Inertial Fusion Energy: Optimising High Energy Density Physics in Complex Geometries

燃煤或石油引起的气候变化，以及国际冲突造成的燃料供应不安全，都突显了开发更安全、更清洁的发电方式的必要性。可再生能源和核裂变在这方面都发挥了重要作用，但都有局限性。风和浪受自然变化的影响，而裂变反应堆需要仔细、长期地管理危险废物。未来一个有吸引力的替代能源是聚变能源，利用与太阳能相同的核反应。为了在地球上创造核聚变，我们“燃烧”氢的同位素(重氢，占世界海洋质量的0.03%)，这是一种巨大的、容易获得的燃料供应。氘与氚(另一种氢同位素)结合在一起，在极端的温度、压力和密度下，它们可以聚变形成氦，并在这样做时释放出大量的能量。该反应不会产生温室气体，而且相对清洁，使用寿命很短、易于处理的废物，但创造聚变所需的条件非常困难。有几种方法可以达到聚变条件，包括使用大磁铁在长时间尺度上捕获热等离子体，或者利用一组激光突然加热和压缩一小块冻结的聚变燃料，使其以球对称的方式内爆。这最后一种方法被称为惯性约束聚变，最近在结果上有了突破，世界上最复杂、最昂贵的激光被用来加热经过精确设计的聚变目标，使其达到引燃的程度，目标内部产生的热量短暂地足以维持聚变燃料的持续燃烧。然而，在目前的激光技术下，将这种方法应用于能源生产将是具有挑战性的。在牛津郡的First Light Fusion公司进行的新实验中，一种不同的融合方法正在开发中。不是激光从四面八方击中燃料舱，而是使用一枚高速炮弹从一侧击中经过特殊加工的金属和塑料目标。在目标内部，炮弹撞击产生的冲击波形成并集中，压缩和加热封闭体积的氚燃料。2022年4月，First Light Fusion发布了他们的第一个结果，表明这种方法提供了一条值得进一步研究的有前景的路线。我们的项目将帝国理工学院、牛津大学和约克大学三所大学与First Light Fusion合作，以及一家致力于人工智能技术的新公司-Machine Discovery-组成合作伙伴关系，将探索First Light Fusion方法中的挑战。我们将共同研究First Light Fusion目标中的热、物质和辐射的流动，这些目标具有复杂的界面，在从超过10亿个大气压到室温的巨大差异的材料压力之间，以及从数百万摄氏度到低于液氮的材料温度之间。通过探索这些令人兴奋的条件，了解热、辐射和物质如何在目标中流动，我们希望能够更好地模拟这些目标的行为。这将使First Light Fusion能够设计出产量更高的实验，从而为“并网”发电开辟道路。高当量实验将需要弹丸以数十公里/S的速度移动，这将通过使用巨大的电流脉冲(5000万安培！)以及由此产生的磁场将大片金属发射到这些超高速来实现。英国目前正在设计并将建造能产生如此大电流的GB 5亿发电机，帮助我国保持其在聚变技术和工业方面的世界领先地位。

Climate change driven by burning coal or oil, and fuel supply insecurity caused by international conflicts highlight the need to develop safer, cleaner ways of generating electrical power. Renewables and nuclear fission both play an important role here, but each has limitations. Wind and waves are subject to natural variations, while fission reactors require careful, long term management of dangerous waste.One attractive alternative for the future is fusion energy, harnessing the same nuclear reactions that power the sun. To create fusion on Earth we "burn" an isotope of hydrogen (deuterium, 0.03% of the mass in the world's oceans), a vast, easy to access fuel supply. The deuterium is combined with tritium (another hydrogen isotope) and under extremes of temperature, pressure and density these can fuse to form Helium and in doing so release huge amounts of energy. The reaction generates no greenhouse gasses, and is relatively clean with very short lived, easy-to-handle waste material, however the conditions required to create fusion are very difficult to make. There are several methods for getting to Fusion conditions, including using large magnets to trap a hot plasma over long timescales, or utilising an array of lasers to suddenly heat and compress a small pellet of frozen fusion fuel, causing it to implode in a spherically symmetric fashion. This last method, called Inertial Confinement Fusion, recently had a breakthrough in results, with the world's most complex, expensive laser, being utilised to heat a precisely engineered fusion target to the point of causing 'ignition' where heat generated within the target was briefly enough to sustain the continued burn of fusion fuel. However, with present laser technology it would be challenging to scale such a method to energy production.In new experiments at First Light Fusion, a company based in Oxfordshire, a different approach to fusion is being developed. Instead of lasers hitting the fuel capsule from all sides, a single high speed projectile is used to hit a specially machined metal and plastic target from just one side. Inside the target, shockwaves from the impact of the projectile are shaped and concentrated, compressing and heating an enclosed volume of Deuterium-Tritium fuel. In April 2022 First Light Fusion released their first results, demonstrating that this method provides a promising route that warrants further research.Our project brings together three universities, Imperial College, Oxford and York in partnership with First Light Fusion and a new company dedicated to AI techniques - Machine Discovery - to form a Partnership that will explore the challenges in the First Light Fusion approach. Working together we will study the flow of heat, matter and radiation in First Light Fusion's targets which have complex interfaces between vastly different material pressures, from over a billion atmospheres to room pressure, and material temperatures, from millions of 0C to those lower than liquid nitrogen. By exploring these exciting conditions and learning how heat, radiation and matter flow in the targets, we hope to be able to better simulate how these targets behave. This will enable First Light Fusion to design much higher yield experiments that could lead the way to 'on grid' power production. The high yield experiments will require projectiles moving at many 10s of km/s which will be achieved by using huge bursts of electrical current - 50 million amperes! - and the magnetic fields this creates to launch large strips of metal to these ultra-high velocities. The £500million generator to make such high currents is presently being designed and will be built in the UK, helping our nation maintain its position as a world leader in fusion technology and industry.