Putting next generation fusion materials on the fast track

当氦在高温下由氢和氚聚变产生时，会释放出大量的高能中子，就像我们的太阳一样。如果受控版本能够在地球上实现，这将有望解决世界的长期能源需求。库勒姆的JET是利用气体等离子体进行磁约束聚变的主要实验堆之一，也是设计国际热核实验堆ITER的重要一步。英国的核聚变技术现在走上了快车道，将需要新一代材料来建造商业反应堆。热核实验堆材料的选择是以几年前提供的材料为基础的，但在决定是使用耐等离子体侵蚀但容易受到辐射损坏并也污染纯等离子体的高温金属时，还是使用有毒(铍)或更容易被侵蚀并可能吸收大量氚燃料(石墨)的轻元素时，需要进行权衡。我们希望为下一代建立材料能力，特别是利用我们在钻石薄膜方面的能力，将碳设计为面向等离子体的墙体材料。该方案旨在利用金刚石的高温稳定性、抗辐射、高原子密度和在氢等离子体存在下无与伦比的化学稳定性等独特性质，在碳砖上大规模涂覆金刚石，以降低侵蚀速度、粉尘形成和氚吸收。这种解决方案能够优先使用低原子序数的面向等离子的材料。碳结构的计算模型将补充实验计划，以优化暴露在辐射下的复合功能材料的化学和物理结构。如果成功，这种方法将使反应堆能够在部件更换之前运行更长的时间，而不会影响氚库存。

Enormous numbers of energetic neutrons are released when helium is produced by the fusion of deuterium and tritium at high temperatures, as in our Sun. This promises to solve the World's long-term energy needs if a controlled version can be carried out on Earth. JET at Culham has been one of the leading experimental reactors for magnetically confined fusion using gaseous plasmas, and has been an important step towards designing the international thermonuclear experimental reactor, ITER. UK fusion technology is now on the fast track and will demand a new generation of materials for commercial reactor construction. The selection of materials for ITER has been based on those available some years ago, but there are trade-offs in deciding whether to use high temperature metals that are resistant to plasma erosion but liable to be damaged by radiation and also contaminate the pure plasma, or to use light elements that are toxic (beryllium) or more easily eroded and may absorb significant amounts of tritium fuel (graphite). We want to establish a materials capability for the next generation, and in particular to exploit our capability in diamond films as a route to designer carbons as plasma-facing wall materials. This proposal intends to coat carbon tiles with diamond on a large scale, in order to lower the erosion rates, dust formation, and tritium absorption, by using the unique properties of diamond, namely high temperature stability, radiation resistance, high atomic density and unsurpassed chemical stability in the presence of hydrogen plasmas. This solution enables the preferred use of low atomic number plasma-facing materials. Computational modelling of carbon structures will complement the experimental programme in optimising the chemical and physical structure of a composite functional material exposed to radiation. If successful, this approach would enable reactors to operate for longer periods before component replacements and without compromising the tritium inventory.