Has Wiffleball Been Created Ever?

[Robthebob]

If he doesnt care about microinstabilities, then I'm sure it's nothing to worry about.

You can't deny the indisputable fact that lifetime of plasma in Tokamaks has many hundred seconds order. Despite to macro and also micro instabilities which are in existance in ANY plasma device. Simply TOKAMAK allow controlling instabilities at this level.

Matters nothing when random disruptions happen and no one seem to understand why they happen, disruptions can cause bad performance or worse, loss of confinement completely. Calm down, Joe.

I still dont get it, for someone as well informed as you, how are you still not acknowledging two huge problems with toks, and they are (toks have the same problem for at least the last 10 years, so almost everyone in the field knows about this, so you ought to know about them, too) inner core material and plasma instability, both macro and micro.

Again, I'm not saying toks cant last into the minutes, I'm sure they can, so can stellerators, but I'm saying it doesnt matter how long you toks can last, if instabilities happen, then what? You can have all the same parameters and have instabilities happen sometimes and not other times. The instability in part of the very design of toks, the plasma current, and I think fluid flow, but I can be wrong, chrismb talked about it a while back.

Oh yeah, the whole too much radiation and it cooks the inner walls so some of the wall material will get into the plasma and instantly soak up tons of energy (this has to do with dusty plasma, there's a reason for doing this type of research), is not a good thing either. In fact the whole, there's no known material that can withstand a burning plasma is a huge problem too.

You know what kind of machine doesnt have any of these instabilities? Stellerators. Why isnt ITER a stellerator machine? By your standard, stellerators, being a steady state machine, are designed to confine longer and have less problems. All your nice H-mode can also be achieved in stellerators too...

Tok guys are way disillusioned, I'm not saying we're not, but before calling someone ugly, look in the mirror for a change.

[Joseph Chikva]

Again, I'm not saying toks cant last into the minutes,...

"Toks lasting minutes" are overcoming Lawson Criterion (product of number density and confinement time). Modern toks do that but can not overcome triple product (product of number density and confinement time and temperature). So, denying by you (and your professors) heating problem is the most significant problem for TOKAMAKs.

I'm sure they can, so can stellerators,...

It does not matter in what you are sure but after doubtless success of TOKAMAKs stellarator program in USA was cancelled. That is the fact that is much more significant than my, yours or any others opinion.

but I'm saying it doesnt matter how long you toks can last, if instabilities happen, then what?

May be you would be surprised but they (instabilities) are occurring in ANY plasma device.
But once again if lifetime of plasma in TOKAMAKs reaches seconds, they are rather controllable in TOKAMAKs. Unlike any other devices.

PS> You wrote too long text. It is rather difficult for me to answer on each little sentence from there. Sorry.

[Joseph Chikva]

I am answering on one more your sentence:

You know what kind of machine doesnt have any of these instabilities? Stellerators.

Only the first googled link Trapped-particle instabilities in quasi-isodynamic stellarators http://www-thphys.physics.ox.ac.uk/rese ... /proll.pdf

In fact, there is not plasma device without instabilities.
In fact, difference between TOKAMAK and Stellarator is not so big as both concepts use combination of poloidal and toroidal fields.
Toroidal in both is created in the same manner: bent into torus solenoid, while poloidal in TOKAMAKs by flowing in plasma current and in Stellarator - mainly by external coils. "Mainly" because as a rule Ohmic heating also used in Stellarators by current also contributing some share in poloidal field.

By the way: is crismb one of your praised teachers?

[Joseph Chikva]

And one more

I still dont get it, for someone as well informed as you, how are you still not acknowledging two huge problems with toks, and they are (toks have the same problem for at least the last 10 years,

Much less problems than in previous 40 years.

[Joseph Chikva]

And one more

Oh yeah, the whole too much radiation and it cooks the inner walls so some of the wall material will get into the plasma and instantly soak up tons of energy (this has to do with dusty plasma, there's a reason for doing this type of research), is not a good thing either. In fact the whole, there's no known material that can withstand a burning plasma is a huge problem too.

First wall is a challenge. And in ITER program's frame beryllium on copper and stainless steel design will be checked.
But actually this challenge is very common for any neutronic approaches.

[D Tibbets]

And one more

I still dont get it, for someone as well informed as you, how are you still not acknowledging two huge problems with toks, and they are (toks have the same problem for at least the last 10 years,

Much less problems than in previous 40 years.

Actually the problems are recognized to be much greater than those perceived 40 years ago. The real questions are :
Are the real problems better understood and are there still unrecognized problems?

Has the understanding of problems been accompanied by reasonable workarounds?


Again I suspect that ITER may reach it's goals. A lot has been learned. That still leaves huge unresolved problems with engineering and economies.

Dan Tibbets

[Joseph Chikva]

Actually the problems are recognized to be much greater than those perceived 40 years ago. The real questions are :
Are the real problems better understood and are there still unrecognized problems?

Has the understanding of problems been accompanied by reasonable workarounds?


Again I suspect that ITER may reach it's goals. A lot has been learned. That still leaves huge unresolved problems with engineering and economies.

Dan Tibbets

This is like as you come nearer to a massif, being sure that it is close.
But by approaching you realize how far your goal is.

Do not talk about economies. Let's solve only technical problems yet. As they still are quite complex. Today we should admitt that TOKAMAKs achieved required confinement. As even 1 sec is already enough in case of enough plasma reactivity.
But enough reactivity plasma has at about 15 keV. If Te=Ti
For estimation of required internal energy:
15keV * 2 (number of spices: ions and electrons) * 840 m^3 (plasma volume) * 10^20 m^-3 (number density) = ~403 MJ
And even neglecting losses for pumping such a big energy in 1 sec into plasma we need 403 MW of power in three different forms: Ohmic heating, RF power and neutral beam injection.
There is not possibility to do that. Real numbers are 10 times lower: about 50 MW. So, we need about 10 sec for pumping. And this is if not to take into account losses!

So, I do not believe to robthebob's teachers and also do not believe in TOKAMAK as well.

But you see TOKAMAK's problems in another place - in instabilities. Commonly stability problem is solved today for TOKAMAK. First TOKAMAKs had plasma lifetime of milliseconds order and today - seconds, tens or even hundreds seconds order.
And returning to economics, why are you and others comparing current Polywells with ITER and not with T-1 TOKAMAK, which was rather simple and cheap machine?

[krenshala]

Why do you guys insist on feeding the troll?

[MSimon]

Why do you guys insist on feeding the troll?

Entertainment.

[dkfenger]

I actually find these threads quite interesting. I skip over Joseph's posts, and read the replies - I find them quite educational.

I do wonder, though, are we talking about somewhat different concepts of Beta? When we speak of Beta=1 in a polywell, what is being confined to that level - just the electrons, or the ionized fuel as well? And is this really comparable to the difficulty of confining a burning plasma?

[Joseph Chikva]

Why do you guys insist on feeding the troll?

Trolls are not people who are agree that ions in Polywell moves strictly radially?

[Joseph Chikva]

I skip over Joseph's posts, and read the replies - I find them quite educational.

If you really seek for education, you should know that beta=1 is impossible for any magnetic confinement concept.
And polywell is the concept of confinement of electrons that create then the potential well for ions.

[Joseph Chikva]

I am not a troll.
I do not like TOKAMAK because it is too costly.
I like polywell because that is cheap. Regardless to its viability.

But at any opportunity I compare TOKAMAK with Polywell. Water with wine.

[ladajo]

I skip over Joseph's posts, and read the replies - I find them quite educational.

If you really seek for education, you should know that beta=1 is impossible for any magnetic confinement concept.
And polywell is the concept of confinement of electrons that create then the potential well for ions.

Well, I guess it is a good thing that Polywell is not magnetically confining ions.

Electro-Dynamic, slowly now, Eeeeleeectrrrroooooo-gasp-dyyyyyyynaaaaaammmmmmiiiiiiiic.

[emc3]

Dan,

Thanks for your rough formula ( Beta= density*voltage (KE of charged particles) / B field strength ) and implication on the simple temperature detection. (not hearsay here )

BUT, When talking about temperature for beta calculation, to my knowledge:

1) scientists are using a small fraction of the total energy, which is only the perpendicular part.

2) to be fair, for 3-D isotropic maxwellian plasma, the energy for any X-Y-Z direction should be about 1/3 of the value you used.

3) for non-maxwellian plasma, perpendicular energy is sth I do not understand: I just can not use "voltage, current and B field strength", that kind of estimation will be way way too high

4) is polywell plasma isotropic? or even close to isotropic? if not, your formula does not work.

5) sb else and you mentioned that beta=1 has been achieved at some point, at what scale?
5a) Size: few millimeter? centimeter, or decimeter?
5b) Time: few micro-second? milli-second, or ...?
5c) Q: the gain?

6) as for the peaking density curve, you mentioned "no other process that would create this density curve while the other machine parameters were kept constant." Sadly, for most of the plasma or machine parameters, you can not keep them constant, even the simple B field

Compare to toks, at the level of T-1 or T-3, early WBs' engineering could be simple, but the physics are not: it's way way too complicated. If some lobbyist tell us that he or sb else understand the wiffleball mechanism, be aware of "The Emperor's New Clothes".

Thanks again, to you and Robthebob

EMC2+

Dan,

Any clue on the "more definitive plasma density testing method"? What's the "less" testing way?

Even if it's 100% accurate, one can not obtain the beta from density alone: am I wrong?

Hearsay and implied information are the real players in "The Emperor's New Clothes".

emc2+

It's not so much hearsay, I mean... I talked to Dr. Gilmore, I did microwave interferometry for undergraduate research, it works... It's also not really hearsay if it literally said on the emc2 progress report on the recovery act website that it's what they're doing. (well it says what they're going to do during first quarter of this year)

No, density alone tells nothing about Beta. The formula is roughly Beta= density*voltage (KE of charged particles) / B field strength.
The point is that they can easily measure the voltage, current and B field strength. The density was the uncertain quantity.
Having accurate and precise information about all three components allows for accurate quantitative measurements.

Qualitatively, even with uncertain values for the three parameters, uncertainties about potential well depth achieved, etc. the shape of the curve of the density measurement (directly related to confinement time) climbing to a peak and then falling implies a best performance peak that is explained by Beta approaching one,then going away from one. I know of no other process that would create this density curve while the other machine parameters were kept constant. In the actual tests I think Beta started out at near infinity, the B field was then turned on and ramped up. The plasma density peaks at Beta= 1 and as the B field continues to strengthen, Beta decreases towards small values-0.5 to 0.1, etc.

Having more accepted quantitative measurements allows for more accepted results and understanding of the machine, but it does not change the basic conclusion of the Beta=1 relationship both from a physics stand point and the proof that the machine can achieve this condition. Except -with the argument that the PMT measurements was not linear or even worse, grossly inaccurate and imprecise to such an extent that the results were statistically nonsense. The more accepted measurement technique(s) makes this argument much harder to defend.

Dan Tibbets