RF excited ion sources
Posted: Tue May 23, 2017 3:15 pm
This is answer some questions from Werner
"@John: You are right! But I did not use the controlling boards. The reason for choosing the BLF188XR was its robustness versus Price. The right device for a plasma generator! Are you also going to use it for this purpose - or just for ham?
I just read that you are very good in designing RF devices: I still do not know how to design the antenna for the plasma. My first idea was just trying to use a copper pipe with 14 turns and give it a try - using the tuner. I also thought about calculating a kind of resonance frequency resulting out of the geometry – but did not succeed. Next try was to use a spectrum analyzer with a VSWR bridge to measure the resonance frequency - did not work. What do you think will be the right way to focus on – from your experience?
BR,
Werner"
Werner looking at your coil it has too many turns about 4 -6 turns is normal. Also ICP systems usually make the coil from copper pipe that contains cooling fluid as the circulating current in the coil is hundreds of RF amps
No you cannot wind the coil on a copper pipe as the pipe acts as a shorted turn which will reduce your circuit Q to zero or like in ordinary transformer speak a shorted turn.
you can also think of using CCP instead of ICP. ICP generally is harder to get the plasma to strike where with capacitivly coupled plasma it lights the plasma staight away.
CCP and ICP ionize through different mechanisms the CCP works with the electric field and the ICP works on the magnetic field component of the electromagnetic wave.
The amplifier i'm making will be used for ham and rf ion source experiments @ work. There is now a new fet the MRF1K8 that is a drop in replacement for the BLF188XR which takes you to 1800 watt if you raise the VDD to 65 volts you can use the W6PQL boards as they are.
Of course you can get further improvement in your ion current by also using a permanent or solenoid coil magnet to help squeeze the plasma into a more concentrated state.
"@John: You are right! But I did not use the controlling boards. The reason for choosing the BLF188XR was its robustness versus Price. The right device for a plasma generator! Are you also going to use it for this purpose - or just for ham?
I just read that you are very good in designing RF devices: I still do not know how to design the antenna for the plasma. My first idea was just trying to use a copper pipe with 14 turns and give it a try - using the tuner. I also thought about calculating a kind of resonance frequency resulting out of the geometry – but did not succeed. Next try was to use a spectrum analyzer with a VSWR bridge to measure the resonance frequency - did not work. What do you think will be the right way to focus on – from your experience?
BR,
Werner"
Werner looking at your coil it has too many turns about 4 -6 turns is normal. Also ICP systems usually make the coil from copper pipe that contains cooling fluid as the circulating current in the coil is hundreds of RF amps
No you cannot wind the coil on a copper pipe as the pipe acts as a shorted turn which will reduce your circuit Q to zero or like in ordinary transformer speak a shorted turn.
you can also think of using CCP instead of ICP. ICP generally is harder to get the plasma to strike where with capacitivly coupled plasma it lights the plasma staight away.
CCP and ICP ionize through different mechanisms the CCP works with the electric field and the ICP works on the magnetic field component of the electromagnetic wave.
The amplifier i'm making will be used for ham and rf ion source experiments @ work. There is now a new fet the MRF1K8 that is a drop in replacement for the BLF188XR which takes you to 1800 watt if you raise the VDD to 65 volts you can use the W6PQL boards as they are.
Of course you can get further improvement in your ion current by also using a permanent or solenoid coil magnet to help squeeze the plasma into a more concentrated state.