# A Magnetic field for thin plasma column confinement

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1. Nov 4, 2018

### Javier Lopez

I have a thin copper tube of 4.4mm inner diameter (inside a long ionizer plasma cannon) and I want to fill in with hydrogen plasma fully ionized at low temperature (100eV), what is recommended magnetic field to have the ions there without touching tha walls?
The plasma life is about 0.5 seconds

2. Nov 4, 2018

Staff Emeritus
You clearly have a piece of instrumentation you don't understand. Posting many messages, each with one tiny aspect of the problem but none that give the whole picture is probably not going to be helpful.

3. Nov 5, 2018

### Javier Lopez

I need a high throughput ion gun as part of the system. I have more troubles, as the magnetic field needed to maintain the protons frar of the container. My idea is to have about 0.2 teslas. It should help having the formula of how many ions would scape as a function of density, ion temperature, percentage of + ions and magnetic field, if not I will try to obtain it and place here.

Here is one of the ideas I could try. The grid is submitted to AC to increase the throughput. In red there is an RF antenna at 2.4GHz to heat the H2 to more than 10 eV. There is also a DC between antenna and grid that I not draw. (I have to isolate part of the tube at right of the grid but PTFE does not work well with H2 or protons):

In theory the pressure is given by $$P=\frac{B^2}{2\mu_0}$$
But in practice it is recommended to increase 5 times. There is a calculus of the confinement time here:
https://www.researchgate.net/public...rmula_and_excel_tables_for_plasma_physics_V07
Formula number 340.

I have about 0.1-2 pascals of H2 but after ionizing and increasing the temperature the pressure is increased also.

Last edited: Nov 5, 2018