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International audience; Although bipolar jets are seen emerging from a wide variety of astrophysical systems, the issue of their formation and morphology beyond their launching is still under study. Our scaled laboratory experiments, representative of young stellar object outflows, reveal that stable and narrow collimation of the entire flow can result from the presence of a poloidal magnetic field whose strength is consistent with observations. The laboratory plasma becomes focused with an interior cavity. This gives rise to a standing conical shock from which the jet emerges. Following simulations of the process at the full astrophysical scale, we conclude that it can also explain recently discovered x-ray emission features observed in low-density regions at the base of protostellar jets, such as the well-studied jet HH 154.

The recent advancements in the eld of laser-driven particle acceleration have made Laser driven Ion Beam Therapy (L-IBT) an attractive alternative to the conventional particle therapy facilities. To bring this emerging technology to clinical application we introduce the Broad Energy Assorted depth-Dose deposition (BEAD) scheme which makes ecient use of the large energy spread and high dose-per-pulse of Laser Accelerated Protons (LAP) and is capable of delivering homogeneous doses to tumors. Furthermore, as a key component of L-IBT solution we present a compact, iso-centric gantry design with 360° rotation capability with an Integrated Shot-to-shot Energy Selection System (ISESS), for efficient transport of LAP with large energy spread to the patient. We show that gantry size could be reduced by a factor of 2-3 compared to conventional gantry systems by utilizing pulsed, air-core magnets.

Laser ion acceleration provides for compact, high-intensity ion sources in the multi-MeV range. Using a pulsed high-field solenoid, for the first time high-intensity laser-accelerated proton bunches could be selected from the continuous exponential spectrum and delivered to large distances, containing more than ${10}^{9}$ particles in a narrow energy interval around a central energy of 9.4 MeV and showing $\ensuremath{\le}30\text{ }\text{ }\mathrm{mrad}$ envelope divergence. The bunches of only a few nanoseconds bunch duration were characterized 2.2 m behind the laser-plasma source with respect to arrival time, energy width, and intensity as well as spatial and temporal bunch profile.

Clinical QA in teletherapy as well as the characterization of experimental radiation sources for future medical applications requires effective methods for measuring three-dimensional (3D) dose distributions generated in a water-equivalent medium. Current dosimeters based on ionization chambers, diodes, thermoluminescence detectors, radiochromic films, or polymer gels exhibit various drawbacks: High quality 3D dose determination is either very sophisticated and expensive or requires high amounts of effort and time for the preparation or read out. New detectors based on scintillator blocks in combination with optical tomography are studied, since they have the potential to facilitate the desired cost-effective, transportable, and long-term stable dosimetry system that is able to determine 3D dose distributions with high spatial resolution in a short time.A portable detector prototype was set up based on a plastic scintillator block and four digital cameras. During irradiation the scintillator emits light, which is detected by the fixed cameras. The light distribution is then reconstructed by optical tomography, using maximum-likelihood expectation maximization. The result of the reconstruction approximates the 3D dose distribution. First performance tests of the prototype using laser light were carried out. Irradiation experiments were performed with ionizing radiation, i.e., bremsstrahlung (6 to 21 MV), electrons (6 to 21 MeV), and protons (68 MeV), provided by clinical and research accelerators.Laser experiments show that the current imaging properties differ from the design specifications: The imaging scale of the optical systems is position dependent, ranging from 0.185 mm/pixel to 0.225 mm/pixel. Nevertheless, the developed dosimetry method is proven to be functional for electron and proton beams. Induced radiation doses of 50 mGy or more made 3D dose reconstructions possible. Taking the imaging properties into account, determined dose profiles are in agreement with reference measurements. An inherent drawback of the scintillator is the nonlinear light output for high stopping-power radiation due to the quenching effect. It impacts the depth dose curves measured with the dosimeter. For single Bragg peak distributions this leads to a peak to plateau ratio of 2.8 instead of 4.5 for the reference ionization chamber measurement. Furthermore, the transmission of the clinical bremsstrahlung beams through the scintillator leads to the saturation of one camera, making dose reconstructions in that case presently not feasible.It is shown that distributions of scintillation light generated by proton or electron beams can be reconstructed by the dosimetry system within minutes. The quenching apparent for proton irradiation, and the yet not precisely determined position dependency of the imaging scale, require further investigation and corrections. Upgrading the prototype with larger or inorganic scintillators would increase the detectable proton and electron energy range. The presented results show that the determination of 3D dose distributions using scintillator blocks and optical tomography is a promising dosimetry method.

The South African population faces many of the global concerns relating to micronutrient deficiency and the impact this has on health and well-being. Moreover, there is a high prevalence of HIV infection, compounded by a high level of co-infection with TB. This pilot study evaluates the impact of a fortified supplementary food on the health and well-being of a cohort of creche children, aged 3 to 6, and adult TB patients drawn from the Presidential Node of Alexandra, Johannesburg, South Africa. A further aim of this study was to evaluate the sensitivity and validity of non-invasive indicators of nutritional status in a field-based population sample. The investigational product, e’Pap, is supported by extensive anecdotal evidence that whole grain cereals with food-style nutrients constitute an effective supplementary food for those suffering from the effects of food insecurity, poor health and well-being, and coping with TB and HIV infection. The results indicate a beneficial effect of e’Pap for both study populations, and particularly for adult TB patients, whose baseline data reflected severe food insecurity and malnutrition in the majority of cases. There is evidence to suggest statistically significant improvements in key micronutrient levels, well-being and energy, hand-grip strength, the Bioelectrical Impedance Analysis (BIA) Illness Marker, and certain clinical indicators. Although Body Mass Index (BMI) and Mid Upper Arm Circumference (MUAC) are frequently used as standard measures to evaluate the efficacy of nutritional interventions, these indicators were not sufficiently sensitive in this study. Nor does weight gain necessarily indicate improved nutritional status. Hand-grip strength, lean body mass, and the BIA Illness Marker seem to be more useful indicators of change in nutritional status.

International audience; The production of strongly magnetized laser plasmas, of interest for laboratory astrophysics and inertial confinement fusion studies, is presented. This is achieved by coupling a 16 kV pulse-power system. This is achieved by coupling a 16 kV pulse-power system, which generates a magnetic field by means of a split coil, with the ELFIE laser facility at Ecole Polytechnique. In order to influence the plasma dynamics in a significant manner, the system can generate, repetitively and without debris, high amplitude magnetic fields (40 T) in a manner compatible with a high-energy laser environment. A description of the system and preliminary results demonstrating the possibility to magnetically collimate plasma jets are given.

Previous works on Ytterbium-doped alcaline-earth fluoride have impressively shown that these materials are suitable for high-peak power operation [1,2] due to their broad emission spectrum comparable with rare-earth doped laser glasses. From the scaling point of view Yb:CaF 2 is the most promising material since crystal growth at large sizes with diameters up to 100 mm and more with high optical quality have been demonstrated so far. Also the thermo-mechanical and thermo-optical properties such as the negative thermal lens of Yb:CaF 2 are superior for high-average power lasers [3]. Moreover, the high saturation fluence (i.e. 80 J/cm2) pushes the potential energy limit of thin disk lasers by about one order of magnitude compared to oxide laser materials such as Yb:YAG. This means that at a given stored energy parasitic lasing is reduced by a low transverse gain [4]. However, the low single-pass gain of Yb:CaF 2 lasers must compensated by a large number of amplifier passes.

Here we present first lasing and tunability results of a diode-pumped Yb:SiO2 multicomponent glass laser. The multicomponent glass consists of 70 mol% SiO2, 20 mol% Al2O3, 9.1 mol% La2O3, and a doping level of 0.875 mol% Yb2O3. Due to the high contingent of SiO2 the spectroscopic properties of the multicomponent glass is similar to Yb-doped fused silica glass. The huge advantage of the here presented multicomponent fused silica glass as gain material is its fabrication technique. It can be produced directly out of a glass melt with large active volume and high optical quality. The Yb-doped multicomponent glass sample in the experiment had a thickness of 1.5 mm and was polished in laser quality. For pumping a fiber coupled laser diode was used with power of 6W at 975nm. The pump absorption was about 60%. In order to increase the pump absorption the non-absorbed pump was re-imaged back into the Yb:SiO2. The laser cavity was a V-shaped resonator and the folding mirror had a curvature of 200mm. This results in a stable confocal resonator with a beam waist of about 50 µm in the glass and 600 µm on the output coupler. The free running laser wavelength was centered around 1055nm. The slope efficiency results in a value of 32%. The wavelength tunability of the laser cavity was achieved inserting a brewster prism (SF10) in between the folding mirror and the output coupler. At a pump level of 5W the laser had a tuning range from 1010 nm to 1080nm.

The characterization of the absolute number of electrons generated by laser wakefield acceleration often relies on absolutely calibrated FUJI imaging plates (IP), although their validity in the regime of extreme peak currents is untested. Here, we present an extensive study on the dependence of the sensitivity of BAS-SR and BAS-MS IP to picosecond electron bunches of varying charge of up to 60 pC, performed at the electron accelerator ELBE, making use of about three orders of magnitude of higher peak intensity than in prior studies. We demonstrate that the response of the IPs shows no saturation effect and that the BAS-SR IP sensitivity of 0.0081 photostimulated luminescence per electron number confirms surprisingly well data from previous works. However, the use of the identical readout system and handling procedures turned out to be crucial and, if unnoticed, may be an important error source.

The system dynamics of a planned system test facility for the hardware in the loop simulation of a hybrid power plant featuring a Turbec T100 and dummy hardware for the SOFC have been investigated. The model of the micro gas turbine including effects like moment of inertia, heat soakage and volume packing has been calibrated against measured cycle data with good accuracy. Special attention has been dedicated to the dynamics of the actuators. Hence their steady state and transient performance has been identified experimentally. In accordance to published data of SOFC the SOFC dummy hardware is designed to be a first order time delay element (PT1). Important aspects of the control strategy as a major part of the operational concept are described. The results show that the chosen control strategy is suitable to control the system test facility within the set boundary conditions with the dynamics of the actuators being a limiting factor.Copyright © 2009 by ASME

The presentation of a control strategy for the most important SOFC / gas turbine hybrid system maneuvers like start-up, shutdown or system-failures is one of the main issues of this paper. For a successful system simulation during different operational states, a coupled model of a gas turbine and a SOFC was combined with the proposed control system. To keep the model structure lean enough for real-time calculation, a non-linear lumped volume model with modular set up was chosen to achieve an accurate reflection of the dynamic effects. The control strategy takes into account the requirements of the gas turbine components but also necessitates safe operation of the SOFC. Specified boundary conditions are strictly to be considered within the control structure to ensure failure-free and safe operation during the entire operation range. In the presented hybrid cycle a possibility of bypassing both, the cold side of the recuperator and the cathode side of the SOFC is suggested. These two bypasses, which introduce two additional actuators to the system, allow the SOFC stack temperature to be kept in its limits more easily.Copyright © 2008 by ASME

Recent oncological studies identified beneficial properties of radiation applied at ultrahigh dose rates, several orders of magnitude higher than the clinical standard of the order of Gy min–1. Sources capable of providing these ultrahigh dose rates are under investigation. Here we show that a stable, compact laser-driven proton source with energies greater than 60 MeV enables radiobiological in vivo studies. We performed a pilot irradiation study on human tumours in a mouse model, showing the concerted preparation of mice and laser accelerator, dose-controlled, tumour-conform irradiation using a laser-driven as well as a clinical reference proton source, and the radiobiological evaluation of irradiated and unirradiated mice for radiation-induced tumour growth delay. The prescribed homogeneous dose of 4 Gy was precisely delivered at the laser-driven source. The results demonstrate a complete laser-driven proton research platform for diverse user-specific small animal models, able to deliver tunable single-shot doses up to around 20 Gy to millimetre-scale volumes on nanosecond timescales, equivalent to around 109 Gy s–1, spatially homogenized and tailored to the sample. The platform provides a unique infrastructure for translational research with protons at ultrahigh dose rates.

Radiation therapy is an important modality in cancer treatment. Compact electron linear accelerators are widely used to provide electron and photon beams with a maximum energy of about 20 MeV for tumor irradiation. Heavy charged particles (protons and heavier ions) due to their superior dose profile over photons and electrons, provide higher tumor dose conformity and healthy tissue sparing. But due to high costs and huge size of existing facilities, ion therapy is limited to few, large centers only.

The thesis at hand addresses design, characterization and experimental testing of pulsed high-field magnets for utilization in the field of laser-plasma physics. The central task was to establish a technology platform that allows to manipulate laser-driven ion sources in a way that the accelerated ions can be used in complex application studies, e.g. radiobiological cell or tumor irradiation. Laser-driven ion acceleration in the regime of target normal sheath acceleration (TNSA) offers the unique opportunity to accelerate particles to kinetic energies of few 10MeV on the micrometer scale. The generated bunches are short, intense, show broad exponentially decaying energy spectra and high divergence. In order to efficiently use the generated particles, it is crucial to gain control over their divergence directly after their production. For most applications it additionally is favorable to reduce the energy spread of the beam. This work shows that the developed pulsed high-field magnets, so-called solenoids (cylindrical magnets), can efficiently capture, transport and focus laser-accelerated protons. The chromaticity of the magnetic lens thereby provides for energy selection. Three prototype solenoids, adapted to fit different application scenarios, and associated current pulse drivers have been developed. The magnets generate fields of several 10 T. Pulse durations are of the order of one millisecond and thus the fields can be considered as quasi-static for laser-plasma interaction processes taking place on the ps- to ns-scale. Their high field strength in combination with abandoning magnetic cores make the solenoids compact and light-weight. The presented experiments focus on a solenoid magnet designed for the capture of divergent laser-driven ion beams. They have been carried out at the 6MV tandetron accelerator and the laser acceleration source Draco of Helmholtz-Zentrum Dresden – Rossendorf as well as at the PHELIX laser of GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt. The results show that the developed technology platform breaks ground for a variety of practical applications of laser ion acceleration. It is shown that laser-driven ion beams can be efficiently injected into conventional accelerator structures to allow for phase space modulation. Furthermore, first practical studies on medical beam guidance systems are presented. Hence, the developed magnets allow to investigate feasibility and potential of the frequently proposed laser-based ion beam therapy of tumor diseases. The pulsed high-field magnets bring us one step closer to the realization of this ambitious endeavor, as they pave the way for compact and efficient beam guidance toward the patient but also, in the phase of translational research, allow to study the radiobiological properties of the novel particle source. In this context, worldwide first irradiation studies with laser-accelerated protons on volumetric tumors in the mouse model have been prepared and their feasibility studied, identifying already met radiobiological criteria and hurdles yet to overcome.

Purpose/Objective(s) The advancement in laser particle acceleration has made Laser-based Ion Beam Therapy (LIBT) an attractive alternative to existing Ion Beam Therapy (IBT) facilities as it has a great potential to reduce size and cost. Ultra-intense laser pulses interact with thin targets and accelerates intense ion bunches on μm scale. Unlike conventional beams, laser-driven ion beams are characterized by short pulses of intense particle flux with peak dose rates exceeding conventional values by 8-9 orders of magnitude, low repetition rate, broad energy spectrum and large divergence. The presented work is an ongoing joint multidisciplinary translational research project of several institutions aiming to establish LIBT. Materials/Methods In addition to laser particle accelerator development, LIBT poses new challenges. Conventional solutions cannot be applied directly as LIBT demands full characterization of radiobiological effects, development of new beam monitoring and dosimetry, a treatment planning system (TPS) for broad energy beams and an optimized gantry with energy selection system. Laser-based technology has been established for cell and small animal irradiation using a fixed beamline and is being utilized for systematic radiobiological studies. For translation to patient irradiation highly compact 360° isocentric proton and carbon gantry systems are designed based on light-weight iron-less pulsed magnets. A dedicated 3D TPS is being developed. Moreover, increasing the laser power to petawatt level is needed to achieve therapeutic ion energies. Results Radiobiologically no overall difference is observed for laser-driven ultra-high dose rates compared to conventional IBT beams. Our double achromatic pulsed gantry systems are ∼2.5 times smaller than conventional IBT gantries. For the gantry realization, key components have been designed and developed. A pulsed solenoid as particle capturing and focusing device was successfully tested. A novel 12 Tesla compact iron-less pulsed 50° sector magnet was developed. In addition, a pulsed high acceptance quadrupole with 230 T/m gradient has been designed and is being realized for tests. Our 3D TPS can be used to explore dose delivery and treatment planning strategies for LIBT. Conclusions The 3D TPS combined with our compact gantry provide a solution for LIBT. The realization and tests of pulsed gantry magnets are being continued. A new conventional proton therapy facility is under commissioning and is additionally equipped with a petawatt laser laboratory and an experimental bunker for further LIBT development toward clinical applicability with the conventional proton beam as reference. Acknowledgment This project was supported by German BMBF grant 03Z1N511 and DFG cluster of excellence MAP.

Nature Communications 9(1), 5292 (2018). doi:10.1038/s41467-018-07756-z, Extreme field gradients intrinsic to relativistic laser-interactions with thin solid targets enable compact MeV proton accelerators with unique bunch characteristics. Yet, direct control of the proton beam profile is usually not possible. Here we present a readily applicable all-optical approach to imprint detailed spatial information from the driving laser pulse onto the proton bunch. In a series of experiments, counter-intuitively, the spatial profile of the energetic proton bunch was found to exhibit identical structures as the fraction of the laser pulse passing around a target of limited size. 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 higher level of proton beam manipulation., Published by Nature Publishing Group UK, [London]