Supply of a wide range of plasmas e.g. for use in biological processes by supplying a barrier discharge using sequentially adjustable phases

摘要

A process and apparatus are claimed for supplying a dielectrically hindered (barrier) discharge over the greater part of each discharge half period such that the pulse-, constant- and fadeout-current phases can be adjusted in sequence. Provision of a dielectrically hindered (barrier) discharge using a change-over switch (2) and a transformer (3) for energy adjustment is such that the discharge device (4) has positive and negative current half-waves (A) of controllable frequency comprising: (i) pulse current phases (B) with a steep current increase from the opposed polarity or from zero which falls off to a value above zero or to an initial value for the following phase; (ii) a constant current phase (B) of value above zero; and (iii) a decay or fadeout current phase (D) of length controlled by the maximum time of phase (C). The process is such that: (a) phase (B) is mainly obtained from the apparent energy of the barrier discharge (5) obtained from the discharge volume (1) as well as the contiguous parasitic capacitative elements and has its amplitude and frequency set by further parasitic inductive elements; (b) the phase (C) amplitude is determined by a transformed, proportionally adjusted and inductively smoothed direct current (6); (c) the period from zero to the maximum of the phase (C)-controllable phase (D) is periodically raised by voltage limitation to a value (E) and is directed to the smoothed direct current (6) which is determined by a unipolar variable alternating input voltage (F), this effect alternatively being achieved by lengthening the positive and/or negative conductive period of the half waves (A) obtained using the switch (12), this decreasing the amplitude of the current; (d) the positive and negative half waves (A) are obtained by alternating the direct current with a limited variable frequency such that the conductive period of the switch (12) is the same as, or greater than, the period of the adjustable variable frequency; and (e) adjustment to the impedance of the dielectrically hindered discharge follows by low leakage transformation of the discharge-providing high voltage. An Independent claim is also included for the apparatus.