 at FWHM) and are available at 6 m distance to the source und thus separated from the harsh laser-matter interaction environment. These successful experiments represent the basis for developing novel laser-driven ion beamlines and accessing highest peak intensities for ultra-short MeV-range ion bunches.