69 research outputs found
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Recent Results of Radiation Hydrodynamic and Turbulence Experiments in Cylindrical Geometry
Brachytherapy for rhabdomyosarcoma: Survey of international clinical practice and development of guidelines.
BACKGROUND AND PURPOSE: The purpose of this study was to address the lack of published data on the use of brachytherapy in pediatric rhabdomyosarcoma by describing current practice as starting point to develop consensus guidelines. MATERIALS AND METHODS: An international expert panel on the treatment of pediatric rhabdomyosarcoma comprising 24 (pediatric) radiation oncologists, brachytherapists and pediatric surgeons met for a Brachytherapy Workshop hosted by the European paediatric Soft tissue Sarcoma Study Group (EpSSG). The panel's clinical experience, the results of a previously distributed questionnaire, and a review of the literature were presented. RESULTS: The survey indicated the most common use of brachytherapy to be in combination with tumor resection, followed by brachytherapy as sole local therapy modality. HDR was increasingly deployed in pediatric practice, especially for genitourinary sites. Brachytherapy planning was mostly by 3D imaging based on CT. Recommendations for patient selection, treatment requirements, implant technique, delineation, dose prescription, dose reporting and clinical management were defined. CONCLUSIONS: Consensus guidelines for the use of brachytherapy in pediatric rhabdomyosarcoma have been developed through multicenter collaboration establishing the basis for future work. These have been adopted for the open EpSSG overarching study for children and adults with Frontline and Relapsed RhabdoMyoSarcoma (FaR-RMS)
Lawson criterion for ignition exceeded in an inertial fusion experiment
For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37Â MJ of fusion for 1.92Â MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion
Simple target models for ion beam fusion systems studies
Some of the target information required for reactor and systems studies is not readily available. In this paper we attempt to improve this situation by developing simple target models that give estimates of DT fuel mass, the masses of other target constituents, the DT burn fraction, and the fraction of energy in neutrons
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Magnetic bunchers for the generation of high peak current, low emittance electron pulses at medium energy
In this paper, we will outline the various physical constraints and issues for magnetic buncher design. Discussion of achromatic design and dispersion and minimizing rf power will be presented. We will provide generic designs for positive and negative dispersion, and describe the effect of curvature in the energy-phase correlation due to the sinusoidal nature of the rf fields on the output pulse shape. Methods to remove the curvature will be examined. Finally this paper will cover simple nonlinear dispersion which can compensate for the curvature
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A current prediction of the ICF gain curve, its uncertainties, and implications for ICF strategy
We present our gain predictions for indirect-drive ICF targets, based on current target physics knowledge. In order to understand the uncertainties involved in predicting the performance of future ICF targets, we have constructed a simple model that contains a few basic features of target operation and estimates the possible effects of other complex target processes via simple parametrizations. We evaluate the scalings and uncertainties in the model parameters using current data, detailed calculations, and estimates of some of the underlying target physics processes. We present Monte-Carlo calculations with this model showing the propagation of the estimated uncertainties to the near-ignition'' and high-gain'' regimes. We estimate the probability of success as a function of required target gain and available driver energy, and illustrate using some current facility-planning scenarios. We discuss the role of potential future experiments in constraining currently-uncertain theoretical models
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Los Alamos hydrodynamic experiments on NOVA
The authors are performing experiments to study hydrodynamic perturbation growth in x-ray driven targets to test models used to analyze the stability of ignition targets. They use cylindrical implosions to directly image perturbation growth and ``feed-through`` to the inner surface in convergent geometry. The implosion trajectories and azimuthal structure of inner and outer marker layers on the cylinder are measured by axial radiography. Perturbation growth of 25 at a convergence ratio of two has been measured on the inner layer, in addition to the effects of hohlraum drive asymmetries, nonlinear mode saturation, mode coupling, and the deceleration phase of the implosion. In other experiments, they are studying the planar analog of instability coupling between the inner surface of a cryogenic ignition capsule and the ablation surface. This instability coupling mechanism provides an important seed for perturbation growth in ignition capsule implosions
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Development of X-ray tracer diagnostics for radiatively-driven ablator experiments [annual report FY1998]
This report covers fiscal year 1998 of our ongoing project to develop tracer X-ray spectroscopic diagnostics for hohlraum environments. This effort focused on an experimental campaign carried out at OMEGA on 25--27 August 1998. This phase of the project heavily emphasized experimental design, diagnostic development, and target fabrication, as well as building up numerical models for the experiments. The spectral diagnostic under development involves using two thin (few 1000 {angstrom}) mid-Z tracers in two witness plates mounted on the side of a hohlraum with the tracers' K{sub a} absorption features seen against an X-ray backlighter. The absorption data are used to sample the time-dependent, localized properties of each witness plate as a radiation wave ablates it. The experiments represented the first application of this diagnostic, in this case to side-by-side doped and undoped plastic to investigate the effects of capsule ablator dopants
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