POPS

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
longstreet
Posts: 165
Joined: Sun Aug 07, 2005 5:35 am
Real name:
Contact:

Re: POPS

Post by longstreet » Mon Oct 31, 2005 4:43 am

I haven't quite figured out what they are doing. Some grid designs I've seen in the context of POPS has either negative or positive inner grids. Both inject electrons into the chamber and modulate the voltages in some way, but I haven't really understood what these all have in common. At first I thought they were just trying to stabalize the old virtual cathode idea of electron confinement, but it seems there is something different going on.

DaveC
Posts: 2346
Joined: Sat Jun 30, 2001 5:13 am
Real name:

Re: POPS

Post by DaveC » Mon Oct 31, 2005 6:23 am

Interesting writeup. In the paper's acknowledgements, there is a mention of thoriated -tungsten wire. This is normally used for filaments, giving good output, at temperatures about 1000K cooler than pure tungsten. Wondering, if they are making grids or cathodes out of the wire.

Dave Cooper

longstreet
Posts: 165
Joined: Sun Aug 07, 2005 5:35 am
Real name:
Contact:

Re: POPS

Post by longstreet » Mon Oct 31, 2005 8:31 am

I think I understand what they are trying to do. The potential in a normal fusor looks like the bell of a horn. But what they want to do is make the potential into a parabola.

As you know from intro physics, any parabola shaped potential energy curve can cause simple harmonic motion. And this means that frequency is independant of amplitude by definition (meaning it has a natural frequency). So, what they do is create such a parabola shaped potential using a distribution of electrons and then drive the thing at it's natural frequency.

It sounds interesting. But I have questions on the actual dynamics of any ions you put in there since their presence alters the potential well. I'm not 100% convinced you can really maintain a parabolla potential if the net charge density is continually changing with the plasma sphere's size.

edit...

I happened to think now that the harmonic motion is really of the size of the plasma sphere and not of the individual ions. So it does make sense, just not in the sense of a single positive ion flying through a parabola shaped potential well. Equilibrium for the plasma sphere is when the ions are evenly distributed throughout the electron field.

Thanks,
Carter

User avatar
Adam Szendrey
Posts: 1333
Joined: Fri Mar 29, 2002 10:36 pm
Real name: Adam Szendrey
Location: Budapest, Hungary

Re: POPS

Post by Adam Szendrey » Mon Oct 31, 2005 11:50 am

And they want to make it modular, with several plasma convergence points. We discussed something like that on these forums aswell. And yes, i have read that too, in a book...it seems there is more truth to it than i thought.

"By applying rf fluctuation to the grid voltage..."
Exactly what i have read...Maybe some of you remember a discussion about modulating the grid voltage in order to trigger an oscillation.

Adam

User avatar
Richard Hull
Moderator
Posts: 11713
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: POPS

Post by Richard Hull » Tue Nov 01, 2005 2:30 pm

Discussions regarding modulating or pulsing the grid in a fusor go back to biblical times on all three fusor sites. Each wave of newbies kick the idea back out onto the playing field.

Lots of ideas, but I have yet to see any one do it, or if they did, they supplied zero data that was of any value in support of the idea.

Hell, someone might actually look into it one day via empirical experiment and report back.

Inquiring minds want to know.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

User avatar
Adam Szendrey
Posts: 1333
Joined: Fri Mar 29, 2002 10:36 pm
Real name: Adam Szendrey
Location: Budapest, Hungary

Re: POPS

Post by Adam Szendrey » Tue Nov 01, 2005 7:46 pm

Well if i can get things together in the college lab, i might be able to contribute...But i don't want to make an ass of my mouth, so i just say "maybe"...

Adam

DaveC
Posts: 2346
Joined: Sat Jun 30, 2001 5:13 am
Real name:

Re: POPS

Post by DaveC » Wed Nov 02, 2005 8:57 am

I don't know if it applies in this case, but some types of plasma systems oscillate at fairly high natural frequencies, 100 or more KHz. But it is not the plasma that's driving the oscillation, but rather the stray inductance in the power supply, is coming into resonance with the capacitance that usually attends the gas discharge system. For Barrier Discharge lamps, this is how the lamp capacitance is determined when the plasma is formed.

After reading the material posted, it would seem that they are claiming the resonant oscillations tend to bring the ions into some sort of phase coherence..which improves the output.

This could also be a result of oscillation induced compression increase or it could be a resonance with their HVPS. Not easily separated, I wouldn't think.

Dave Cooper

User avatar
Donald McKinley
Posts: 185
Joined: Wed Nov 02, 2005 3:53 am
Real name: Donald McKinley

Re: POPS

Post by Donald McKinley » Mon Nov 07, 2005 1:03 am

from the web article link in Mike Smiths first post in this thread:

"Tuning the "external" radio-frequency (rf) electric fields to this naturally occurring mode allows the ion motions to be phase-locked."

Sounds like they put a maritime radio tuner up to the fuser, picked up the loudest harmonic, and started amplifying back to the fuser.

They are just attempting to resupply the energy that is lost from coulomb interactions by baking the fuser in a resonant frequency rf oven. They aren't even introducing resonance. The resonance already exists.

It seems that the plasma should already be phase locked, correct me if I'm wrong, otherwise it wouldn't form virtual cathodes and anodes.It looks like the new part is the concern for measuring resonances (a la Tesla) and applying the knowledge to "poke" the fields.

Interesting experiment. This is a very worthy goal. Resonances seem to me to be the right way to go. I would expect the need for a large number of iterations though before designing a monster with thousands of tubes. I would be surprised though if just a single harmonic, and one with such a large wavelength were the most important one. 380KHz has a wavelength of 789 meters. I expect a revision of this seemingly spurious number.

I envision a little more directed approach to the control of resonances. There are quite a few of them. I wouldn't be surprised if there were more than a few which need their own broadcast back into the fuser. Nuclear Magnetic Resonance imaging probably could supply some inspiration on this topic.

Conrad Farnsworth
Posts: 135
Joined: Thu Jul 08, 2010 1:35 am
Real name: Conrad Farnsworth

Re: POPS

Post by Conrad Farnsworth » Sun Dec 05, 2010 7:50 pm

I have been doing SOME searching around and would like to start "pulsing" my electrical input (for the sake of a science experiment) and since "they supplied zero data that was of any value in support of the idea." Since I'm a newb, POPS goes right over my head (any english explanations?). So, in short, would oscillating or pulsing the input power have any affect at all on the efficiency?
Sorry in advance if this is the wrong section for this.
-Conrad

Starfire
Posts: 1482
Joined: Wed Oct 24, 2001 6:14 pm
Real name:

Re: POPS

Post by Starfire » Mon Dec 06, 2010 12:07 am

The great advantage of pulses is that you can use more power for a shorter time - beyond that which would distroy apparatus otherwise.

Apparatus may withstand a short burst of power at a level which would distroy it, if continuously applied.

Efficiency remains the same for a given power but remember that power is 'work done in time' - 100 watts for 1 sec is the same power as 100,000 watts for 1 milli sec .

Post Reply