Understanding the growth of hydrodynamic instabilities in Inertial Confinement Fusion

Summary

The National Ignition Facility (NIF) in the USA has managed to achieve a fusion fuel gain of 1 in landmark experiments. However, the targeted gain is substantially higher than this value. Here, we partner with the NIF to develop algorithms and run computations to advance our understanding of the hydrodynamics instability and turbulence during the implosion process. Should this be understood and controlled, then much higher fuel gains are possible. This project builds on more than a decade’s work developing algorithms to simulate compressible turbulent mixing due to shock waves, and is currently supported by an Australian Research Council Discovery Project.

Supervisor(s)

Dr Ben Thornber

Research Location

Aerospace, Mechanical and Mechatronic Engineering

Program Type

Masters/PHD

Synopsis

Meeting the global energy demands for the second half of the 21st century is the key challenge of our civilisation. A future energy source which could address this with ease is nuclear fusion. The energy released from fusing one gram of Deuterium is 100,000kWh which is equivalent to burning 15 tonnes of coal. Given that there is 33g of Deuterium in every ton of sea water, the oceans could supply the world's future energy needs for over a thousand years even with conversion efficiencies of a fraction of a percent. With this in mind, fusion is the ultimate power source. Recently a landmark result has been obtained: for the first time on a laboratory scale a fusion reaction has generated a fuel gain of greater than 1. This outstanding achievement has been recorded at the US National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). This is a $4bn program aiming to demonstrate nuclear fusion of millimetre sized capsules containing Deuterium-Tritium (DT) fuel, in a technique known as Inertial Confinement Fusion (ICF). In ICF, fusion is attained through rapid compression of fusion fuel driven by 192 lasers delivering up to 500 Tera-Watt pulses over a period of nanoseconds. Despite this achievement, a practical power source would require a gain many times greater than the total laser power employed, which at present is 1.5MJ for a yield of about 15kJ. If fusion ignition can be achieved, the energy released will be approximately 1000 times greater than the current experiments. This significant gap must be closed before a practical power station can be realised. So why are the capsules under-performing? As the capsule implodes the initially solid material is transformed into a dense plasma by the high temperatures and pressures. The shell (also called `ablator') of the capsule and the layers of DT fuel within the capsule are not perfectly smooth, and this unavoidable surface roughness seeds fluid instabilities at the interfaces between the different layers. The amplitude of the surface roughness initially grows exponentially in time, and at peak compression can be 1000 times larger than the initial roughness height. This growth leads to penetration and mixing of the ablator into the nuclear fuel. This PhD will focus on the development of state-of-the-art massively parallel fluid dynamics software within the School of AMME to further our understanding of the development of these instabilities in NIF-like conditions. This project is in collaboration with scientists at Lawrence Livermore National Laboratory. The ideal student will have an affinity for programming (or keen to learn), at least an Honours 1 WAM and a solid mathematical/engineering/physics background.

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Keywords

Understanding the growth of hydrodynamic instabilities in Inertial Confinement Fusion

Opportunity ID

The opportunity ID for this research opportunity is: 2275

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