Wire Array Z-Pinch Driven High Energy Density Physics Experiments

High Energy Density Physics (HEDP) studies the behaviour of matter in extremes of temperature, density and pressure. Often this involves heating material to millions of degrees, or subjecting it to Mega-bars of pressure, increasing its density to many times beyond that normally encountered. HEDP is becoming increasingly important to both science and industry / for instance HEDP describes the behaviour of matter in the sun and planetary cores, whilst applications of HEDP include the manufacture of more refined integrated circuits, helping provide the year on year increase in computing power. Perhaps the greatest application of HEDP is yet to emerge: the creation of controlled nuclear fusion, providing a clean energy source of near unlimited reserves.Experiments continually push the boundaries of HEDP, exploring both the fundamental physics issues at its heart, and science that uses these phenomena as its basis. In order to expand the densities, temperatures and pressures available for HEDP studies some of the worlds largest scientific facilities are under construction, including lasers capable of delivering millions of joules of energy in billionths of a second. Further, in order to understand these experiments the worlds most powerful supercomputers are built.The facilities required to perform HEDP experiments are usually large and expensive to run, limiting access to university researchers. This proposal seeks to develop a new source for HEDP experiments that could examine phenomena complementary to those investigated at large facilities, in a system that can be scaled down to university laboratories. To achieve this large, fast rising currents (millions of amps being generated in fractions of a microsecond) will be applied to cylindrical arrangements of fine metallic wires, producing what is known as a wire array z-pinch. Initially the wires in an array gradually 'boil' into plasma*, whilst the magnetic field created around the wires sweeps the plasma towards the axis of the array. Accumulation of material from each of the wires at the axis results in the formation of a dense, stable 'precursor' plasma column with a temperature of millions of degrees. The wires continue to act as sources of plasma until the majority of their mass has been removed, triggering the start of the arrays 'implosion'. This sweeps up plasma on its way towards the axis, accelerating it to speeds in excess of 200kms-1 - at which point it has the same kinetic energy as a tank shell. Colliding with the precursor the implosion releases terrawatts (1000 000 000 000s of watts) of X-rays in a pulse lasting a fraction of a millionth of a second.This fellowship will focus on ways to use the plasma and X-ray pulse from an array to study HEDP phenomena. Measurements of the material in the precursor plasma column will be used to provide information on energy transport mechanisms in stars. The precursor will also be redirected out of the array into a hypersonic plasma jet, which will be impacted onto target materials, driving them unstable over extremely long times. This data will be compared to fluid models that determine processes including the efficiency of fusion reactions and the formation of nebulae. In a final set of experiments the implosion of an array will be focussed to a tight point rather than a long column, significantly increasing the already huge temperatures available to experimenters. All of this work will be in a basement of a university in South Kensington. * Plasma is the 4th state of matter after solids, liquids and gases. Heating a solid it melts into a liquid, then this boils into a gas. If we continue to heat a gas the electrons will aquire enough energy to leave their orbits around the gas nuclei; hence plasma is often referred to as an ionised gas. Like metals, plasmas can be excellent conductors, and are subject to magnetic and electrical forces.