Plasmas are indissociable from microwave science. Effectively, the most fundamental properties of any plasma arise from its plasma frequency. However, combining plasma physics with electromagnetic (EM) wave propagation is challenging for physics students. An EM cavity poses an excellent opportunity to understand the behavior of EM standing waves, the issues related to transmitted and reflected power in waveguides, coupling, and how free charges in the plasma affect its resonant frequency and quality factor, interlinking the properties of matter with wave propagation. The inclusion of an external magnetic field allows students to explore the underlying principles of magnetic confinement in a linear geometry.

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The detector measurements that serve as a basis for the tomographic reconstruction of plasma radiation profiles can be affected by a number of issues. In this work, we are especially concerned about reflections inside the vessel that appear as direct incidences, when in fact those contributions come from points that are outside the line of sight of a detector. This problem occurs in devices such as ISTTOK, where the surface of the inner vessel acts as an optical system capable of reflecting light. To assess the contribution of those reflections to the detector signals, we used an experimental setup comprising a cylindrical gas-discharge lamp placed at several radial and angular positions inside the vessel. As detectors, we used two photodiode arrays, one placed on the equatorial plane and the other at the top of the vessel. At the same time, we modelled this experimental setup in a ray-tracing simulation software so that, once the experimental data agrees with the simulation data, we can use this simulated environment to study the effect of reflections in realistic plasma profiles. When properly calibrated, such simulated environment can be used to generate large volumes of high-quality data to train a neural network for plasma tomography.

Remote controlled laboratories had a great push during the COVID-19 pandemic. In fact, they were already out there but lacking in visibility. This external trigger pushed the academy to face a global challenge to start offering remote experiments more consistently and maturely. Instituto Superior Técnico (IST) has been offering several remote experiments since 2000 but with the need for an update due to technological aging. As such, the framework for remote experiments in education (FREE) was created based on new web technologies. In addition to the most diverse experiments that had already been developed, FREE includes two experiments that aimed at advanced-level physics students: the Langmuir probe and the electromagnetic (EM) cavity. Both allow users to configure the various parameters and to access the results in real time or check back later. All this access is done using a browser (on a PC or mobile phone) without the need to install additional software. The results of an experimental execution are stored in a database and are downloadable, allowing users to do various analyses and to determine the corresponding plasma density and temperature. In this paper, we will introduce how FREE was used in the implementation of both experiments and give an insight into their didactic approach, such as: (i) how to perform an experimental execution, (ii) the typical data set obtained with, and (iii) the corresponding analysis necessary for the user to retrieve information from it.