Wire Array Z-Pinch Driven High Energy Density Physics Experiments

高能密度物理学（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，或使其承受百万巴的压力，将其密度增加到通常遇到的密度的许多倍。HEDP对科学和工业都变得越来越重要，例如，HEDP描述了太阳和行星核心中的物质行为，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：可控核聚变的创造，提供一种近乎无限储量的清洁能源。实验不断推动HEDP的边界，探索其核心的基本物理问题，以及将这些现象作为基础的科学。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，包括能够在十亿分之一秒内提供数百万焦耳能量的激光器。此外，为了理解这些实验，世界上最强大的超级计算机被建造出来。进行HEDP实验所需的设备通常很大，运行费用昂贵，限制了大学研究人员的使用。该提案寻求开发HEDP实验的新来源，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调查相补充的现象。为了实现这种大而快速上升的电流（在微秒内产生数百万安培），将应用于细金属线的圆柱形排列，产生所谓的线阵列z-pinch。最初，阵列中的导线逐渐“沸腾”成等离子体*，而导线周围产生的磁场将等离子体扫向阵列的轴线。从轴线上的每根导线上积累的物质形成了一个致密、稳定的“前体”等离子体柱，温度高达数百万度。电线继续充当等离子体的来源，直到它们的大部分质量被移除，触发阵列“内爆”的开始。在等离子体向轴移动的过程中，等离子体被扫过，加速到时速超过200km -1，此时等离子体的动能相当于一枚坦克炮弹。与前体碰撞后，内爆释放出太瓦（1000万亿亿瓦）的x射线脉冲，持续时间为百万分之一秒。该奖学金将重点研究如何利用阵列的等离子体和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恒星中能量传输机制的信息。前驱体也将从阵列中重新定向到高超音速等离子体射流中，这将影响到目标材料，使它们在极长时间内不稳定。这些数据将与流体模型进行比较，以确定包括聚变反应效率和星云形成在内的过程。在最后一组实验中，阵列的内爆将集中在一个紧点上，而不是一个长柱上，这将大大提高实验人员可用的已经很高的温度。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。加热固体，它会融化成液体，然后沸腾成气体。如果我们继续加热气体，电子就会获得足够的能量，离开围绕气体原子核的轨道；因此，等离子体通常被称为电离气体。和金属一样，等离子体也是优秀的导体，并且会受到磁力和电场的影响。

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.