corona between their interfaces it can be important to keep a material such as macor away from the discharge as such a material can tend to u201c flake off u201d particles when exposed to a discharge silica thus can be preferable for certain applications since aluminum has a thermal expansion coefficient of approximately three times that of macor it can be important to leave about 0 001 to 0 002 of an inch clearance between the ends of the electrode and the trench machined in the macor into which the electrode is placed no corona was found to occur within this separation up to a pressure of about 600 torr with the application of 12 kw of rf peak power at 100 mhz in a 2 5 microsecond wide rf pulse deposited into a discharge contained within a 1 5 mm deep by 3 0 mm wide beo wave guide for larger clearances between the ends of the electrode and the trench machined in the macor or at sufficiently higher rf energy deposited into the discharge corona did occur in the separation in such cases the corona within the separation could be extinguished by reducing the inductances of the last coils on each end of the electrodes lowering the inductance of these two inductors in effect lowers the voltage on each end of the electrode without causing an appreciable.