Maintaining the Goal to Approach Ignition Conditions

Given the limitations of relevant theory and available experimental results at the current stage of fusion research, reaching regimes close to ignition conditions is necessary in order to investigate the physics of meaningful fusion burning plasmas. Among various options considered at the present, the line of axisymmetric high magnetic field, and compact machines remains the most promising and realistic for this objective, with the adopted demonstrated ability to produce high pressure, well confined and pure plasmas. Ignitor, the first machine to be proposed and fully designed [1] for this goal, has adopted well proven high temperature superconducting magnets (MgB2) for its largest poloidal field coils [2]. When considering different superconducting materials [3] for the other higher field coils, the guiding concern is the difficulty to include an adequate protection system against the onset of quench events. In particular, given the combination of high magnet currents and compact dimensions (e.g. major radius $R₀\sime1.32m$) estimated to be needed in order to approach ignition, the chosen option remains that of the Copper solution [2] for both the toroidal magnet and the central solenoid. Another key component of the machine that is in need to be upgraded is the ICRH system as it can lead to optimize [2] the heating approach to ignition and to access non-thermal fusion burning processes [4].

[1] B. Coppi, Comments Plasma Phys. Cont. Fusion, 3, 47 (1977).

[2] B. Coppi, A. Airoldi, R. Albanese, et al., Nucl. Fusion 53 104013 (2013).

[3] P. Bruzzone et al., Nucl. Fusion 58, 103001 (2018).

[4] B. Coppi and B. Basu, Nucl. Fusion 64, 126037 (2024).