Fusor as an oscillator....A serious discussion

This area is for ADVANCED theory and discussions only. If you just joined fusor.net, chances are this is NOT the area for you to be posting.
User avatar
Richard Hull
Moderator
Posts: 14976
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Fusor as an oscillator....A serious discussion

Post by Richard Hull »

With the passing of Doug Coulter and the far ranging discussions around his Gonzo event claim. Bill Fain has mentioned and followed up on some of Doug's bizarre claim of a massive neutron burst from his fusor a number of years ago. Apparently, Doug felt strongly that the fusor entered into some sort of feedback/oscillation mode that caused the singular event claimed by him, yet never replicated.

While no one here has ever observed this modality, such discussions are no stranger to these forums. The oldest 3 or 4 guys here may remember active discussions and even electronic schematics of proposed hydrogen thyratron driver/pulser concept designed to allow for up to 1 kilohertz 100 ampere pulsed thumps for fusor operation. Likewise, there were some limited discussions related to a relaxation operation modality.

Like so much wind over the decks here, this work, (sorry, flap jawing), passed on to oblivion as no one put their foot in the path 20 years ago. I certainly had the H2 thyratrons and have experience in their full development and use in Tesla coils to replace the rather inefficient spark gap in the 1990's. In addition, I have done work over 40 years ago with electronic relaxation oscillators. As such, I put a huge amount of blame for failure to pursue this line of discussion with active experiment on me.

As such, let this be an opening for serious discussion on the topic of pulsed or even self-oscillatory fusor operation.

Way back, while vacuum tubes ruled and I was in college, we were taught to diagram "equivalent circuits". It turns out that in active circuitry, especially RF circuitry and even digital circuitry, the world goes surprisingly inductive and capacitive in ways that can fool one with a simple schematic into a world of hurt and disappointment. Thus, engineers are taught when trouble arises when some circuit should work and does not or is acting "funny", you need to draw an equivalent circuit. This is hyper critical in much of today's ultra high frequency work where "strip lines" replace components.

As such, this old boy is reaching around in the dust bin of his ossifying brain to seek continuous help in modifying my equivalent circuit of the fusor.....See below.

In this circuit you will see the fusor as a perhaps overly complex entity. (I tried to cover all bases.)

As you can see, the fusor is a complex electro-mechanical jumble. The key mechanical variable is the gas pressure, as this is often varied all through the start up and running of the fusor. It controls most of the electronic variables except for the capacitance Cf.

It would be so much easier to deal with if the fusor was a fixed gas diode, (as drawn), but it is not. The capacitance of the fusor could be the ultimate key factor in relaxation mode operation. As a gas diode, the fusor is a regulator tube of sorts. we see this as it mimes the non-linear action of the NE-2 neon bulb. It takes a higher voltage to strike the plasma that to sustain it as it regulates against the ballast resistor at a lower voltage which is "V sustain" or "Vreg" typically this is gas specific and invariant in a true vacuum regulator. But noooo!.... As we play with the system at varying gas pressures near Townsend discharge and arc conditions! This is why we can have voltages across the fusor of 40kv or more by monkeying with gas pressure current and voltage.

The typical NE-2 relaxation circuit known well by electronic engineers and advanced hobbyist consists of a DC power supply with a single resistor in series to a NE-2 lamp with a capacitor across it. The frequency of oscillation, (blinking rate of the lamp), is determined by the RC time constant needed to charge the capacitor to where the lamp gas ignites, shorting the capacitor, turning off the lamp and the cycle repeats.

Now see if you agree or would change my diagram and be thinking about how we might get to have the fusor go into a high frequency relaxation mode.

Suggestion: The low net capacitance in HF power supplies might be a great way to see this effect as we want ultra low net parallel capacitance to increase the frequency in a relaxation oscillator. Is there a sweet spot gas pressure where this oscillation is used? I would think the lower the better (ion transit times)....You can go nuts thinking about this. Is there a point in running and adjusting all the electronic variables with low capacitance power supplies where the noise in the neutron electronic detection is just where the fusor breaks over into high power near RF oscillation? With my 60HZ DC supply I have never witnessed such sudden neutron count bursts unless the fusor gets extremely hot and the grid goes white hot as electron runaway occurs, current goes through the roof! (1-3 seconds needed to kill the HV.)

Richard Hull
Attachments
Equivalent circuit.jpg
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Joe Gayo
Posts: 404
Joined: Sun Jan 06, 2019 9:34 pm
Real name: Joe Gayo
Location: USA

Re: Fusor as an oscillator....A serious discussion

Post by Joe Gayo »

The capacitance from the HV cable shield would be in parallel not series.
User avatar
Bob Reite
Posts: 576
Joined: Sun Aug 25, 2013 9:03 pm
Real name: Bob Reite
Location: Wilkes Barre/Scranton area

Re: Fusor as an oscillator....A serious discussion

Post by Bob Reite »

Ah! This looks like a good place to discuss what I think was happing with Doug's fusor seven years ago. Doug had mentioned that it was self oscillating, behaving like a Hartly or blocking oscillator. But from all the photos I have seen that is not what he had. There was no deliberate electrical coupling between his main grid and ion grid. What I think that he really had accidentally created was a tuned grid - tuned plate oscillator. The feedback is through the grid-plate capacitance, or in the case of Doug's fusor, the capacitance between the main grid and the ion grid. Doug told me that the mode was most likely to work if the pressure was too low for the system to "light off" with just the main grid at 40 KV. Applying potential to the ion grid would trigger plasma start.

The setting was somewhat critical, when we were planning to replace the mode just before Doug passed away. Doug was concerned that a 256 byte word wold not give enough resolution to fine tune this voltage remotely, but I proposed using a voltage divider at the output of the DA to give us the resolution we needed at the region of interest.

I'm going to hazard a guess that the mechanism by how this would work would be deuteron bunching, similar to electron bunching in a klystron tube, which would make fusion more likely.

I also think that the real magic was not in the actual resonant frequency of the main coils, which we estimate to be in the 1.8 MHz region, but some parasitic oscillation, possibly up at VHF, but I won't know until I get Doug's fusor reassembled as close to the configuration of seven years ago and bring it on line.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
User avatar
Richard Hull
Moderator
Posts: 14976
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Fusor as an oscillator....A serious discussion

Post by Richard Hull »

Thanks Joe. I hoped others might find additions and errors to the simple diagram. I will correct it immediately. You get the credit for the correction.

Bob you just might be right about VHF oscillations. I worry about the interference if it is in the high power range with even the finest neutrons system isolation. Anyway you will noodle it out. The ionizer grid was a key feature in the simple Hirsch-Meeks fusor patent. They just DC biased this grid and no one mentioned to me about any oscillations during their time with it.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Richard Hull
Moderator
Posts: 14976
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Fusor as an oscillator....A serious discussion

Post by Richard Hull »

While hunting for Richard Hesters H2 thyratron circuit of 17 years ago I can across A Jon Rosentstiel burst event!!! Oh how fast such things just sink into the mire of the ever moving forums.... I'm kinda' surprised Jon didn't chime in on this. I am glad I stumbled onto it

viewtopic.php?f=6&t=2304

Read it and cogitate. Jon does his mea culpa in missing the opportunity to check the activation immediately after the event. I guess we need to be ready with some kind of chunk of rhodium, silver or indium in a ready moderator with every fusion run, coupled with an instantly available GM counter, even if we aren't planning on doing activation. It will be the proof of any true Gonzo mode or "run-way pudding".
Needless to say, you will need some base level calibration. Suggestion: Run your fusor at the mega mark that suits you for a suitable period and then immediately GM your activation copy this GM reading down.
If in future you think you have a runaway, immediately pull out the reference element and if it is immediately far above your normal cal rate, you have done it!

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Joe Gayo
Posts: 404
Joined: Sun Jan 06, 2019 9:34 pm
Real name: Joe Gayo
Location: USA

Re: Fusor as an oscillator....A serious discussion

Post by Joe Gayo »

Practically all plasmas have oscillations/waves. I've directly measured ion acoustic waves with a biased electric probe in the plasma (attached).
Attachments
Wave
Wave
User avatar
Jim Kovalchick
Posts: 716
Joined: Wed Apr 13, 2011 8:00 pm
Real name:

Re: Fusor as an oscillator....A serious discussion

Post by Jim Kovalchick »

Jon's anomalous event sounds almost exactly like the ones I have observed. I know Mark theorizes that I saw noise, but stability of the voltage and current just as Jon described tells me otherwise.
User avatar
Mark Rowley
Posts: 908
Joined: Sun Dec 29, 2002 12:20 am
Real name: Mark Rowley
Location: Sacramento California
Contact:

Re: Fusor as an oscillator....A serious discussion

Post by Mark Rowley »

Well, it’ll be interesting to see. We just need replication with some good neutron detection gear. I’m with Richard on the requirement for activation to fully confirm the results.

Jon, with 17yrs experience since that time are you convinced it was a true neutron burst event?

Mark Rowley
Jon Rosenstiel
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Fusor as an oscillator....A serious discussion

Post by Jon Rosenstiel »

Mark,

No, I’m not convinced it was a true burst event. Although there were no signs of noise, noise is still the most logical culprit.

Jon Rosenstiel
Frank Sanns
Site Admin
Posts: 2117
Joined: Fri Jun 14, 2002 2:26 pm
Real name: Frank Sanns

Re: Fusor as an oscillator....A serious discussion

Post by Frank Sanns »

Seems many of us were investigating natural and forced oscillations back then. Mean free path and POPS was the discussion as was multiple grids.

Here is one link to one of the thread about the use of an RF amplifier to push the oscillations in the 10mhz to 13mhz region.

viewtopic.php?f=25&t=3557&p=23007&hilit ... ier#p23007


I will also point out that the entire Fusor electrical path is an oscillator and all of the electrical detection equipment is an antenna and multi band receiver. I had measured multiple RF frequencies coming off of my Fusor. At one of the HEAS I brought one of my near field frequency counters. Richard’s Fusor had a strong RF output around 52 MHz. His electrical HV feed line was just the right length to be a good antenna radiator at that frequency. There were other frequencies but that was the strongest. Had his neutron counter cable been the same length then RF coupling would have been a noise nightmare. Fortunately it was not.

Ballast resistors and chokes were on my HV line for all of my standard runs. Back then, scintillation probes were still in use as we upgraded to Boron tubes then on to He3 tubes. They all had their advantages and their susceptibilities. An oscilloscope was always running on the pulse output of the probe to be sure it was the neutron signature and not electrical noise of any kind.

I have a well behaved system but if the experiment is a new one, you can bet that I have at least two separate detectors going for redundancy in measurements. Those of you attending HEAS know that I alway have my Electronic dosimeter running the entire time. It is one more data point if any anomalous event were to happen.

The lore of these one time events have been repeated many times by many going all of the way back to the early Fusors. So far, RF noise and thermionic runaways seem to be the explanation of the events. No lucky donkeys yet. At least none with verifiable or reproducible proof.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
Cai Arcos
Posts: 163
Joined: Fri Oct 12, 2018 9:30 am
Real name: Cai Arcos
Location: Barcelona, Spain.

Re: Fusor as an oscillator....A serious discussion

Post by Cai Arcos »

I have thought a little bit about this topic, and wanted to share some ideas:

1.- I believe in it's important to discuss common fusors and Doug fusors somewhat separately. Normal fusors are two terminal devices, while Doug used another grid as an ion source. I already commented on this on another thread, but it's three grid configuration was quite similar to a Plasmatron, with the region between the anode and main cathode (the central grid) operated in such a way as to avoid breakdown. Then, the ion source grid can be used to modulate the plasma density. This produces gain (the "gas PNP device" or "plasma triode" Doug used to write about). Having gain, making an oscillator seems possible.
Some previous posts (http://www.coultersmithing.com/forums/v ... grid#p4854) for instance, very strongly seems to reassemble a blocking oscillator, and it would make sense for the current peaks shown in that mode of operation to be accompanied by very high ion density regions, which due to the it's short duration suffers less from space charge effects.

2.- Regarding coherent ion motions, it seems hard for me to believe this as the origin of oscillations. In order for coherent oscillations (Barkhausen-Kurtz oscillations) to form, one needs a few passes of the ions, so that the may lock in phase. This necessarily requires a mean free path large enough, which at the pressures of interest just isn't there. (That's just one requirement, one also requires a high enough current as to have a low enough negative resistance)
That isn't to say that ion bunching occurring as a result of some ion transit time mechanism isn't possible. If I understand correctly the literature that existed around BK oscillators, bunching could be induced by applying a voltage whose period coincides with the ion transit times, even when the oscillations didn't occur on their own. As a matter of fact, I found this short paper (https://www.nature.com/articles/1411009a0) which pretty much describes and includes references to this. It seems to me that this is the "driven recirculation" Doug talked about.

Just some thoughts I wanted to add to this great discussion.
Frank Sanns
Site Admin
Posts: 2117
Joined: Fri Jun 14, 2002 2:26 pm
Real name: Frank Sanns

Re: Fusor as an oscillator....A serious discussion

Post by Frank Sanns »

Some of us have run multiple grids with and without the possibility of recirculation. Biases can be plus or minus the full inner grid potential, reversed, or oscillated. This photo is just one of the configs to examine plasma extinction and the ringing that happens during which.

I also keep hearing the ugly word of mean free path again. It was my understanding that I put that misconception to rest a decade and a half ago. The MFP in a fusor using deuterium is on the order of multiple meters and not just centimeters.
Attachments
FrankSLevitatedPit.jpg
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
User avatar
Richard Hull
Moderator
Posts: 14976
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Fusor as an oscillator....A serious discussion

Post by Richard Hull »

I remember and took Frank's now ancient post to heart. MFP is also thermally determined. Hot, (high energy deuterons) are not lazy room temperature ions as figured in the normal vacuum sense.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Joe Gayo
Posts: 404
Joined: Sun Jan 06, 2019 9:34 pm
Real name: Joe Gayo
Location: USA

Re: Fusor as an oscillator....A serious discussion

Post by Joe Gayo »

@Frank

The mean free path for high energy molecular deuterium to charge exchange with background neutrals at pressures present is amateur fusors is centimeters at best.
(https://www.osti.gov/servlets/purl/4028813)
DionChargeExchange.PNG
D2ionChargeExchange.PNG
length[cm] = 1 / (density [atoms/cm^3] * sigma [cm^2/atoms])

density = (0.01 Torr * 1 cm^3) / (gas constant * 300 Kelvin) = 3.22 * 10^14 atoms/cc
sigma = 10 * 10^-16 cm^2/atom
length = 3.1cm

And one can see from the graph that getting too high energy is improbable... The system is dominated by fast neutrals and much lower than cathode potential ions (1/5th based on published research)
Last edited by Joe Gayo on Thu May 27, 2021 6:19 pm, edited 1 time in total.
Frank Sanns
Site Admin
Posts: 2117
Joined: Fri Jun 14, 2002 2:26 pm
Real name: Frank Sanns

Re: Fusor as an oscillator....A serious discussion

Post by Frank Sanns »

Lets do a calculation to see what comes out. The formula for MFP is:
Screen Shot 2021-05-27 at 4.43.07 PM.png
Solving the equation give the mean free path for D2 at room temperature and 15 microns to be 12 cm. The fusor is not Maxwellian so the temperature is far different for the accelerated deuterons than it is for the bulk of the chamber.

The T in the equation is 136,000 times higher for a 35 keV deuterium ion than it is for deuterium at room temperature. Naively using this number would give a MFP of 1.6 Km. Because of the charge, it is far far less that but it must also be much greater than the room temperature MFP of 12 cm.

A near collision with a neutral atom and a deuteron, does not mean it stops or gets captured. Even if captured, only 13 eV is lost in an electrical reaction but most will be deflections with a change in direction of momentum but not a loss in KE. A full neutralization will only make it a fast neutral that is still moving at fusion speeds. Electrons will be picked up and knocked back off many times during its velocity loss back down to the bulk plasma velocities.

If the MFP were only 1 cm, then no fusor bigger than 1 cm across would work as well as they do. If the MFP were not larger than the largest fusor, there would be a trail off in efficiency in the larger fusors which is not seen. Sure the little cube fusors wall load quicker and get great numbers but they are the same magnitudes as the largest of them.

The MFP of the hot ions has to be enough for multiple passes. Also see my work on Ion path in Fusor. The trajectories of charged ions across more than one path length of half a meter or greater are the only explanation of how ions could end up where they do after accelerating towards, passing through, and exiting the central grid.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
User avatar
Joe Gayo
Posts: 404
Joined: Sun Jan 06, 2019 9:34 pm
Real name: Joe Gayo
Location: USA

Re: Fusor as an oscillator....A serious discussion

Post by Joe Gayo »

@Frank

I don't think we are going to agree. We don't need to. I would like to see recent IEC research that suggests your perspective is correct.

Of course, my post is based on probabilities, as all observed physics is based on probability. It's not a hard limit. Some will travel longer and gain higher energy, but most will have charge exchange collisions several times.

The idea that the bulk of ions are oscillating around the cathode many times is not plausible.

Here is my submission:
https://www.researchgate.net/publicatio ... ent_plasma

It says:
- Ion energy peaks around 1/5 cathode voltage (of course there are higher and lower)
- Charge exchange dominates producing fast neutrals or anions (wall collisions)
Last edited by Joe Gayo on Thu May 27, 2021 5:53 pm, edited 1 time in total.
JoeBallantyne
Posts: 313
Joined: Tue Jul 20, 2010 4:08 pm
Real name: Joe Ballantyne
Location: Redmond, WA

Re: Fusor as an oscillator....A serious discussion

Post by JoeBallantyne »

Hi Joe -

I'm curious how you got the sigma @50KV of 10x10e-16 in your calculation.

Neither of the graphs have any data at 50kev - the top one ends at about 20kev for deuterium, and the bottom one is in units of ev, not kev.

Joe.
User avatar
Joe Gayo
Posts: 404
Joined: Sun Jan 06, 2019 9:34 pm
Real name: Joe Gayo
Location: USA

Re: Fusor as an oscillator....A serious discussion

Post by Joe Gayo »

@Joe

D2 energy / 2 = D energy (equivalent velocity)

The top graph roughly shows D+ to 25kV, which is 50kV D2+ in terms of velocity


Take a look at my old post - viewtopic.php?t=12634
Last edited by Joe Gayo on Thu May 27, 2021 6:20 pm, edited 1 time in total.
JoeBallantyne
Posts: 313
Joined: Tue Jul 20, 2010 4:08 pm
Real name: Joe Ballantyne
Location: Redmond, WA

Re: Fusor as an oscillator....A serious discussion

Post by JoeBallantyne »

It looks to me like both graphs end at about 13kev. The one that is labeled d+D2 stops at about 13kev on the Ed+ scale at the top. The one that is labled p+D2 also ends at about 13kev on the top scale for Eh+. It looks to me like the top Eh+ scale applies to the p+D2 graph as h+ is p, and that the second from the top Ed+ scale applies to the d+D2 graph as d+ is d. That would mean that the max accelerating voltage used to create those graphs was about 13KV. Furthermore the p+D2 graph is clearly dropping fast even at 13kev which is a long way from 50kev. It is not clear what the d+D2 graph is going to do at higher energies.

Granted I could be wrong, but that is what I see when I look at that top graph.

Joe.
User avatar
Joe Gayo
Posts: 404
Joined: Sun Jan 06, 2019 9:34 pm
Real name: Joe Gayo
Location: USA

Re: Fusor as an oscillator....A serious discussion

Post by Joe Gayo »

@Joe

My post was about an approximation of the scale of travel. The ions aren't instantly at any level of KeV, they accelerate in the electric field gradient (V/cm).

We can quibble about whether they travel 2cm or 10cm but the bottom line is the same.

I edited it to convey the exact same point ... if you want meters then the chamber pressure needs to be orders of magnitude lower.
JoeBallantyne
Posts: 313
Joined: Tue Jul 20, 2010 4:08 pm
Real name: Joe Ballantyne
Location: Redmond, WA

Re: Fusor as an oscillator....A serious discussion

Post by JoeBallantyne »

Assuming that the d+D2 graph at higher energies curves in a similar way to the h+D2 graph, and that they both fall as fast as they rise in the lower energy region, you could arguably say that the cross section might be as much as a factor of 10 smaller - 1*10e-16, which would make the MFP 10 times longer or on the order of 30cm or so. Most amateur fusors don't have chambers that big.

Joe.
User avatar
Joe Gayo
Posts: 404
Joined: Sun Jan 06, 2019 9:34 pm
Real name: Joe Gayo
Location: USA

Re: Fusor as an oscillator....A serious discussion

Post by Joe Gayo »

Joe

You have to get to that point in the curve. I'm done arguing. I've shared all the necessary information to see what's happing.

I'm going back to work on my devices to make more neutrons.

Good luck.
Frank Sanns
Site Admin
Posts: 2117
Joined: Fri Jun 14, 2002 2:26 pm
Real name: Frank Sanns

Re: Fusor as an oscillator....A serious discussion

Post by Frank Sanns »

We do not have to agree and I get it. I have been through the graphs and done the calculations. At the end of the day though, experimental evidence has to be considered as it is the real environment that we are working in.

To add some facts, essentially 100% off all electrons, at all of potentials within the operating fusor are lost to wall heating. They provide essentially zero ionizations. Any ionization that is done is essentially only by ions and fast neutral atoms and molecules.

The ionizations are made visible by the recombination of electrons and falling energy levels from previously ionized gas. This gives a clearly visible marker to where the ions are in the fusor.

I had been intrigued on how these long star trails do not stop at the outer grid (10 inches in my case) but pass on to the outer chamber, sometimes 4 inches past that. This cannot occur if an ion on the other side of the fusor is accelerated to to potential and then loses the potential on the way out. Conservation of energy says it can't go higher than the energy put in just like dropping a ball on the ground can't go any higher than the height from which it was dropped. However, every single day of operation, I see complete violation of this conservation law. The only answer is that there are tangential paths from a previous fall. Energy is maintained and the momentum vector changes direction for the next path. This residual energy is the only explanation for the longer exit paths than the entrance one.

The heat marks on the inside of all of our fusors are the result of these ions hitting the walls with significant residual energy and even enough to cause fusion pithing the wall itself. That energy cannot come from simply falling through a potential and losing that energy on the exit.

Here is a photo of the electrons origins and patterns on the wall of a temporary Pyrex spherical insulation within my fusor. Notice no visible plasma where the electrons are accelerated toward the walls, in this case and insulator that fluoresces in the electron beam. It is in the Images section under Tickling the Fusor Dragon.
Attachments
Sequence 01_3790Traces - Copy-2.jpg
Sequence 01_3790Crop-2.jpg
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
JoeBallantyne
Posts: 313
Joined: Tue Jul 20, 2010 4:08 pm
Real name: Joe Ballantyne
Location: Redmond, WA

Re: Fusor as an oscillator....A serious discussion

Post by JoeBallantyne »

@Joe - My intention was not to argue, or be difficult. Simply to try to understand where you got the numbers you were plugging into your equations. I agree with you that the MFP is most likely on the order of cm or 10s of cm, not meters or 10s of meters for a fusor that is running at 5-15 microns (5*10e-3 torr). My understanding is that your fusor runs at MUCH lower pressures like 10e-5 torr. Which would mean that your MFP ought to be significantly higher.

@Frank - Assuming your fusor has a visible plasma ball in the center (Joe Gayo's does not as his pressures are much lower.) Then there will be at least some transfer of energy between ions in the plasma, and there will therefore be some percentage of the ions that actually end up with a higher speed than what you are driving the plasma with. ie: some of the ions will come out hotter than the hottest ions you are sending in. And they will smash into the walls and get lost. I don't know that anyone has proven exactly what kind of energy distribution there is in the plasma in the center of a typical fusor, but I suspect it may be more Maxwellian than most want to admit. In which case the tail of the distribution could have ions with energies higher than the ones you are driving the plasma with.

From what you are describing, that MUST be the case, as you said there are visible indications of activity outside your anode.

Joe.
User avatar
Dennis P Brown
Posts: 3147
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: Fusor as an oscillator....A serious discussion

Post by Dennis P Brown »

While most power supplies are more Lorentzian in out put power, these also have tails; further, as I understand, any semi-sharp or sharp metal surface can and will create significantly higher potentials allowing a small number of electrons to accelerate well above the PS normal potential - this is often exploited with needle point discharges. Of course, the average of all power the supply can achieve is conserved.
Post Reply

Return to “Advanced Technical Discussion Area”