Advanced high-magnetic field nuclear fusion reactors

Fusion power offers the prospect of an almost inexhaustible source of energy for future generations. Although this may be true, it also presents so far insurmountable scientific and engineering challenges. Under these circumstances, today, many countries take part in fusion research to some extent, led by the European Union, the USA, Russia and Japan, with vigorous programs also underway in China, Brazil, Canada, and Korea. Nuclear fusion reactor studies are mostly devoted to the Deuterium-Tritium (DT) fuel cycle. Neutron-induced transmutation of materials in a DT fusion power plant will give rise to the potential for long-term neutron-induced radioactivity in structures. To ensure the attractive safety and environmental characteristics of fusion power, careful design choices are necessary: the reliance on deuterium and tritium as the sole fusion fuels must be reconsidered, given the recent availability of new superconducting materials at high temperature, which could enable to obtain the high magnetic fields necessary for the confinement of Deuterium- Helium3 (DHe3) plasmas. As a first step to explore the possibilities of DHe3 plasmas, a DT burning plasma experiment at high field and plasma densities, which can be much closer to the required parameters than present-day experiments, is particularly attractive. Compact high-field experiments were the first to be proposed in order to achieve fusion ignition conditions based on existing technology and the known properties of high-density plasmas: in previous studies, a feasibility study of a high-field DHe3 experiment of larger dimensions and higher fusion power than Ignitor, however based on Ignitor technologies, brought to the proposal of the 4 Candor fusion experiment. Unlike Ignitor, Candor would operate with values of poloidal beta around unity and the central part of the plasma column in the Second Stability region. The toroidal field coils are divided into two sets of coils and the central solenoid (air core transformer) is placed between them in the inboard part. In the recent years, a new generation of reactor designs has emerged. At the MIT, an innovative design was created: ARC, the Affordable Robust Compact reactor, and the SPARC experimental tokamak. ARC takes advantage of the recent progress in fusion technology, such as high temperature superconductors, that permit to decrease the dimension of the machine, reaching at the same time high magnetic fields. In this work, a revised design of Candor is proposed, based on the new technologies: this tokamak is capable of reaching DHe3 ignition on the basis of existing technologies and knowledge of plasma, without any optimistic extrapolation.