MSimon wrote:Yeah. I looked at your pictures. What exactly do they represent?
The colour map is local electrical potential. The arrows are electric field. It's axisymmetric around the vertical axis (the left side of the coloured area).
Here is my picture.
Great. Turn it 90 degrees counterclockwise and you have the one I modeled (the first picture has that ground arrangement).
When the alpha enters the drift tube it has 2 eV. Assuming it is traveling along the zero potential line where exactly is it going to get any energy? Is it going to climb the field lines without any work and then get accelerated by the aprox. 1 MeV drive voltage? What are the tunneling probabilities of that?
There isn't a zero potential line straight down the axis between the source and the target. If there were, no deceleration would occur because there wouldn't be any electric field along that line. As it is now, there's a 'hill' of potential that the alpha climbs (because of its high initial kinetic energy) and then goes back down the far side of (regaining all its kinetic energy in the process).
In fact if you will draw the field you would see that it actually would serve as a funnel for the alphas.
I DID draw the field. Well, the software did. Those arrows. It's not as easy to see as lines would have been, I guess, but all you really have to do is look at the colour gradients, because those are the field (the potential gradient) too.
Yes, there's a funnelling effect. No, it doesn't have the result you describe.
You cannot understand electrostatic accelerators without drawing the eqipotential lines.
Actually, you can see those because the quality of the plots isn't super high. They are the divisions between colours.
Particles can change velocity without doing work. They can not change speed without doing work. Something about 1/2 mv^2. Constant magnetic fields are conservative because they change velocity without changing speed. Electrostatic fields (if you cross the field lines) are not conservative because work is being done. Speed changes not just velocity.
That's not what "conservative field" means. Maybe you should Google it...