Has Wiffleball Been Created Ever?

[mvanwink5]

If the energy distribution is non-maxwellian, then the energy profile is more important than the "temperature," no? And, by theory, the profile for electrons should be different than that for ions, so that would be important too. After all, the plasma is contained not just by magnetic fields, but also by the potential well. There really is a lot of information here on site if you are really interested. Just saying...
Best regards

[Joseph Chikva]

No they are not the same thing. Confinement time, as in energy or particle confinement time, is the time scale for energy and particle transport out of the machine, which is independent of how long the machine runs.

So, are you stating that TOKAMAK most of time runs without plasma?

[Joseph Chikva]

Ah. So you are aware of the instabilities. If they can't be brought under control with the current ITER design the confinement will not be near as long as projected. It would be on the order of 1 second not 1,000.

How that would not be paradoxical I know a little about instabilities that are observed in any plasma device without any exceptions.
-So, are you stating that ITER will have lifetime of plasma less than e.g. JET?
-And do you think that confinement time of seconds order is possible without controlling of instabilities?

[MSimon]

Ah. So you are aware of the instabilities. If they can't be brought under control with the current ITER design the confinement will not be near as long as projected. It would be on the order of 1 second not 1,000.

How that would not be paradoxical I know a little about instabilities that are observed in any plasma device without any exceptions.
-So, are you stating that ITER will have lifetime of plasma less than e.g. JET?
-And do you think that confinement time of seconds order is possible without controlling of instabilities?

The instabilities appear within seconds of plasma formation and cause a quench of the plasma (contact with the walls much greater than designed).

So a second or a few seconds of operation is possible. One thousand seconds of continuous operation is out of the question if the instabilities are not "corrected". The current theory of correction is to drain off some plasma energy (using electromagnets). As far as I know it has never been tested. It is engineering theory at this point.

[Joseph Chikva]

The instabilities appear within seconds of plasma formation and cause a quench of the plasma (contact with the walls much greater than designed).

So a second or a few seconds of operation is possible. One thousand seconds of continuous operation is out of the question if the instabilities are not "corrected". The current theory of correction is to drain off some plasma energy (using electromagnets). As far as I know it has never been tested. It is engineering theory at this point.

Mr. MSimon, saying "continuous operation" for 1000 seconds you are forgetting that plasma lifetime has another scale than our life. As for plasma even 1 second is rather long time. Especially when number density has 10^20 m^-3 order.
This was the desired goal in 70th. As this means overcoming of Lawson Criterion. So, quite "continuous operation".

As characheteristic timescale of the most instabilities development has a microseconds order (million times shorter than 1 sec).
Simply, ТОКАМАК concept slows down the development of instabilities allowing to plasma living hundreds seconds. And this is the fact.

The Tore Supra Tokamak that is part of the Cadarache nuclear research centre holds the record for the longest plasma duration time of any tokamak: six minutes and 30 seconds.

six minutes and 30 seconds=390 sec. Not almost "continuous operation"?

[MSimon]

The instabilities appear within seconds of plasma formation and cause a quench of the plasma (contact with the walls much greater than designed).

So a second or a few seconds of operation is possible. One thousand seconds of continuous operation is out of the question if the instabilities are not "corrected". The current theory of correction is to drain off some plasma energy (using electromagnets). As far as I know it has never been tested. It is engineering theory at this point.

Mr. MSimon, saying "continuous operation" for 1000 seconds you are forgetting that plasma lifetime has another scale than our life. As for plasma even 1 second is rather long time. Especially when number density has 10^20 m^-3 order.
This was the desired goal in 70th. As this means overcoming of Lawson Criterion. So, quite "continuous operation".

As characheteristic timescale of the most instabilities development has a microseconds order (million times shorter than 1 sec).
Simply, ТОКАМАК concept slows down the development of instabilities allowing to plasma living hundreds seconds. And this is the fact.

The Tore Supra Tokamak that is part of the Cadarache nuclear research centre holds the record for the longest plasma duration time of any tokamak: six minutes and 30 seconds.

six minutes and 30 seconds=390 sec. Not almost "continuous operation"?

Obviously ITER is not repeating and expanding that experiment. Otherwise the extra electromagnets to correct instabilities would not be needed.

And yes microseconds is the speed at which the correction needs to take place, but instabilities seem to take about a second to form.

[Joseph Chikva]

but instabilities seem to take about a second to form.

Instabilities were only the reason why lifetime of plasma in other experiments did not exceed milliseconds. While

For the duration of each 1 000 second plasma pulse during ITER operation, the ballet of increasing and decreasing voltage will continue in the modules, carefully choreographed to build the plasma current up to a plateau of 15 MA for around 400 seconds, before ramping down again to zero.

[Robthebob]

We do not go around question various labs and experiments' validity, because they refuse to show every single thing to you.

Most shot data are not published, because that's stupid. No one at a conference is going to care about looking at 10s thousands of pages of numbers. They care about the semi-analyzed data; numbers that are conclusions of the raw data, and you use these conclusions to draw more refined conclusions.

While its true that most public labs and experiments publish their specs, instrumentation, etc, what about private research? Do you always question the validity of those labs and experiments? They dont publish everything.

PS: Dont argue with Joe about ITER, even my teachers arent as qualified as he is. If he doesnt care about microinstabilities, then I'm sure it's nothing to worry about. I mean sure the plasma can be confined that long, but can you deal with instabilities that just randomly pop up, grow and cause a disruption? I'm sure it's nothing to worry about.

[MSimon]

PS: Dont argue with Joe about ITER, even my teachers arent as qualified as he is. If he doesnt care about microinstabilities, then I'm sure it's nothing to worry about. I mean sure the plasma can be confined that long, but can you deal with instabilities that just randomly pop up, grow and cause a disruption? I'm sure it's nothing to worry about.

LULZ

[hanelyp]

PS: Dont argue with Joe about ITER, even my teachers arent as qualified as he is. ...

This is exactly what I worry about not challenging Joe when he makes base level errors, someone taking him as the authority he claims to be. As many times as he has quoted material out of context, claiming something the material doesn't support, I don't take anything he says as reliable.

[hanelyp]

No they are not the same thing. Confinement time, as in energy or particle confinement time, is the time scale for energy and particle transport out of the machine, which is independent of how long the machine runs.

So, are you stating that TOKAMAK most of time runs without plasma?

- Energy and particle confinement time aren't the same thing, though they are related. In any magnetic confinement plasma device energy is lost to EM radiation. In a polywell, electrons can be lost without losing much energy by making electrons work against an electric field to escape the system.

- The plasma can be maintained for an extended period despite loss if particles and energy are fed in to replace losses. In a hypothetical tokomak running in ignition, energy production from fusion matches energy losses of various forms. In current tokomaks that run short of ignition, energy must be fed in to keep the plasma hot. Particles lost through diffusion or plasma turbulence must also be replaced by some means.

[Joseph Chikva]

- Energy and particle confinement time aren't the same thing.

I am sure you meant "plasma confinement" and not "particle confinement"
"Energy confinement" and "confinement" also are not the same terms.

Magnetic confinement fusion is an approach to generating fusion power that uses magnetic fields to confine the hot fusion fuel in the form of a plasma.

Time how long to keep plasma separatly from the walls - lifetime of plasma.

The energy confinement time is defined as a function of the global plasma energy content, W, and the applied total heating power, P:

At least we in former SU use two these terms separately.

[Joseph Chikva]

PS: Dont argue with Joe about ITER, even my teachers arent as qualified as he is. ...

This is exactly what I worry about not challenging Joe when he makes base level errors, someone taking him as the authority he claims to be. As many times as he has quoted material out of context, claiming something the material doesn't support, I don't take anything he says as reliable.

I am not mistaken regarding you?
are you the man saying "uniform current distributon" when should say "current"? Is in TOKAMAK a uniform current distribution?
I am saying "never". And you?

Then let's what "base level errors" I make.

[Joseph Chikva]

PS: Dont argue with Joe about ITER, even my teachers arent as qualified as he is.

I am not competting with your teachers. But when they said "H-mode is not well understood". I only said that H-mode discovered in 90s by Dr. Wagner has been researched till now by at least one generation of TOKAMAK researchers. So, at least several thousands people understand well. Unlike your teachers who stuck in 70s.

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.

[D Tibbets]

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