Description
The Novatron is an innovative mirror-cusp device which theoretically overcomes the major challenges limiting the classic mirror machines. Interchange instabilities and neoclassical transport losses are resolved in Novatron due to the favorable magnetic curvature and axisymmetric geometry [1,2]. In addition, the physical aspect ratio of the device enables a large plasma to Larmor radius ratio, suppressing DCLC instabilities. Therefore, the Novatron has the potential to confine stable fusion plasmas.
The first machine of its kind, N1, has been constructed at the Alfvén Laboratory at the Royal Institute of Technology (KTH) Stockholm, Sweden. The ability to switch between magnetic field configurations in N1, from an ill-curved magnetic geometry into the favorable Novatron magnetic configuration, offers a means to demonstrate the outperformance of the Novatron topology. To study our plasma, we have commissioned several types of diagnostics, i.e., multiple Langmuir probes, cameras, Balmer-line filtered photodiodes, an interferometer system, vacuum gauges, and a spectrometer.
Hydrogen-fueled gas ionizations with excellent repeatability have been successfully carried out in N1, and the data of all mentioned diagnostics has been acquired. The experimental architecture consists mainly of two parts: an experiment controller system, and a data storage and management system. The first comprises a LabView based structure from which we can control all the initial experimental parameters, e.g., magnetic strength, fueling, and ECR heating. This permits the triggering of diagnostic subsystems with precise temporal synchronization. The second one is an SQL database with a HSDS backend into which datasets of all diagnostics are stored and managed for post processing analysis.
Here we will present the first commissioned datasets of the above-mentioned diagnostics and extracted plasma parameters. We pose a strong focus on the ionisation of neutral gas, and how this ionisation behaves under various initial experimental parameters, such as ECR heating power, initial gas pressure, or magnetic configuration.
Further improvements to each diagnostic will provide us with more information about plasma shapes, confinement, and instability tests. At the same time, upgrades to the N1 machine (such as ponderomotive plugging and ICR heating) will improve its confinement and plasma heating capabilities.
[1] K. Lindvall, et al. ‘Novatron: Equilibrium and stability’, Phys. Plasmas 32, 072509 (2025)
[2] J. Jäderberg et al. ‘Introducing the Novatron, a novel fusion reactor concept’. Preprint, arXiv 2310.16711, 2023