Wire Array Z-Pinch Driven High Energy Density Physics Experiments

高能量密度物理(HEDP)研究物质在极端温度、密度和压力下的行为。这通常涉及到将材料加热到数百万度，或使其承受兆巴的压力，将其密度增加到通常情况下的许多倍。HEDP对科学和工业都变得越来越重要/例如，HEDP描述物质在太阳和行星核中的行为，而HEDP的应用包括制造更精细的集成电路，帮助提供逐年增加的计算能力。也许HEDP最伟大的应用尚未出现：创造受控核聚变，提供近乎无限储量的清洁能源。实验不断突破HEDP的界限，探索其核心的基本物理问题，以及以这些现象为基础的科学。为了扩大HEDP研究的密度、温度和压力，一些世界上最大的科学设施正在建设中，其中包括能够在十亿分之一秒内传输数百万焦耳能量的激光。此外，为了理解这些实验，建造了世界上最强大的超级计算机。进行HEDP实验所需的设备通常很大，运行起来也很昂贵，限制了大学研究人员的访问。这项提议寻求为HEDP实验开发一种新的来源，该来源可以在一个可以缩小到大学实验室的系统中检查与大型设施中所研究的现象互补的现象。为了实现这一点，将把大的、快速上升的电流(在几分之一微秒内产生数百万安培)施加到细金属丝的圆柱形排列上，从而产生所谓的丝阵列Z-Pinch。最初，阵列中的导线逐渐‘沸腾’成等离子体*，同时在导线周围产生的磁场将等离子体扫向阵列的轴线。每根导线在轴线上积累的物质形成了一个密度高、稳定的、温度达数百万度的“前体”等离子体柱。这些导线继续充当等离子的来源，直到它们的大部分质量被移除，从而触发了阵列“内爆”的开始。这会在其朝向轴线的过程中扫射等离子体，将其加速到超过200公里-1的速度-在这一点上，它具有与坦克炮弹相同的动能。内爆与前驱物质相撞，在一个持续了百万分之一秒的脉冲中释放出太瓦(1000,000,000,000瓦)的X射线。这项研究将集中在如何利用阵列中的等离子体和X射线脉冲来研究HEDP现象。对前体等离子体柱中物质的测量将用于提供关于恒星中能量传输机制的信息。前体还将被重定向出阵列，进入高超声速等离子射流，撞击到目标材料上，使它们在极长的时间内不稳定。这些数据将与确定包括聚变反应效率和星云形成在内的过程的流体模型进行比较。在最后一组实验中，阵列的内爆将被聚焦到一个紧密点，而不是长柱，这将显著增加实验者可以获得的已经很高的温度。所有这些工作都将在南肯辛顿一所大学的地下室里进行。*等离子体是继固体、液体和气体之后的第四种物质状态。将固体加热，它会熔化成液体，然后再沸腾成气体。如果我们继续加热气体，电子将获得足够的能量，离开它们围绕气核的轨道；因此，等离子体通常被称为电离气体。和金属一样，等离子体也是很好的导体，受到磁力和电场力的影响。

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.