[rolnor]

And what happens if they are not confined, they will be become a very thin gas? It must be possible to model this.

[Borek]

Simple physics.

But start by estimating force with which one mole of Cl- anions (so basically 96500 Coulombs) repels other mole of Cl^- if kept at 1m from each other. Compare that number with the force with which Earth attracts Moon.

Good luck preparing sample of pure Cl^- larger that just few atoms

[rolnor]

So it will maybe be like an explosion if you gave a conc. sample and release the pressure. But will be a gas, afterwards, a very thin gas. I consider the force keeping the ions together is the gravity on earth. The coloumb force decrease with the squared distance so it will not be endlessly strong force repelling the ions.

[Borek]

I consider the force keeping the ions together is the gravity on earth.

To some extent, but gases expand to occupy whole available volume.

The coloumb force decrease with the squared distance so it will not be endlessly strong force repelling the ions.

Have you compared the numbers I suggested you to calculate?

[rolnor]

No, but have you thought what happens if the ions are separated by 10cm? The coloumb forces are not so strong then. I am talking about really thin gas. You can have a beam of electrons that is dense, and these also repell with the same force as Cl- ions, this beam does not spread immediatly.

[Borek]

Sure, doable, that's a high vacuum, interstellar plasma, whatever. That falls into what I call "exotic conditions". And it would still attract everything with positive charge, so it won't last.

[rolnor]

I sad thin gas, and I am was right. Read my updated post about electron beams.

[Corribus]

Electron beams and ion beams are confined and focused using strong electromagnetic fields. Once the field is gone, the ions diverge immediately.

[rolnor]

No, I have seen electronbeam that is a straight line without magnetic field. It was an experiment where you direct a electron beam on a rotor and this starts to spinn, it proves that electrons have mass.

[Borek]

No, I have seen electronbeam that is a straight line without magnetic field.

And how was the beam generated?

Sure, once they leave the magnetic field they can travel together for a short time, but the beam diverges quite fast. In no way you could call it stable. It looks stable only because they move at high speed so they have no time to diverge before hitting the target. Electrons in an old CRT monitor travelled at speeds measured in tenths of c, it took them just a few ns to reach the target.

Again: do the calculation I suggested. Just a mole of ions, small fraction of what you have inside

[Corribus]

@rolnor

The electron beam appears straight in the sense that you know where the beam is produced and you can draw a straight line between it and your target. But the beam is not perfectly collimated.

I thought to make an argument based on beam divergence angles. A laser (which shapes light by matter-based optics) has a beam divergence based on fundamental properties of light; a typical green laser pointer has divergence typically on the order of about a milliradian, or ~0.05 deg. See for example this one by Edmund Optics. All particle beams have divergence, not just lasers. I’m no expert but here’s an example of a divergence angle measurement on an electron beam (Kim et al 2020 Nuclear Inst. Methods Phys. A, 953, 163054): they measured approx. 2 deg. That’s several orders of magnitude higher divergence in a high-powered electron beam than an inexpensive laser pointer. I found similar values for some positively charged ion beams, e.g. here (Pai and Venkatramani, Rev Sci Inst. 1992, 63, 5234).

Now I have to stop and give you a big sarcastic thank you, rolnor. It was about this point I got lost for three hours reading about the physics of charged particle beams. At first I assume the large divergence in electron beams was due to simple Coulomb repulsion; squeaky clean argument.  But (no surprise) it seems to be due to much more goofy quantum s#*$ than that. The article I linked to on electron beam divergence angles attributed the divergence to the property called ‘emittance’. So I looked that up and got thoroughly shot down the rabbit hole like I was fired from (ha) an electron gun. If you don't believe me, just google "particle beam emittance". Yikes. Anyway, long story short, the equations for transverse momentum components of the high energy beam emittance do indeed contain a factor proportional to the particle charge (example, but don't say I didn't warn you), so … yeah... I guess I was kind of right. Even though it hardly feels like a victory 😉.

[rolnor]

But was I wrong?

Its nice that you go to such a length in your study of electron beams.
If coloumb forces in a beam would be enormous the electrons would still spread out even in a few nanoseconds, a magnetic field have this effect, this is how an old TV works to create the image in the screen?
You see the copper coil-wire in this image, the magnetic field generated spreads the beam If you get a ordinary permanent magnet close to a old TV-tube, the image gets distorted.

https://www.google.com/search?q=tv-tube&rlz=1C9BKJA_enSE868SE868&oq=tv-tube&aqs=chrome..69i57j0l3.6006j0j4&hl=sv&sourceid=chrome-mobile&ie=UTF-8#imgdii=zXZBc69bBUMnHM&imgrc=6CadaTBRK_Fv7M

[rolnor]

You state it would be a interstellar vaccum-gas. Thats a thin gas so why are you arguing? You agree with me obviously?

[Borek]

Two people read your statements as "ah, these charges don't mean anything, nothing to fuss about", when the situation is exactly the opposite - they are the most important, game changing elements of the situation.