Saturday, December 22, 2007

Bussard Fusion Update

The New Mexican has some interesting news about the progress on Bussard Fusion Reactor.
Last August, as Bussard was losing his battle with cancer, the funds were restored with the support of Alan Roberts, EMC2's longtime Navy contract monitor. The company now has $1.8 million to pursue his work. If it is successful verifying the 2005 results, it would seek funding for a full-scale model, big enough to make net power, Nebel said. Bussard has estimated that such a demonstration model would cost about $200 million to build.

"Unless somebody can repeat and show other people that it's operating, it's really not scientifically acceptable," Hirsch said. But "if the idea works the way he thinks it could, and there's a good chance he's right, it will not take very big machine to show net energy."

The latest device, WB-7 (the WB refers to the children's toy Wiffle Ball), is currently under construction at a machine shop in San Diego and will be shipped to Santa Fe, where a small group of scientists is setting up a testing facility in an office park off Rufina Street. The device, like previous ones, was designed by engineer Mike Skillercorn.

"These are garage-scale experiments," said Nebel, pointing to the stock tank purchased at a local feed store. "We shop at interesting places," he added, mentioning both Home Depot and the Black Hole in Los Alamos.

Although Europeans are building a huge device to demonstrate the scientific and technical feasibility of fusion power, the U.S. has spent relatively little — about $300 million a year — on fusion research. Much of that has been focused on a competing idea called Tokamak, a program that Bussard and Hirsch started at the Atomic Energy Commission in the 1970s, which uses deuterium and tritium as fuel. Later both determined that the concept, which produces a lot of radioactivity, was impractical from an engineering standpoint.

With his own device, Hirsch said, Bussard was "swimming upstream as far as fusion community was concerned." Still, he was able to get about $14 million in funding from the Navy for his work.

Bussard felt enormous pressure to solve the fusion problems. In a letter to an Internet forum on his 2005 results, Bussard wrote that he believed that "the survival of our high-tech civilizations depends on getting off of fossil fuels ASAP, and — if we do not — we will descend into a growing series of 'oil wars' and energy confrontations that can lead only to a huge cataclysm. Which CAN be circumvented if only we build the clean fusion machines in our time."
That is one of the reasons I support this research. Civilization depends on it.
Nearly a year after shutting down the lab, Bussard presented his work — for the first time in more than a decade — to the International Astronautical Congress. He later discussed his results with Google, the online search engine company in a talk titled, "Should Google Go Nuclear?" that is widely available on the Internet. Before his death, he also set up a nonprofit organization to solicit donations to restart the work. Information is at

Bussard's wife, Dolly Gray, who co-founded EMC2 with him in 1985 and served as its president and CEO, has helped assemble the small team of scientists in Santa Fe. Besides Nebel, 54, the group includes Jaeyoung Park, a 37-year-old physicist who is also on leave from LANL; Mike Wray, the physicist who ran the key 2005 tests, and Wray's brother, Kevin, who is the computer guru for the operation.

"If this works, it's going to be a big deal. It could take the entire energy market," Nebel said. "And drag the oil companies into the 21st century," Gray added.

Someday, they said, if they're right, a machine just 20 times bigger than the one sitting in the corner on Parkway Drive could run the city of Santa Fe.
Park and Nebel [pdf] are the researchers who discovered the POPS effect which was corroborated in part by computer simulations done at MIT by McGuire[pdf] and Dietrich[pdf].

I estimate we will see the results of these experiments some time between March and May of the coming year. I have my fingers crossed.

The New Mexican article has a great review of Dr. Bussard's life. You should go and read the whole thing.

Here is a tribute I wrote to Dr. Bussard. It has lots of links to the science of the Bussard reactor.

Wednesday, December 19, 2007

ITER Budget Cut

Science Magazine reports that the Federal Science budget has cut ITER funds to zero.
The bill set the budget at DOE's Office of Science at $4.055 billion--$342 million short of the requested amount--and the shortfall comes mainly out of two programs: fusion sciences and high-energy physics. Congress realized some savings by allotting nothing for U.S. participation in the international fusion reactor experiment, ITER, which is set to begin construction next year in Cadarache, France (ScienceNOW, 21 November 2006). Although appropriators expressly forbid DOE to shuffle money from other programs to satisfy its planned $149 million contribution in 2008, Marburger predicts that the prohibition will not stand. "I can't see DOE not living up to its obligations," he says. "The department will have to use its money to stay in the project, so [the language] really just amounts to another earmark."
I have heard rumors that Congress is interested in the Bussard Fusion Reactor. If it works out (Bussard Fusion Reactor Funded) ITER (a tokamak design) would be a waste. Or as Plasma Physicist Dr. Nicholas Krall said, "We spent $15 billion dollars studying tokamaks and what we learned about them is that they are no damn good."

We will know the answer in 3 to 6 months. At that point in time if Bussard IEC Fusion Reactors look like a dead end the budget for ITER can always be restored. Or the money could be put into other IEC devices. The advantage of IEC is that the budgets required for confirming experiments are small and the time frame for proof or disproof is short. Years, not decades or centuries.

Saturday, December 1, 2007

Transimpedance Amplifiers

A while back I made an off hand comment (can't remember where) about using a transimpedance amplifier to bring broader bandwidth diagnostics to the plasma community in general and IEC Fusion in particular.

Let me start with the MIT paper [pdf] by Carl C. Dietrich. Let us look at his Ion Detector on page 49 of the pdf. He has a nice picture of the probe on that page. On the following page he gets to the heart of the matter, a schematic representation of the detector circuitry. For frequency response estimation purposes the detector can be modeled as a 100K resistor in parallel with a 100 pF capacitor (which accounts for a probe capacitance of 5pF). The 3 dB roll off point is = .15/(R*C) - within 5%. which would be .15/(1E5*1E-10) = .15E5 = 15KHz. Pitiful. I think the scope impedance and frequency response is so limited because he has to use the very highest gain (where scope bandwidth is less) to see any signal at all. So we can estimate the signal at 1 mV p-p. Into 100 K ohms that means a current of 1E-8 Amps. About 10 nano Amps.

Can we do better? Yes. But we have to do a couple of things. One is to reduce the input impedance to get wider bandwidth and second we are going to have to amplify that current. Thanks to the proliferation of fiberoptic technology we have exactly the tool we need to do the job.

I like the Philips SA5211. It is low noise and high gain with a maximum output swing of a few volts with a 5 volt supply. It is also bipolar technology tending to make the input a bit more robust than JFET or MOSFET input technology.

So let us start with gain. The transimpedance gain (minimum) is about 20K ohms differential. What does that mean? A current of 1E-8 Amps will be multiplied by that resistance to give 2E-4 volts change between the two outputs. About 200 uV p-p or about 70 uV rms. That is a fair signal for spectrum analyzer and other RF work. Feed that into a transformer like the Mini-Circuits T1-6T and you have a package with good gain from 30 KHz out to 150 MHz and almost flat from 300KHz to 50 MHz. To look at lower frequency signals I'd use an ordinary instrumentation op amp from the differential output of the transimpedance amplifier. The AD8253[pdf] looks nice with a bandwidth of 3 MHz at a gain of 100 (40 dB). That gets us to 20 mV p-p at the output for signals in the audio to low RF range. Not bad. For the higher frequency signals I'd follow the transimpedance amplifier with a couple of 20 dB gain stages (at least) to get the signals up to the mid mV range. I like the Mini-Circuits MAR-8A which is rated out to 1,000 MHz (25 dB gain typ) and is not too hot in the high frequency gain department so that taming the circuit will not be too difficult. It also has gain from DC to 1,000 MHz - meaning we can use it to amplify RF in the mid kHz range without problems. Some amplifiers of the type do not like low frequencies because the slow waves can cause the circuits to either over heat or become unstable.

So now we are facing the last question. Bandwidth. The feedback resistance for the transimpedance amp is about 14K (I used 10 K - above multiplied by 2X to account for the differential output) with the gain of the input stage a factor of 70. So what is the input impedance seen by our current (ion) source? That would be 14K divided by the gain of the input stage (70) or 200 ohms. It has an input capacitance of 4 pF. Let us say the probe is another 6 pF or 10 pF total. Double that to account for a lot of slop in the installation.

Let us plug that into our frequency formula: .15/(200*2E-11) = 37 MHz. Not too shabby. We can double that without too much effort if we work to keep stray capacitance down. Which means that our SA5211 at 200 MHz bandwidth should be more than adequate for the job with the subsequent Mini-Circuits amplifiers making a very small contribution to reduced high frequency gain.

So there you have it - a very nice high frequency ion probe. With a minimum AC signal of 1E-8 Amps p-p and a maximum signal of 4E-5 Amps p-p (at the transimpedance amplifier - gains of the other amplifiers would need adjusting if the signal is near maximum).

Update: The 1E-8 Amp current limit is where the signal = the noise for a 50 MHz bandwidth. If a narrow band detector is used (1 KHz) the detection limit goes down to 1E-10 Amps p-p.