Device for producing a plasma comprising a plasma ignition unit

A device for producing a plasma, configured to generate a plasma from a reaction gas, wherein the device for producing a plasma comprises:

• a microwave generator operating a source wave at a given source frequency comprised within a microwave frequency range;
• a waveguide coupled to the microwave generator and configured to guide an excitation wave;
• a dielectric tube extending longitudinally along an axis of extension, the dielectric tube being configured to receive the plasma, such that the dielectric tube passes right through the waveguide;
• a duct, configured to envelop the dielectric tube so as to hold said dielectric tube in position;
• and
• a reaction gas injection unit configured to introduce the reaction gas into the dielectric tube;
• the device for producing a plasma further comprises a plasma ignition unit comprising:
• an ignition electrode extending longitudinally along the axis of extension and comprising a proximal body portion and a distal body portion, wherein the distal body portion comprises a securing member;
• a securing unit made of dielectric material configured to receive the securing member of the ignition electrode;
• and
• a moving unit configured to receive the securing unit and to move both said securing unit and the ignition electrode together from a first position in which the ignition electrode is outside the waveguide to a second position in which at least one part of the proximal body portion of the ignition electrode is disposed in the dielectric tube and in the waveguide;
• wherein the ignition electrode is configured to generate an electric field from the excitation wave and allow ignition of the plasma when said ignition electrode is in the second position;
• and
• wherein the ignition electrode has an overall length along the axis of extension which is comprised between 35% and 65% of a source wavelength corresponding to a celerity of the source wave divided by the source frequency.