Abstract: A plasma torch for the treatment of gases of particles, or for the deposition of particles onto a substrate, which has two concentrical electrodes coaxially mounted onto a support. The gases or particles to be treated or deposited are injected through an injection passage that is coaxial with the central electrode and opens centrally into an outlet nozzle so as to inject the gases or particles centrally and coaxially within the center of the flame torch without unduly affecting the characteristics of the plasma. In use, the central electrode extends well downstream of the peripheral electrode, whereby the electric arc may not block the injection passage. Moreover, a magnetic field is generated externally to the electrodes in the direction parallel to the annular passage defined between the electrodes in order to rotate the electric arc within the passage and thus reduces the erosion of the electrodes while ensuring better heating of the plasma gas.