# I Ion sensor for 1e20 ions/m3 density

Tags:
1. Nov 2, 2018

### 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?

Last edited: Nov 2, 2018
2. Nov 7, 2018

### PF_Help_Bot

Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.

3. Nov 7, 2018

### 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

4. Nov 8, 2018

### 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?

Last edited: Nov 8, 2018
5. Nov 8, 2018

### trurle

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

6. Nov 8, 2018

### 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?

Last edited: Nov 8, 2018
7. Nov 8, 2018

### trurle

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.

8. Nov 29, 2018

### Javier Lopez

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

9. Nov 29, 2018

### trurle

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