Suppression Of ELMs in Toks

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MSimon
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Suppression Of ELMs in Toks

Postby MSimon » Sat Jan 30, 2010 11:22 am

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http://www.iop.org/EJ/article/-alert=34 ... a2a520a788

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Large type-I edge localized modes (ELMs) are completely suppressed in hybrid discharges for the first time by applying an edge resonant perturbation (RMP) using an internal coil set with toroidal mode number n = 3. This is an important advance in developing hybrid discharges as a baseline operating scenario for ITER. In these experiments on the DIII-D tokamak, the ELM suppression lasts for ∼ 1 s in plasmas with normalized beta up to βN = 2.5 (volume average beta up to β = 3.4%) and a fusion performance factor as high as βNH98y2/q2 95 = 0.20, which equals the value for the Q = 10 scenario in ITER. A strong interaction between the 3/2 neoclassical tearing mode and the RMP, which slows the pedestal toroidal rotation, limits the achievable βN and the duration of ELM suppression.


They apply audio frequency currents (2 to 20 KHz) to auxiliary coils in the tokamak. The suppression only lasts for a few seconds. It appears to mode lock the plasma for a while.

Compare this with the Polywell where oscillations are encouraged at the plasma natural frequency and may be enhanced by POPS.

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Nik
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Whatever exceeds break-even...

Postby Nik » Sat Jan 30, 2010 5:45 pm

IIRC, there's been a LOT of work on 'tickling' Tokomac plasmas to prevent unwanted resonance modes developing.

IIRC, the process was once described as running trucks across 'Galloping Gertie' bridge to suppress the catastrophic 'natural' oscillation modes...

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Re: Whatever exceeds break-even...

Postby MSimon » Sat Jan 30, 2010 6:21 pm

Nik wrote:IIRC, there's been a LOT of work on 'tickling' Tokomac plasmas to prevent unwanted resonance modes developing.

IIRC, the process was once described as running trucks across 'Galloping Gertie' bridge to suppress the catastrophic 'natural' oscillation modes...


And note: they only damped mode 1. And only for a short time what about other modes?

And note: this is the second major review in a year's time:

http://www.iop.org/EJ/abstract/0029-5515/49/6/065012/
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chrismb
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Postby chrismb » Sat Jan 30, 2010 7:25 pm

Sounds to me like this is a report that they've just now managed to achieve in D-III what has already been done in JET.

kcdodd
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Postby kcdodd » Fri Feb 12, 2010 11:52 pm

Apparently there is also opposition to this idea in iter for the simple fact that you could not have internal coils in a power-plant design.
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Postby Art Carlson » Sat Feb 13, 2010 7:54 am

I talked to a tokamak friend last week, and he said this is the Next Big Thing. Everybody (ASDEX-Upgrade, JET, ...) is building internal coils into their machine to suppress ELMs. Whether this is a breakthrough or a sign of desperation is a matter of opinion.

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Postby chrismb » Sat Feb 13, 2010 8:28 am

I was told that the addition of ELM disruption coils was one of the big re-designs incorporated into the *new* ITER design. It [the redesign] was why the budge jumped around 2001.

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Postby MSimon » Sat Feb 13, 2010 10:06 pm

chrismb wrote:I was told that the addition of ELM disruption coils was one of the big re-designs incorporated into the *new* ITER design. It [the redesign] was why the budge jumped around 2001.


You know, with just a few more design modifications they could turn ITER into a Polywell.
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