158,893 research outputs found
Heavy-Ion Fusion Targets with 'Diffuse' Spherical Radiation Converter
No full textSpherically symmetric targets for indirect-drive heavy-ion fusion are studied, in which the fusion capsule is enclosed in a low-density thick spherical shell, where the ion beams are stopped and their energy is converted into thermal radiation. The thermal radiation then drives the implosion of the fusion capsule, with mininum hydrodynamic coupling between the energy deposition region and the ablation layer. The conditions for effective hydrodynamic decoupling have been derived. It is found that with the use of heavy ions with energy about or below 8 GeV, the beam-to-fuel energy coupling efficiency can be as large as in foreseen conventional hohlraums. On the other hand, these targets only allow for a low dynamic range of pulse shaping, which results in rather poor entropy shaping and modest fuel gain. Robust targets have been designed, which achieve energy gain G approximate to 30, when driven by shaped pulses of 12.5 MJ of 8.5 GeV Bi ions. Inclusion of a high-density pusher, which increases the fuel compression leads to higher gain at lower beam energy, but two-dimensional simulations demonstrate the extremely violent instability of the fuel-pusher interface
Spherically Symmetric Radiation Converters for Ion Beam Fusion
No full textThick spherical shells, irradiated nearly symmetrically by ion beams, can convert efficiently ion beam energy to thermal radiation, with parameters of relevance to inertial confinement fusion. The evolution of such radiation converters has been studied by means of an analytic model, in turn validated by 1D radiation hydrodynamic simulations. Expressions are derived for the overall conversion efficiency, the heating time and the radiation temperature as a function of the beam and target parameters. Conditions are also derived for the effective hydrodynamic insulation between the converter and the fusion capsule contained inside the converter. For realistic heavy ion beam parameters (e.g. 6-8 GeV Bi beams, with total energy of 10 MJ and power about 700 TW) such converters can achieve an efficiency adequate for fusion applications, but only allow for a modest dynamic range of pulse shaping
Implosion of Reactor Size, Gas Filled, Spherical Shell Targets Driven by Shaped Pressure Pulses
No full textThe implosion of a family of reactor‐size targets for inertial confinement fusion (ICF) is studied analytically and numerically. The targets consist of a deuterium–tritium (D–T) shell filled with D–T vapor and they are imploded by a multistep pressure pulse designed in such a way that the final hot spot is formed mainly from the initially gaseous fuel. The formation of the hot spot is described by means of a relatively simple model, and scaling laws for the quantities that characterize the state of the initially gaseous part of the fuel prior to ignition are derived. The results of the model are compared with one‐dimensional fluid simulations, and good agreement is found. A parametric study of the fuel energy gain is then presented; the dependence of the gain and of the hot spot convergence ratio on the pulse parameters and on the filling gas density is analyzed. It is also shown that a substantial increase in the gain (for a given target and pulse energy) can be achieved by replacing the last step of the pulse with an exponential ramp
Evaluation of the Time and Frequency Transfer Capabilities of a network of GNSS receivers located in timing laboratories
No full textNear-real time synchronization through a network of GNSS receivers located in timinglaboratories
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Time and Frequency Transfer througha network of GNSS receivers located in Timing Laboratories
No full textTime and Frequency Transfer through a network of GNSS recerivers located in Timing Laboratories
No full textIgnition Conditions and Fuel Energy Gain of Spark-Ignited and Volume-Ignited ICF Targets
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