I am trying to compile all the fusion experiment projects into one table for comparison. Would you like to help me with Polywell, or any other project you know well?
This is the original discussion:
viewtopic.php?t=1578
What are the breaktrhrous required for the Polywell to work?
My twopenny worth (these are the things I would expect to see before placing the bets);
[I've put my personal opinions of percentages of likely success on these points]
Polywell;
i) demonstrate that electrons can be sufficiently well-confined both in physical and velocity space, (viz. in a low energy mode) so that they can act as a central electrode (as per a standard fusor) [5%]
ii) that ions are not scattered circumferentially and that ion paths remain radial (i.e. That the volume will not thermalise through Coulomb collisions) [0.1%]
iii) that ion energy loss through coulomb collisions (and ionisation of background neutrals) is recovered by the process of 'annealing' [0.1%]
iv) that vacuum pumping technology can cope with the required output flux of the fusion products at rated power. [0.001%]
v) that alpha sputtering of the containment vessel doesn't contaminate the reactants. [50%]
Tokamak;
i) demonstrate that Edge Localised Modes can be continuously controlled in H-mode without any risk of collapse of the plasma [5%]
ii) demonstrate that thermal transports can drive 'banana' orbits which will replace the current inductive [flat-top saturation] drive and provide continuous toroidal current [20%]
iii) that divertors of sufficient thermal capacity can be manufactured that do not suffer significant erosion at a continuous >20MW/m^2 [40%]
iv) that tritium breeding is viable [80%]
ICF
i) that the Rayleigh instability time is longer than the requirement for fusion confinement time, [0.1%]
ii) that uniform compression can be achieved [1%]
iii) that the fuel delivery system (Hohlraums) can operate at the required rate for net-power [20%]
iv) that the Hohlraum technology manufacture can be commercially viable (currently all gold) [50%]
v) that the laser optics can run continuously with high power laser without clouding [2%]
vi) tritium breeding [50%]
DPF
i) that the confinement time criteria can be met to achieve net power (to include X-ray conversion?) [5%]
ii) that equipment erosion is operationally tolerable [20%]
iii) that the pulsed power is operationally capable for continuous pulses without being compromised due to degradation [20%]
any other approaches you'd like me to comment on?..
[I've put my personal opinions of percentages of likely success on these points]
Polywell;
i) demonstrate that electrons can be sufficiently well-confined both in physical and velocity space, (viz. in a low energy mode) so that they can act as a central electrode (as per a standard fusor) [5%]
ii) that ions are not scattered circumferentially and that ion paths remain radial (i.e. That the volume will not thermalise through Coulomb collisions) [0.1%]
iii) that ion energy loss through coulomb collisions (and ionisation of background neutrals) is recovered by the process of 'annealing' [0.1%]
iv) that vacuum pumping technology can cope with the required output flux of the fusion products at rated power. [0.001%]
v) that alpha sputtering of the containment vessel doesn't contaminate the reactants. [50%]
Tokamak;
i) demonstrate that Edge Localised Modes can be continuously controlled in H-mode without any risk of collapse of the plasma [5%]
ii) demonstrate that thermal transports can drive 'banana' orbits which will replace the current inductive [flat-top saturation] drive and provide continuous toroidal current [20%]
iii) that divertors of sufficient thermal capacity can be manufactured that do not suffer significant erosion at a continuous >20MW/m^2 [40%]
iv) that tritium breeding is viable [80%]
ICF
i) that the Rayleigh instability time is longer than the requirement for fusion confinement time, [0.1%]
ii) that uniform compression can be achieved [1%]
iii) that the fuel delivery system (Hohlraums) can operate at the required rate for net-power [20%]
iv) that the Hohlraum technology manufacture can be commercially viable (currently all gold) [50%]
v) that the laser optics can run continuously with high power laser without clouding [2%]
vi) tritium breeding [50%]
DPF
i) that the confinement time criteria can be met to achieve net power (to include X-ray conversion?) [5%]
ii) that equipment erosion is operationally tolerable [20%]
iii) that the pulsed power is operationally capable for continuous pulses without being compromised due to degradation [20%]
any other approaches you'd like me to comment on?..
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alexjrgreen
- Posts: 815
- Joined: Thu Nov 13, 2008 4:03 pm
- Location: UK
Thanks for recognising the importance of this.chrismb wrote:My twopenny worth (these are the things I would expect to see before placing the bets);
[I've put my personal opinions of percentages of likely success on these points]
Polywell;
i) demonstrate that electrons can be sufficiently well-confined both in physical and velocity space, (viz. in a low energy mode) so that they can act as a central electrode (as per a standard fusor) [5%]
Ars artis est celare artem.
Hirsch Meeks and the Penning fusion experiment both gave some indication that ion confinement by 'managed' electrons was possible. In these cases the electrons were held by electrostatic and Penning (ExB) fields, respectively, but they never showed any fusion. I'm still doubtful, but will recognise some degree of plausibility with it if only because others have considered it so.alexjrgreen wrote:Thanks for recognising the importance of this.chrismb wrote:My twopenny worth (these are the things I would expect to see before placing the bets);
[I've put my personal opinions of percentages of likely success on these points]
Polywell;
i) demonstrate that electrons can be sufficiently well-confined both in physical and velocity space, (viz. in a low energy mode) so that they can act as a central electrode (as per a standard fusor) [5%]
I assume you are refering to Penning traps for no fusion results. I don't know about them, but fusors of several types have shown D-D fusion. I think it is the Hirsch Meeks varient that still holds the fusor record of ~ 100 billion neutrons per second.chrismb wrote:Hirsch Meeks and the Penning fusion experiment both gave some indication that ion confinement by 'managed' electrons was possible. In these cases the electrons were held by electrostatic and Penning (ExB) fields, respectively, but they never showed any fusion. I'm still doubtful, but will recognise some degree of plausibility with it if only because others have considered it so.alexjrgreen wrote:Thanks for recognising the importance of this.chrismb wrote:My twopenny worth (these are the things I would expect to see before placing the bets);
[I've put my personal opinions of percentages of likely success on these points]
Polywell;
i) demonstrate that electrons can be sufficiently well-confined both in physical and velocity space, (viz. in a low energy mode) so that they can act as a central electrode (as per a standard fusor) [5%]
Also, what sre your prognostication on the FRc?
Dan Tibbets
To error is human... and I'm very human.
There seems to be a nice list of projects here:chrismb wrote:My twopenny worth (these are the things I would expect to see before placing the bets);
...
http://en.wikipedia.org/wiki/List_of_fu ... chnologies
Unfortunately I am not sure which ones are still under-work. Anything you want to comment on is helpful, but I think you already described the most important ones except for MTF (General Fusion's Magnetized Target Fusion).
Yes, that was my list I was working on that got cribbed onto Wiki:Breakable wrote:There seems to be a nice list of projects here:chrismb wrote:My twopenny worth (these are the things I would expect to see before placing the bets);
...
http://en.wikipedia.org/wiki/List_of_fu ... chnologies
Unfortunately I am not sure which ones are still under-work. Anything you want to comment on is helpful, but I think you already described the most important ones except for MTF (General Fusion's Magnetized Target Fusion).
viewtopic.php?p=19359#19359
Only fixed cathode variants have ever shown fusion.D Tibbets wrote: I assume you are refering to Penning traps for no fusion results. I don't know about them, but fusors of several types have shown D-D fusion. I think it is the Hirsch Meeks varient that still holds the fusor record of ~ 100 billion neutrons per second. Also, what sre your prognostication on the FRc?
On FRCs (I presume you mean the Tri-Alpha approach rather than the FRC toroid types. FRCs appear variously amongst some of the other fusion approaches.); as far as I understand it, this works because it works and a theory has been contrived retrospectively to try to explain it. Essentially, this shows that there are too many unknown unknowns (unlike above, these are the known unknowns). This is true of General Fusion's approach as well. These both have 'new physics' they are proposing and seeking to demonstrate. The former needs to show that an FRC 'slug' can mix in a non-chaotic manner with another over a timescale longer than the required confinement period. The latter needs to show that acoustic waves can actually create a confinement period long enough for net fusion. I do not think either of these matters are yet within anyone's real understanding, and it will be so until futher experiments give some refined results. Both are plausible, neither seem even half-demonstrated.
The only other I've not mentioned that should be ripe for real discussion are stellarators. I've got a warm, cosy feeling about these because they implicitly self-generate toroidal current and are already demonstrably more stable than tokamaks. But I'm not far enough in my understanding of them to feel able to comment. My basic understanding makes me think it's all in the wibbly-wobbly fields they generate and it is only recently been possible to actually begin to design coils to generate these fields due to advancements in computer power. If I was given money to put a bet on one of the well-known approaches, then I'd stick it on Stellarators.
The correct formula should be to multiply all probabilities (instead of averaging them as I thought before), so the outcome is:
Polywell
0.05*0.001*0.001*0.00001*0.5 *100% = 0.000000000025%
Tokamak
0.05*0.2*0.4*0.8 *100% = 0.32%
ICF
0.001*0.01*0.2*0.5*0.02*0.5 *100% = 0.000001%
DPF
0.05*0.2*0.2 *100%=0.2%
So the conclusion is that we just need another 500 DPF or 312.5 Tokamaks and we should be there with 100% probability. Alternatively we just need one very very very lucky Polywell
Anyone cares to discuss the odds?
Polywell
0.05*0.001*0.001*0.00001*0.5 *100% = 0.000000000025%
Tokamak
0.05*0.2*0.4*0.8 *100% = 0.32%
ICF
0.001*0.01*0.2*0.5*0.02*0.5 *100% = 0.000001%
DPF
0.05*0.2*0.2 *100%=0.2%
So the conclusion is that we just need another 500 DPF or 312.5 Tokamaks and we should be there with 100% probability. Alternatively we just need one very very very lucky Polywell
Anyone cares to discuss the odds?