I have done some approximate calculations to see if focusing the beam using timing would have a chance of breakeven.
For a 1/2 metre diameter fusor with 2micron focus, My calcualations show that breakeven may be possible. In the attached spreadsheet, you can change the blue cells and see the effect. The answers fit in the middle/ low range of the lawson criteria for breakeven.
The design assumes a normal grid fusor with pulses timed to ensure focus in the Z direction. Other assumptions are in the comments field.
What do you think?
Reference threads
viewtopic.php?f=6&t=2420#p11930
list.php?bn=fusor_construction&expnd;=1 ... 1078770428
viewtopic.php?f=6&t=2415#p11925
Paul Riley
Simplified Spherical Z focus, updated spreadsheet
Simplified Spherical Z focus, updated spreadsheet
- Attachments
-
- Grid with z focus calcs.xls
- (32.5 KiB) Downloaded 248 times
Pulsed fusor design
Have any of the pulsed fusor experimenters tried varying parameters (voltage, pulse time and frequency etc) .
If so with what results?
Paul
If so with what results?
Paul
Re: Simplified Spherical Z focus, updated spreadsheet
2 microns seems a bit optimistic for the focus to me...
Re: Simplified Spherical Z focus, updated spreadsheet
Greg,
2 um to start the experiment is too hard. What I think we need to do is experiment with using a larger focus point and see if the idea gives an efficiency gain. Once there is enough confidence we can make the focus smaller and see if it meets with theoretical predictions. If it does, there will be plenty of interest in getting down to 2um, which is quite tame in the optical world.
I think the lure of breakeven, if believable, would provide the enthusiasm
2 um to start the experiment is too hard. What I think we need to do is experiment with using a larger focus point and see if the idea gives an efficiency gain. Once there is enough confidence we can make the focus smaller and see if it meets with theoretical predictions. If it does, there will be plenty of interest in getting down to 2um, which is quite tame in the optical world.
I think the lure of breakeven, if believable, would provide the enthusiasm
Re: Simplified Spherical Z focus, updated spreadsheet
No doubt as a pulse device this seems the best road, the only problem is that it requires a huge inner grid radius compared to the outher shell radius, unless you allow the differences in voltage to be very high.
Watch this space
Greg,
When I first started on this idea, I too thought that the radii needed to be similar. However, since I started my simulation I am not so sure. I think there is a solution that starts with a small (pulsed) voltage building up the velocity that could be used with a small radius inner grid.
I need some time to do the simulation .. and the maths. (I am a bit rusty on this).
Paul
When I first started on this idea, I too thought that the radii needed to be similar. However, since I started my simulation I am not so sure. I think there is a solution that starts with a small (pulsed) voltage building up the velocity that could be used with a small radius inner grid.
I need some time to do the simulation .. and the maths. (I am a bit rusty on this).
Paul
Crude but simple focussing
The spreadsheet simulator shows how you can get more output with simple circuitry. Not perfect but should give a significant improvement.
What do you think?
NB to use the simulation, copy the last row in the detail sheet down to row 6100. (File too big to send complete)
Regards
Paul
What do you think?
NB to use the simulation, copy the last row in the detail sheet down to row 6100. (File too big to send complete)
Regards
Paul
- Attachments
-
- Grid with z focus calcsv3.zip
- (969.61 KiB) Downloaded 256 times
Re: Crude but simple focussing
Hi Paul:
I have done experiments with frequency,changing grid sizes,
Varying pre pulse glow parameters.
The frequency I've used is in the low range of 100 cps max.
The grid ratio that seems to work the best is a 4 to 1 ratio.
I create a glow discharge between the outer grid and the inner grid then apply the hv pulse. The best results have been with 7 kv @ 100 ma AC. I don't know how small the fusor focus gets.
However the temperature must be high due to the xray output
2 rads...we bite. I'm still trying to get high speed digital photography to work. However the uv and visible light tend to destroy ccd chips.
Happy Fusoring!
Larry Leins
Fusor Tech
I have done experiments with frequency,changing grid sizes,
Varying pre pulse glow parameters.
The frequency I've used is in the low range of 100 cps max.
The grid ratio that seems to work the best is a 4 to 1 ratio.
I create a glow discharge between the outer grid and the inner grid then apply the hv pulse. The best results have been with 7 kv @ 100 ma AC. I don't know how small the fusor focus gets.
However the temperature must be high due to the xray output
2 rads...we bite. I'm still trying to get high speed digital photography to work. However the uv and visible light tend to destroy ccd chips.
Happy Fusoring!
Larry Leins
Fusor Tech
Re: Crude but simple focussing
The simulation shows that you can get considerable gain by focussing in the z (i.e. time) axis in three phases:
1). from an initial random distribution to get all the ions moving towards the centre by applying a short pulse (in your case 7kV.
2). apply a low voltage to accelerate the ions near the case so that they all converge at the centre at the same time.
3). Apply full fusor voltage as the bunched ions get near to the case.
The low voltage and timings are critical to success.
If you let me have your fusor dimensions I can set up a simulation for you... or just use the spreadsheet.
Have fun
Paul
1). from an initial random distribution to get all the ions moving towards the centre by applying a short pulse (in your case 7kV.
2). apply a low voltage to accelerate the ions near the case so that they all converge at the centre at the same time.
3). Apply full fusor voltage as the bunched ions get near to the case.
The low voltage and timings are critical to success.
If you let me have your fusor dimensions I can set up a simulation for you... or just use the spreadsheet.
Have fun
Paul
Re: Crude but simple focussing
Hi Paul :
Yeah I thought about it once .
Oh BTW the 7kv does not acellerate at all.
Being ac no appreciable forward acceleration would be present.
The purpose of the preglow is to provide large quanties of ions and electrons in plasma form. When the hv pulse hits the grids the electrons rebound to the wall and the ions goto the grid.
The point of the pulse method I use is to shorten the path of the Electron to the case and to prevent large numbers of electrons from the grid be accelerated from the inner grid. Each electron is a loss of energy. This method is far from perfect but the electron losses are less than a continious fusor due to the abrupt run length.
It's called velocity vectoring were you give the slowest particles time to speed up to the faster particles before another acceleration is applied. I have tried using a 1/2 sawtooth
waveform where the waveform rises then drops suddenly.
It worked to a degree. But maybe your way is better....Just build it and see I guess.
Happy Fusoring!
Larry Leins
Fusor Tech
Yeah I thought about it once .
Oh BTW the 7kv does not acellerate at all.
Being ac no appreciable forward acceleration would be present.
The purpose of the preglow is to provide large quanties of ions and electrons in plasma form. When the hv pulse hits the grids the electrons rebound to the wall and the ions goto the grid.
The point of the pulse method I use is to shorten the path of the Electron to the case and to prevent large numbers of electrons from the grid be accelerated from the inner grid. Each electron is a loss of energy. This method is far from perfect but the electron losses are less than a continious fusor due to the abrupt run length.
It's called velocity vectoring were you give the slowest particles time to speed up to the faster particles before another acceleration is applied. I have tried using a 1/2 sawtooth
waveform where the waveform rises then drops suddenly.
It worked to a degree. But maybe your way is better....Just build it and see I guess.
Happy Fusoring!
Larry Leins
Fusor Tech
Re: Crude but simple focussing
I am not following the process here...
If your ions begin to move... at different places, they will all receive different accelerating forces... and have different ultimate velocities...
How can they all collide.?
Dave Cooper
If your ions begin to move... at different places, they will all receive different accelerating forces... and have different ultimate velocities...
How can they all collide.?
Dave Cooper
Re: Crude but simple focussing
The ions further away from the focus have just enough extra velocity to make them hit the focus at the same time as the slower ones nearer the focus point.
Effectively one needs to keep the same time T (i.e. the time from any position to the focus) the same for all ions.
The spreadsheet contains the formula, if you like I could post the math separately.
Regards
Paul
Effectively one needs to keep the same time T (i.e. the time from any position to the focus) the same for all ions.
The spreadsheet contains the formula, if you like I could post the math separately.
Regards
Paul
Re: Crude but simple focussing
Larry,
Initially I too thought that a saw tooth was the right waveform. My simulation shows that this is not the case. A saw tooth just increases the relative velocity of the ions, but does nothing for focus in the time (Z) direction. To get the ions to bunch, you need to decide what diameter of focus you are trying to achieve. Then assuming you want all ions to have similar velocity (to minimise energy input). This fixes the quantity: Volts x pulse time. Why? Because the pulse accelerates all the ions to (about) the same speed. The ones near the grid move out of the electric field. In order for the ions still in the field to hit the focus at the same time, all you need is a small grid case voltage. (For a small diameter focus, they need very little extra acceleration to catch up the ones in front).
I would like to try the idea out (once the math is checked) but I am a theorist more than experimentalist.
BTW I like the idea of ac to get the plasma going. I must calculate the minimum voltage needed. To get a plasma, 7kV sounds very high; you will get almost fusion temperatures… many orders higher than needed for dissociation into electronics and ions.
Paul
Initially I too thought that a saw tooth was the right waveform. My simulation shows that this is not the case. A saw tooth just increases the relative velocity of the ions, but does nothing for focus in the time (Z) direction. To get the ions to bunch, you need to decide what diameter of focus you are trying to achieve. Then assuming you want all ions to have similar velocity (to minimise energy input). This fixes the quantity: Volts x pulse time. Why? Because the pulse accelerates all the ions to (about) the same speed. The ones near the grid move out of the electric field. In order for the ions still in the field to hit the focus at the same time, all you need is a small grid case voltage. (For a small diameter focus, they need very little extra acceleration to catch up the ones in front).
I would like to try the idea out (once the math is checked) but I am a theorist more than experimentalist.
BTW I like the idea of ac to get the plasma going. I must calculate the minimum voltage needed. To get a plasma, 7kV sounds very high; you will get almost fusion temperatures… many orders higher than needed for dissociation into electronics and ions.
Paul
Re: Crude but simple focussing
I was curious if you guys think that relativitsic math is to be considered in any of this. Such as the deBroglie wavelength and the wave nature of electrons. Yes, you intrinsically are aware of this, gathered from your prior language including orginal application from electron microscope technology. But I have not read anything yet in these terms.
With a rough look into calcualtions at say 50keV your electron has a velocity of ~0.41c. And more to the point, in my experience with lasers, specifically materials processing, the limit prior to and not exceeding the diffraction limit for focusing a beam can be realized through circular polarization. So to suggest, that maybe you might find this view and information useful being that the wavelength at this velocity is ~5355 fermi or in the soft gamma ray freq.
On that approach I don't know what other effects there are to be noted at these velcocities, as at 100keV your at ~0.55c and 250keV (say for your LINAC) your at ~0.74c Such that you could use them with notion of local groupings, cohrence or that with interactions of forces on that level.
Respectfully,
Darius
With a rough look into calcualtions at say 50keV your electron has a velocity of ~0.41c. And more to the point, in my experience with lasers, specifically materials processing, the limit prior to and not exceeding the diffraction limit for focusing a beam can be realized through circular polarization. So to suggest, that maybe you might find this view and information useful being that the wavelength at this velocity is ~5355 fermi or in the soft gamma ray freq.
On that approach I don't know what other effects there are to be noted at these velcocities, as at 100keV your at ~0.55c and 250keV (say for your LINAC) your at ~0.74c Such that you could use them with notion of local groupings, cohrence or that with interactions of forces on that level.
Respectfully,
Darius
Re: Crude but simple focussing
Darius - good points. For electrons, one needs to be aware of the relativistic effects above ~ 50KeV. For beam trajectories, this is especially important. Above about 10 KeV, electron trajectories begin to deviate from the field lines and focus calculations need to keep this in mind. This is taken into consideration (usually) automatically by the trajectory plotting engine after the fields are determined.
Here we are concerned with the deuterium ion, about 3672 times the mass of the electron, so velocities are considerably slower. All the voltages normally considered for fusion, leave the ions below the velocity where relatvistic effects are noticeable.
As to the more detailed issues of actually focussing these ions and what really occurs when they get withing fusing range... I think everyone's doing a bit of guessing here.
Dave Cooper
Here we are concerned with the deuterium ion, about 3672 times the mass of the electron, so velocities are considerably slower. All the voltages normally considered for fusion, leave the ions below the velocity where relatvistic effects are noticeable.
As to the more detailed issues of actually focussing these ions and what really occurs when they get withing fusing range... I think everyone's doing a bit of guessing here.
Dave Cooper
Re: Crude but simple focussing
Dave,
I posted this reply in two threads, viewtopic.php?f=15&t=6996#p49201
If you check out the subsequent replies and responses with Paul Riley, (if you havn't already) you will see I echoed your sentiment, more or less. We went on to calrify some respective opinions.
I wanted to focus, well ....on focusing. And the mechanics of all probable incorporables in doing this......but, I get my ideas and personality, as you guys might see it in this forum, mostly from my work with heat engines, and lasers.
Lasers are just about the most well understood devices operationally. When I set out to design something that converts from one energy source to another, I think quantum rules, and simple joule/molar calculations everything else is material science and alignment(although the terminology is more conducive to a laser, of hand, I do not show prejudice in private thought). The devices inherently run themselves..... the feeling I get from here is something different here. But I would want to stress which is the subject of every Nobel prize out there, and that is of that which connects the behavior of everything. I propose that this information is mostly here for us, and we just have to apply it to this to the larger dynamics going on in the fusor.
One of Einstein's first great papers was that on the photoelectric effect...not unlike in real life ... he benefited well with his first impression encounter conversation with mother nature....most can't get past here awesome outward presence.
Darius
I posted this reply in two threads, viewtopic.php?f=15&t=6996#p49201
If you check out the subsequent replies and responses with Paul Riley, (if you havn't already) you will see I echoed your sentiment, more or less. We went on to calrify some respective opinions.
I wanted to focus, well ....on focusing. And the mechanics of all probable incorporables in doing this......but, I get my ideas and personality, as you guys might see it in this forum, mostly from my work with heat engines, and lasers.
Lasers are just about the most well understood devices operationally. When I set out to design something that converts from one energy source to another, I think quantum rules, and simple joule/molar calculations everything else is material science and alignment(although the terminology is more conducive to a laser, of hand, I do not show prejudice in private thought). The devices inherently run themselves..... the feeling I get from here is something different here. But I would want to stress which is the subject of every Nobel prize out there, and that is of that which connects the behavior of everything. I propose that this information is mostly here for us, and we just have to apply it to this to the larger dynamics going on in the fusor.
One of Einstein's first great papers was that on the photoelectric effect...not unlike in real life ... he benefited well with his first impression encounter conversation with mother nature....most can't get past here awesome outward presence.
Darius