First homemade grid for TCV diagnostics
The Swiss Plasma Center has produced the first entirely Swiss-made grid for Diagnostic Neutral Beam Injector (DNBI), a key component of the neutral beam injector which is used for plasma properties measurements.
Originally manufactured in Russia, the DNBI on TCV faced performance issues due to a deformed grid of the ion optical system. In response, Matthieu designed the replacement grid with support from SPC Neutral Beam Injector (NBI) scientist Aleksandr L. The grid was machined by Vincent at our mechanical workshop and installed in August 2024.
Early tests suggest improved beam quality, and if these results are confirmed, this first high-precision grid could mark a step toward developing and producing new ion optical systems at SPC, not only for TCV neutral beams but also for similar NBIs in labs worldwide.
Optimizing power transmission: the “Matching Box”
For various experiments, the Low Temperature Plasma Physics and Applications group uses a device that optimizes power transmission between a radio-frequency (RF) generator and a resonant antenna, used to generate ‘cold’ plasmas.
This device, called a ‘Matching Box’, primarily consists of two adjustable vacuum capacitors, two water-cooled coils, and an I-V-phi probe that characterizes the input impedance of the matching box.
In collaboration with the SPC Electronics Service, a control unit was developed and implemented to operate two stepper motors coupled to these variable capacitors.
This unit continuously adjusts the position of the motors, maintaining the RF system’s input impedance at 50 ohms, thereby transferring the maximum amount of power to the antenna, which then induces the plasma.
Particular attention was paid to the microcontroller integrated into this unit.
An Arduino architecture with open-source code, easily accessible, facilitates future developments as well as adaptations to various machines at SPC or for international collaborations. Currently, about ten of these controllers have already been adapted to RF systems.
Latest prototype conductor at PSI
For more than 10 years, the Applied Superconductivity Group in Villigen has been developing conductors for the EUROfusion DEMO tokamak. In May and July 2024, Federica Demattè tested the latest prototype conductor aiming to reach 100 kA in 11 T magnetic field in the SULTAN test facility as part of her PhD Thesis.
Even though the performance of the conductor was jeopardized by the underperforming Nb3Sn superconducting strands, out of which the cable was manufactured, the low AC losses confirm that our “react&wind” conductor design is suitable for both toroidal coil and central solenoid.