Ion sensor for 1e20 ions/m3 density

[Javier Lopez]

What kind of ion sensor can I use in the range 1e19to 1e22 ions/m3?
(corresponds to 0.1 to 5 pascals if non ionized)
Does it exist any sensor based in the charge capacity?

 

[trurle]

You can measure up to 4e19 densities by detecting plasma cutoff (resonance) frequency with network analyser; for higher densities i afraid you need conduction-based measurement setup - basically cold cathode ionization gauge, but biased well below breakdown to measure ions only

 

[Javier Lopez]

thank you, I will look for that and write about here
Does the resonance is related to ion gyroradius in a magnetic field? How to avoid electron running in opposite direction?
There is any ion density probe based on space charge?

 

[trurle]

thank you, I will look for that and write about here
Does the resonance is related to ion gyroradius in a magnetic field? How to avoid electron running in opposite direction?
There is any ion density probe based on space charge?

No, resonance i mean is Langmuir waves (do not mistake with completely different Langmuir probe method)

 

[Javier Lopez]

Very good! that works also with ions, not only electrons!.
I suppose this is the formula (where e & m are charge in coulombs and ion mass in Kg):
$$n_0=\frac{w^2*\epsilon_0*m}{e^2}$$
Do you use V2 to send and V3 langmuir probe to receive?

 

[trurle]

Very good! that works also with ions, not only electrons!.
I suppose this is the formula (where e & m are charge in coulombs and ion mass in Kg):
$$n_0=\frac{w^2*\epsilon_0*m}{e^2}$$
Do you use V2 to send and V3 langmuir probe to receive?

Yes, the equation above is for Langmuir wave frequency conversion to concentration.
Regarding second question, i do not completely understand but likely it related to triple Langmuir probe. It is a specialized setup and i did not use it before.

 

[Javier Lopez]

There are some Langmuir tripole probe with 4 electrodes, what is the function of the 4th pole?

 

[trurle]

Looks like scanning probe - a switchable electrode array. Roles of each electrode is user-defined.