Wednesday, February 15, 2006

ITER Physicists Reply To Focus Fusion

Thanks to these Froggy guys (whom I found in my referrers today) for pointing out this reply from the ITER boys as to the feasibility of focus fusion:
From: Bill Spears
To: Sterling D. Allan
Sent: Thursday, November 10, 2005 11:46 AM
Subject: Re: comment please: Tokamak has serious competitor in Focus Fusion

Dear Sterling,

Sorry for the delay in replying. It takes time to give you a reasoned reply and not just shoot from the hip. It also takes time to read and understand detailed scientific reports to make sure you are not missing something. I asked Dr. Michiya Shimada, our Head of Physics Unit, to review the material and make a comment. After he and his people reviewed the background papers indicated in your article, he concluded:

"The plasma focus isn't going to be a rival of the tokamak unless there's some very strange physics nobody has seen before.

Using the plasma parameters quoted in their publication, the proton-boron fusion energy obtainable in a plasma focus discharge is estimated to be 0.6 x 10-4 J, which is a fraction of a billionth of the electrical energy spent to create this plasma (~ 160 kJ). The point is that the plasma volume is very small (~ 6 x 10-9 cm3) and the discharge duration very short (~ 1 x 10-8 s).

The dense plasma focus has been studied extensively in the early years of fusion research. They might find it interesting to compare their results with those obtained a few decades ago to see whether anything new has really been discovered here."

I hope you find that a significantly strong counter-remark to your original article to be worth publishing also this viewpoint.

Best regards,


The FF guys respond:
From: Eric Lerner
To: Sterling D. Allan
Sent: Thursday, November 10, 2005 7:32 PM
Subject: Re: ITER response: Tokamak has serious competitor in Focus Fusion

Dr. Shimada did not read the papers carefully enough. His calculation is based on the plasma parameters that we actually achieved in our last experiments in 2001. We did not claim that those parameters are near breakeven. They were not even optimal for the current we achieved, because the radius of the anode (the inner electrode) on this device could not be changed

What the paper does demonstrate is that scaling laws that have both good theoretical foundations and experimental backing indicate that break-even parameters can be achieved with a somewhat higher current but a physically smaller device. With the parameters that we expect to reach in our next set of experiments, fusion yield per shot should be of the order of 5-20 KJ. No strange physics is needed. We are aiming for a 40-fold increase in plasmoid magnetic field and fusion yield (at fixed ion temperature) scales as B4. Temperature will also be higher.

Eric Lerner
I dunno. You'll have to show me you know what you're doing, guys. Also, for giggles' sake, here's a Slashdot thread on this stuff. Science by press release isn't the most compelling thing on the planet.