Design of an ech system for a small modular stellarator

Summary form only given. Electron cyclotron heating (ECH) is one of the most common methods used for heating stellarator plasmas, providing both ionization for startup and net-current free heating during the discharge. This paper presents the design of the ECH heating system for the SCR-1, a small modular stellarator under construction at the Instituto Tecnológico de Costa Rica (ITCR) University in Costa Rica. The SCR-1 is a small (Major radius 238mm, mean plasma radius 42.2mm) low budget device, using a 2 period magnetic field with rotational transform (iota=0.3), a peak field strength of 8.78×10<;sup>;-2<;/sup>; T and expected to achieve a 15eV temperature.The heating system will eventually be composed of two magnetrons operating in CW mode at the first harmonic frequency of 2.45 GHz. The first phase of the project will see a 2kW system installed, with a future addition of a second 3kW magnetron on a separate beam-line to give a nominal total of 5kW output power. The current design focuses on the first magnetron and beam-line which will consist of a three phase power supply unit with a microcontroller for over current detection and power percentage control and an Alter Power Systems water cooled CW magnetron working at 2.45GHz with a max power output of 2kW. It will be carried to the torus through a waveguide with an R26/WR 340 industrial isolation system with water load and a monitoring probe for magnetron safeguard, a directional coupler measurement system and an aluminium WR 340, 3 stub tuner for impedance coupling finally to meet the torus quartz λ/2 window. The main aim of this design is to optimize the efficiency of the energy transfer process by reducing the refraction coefficient and optimal tuning of the impedance coupling; and to ensure suitable skin depth to heat the core of the plasma. We present calculations of skin depth, complex refraction coefficient and collisionality in a set of different density profiles- with an average value of 7.45x10¹⁶ m^-3. The analysis is made with the aid of software simulations to obtain the magnetic surfaces and thus optimize the selection of ECH power injection angles.