RF power supply and impedance matching

[dee25pak]

dear steve_rb you have made the coil and ignited the plasma using it. whether you had measured Q of the coil, before using it? if yes what is the effect of Q of coil on the ignition of the plasma. Whether you tried to maximize the Q of the coil at the time of winding?

 

[steve_rb]

no. I have no experience with Q. I haven't measured Q and have nothing done about Q. How can I measure the Q and How should I maximize it?

 

[steve_rb]

What I found recently is importance of the ignitor. I fond ingnitor should be made such that to creat a long axial momentary arc for plasma successfull start. Ignitor arc lengt should be equal to the torch flame lenght. Most places I have seen they have used tesla coil for this but in recent ICP spectrometers I am not sure how to creat this long arc. Anyone has anything to add?

 

[dee25pak]

The Q of an inductor is defined as the ration of its reactance to resistance. ie. jwL/R.
But the real inductor at high frequency also have a parasitic capacitance associated with it. Because of presence of this capacitor even a simple inductor acts like a resonant circuit and shows resonant behavior. The Q of the inductor is zero at the resonant frequency. So the inductor design should be such that the operating frequency must be very much less than the first resonant frequency of the inductor with possibly maximum Q at the operating frequency.

 

[steve_rb]

What you have mentioned is in theory but I need practical hands on advice.
My RF generator is 13.56 MHZ and I have seen most coils in this frequency have two or three turns and they made of 6mm OD copper tubing. Coil winding diameter is about 50-60 mm. I have no experience with designing such coils and I need help with this. At least a simple rough design indicating steps I should follow for designing the coil will be appriciated?