I doubt that it is possible if taking into account that we will have only axial magnetic field in merging zone.
He already did it though, albeit at a smaller scale.
He did toroids as I understand and not confined merged one.
May be I am not understand the mechanism correctly but it is well known that only axial field is not enough for confinement. And he needs confinement time of milliseconds which is not trivial to achieve for claimed density.
Yes he did collide two FRC plasmoids in the IPA experiments. Unless I missunderstood something.
He is not aiming to confine the plasmoids, he is colliding them. He wants to do a pulsded device, not a steady state device.
Skipjack wrote:Yes he did collide two FRC plasmoids in the IPA experiments. Unless I missunderstood something.
He is not aiming to confine the plasmoids, he is colliding them. He wants to do a pulsded device, not a steady state device.
... and they merge after collision, that was also explicit: The FRCs undergo magnetic reconnection and become one FRC with some percentage of the.collision energy thermalized in the plasma.
And then the hammer comes down in the form of a magnetic compression "squeeze."
An interesting note in the paper is that not only did they expect the FRC plasmoids to collide but their 2-D models showed that the FRCs would actually bounce,... and bounce enough to prevent merging and reconnection.
But that turned out not to be the case and the FRCs did merge.
Skipjack wrote:Joseph, I guess you dont have access to the paper?
I have. And what?
• Is there is written that merged plasmoid squeezed by time dependent field? Or field is not time dependent?
• Where there written about forces acting during merging? As I am sure that nothing else than viscosity will hold plasmoids during merging vs. inertia of supersonic motion. As I know that confinement by axial field in axial motion is impossible. Are there in plasmoids any gradient currents in merging moment?
And I asking this as you claim something that I really do not understand and could not find answer in that paper. So, you know and I - not.
Joseph Chikva wrote:Where there written about forces acting during merging? As I am sure that nothing else than viscosity will hold plasmoids during merging vs. inertia of supersonic motion.
I'm not sure. I think flux from the opposing FRC could do it, but really don't know.
tomclarke wrote:I'm not sure. I think flux from the opposing FRC could do it, but really don't know.
FRC is droplet moving with 250 km/s. Yes?
Is there any spin? I am really attempting to understand.
If we look at draft of Helion I see the area where plasmoid is created, accelerated and directed along the decreasing diameter tube's axis.
As I understand that tube is a long solenoid with increasing by length axial field.
And then there in merging zone (collision zone) is a one big solenoid field of which will directed along to direction of one plasmoid and oppositely to another.
Plasmoid permanently moves along lines of an axial magnetic field.
I do not see any way how forces braking one plasmoid by another will be created.
As linear size of plasmoid is only 7 cm, velocity 250km/s can you imagine how strong forces are necessary for that?
As I understand that tube is a long solenoid with increasing by length axial field.
If I understand it correctly, an FRC is basically an infinitely elongated toroid like a stretched out Tokamak.
The confinment times do not have to be very long, from what I understand, as the device is pulsed and he can recover a lot to the energy at the ends of the device.
As I understand that tube is a long solenoid with increasing by length axial field.
If I understand it correctly, an FRC is basically an infinitely elongated toroid like a stretched out Tokamak.
The confinment times do not have to be very long, from what I understand, as the device is pulsed and he can recover a lot to the energy at the ends of the device.
We can say that sphere is a special case of torus. FRC is not extended ТОКАМАК but can be compared with small aspect ratio ТОКАМАК. Similarly to Spheromak.
For the declared number density of 10^23 m^-3 required confinement time should has an order of at least milliseconds.
I have counted up the required deceleration rate and that has an order of magnitude of 10^12 m/s^2.
If such deceleration rate would be provided by electric field, required intensity would has an order 25000 V/m. And that is not a weak field.
And till now I am not understanding what should provide the required deceleration.
The reason that Tri-Alpha's reactor looks so much like Helion's is that Slough helped Tri-Alpha design it. IIRC, Tri-Alpha's claim to uniqueness was that they were using the FRC in a similar manner to the gas-dynamic trap: the reactions would take place between a high-energy beam population and a low-energy bulk plasma. I'm guessing the high-energy beam would be hydrogen, with a mixed boron & hydrogen bulk plasma. Supposedly this takes advantage of the peak cross-section for p-B11 fusion.
Joseph:
Keep in mind that the plasmoid masses are extremely low, (F=m*a, a is high, m is low). But you are right that the collisions are relatively violent events. I think most of the energy is handled by the electromagnetic fields, since particle-particle collisions would probably not be sufficient to keep the two plasmoids from passing through each other.
The idea is for the two plasmoids to collide & combine after being accelerated, and then a theta pinch is applied to the resulting FRC to compress it. There may or may not be a slight mirror field to help center the FRC in the theta pinch once the collision takes place.
Solo wrote:The reason that Tri-Alpha's reactor looks so much like Helion's is that Slough helped Tri-Alpha design it. IIRC, Tri-Alpha's claim to uniqueness was that they were using the FRC in a similar manner to the gas-dynamic trap: the reactions would take place between a high-energy beam population and a low-energy bulk plasma. I'm guessing the high-energy beam would be hydrogen, with a mixed boron & hydrogen bulk plasma. Supposedly this takes advantage of the peak cross-section for p-B11 fusion.
Joseph:
Keep in mind that the plasmoid masses are extremely low, (F=m*a, a is high, m is low). But you are right that the collisions are relatively violent events. I think most of the energy is handled by the electromagnetic fields, since particle-particle collisions would probably not be sufficient to keep the two plasmoids from passing through each other.
The idea is for the two plasmoids to collide & combine after being accelerated, and then a theta pinch is applied to the resulting FRC to compress it. There may or may not be a slight mirror field to help center the FRC in the theta pinch once the collision takes place.
I have calculated:
plasmoid mass in case of number density 10^23 and linear size 7 cm has an order 10^-8 kg (if we have equal quantity of D and T).
F=m*a =1^-8*10^12=10^4N or in the other word the force equal to weight of about 1 ton mass is required.
So, are you saying that theta pinch will occur in collision zone and its azimuthal currents will create forces for stopping plasmoids?
So, if you saying theta pinch, magnetic field there is time dependent.
Induced currents will be directed in one direction for both plasmoids => acting forces too.
Consequently Lorenz forces experienced by both plasmoids will directed at the same direction and so one plasmoid will be decelerated and the second accelerated.
Am I right?
Have you heard the joke about the 3 blind men describing an elephant?
If someone has the time to really study the paper, he/she could become our resident expert and answer most of the questions asked here-in, based on reported experimental data. Not me, I don't do well at explaining, but I can point you back to the source paper.
Aero wrote:Have you heard the joke about the 3 blind men describing an elephant?
If someone has the time to really study the paper, he/she could become our resident expert and answer most of the questions asked here-in, based on reported experimental data. Not me, I don't do well at explaining, but I can point you back to the source paper.
I would be interested in an evaluation of the conceptual design presented in the paper as applied to spacecraft power.
The authors propose a 60 MW (thermal?) cylindrical device ~2 m long and ~0.5 m diameter. Estimating the density at 5 metric tons per cubic meter gives a power source of about 2 tons mass. Couple that to a VASIMR engine about 70% efficient with an exhaust velocity, Ve, of 50 km/sec. ending up with about 60 MW * 0.33 * 0.7 ~= 14MW exhaust energy. (Assuming thermal to electric conversion at 33%) Now using energy = 1/2 m Ve^2 and thrust = m Ve, I would solve for exhaust mass then thrust if I were confident of the correct units to use. Once I know thrust, space vehicle acceleration is easy for any speculated vehicle mass.