Helion Energy to demonstrate net electricity production by 2024

[Skipjack]

It will be a fully structured FRC only IF they will be able to overcome the rotational instabilities that are limiting the confinement time.
And this is one of those big "IF" that has been plaguing them (and TAE) from 2010 and that both are still struggling with up to the start of 2022 according their own reports.

The goal is not to stabilize the FRC against tilt forever, but just for about 1ms. Trenta was at 0.5 ms.
The confinement time scales as r^2.6. That was confirmed over several prototypes. What also helps them is that their FRCs are highly elongated, which reduces stability concerns.
So you increase the radius (as they are doing for Polaris and then again for subsequent power plants) and the confinement time will increase enough for their needs. I assume that the final power plant will have a 33% to 50% increase in radius over Trenta. Not sure where exactly Polaris falls in there. I am not sure if it is quite full power plant scale. What I do know is that they want to keep the overall diameter of the machine at or below 3 meters to keep it road transportable.

[Giorgio]

It will be a fully structured FRC only IF they will be able to overcome the rotational instabilities that are limiting the confinement time.
And this is one of those big "IF" that has been plaguing them (and TAE) from 2010 and that both are still struggling with up to the start of 2022 according their own reports.

The goal is not to stabilize the FRC against tilt forever, but just for about 1ms. Trenta was at 0.5 ms.
The confinement time scales as r^2.6. That was confirmed over several prototypes. What also helps them is that their FRCs are highly elongated, which reduces stability concerns.
So you increase the radius (as they are doing for Polaris and then again for subsequent power plants) and the confinement time will increase enough for their needs. I assume that the final power plant will have a 33% to 50% increase in radius over Trenta. Not sure where exactly Polaris falls in there. I am not sure if it is quite full power plant scale. What I do know is that they want to keep the overall diameter of the machine at or below 3 meters to keep it road transportable.

Tilt instabilities (misalignment of the FRC own magnetic dipole with the external magnetic field) are not the main concern.
Rotational instabilities (due to the centrifugal force of the plasma) at the n=2 mode are the main issue. These are the typical disruptive instability in all the FRC machines.
Helion and TAE have been struggling with this issue (among many others) for the last decade at least.

Trenta was able to reach 0.5 ms because that's the moment when the n=2 rotational instabilities kick in and disrupt everything. From the public results it seems that all the systems that they envisioned to control these instabilities in Trenta didn't give the expected results. Hopefully they learned enough to fix it into Polaris, but is hard to guess unless they will disclose it openly.
The point is that until now we still do not have yet a solid theory+model of the formation and evolution of these type or instabilities to fully understand how to control them, it's mainly a trial and error job.

Also don't give too much weight on the confinement time scales models. It is based on outdated models with too many assumptions to simplify the math. We will know it's validity only once the machine is running.

[Skipjack]

Rotational instabilities (due to the centrifugal force of the plasma) at the n=2 mode are the main issue. These are the typical disruptive instability in all the FRC machines.
Helion and TAE have been struggling with this issue (among many others) for the last decade at least.

n=2 instabilities are not an issue for Helion since their pulses are too short.

From the public results it seems that all the systems that they envisioned to control these instabilities in Trenta didn't give the expected results.

I looked at the results too and did not see that. What exactly are you referring to? I am not aware of any active system that Helion have in place to actively control instabilities, except passively through higher temperature (FRCs get more stable with temperature) and greater radius/elongation. Now TAE is a different story (with their neutral beam injection), but they are aiming for steady state and not pulsed.
From all I have heard, they and their investors were very pleased with the results of Trenta, even after just one year. They were actually better than expected, not worse.
And n=2 instability is not a concern for Helion because

Also don't give too much weight on the confinement time scales models. It is based on outdated models with too many assumptions to simplify the math. We will know it's validity only once the machine is running.

Model that was confirmed over 6, ever larger prototypes? For reference, Trenta had about 10 times the confinement time of Venti...

[Giorgio]

Rotational instabilities (due to the centrifugal force of the plasma) at the n=2 mode are the main issue. These are the typical disruptive instability in all the FRC machines.
Helion and TAE have been struggling with this issue (among many others) for the last decade at least.

n=2 instabilities are not an issue for Helion since their pulses are too short.

I will dig for you the Helion report and the video where they speak about it and post it later, but this issue is well known since earlier than 2010. I do remember even some ARPA reports from Slough when they started to investigate it.

And while their pulse is short, without an active system to stabilize the field I strongly doubt that they will ever be able to reach the confinement times they are targeting for their fusion cycle as the n=2 instabilities will limit stability to 50 uSec. This is why they was able to demonstrate a field stability of only 40 uSec with Trenta.

From the public results it seems that all the systems that they envisioned to control these instabilities in Trenta didn't give the expected results.

I looked at the results too and did not see that. What exactly are you referring to? I am not aware of any active system that Helion have in place to actively control instabilities, except passively through higher temperature (FRCs get more stable with temperature) and greater radius/elongation.

The control system you are referring to is to remove TILT instabilities, not rotational instabilities. Tilt instabilities should be under control.
In the video they mentioned that the data presented was not including any rotational instability control measure, which didn't made it clear (to me) if what they envisioned didn't work or if Trenta was born without any system to control these type of instabilities or if they didn't want to disclose the data for proprietary reasons.
Let me find everything for you after this post.

Also don't give too much weight on the confinement time scales models. It is based on outdated models with too many assumptions to simplify the math. We will know it's validity only once the machine is running.

Model that was confirmed over 6, ever larger prototypes? For reference, Trenta had about 10 times the confinement time of Venti...

It's a model based on the level reached by actual experimental data and extrapolated toward higher levels in the hope that nothing different will happen when we scale. We have no scientific evidence that this model will hold, we can keep the hope, but we will know only once we scale.
And as a matter of fact I think that the scaling value you indicated has been already slightly reduced after the Trenta campaign.

[Giorgio]

Here as promised:

1) Helion news release:
Quote:
Fusion reaction rates and particle confinement meet or exceed traditional modified-Lower Hybrid Drift
(LHD) FRC energy confinement and overall configuration time is limited as expected by the
onset of n=2 rotational instability.


2) Video presentation of Trenta campaign:
At time 10:12 Speaks about Rotational instabilities and lack of mitigation systems as I discussed in previous post
At time 12:11 Confinement times now go with r^2.1

From the public results it seems that all the systems that they envisioned to control these instabilities in Trenta didn't give the expected results.

From all I have heard, they and their investors were very pleased with the results of Trenta, even after just one year. They were actually better than expected, not worse.

They did a hell of a job solving a ton of issues, and I am sure that investors are pleased of the results, as I am also pretty sure that they showed to investors plenty of data that they didn't publicly disclose.
They still have a lot of issues to put under control, some are purely engineering issues while some other (like the rotational instabilities and other we discussed in previous posts) are more tough to handle as (for what we know) they still lack a clear understanding of them.
And this was the reason why I placed them behind ZAP in the start of this discussion.

[Skipjack]

The video is here and I have watched it quite a few times:
https://www.youtube.com/watch?v=wHirlGXlJ38

You might want to watch it again, especially starting at 6:55. The equation you want to look at for tilt instability is s*/e < 5
With the crucial point that David makes at 7:33:
"this enables to build systems that have a theoretical stability limit in MHD stability the us or ns level but actually extend them to 100s of us or ms".

As for them doing any active stabilization against n=2 instability he says at 10:00:
"In all of the data we are showing here, there was no actual edge biasing or other stability mitigation. So these plasmas were terminated not on a tilt instability timescale, but on a rotational instability growth. There is no addition of any kind of stabilizing system in what we are showing here today."

Now from their poster presented at the same conference, I know that their pulse length is about 0.5 ms, which is the Taue achieved with Trenta.
The point is that their pulse length is below the onset time of n=2 instabilities and they do not need nor want longer pulses.

At time 10:12 Speaks about Rotational instabilities and lack of mitigation systems as I discussed in previous post

Which is what I said. They don't have and do not need mitigation systems because their pulses do not need to be long enough for n=2 instabilities to occur.

At time 10:12 Speaks about Rotational instabilities and lack of mitigation systems as I discussed in previous post
At time 12:11 Confinement times now go with r^2.1

There are different radii at play here. This is the separatrix radius that seems to be scaling better than the rs^2 stated by John Slough in 2009.
I am not sure which of the radii David was referring to when he mentioned r^2.6 to me a while ago. I am asking him for clarification.

[Giorgio]

You might want to watch it again, especially starting at 6:55. The equation you want to look at for tilt instability is s*/e < 5
With the crucial point that David makes at 7:33:
"this enables to build systems that have a theoretical stability limit in MHD stability the us or ns level but actually extend them to 100s of us or ms".

As for them doing any active stabilization against n=2 instability he says at 10:00:
"In all of the data we are showing here, there was no actual edge biasing or other stability mitigation. So these plasmas were terminated not on a tilt instability timescale, but on a rotational instability growth. There is no addition of any kind of stabilizing system in what we are showing here today."

That's exactly what I am saying from the start. Tilt Instabilities is not the issue, n=2 rotational instabilities are the issue. Unless you fix that you cannot have a stable field over 40 uSec.

Now from their poster presented at the same conference, I know that their pulse length is about 0.5 ms, which is the Tauie achieved with Trenta.
The point is that their pulse length is below the onset time of n=2 instabilities and they do not need nor want longer pulses.

No, for what I remember they need 100 uSec of stable field in the commercial reactor.

[Skipjack]

That's exactly what I am saying from the start. Tilt Instabilities is not the issue, n=2 rotational instabilities are the issue. Unless you fix that you cannot have a stable field over 40 uSec.

Nope the n=2 instabilities set on AFTER the tilt instabilities and the onset of those is extended to the ms range as David mentions in the video.

From what I remember, they are aiming for ~1ms. I would like to see a reference to the 100 us.

[Giorgio]

That's exactly what I am saying from the start. Tilt Instabilities is not the issue, n=2 rotational instabilities are the issue. Unless you fix that you cannot have a stable field over 40 uSec.

Nope the n=2 instabilities set on AFTER the tilt instabilities and the onset of those is extended to the ms range as David mentions in the video.

From what I remember, they are aiming for ~1ms. I would like to see a reference to the 100 us.

According the picture you linked Tpulse < 0.5 ms (500 us), so the 100 us that I was remembering is into that range, and anyhow anything above 40 us will require to solve the issues of the n=2 rotational instabilities. I will look anyhow for the source for your reference tomorrow .

And if they are aiming for 1 ms (1000 us) as you remember, than the rotational instability issue would even more complicated.

[Skipjack]

According the picture you linked Tpulse < 0.5 ms (500 us), so the 100 us that I was remembering is into that range, and anyhow anything above 40 us will require to solve the issues of the n=2 rotational instabilities. I will look anyhow for the source for your reference tomorrow .
And if they are aiming for 1 ms (1000 us) as you remember, than the rotational instability issue would even more complicated.

This value is for Trenta and not the power plant.

[Giorgio]

According the picture you linked Tpulse < 0.5 ms (500 us), so the 100 us that I was remembering is into that range, and anyhow anything above 40 us will require to solve the issues of the n=2 rotational instabilities. I will look anyhow for the source for your reference tomorrow .
And if they are aiming for 1 ms (1000 us) as you remember, than the rotational instability issue would even more complicated.

This value is for Trenta and not the power plant.

Indeed I checked and you are correct, the 1 ms value was for the Trenta and they (officially) didn't reach it as confinement stopped at 0.04 ms due to the rotational instabilities as I have been saying.

In the commercial reactor they plan to increase the plasma density and magnetic field to be able to reduce the burning time, but we are still way above the 40 us that they reached with Trenta (as also the picture you linked before shows).

Again, it might as well be that they solved the issue and didn't want to disclose it, no one knows, but the issue is real and is there from 15 years waiting to be solved as it is a roadblock for everyone working with FRCs and hoping to get to Q>1.

[Munchausen]

Again, it might as well be that they solved the issue and didn't want to disclose it, no one knows, but the issue is real and is there from 15 years waiting to be solved as it is a roadblock for everyone working with FRCs and hoping to get to Q>1.

Is this what Dennis Whyte has in mind when he says that FRC:s are a thousand times to leaky?

Is it the long enough parameter in hot enough, dense enough, long enough?

[Skipjack]

Indeed I checked and you are correct, the 1 ms value was for the Trenta and they (officially) didn't reach it as confinement stopped at 0.04 ms due to the rotational instabilities as I have been saying.

Reference please!
Venti was the one with 0.04 ms TauE, IIRC. Trenta did significantly better, AFAIK.

[Skipjack]

Again, it might as well be that they solved the issue and didn't want to disclose it, no one knows, but the issue is real and is there from 15 years waiting to be solved as it is a roadblock for everyone working with FRCs and hoping to get to Q>1.

Is this what Dennis Whyte has in mind when he says that FRC:s are a thousand times to leaky?

Is it the long enough parameter in hot enough, dense enough, long enough?

Meh, it is exaggerated. FRCs have a much higher beta than Tokamaks and they can be 1000 times as dense with relatively simple magnets.

[mvanwink5]

Helion is focusing on factory production & improving already acceptable lifetimes for diverter. Helion is not the only one that feels that the 'science' is proven & that engineering demonstration is a matter of building the prototype. For instance, General Fusion has tested FRC compression with explosive driven compression chambers, & their liquid metal piston driven compression design was their hold up.

Perhaps publications do not include test data, but huge committed investment money by savvy investors whose money is dear to them, as opposed to public money for politicians, is good enough for me.

On the other hand, plasma compression is unproven for Zap, & they admit that their latest modeling is where their confidence lies. Also, their machine is not that expensive to build & the reason their time line for Q>1 is short (2023 as I recall, & their machine is up & running as we speak). So, I put Zap in my '?' column until they reach Q>1, & even then until commercial compression levels are reached I harbor doubts that some instability might appear.

Yet, I am quite interested in the current debate.