Pulsing fusion

For posts specifically relating to fusor design, construction, and operation.
Conrad Farnsworth
Posts: 135
Joined: Thu Jul 08, 2010 1:35 am
Real name: Conrad Farnsworth

Pulsing fusion

Post by Conrad Farnsworth » Thu Dec 09, 2010 12:36 am

This is an extension of the POPS post we have been slowly getting off track of. I would first like to ask what the difference between a thyratron and a vacuum tube is. Ascetically, they look the same, and I cannot distinguish any differences between them as far as information goes (although I do not gather information that well when I read). Anyone wanna shed light?

It is also worthy to note that I have no prior training or education on electronics or electricity but am working hard on gathering as much information as I can on the subjects.
-Conrad

Tyler Christensen
Site Admin
Posts: 551
Joined: Tue Feb 24, 2009 2:08 am
Real name:

Re: Pulsing fusion

Post by Tyler Christensen » Thu Dec 09, 2010 1:40 am

A thyratron is a vacuum tube, in the same way a golden retriever is a dog. A thyratron takes a trigger input (depending on the size and type of tube, sometimes up to several kV). When this trigger is provided, it is a completed closed circuit from the anode to the cathode of the tube. Thyratrons can pulse up to tens if not hundreds of thousands of amps out of a capacitor bank in a very short time length. They are a low duty cycle (you won't get POPs mhz range, thyratrons operate up to around a khz rep rate, but large high voltage ones much lower.

You're probably confusing it with a triode which is an amplifying tube, it would never allow tens of thousands of amps of pulsing through, but it could amplify easily through 10mhz.

David D Speck MD
Posts: 129
Joined: Sat Jan 26, 2008 7:05 pm
Real name: David D. Speck MD
Location: Auburn, NY

Re: Pulsing fusion

Post by David D Speck MD » Thu Dec 09, 2010 1:42 am

Conrad,

Thyratrons are indeed a subtype of vacuum tube diodes. They have an all-or-nothing operational response. Once triggered on, they remain in full conduction until the forward current drops below some threshold, or reverses direction. They then return to a nonconducting state until triggered again. Most thyratrons degrade rapidly with the application of large reverse potentials.

Most common three (or more) element vacuum tubes have a variable conduction property, by which their plate current varies in proportion to the voltage applied to the control grid(s).

Thyratrons are vacuum tube analogs of silicon controlled rectifiers, while common 3(+) element vacuum tubes are similar to field effect transistors.

Dave

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

Re: Pulsing fusion

Post by Conrad Farnsworth » Thu Dec 09, 2010 3:24 am

Tyler,

Thats what I was getting it confused with a triode. Why not use a triode to pulse low end DC current, then amplify it via a CW multiplier? Would that work? Or would the capacitors turn it into a sine wave?

-Conrad

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

Re: Pulsing fusion

Post by Starfire » Thu Dec 09, 2010 12:10 pm

Thyratrons avalange - that is, they will pass full current very quickly with holdoff until triggered.

PS. don't take any notice of the debate between Carl & Richard and myself, we are old antagonists but still respect each other and agree to disagree occasionally and try to avoid flamming

The forum is a place for debate and disaggreement and we try to avoid personallties
also don't be afraid to be wrong.

Carl is sound and genuine and provides an anchor of reallity and Richard brings wisdom. Both offer healthy critism and are respected if a little abrupt or dry on occasion.

User avatar
Richard Hull
Moderator
Posts: 11936
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Pulsing fusion

Post by Richard Hull » Thu Dec 09, 2010 3:55 pm

There are thyratrons and then there are thyratrons. It depends on application. There are mercury thyratrons, hydrogen thyratrons, deuterium thyratrons, Kytrons, Sprytrons, Ignitrons, etc. All are glass, vacuum type tubes. All are all-on or all-off switches working off trigger pulses that start the conduction cycle.

You will never learn a lot related to them until you self-direct yourself to learn about them in great detail.

Not all thyratron type switches need filaments, but the higher power ones that do, require monsterous filament power by normal vacuum tube standards. This means special tranformers that are just not encountered in today's world of electronics.

Ultra high power hydrogen/deuterium types require "reservoir" voltages that are often odd voltages and at high currents.

There are key issues in pulse work that are rarely encountered by anyone not directly involved in the process, daily. Without critical key instrumentation, you are whistling in the wind. Without the knowledge of how to use them, and interpret the results, you might as well not have them. It is a special game, especially with increasing pulsed power switching rep-rates.

An example is the magnetron example so poorly explained in a previous post where pico second pulses are possible, but there is not much real peak pulse power in any individual pulse. The energy storage of the magnetron is due to its own internal capacity which is, by its very design, near zero. Thus, each pulse has a rather tiny peak power. Due to its operating frequency, the time ordered average power output appears high while the peak pulse power is vanishingly small, mostly due to the low operating voltage of a bit over 1000 volts.

In general, the higher delivered peak power the lower the repetition rate. A bit of a work around involves ever high voltages which allow smaller capacties which allow the rep-rate to be pushed a bit. At higher voltages especially where fusion is done, switching devices "thin-out" in both number and type while expense increases dramatically. Limitations are reached and this is why pico second pulses are not allowed at high power with any sort of high rep-rate.

Again, self-direct yourself and get texts on this study. No one here can or will spoon feed the full story to you. We don't have the time or inclination and you don't have the instrumentation to follow the effort in a scientific manner. Until you are properly outfitted and have the hardware, books and a lot of reading are all you have and where you should be spending your time if really interested.

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.

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

Re: Pulsing fusion

Post by Starfire » Fri Dec 10, 2010 1:42 pm

Opps! - I did tell you heh! heh! heh! but dont be discouraged - good work can be done and much learned on a small buget. You will need a basic Neutron detector at lest.

I reiterate; -
>A simple sparkgap filled with D2 will get you a Neutron burst when discharged.

A typical example of this is the coaxial sparkgap as used by Eric Lener for focus fusion which produces Neutrons and is well documented or a differiental spark gap which no other worker to my knowledge has tried - ( I have built several years ago ), so many geometry's can yet be explored. These devices can be made cheaply. Think outside the box and don't limit yourself because the physic's says ' you can't do that ' - experiment.

You only need a cap or two, a power supply and a DIY sparkgap. Good Luck.

User avatar
Chris Bradley
Posts: 2930
Joined: Fri May 02, 2008 11:05 am
Real name:

Re: Pulsing fusion

Post by Chris Bradley » Fri Dec 10, 2010 3:57 pm

Conrad,

I'd just like to comment on the connection you have drawn with pulsed operation and POPS (because the stated purpose of POPS is much the same as the work I am doing): There isn't really a connection!

You can read a description of POPS on http://www.lanl.gov/p/rh_pp_park.shtml .

The essence of it is that by using periodic fields, ions that drop behind the field's frequency (because of Coulomb collisions) will momentarily experience a greater electric field force than the rest, until they are duly accelerated back into synchrony with the field. One might then suppose that the ions will not thermalise.

If you can avoid the ions thermalising then there is a small window of opportunity for hope to flourish that some net energy can be sucked out, but if you allow ions to thermalise then best to give up all hope now.

That web page may express it better than me. It describes this by saying;
>"Though useful for practical neutron sources, the existing IEC fusion devices suffer low fusion yields, ~ 0.01% of input power. This is because the Coulomb-collision cross section is much greater than the fusion-collision cross section by several orders of magnitude. The ion beams in the IEC device rapidly lose the energy by Coulomb collisions before producing fusion reactions, leading to a net loss in energy....Tuning the external radio-frequency (rf) electric fields to this naturally occurring [POPS] mode allows the ion motions to be phase-locked."

Some of the posts from that 2005 thread you added to describes some of this quite neatly.

In the discussion you are having here on pulsed operation, I can't tell if you are talking about phase-locking ions in the way that POPS describes. So it may be useful for you to consider (and would be easier to follow!) whether you are aiming to look at pulsed fusor operation [which is of interest nonetheless because higher instantaneous voltages should mean higher fusion cross-sections] or whether you are aiming for a periodic voltage that aims to phase-lock ions and reduce thermalisation.

User avatar
Carl Willis
Posts: 2841
Joined: Thu Jul 26, 2001 11:33 pm
Real name: Carl Willis
Location: Albuquerque, New Mexico, USA
Contact:

Re: Pulsing fusion

Post by Carl Willis » Fri Dec 10, 2010 5:33 pm

John:

>a differiental spark gap which no other worker to my knowledge has tried - ( I have built several years ago ), so many geometry's can yet be explored. These devices can be made cheaply. Think outside the box and don't limit yourself because the physic's says ' you can't do that ' - experiment.

Before you comment one more time to repeat your claims about neutron-emitting spark gaps, before you offer any more "advice" on this topic, go compose a post (in a new thread) describing your own apparatus, methods, results.

At this point, your persistent refusal to be usefully detailed is a stain on your credibility in my eyes. Very few legitimate contributors have ever had a problem with the prevailing standards of disclosure here.

-Carl
Carl Willis
http://carlwillis.wordpress.com/
TEL: +1-505-412-3277

User avatar
Richard Hull
Moderator
Posts: 11936
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Pulsing fusion

Post by Richard Hull » Fri Dec 10, 2010 6:08 pm

Note: No one has demonstrated to some definitive, unassailable point here, with images, that any fusion is done in a high intensity arc discharge. At some level this is theoretically possible if enough energy is applied. It has just not been shown here before critical review using acceptable instrumentation.

Next, such a system can't produce continuous or rapid rep-rate fusion, if successful. As noted, no one has proven "arc" fusion here or stated what the minimum energy is needed to do it in and arc-deuterium environment or what kind of neutron numbers per pulse are produced.

The difficulty in this scenario has to do with time constants to recharge the energy cap, stiffness (dynamic impedance) of the HV charging supply, inductance in the system and lot of other variables.

Acceptable neutron measurement would demand activation analysis or a light and heat shielded bubble detector only! No electronic neutron counter could be depended on to the satisfaction of those here who know how to use one or have used one extensively.

Again, no one has talked neutron numbers here, pulse rep-rate or pulse energy per delivered fusion event. Instead, we get sophistries and excuses about no willingness to discuss with precision what is being done or achieved in a manner that is acceptable to the standard, jaundiced and critical eye.

If possible or achieved, this is simple hot fusion and is nothing elegant, at that, with nearly 100% of the expended energy going into waste heat and light. So, it would be far worse than a fusor and not continuous fusion delivery. Sort of a very noisey and power wasteful putt-putt boat type affair in its finest iteration.

Feel free to experiment, of course. Just don't expect us to believe a word related to fusion without the same proof that we demand of anyone else here with a regular fusor or accelerator device.

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.

Post Reply