electrostatic ion accelerator

[starwarsmat]

Hello, I am planning on building an electrostatic ion accelerator by having a tube with parallel plate capacitors to have a negatively charge plate facing one direction and an electrode to generate the ions for repulsion. now my question is if I have the wire from the negative side of my high voltage source split so as to branch between the capacitor and the electrode would this decrease the voltage to either source? and my second question is what are ways to increase the charge density created by the corona from the electrode aside from just increasing the voltage into the electrode.

[Sensei]

To have nice corona discharge increase area by using array of pins (all connected).

f.e.

 

Corona discharge appears at positively charged electrode preliminarily (that has absence of electrons).
Because electrode is stealing electrons from neutrally charged gas medium.
It slowly starts going through medium (air medium that has stolen electrons is stealing again from their neighborhoods).
Where it happens we can see violet or blue photons.

I will try making slow motion video of this effect when I will be back from shop..

 

Here is video, 40000 volts:

On the left there is positive electrode (stealing electrons from air), on the right there is negative electrode.

 

Unfortunately didn't managed to take high speed, just regular.

 

On slow motion it's visible that thunderbolt goes from positive electrode to negative electrode.

 

After extending distance I had explosion of capacitor (also recorded on another video)

As always the same, the first one in ladder.

It's always scary thing when it happens.

Edited April 3, 2015 by Sensei

[starwarsmat]

Thank you for your response. What voltage source are you using for your experiments and and what material would be best for the array of pins to get the highest charge density or is the material irrelevant as long as it is a conductor?

Edited April 6, 2015 by starwarsmat

[Enthalpy]

The material needs sharp spikes, as these concentrate the electric field at their tip. The needle's length and area isn't important. The material would matter much in vacuum, but far less in air, and some small conductivity suffices. Graphite fibres are often used for being thin and decently strong.

[Sensei]

What voltage source are you using for your experiments

In video there was used approximately 40,000 Volts. Cockcroft-Walton generator. 120+ capacitors (0.13 usd per each).

Total costs 25 usd (capacitors, rectifying diodes, breadboards).

 

With smaller voltage there is needed smaller distance between electrodes to ionize medium.

3 kV is good for maybe 1-2 mm distance between them.

Don't let capacitors load for too long when spark doesn't appear, because you will have explosion of capacitor (a while after recording that video I wanted to record video of longer distance, and waited too long, and 1st capacitor in ladder exploded terribly).

I am using electrolytic capacitors so they start boiling when they're overloaded and it can be heard.

Shut down everything if they start making weird sound.

Couple seconds delay and there will be large explosion (could be even 20x20x20 cm^3 large).

 

After putting electrodes to test tube (and locking from both sides), frequency of electric arc spark appearing between electrodes will increase.

After attaching pipe to vacuum pump you can get even smaller voltage needed/largely increase distance between electrodes.

 

Be careful with Hydrogen (from electrolysis). Tiny amount of Oxygen that could get inside of tube while starting it, could blow up everything.

I had once such explosion.. Pieces of glass flied in all directions (and my head was 30 centimeters from explosion center).

 

and and what material would be best for the array of pins to get the highest charge density or is the material irrelevant as long as it is a conductor?

In video there was used iron. But you can experiment with different metals like copper, aluminum for a start.

f.e. carbon (graphite) will result in red electric arc, if I recall correctly,

and sodium will result in yellow electric arc.

 

Experiment with different materials, to see how they behave.

Put electrode to solution with different metal salt, for days or weeks, so it will gather on its surface, then try using as electrode.

Edited April 7, 2015 by Sensei

[starwarsmat]

Would the metal I use for the parallel plate capacitor matter as none of the formulas seem to take it into their equations only the permittivity of the region between the two plates?

[Enthalpy]

Essentially, no. It's mainly a matter of shape and of gas composition. So, take a long-lasting material.