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I’m sure it’s been regulated as a radiation source. I’m confident it doesn’t have a site license for a power plant, the environmental impact study is not complete, the public hearings haven’t taken place and neither the EPA nor NRC have validated the design of the reactor. All these steps have to be completed and they are costly, time intensive steps.

Aneutronic fusion is the holy grail of fusion energy. Mr. Lerner is not the first nor will he be the last say it. Many scientists believe that if fusion is to be successful, aneutronic fusion is the only way. The idea has plenty of support. It is the people working on aneutronic fusion that generally turn scientists off. Optimism with little data doesn’t impress scientist. Sub-par performance with extreme optimism does not impress scientists. FoFu-1 just caught up with other machines around the world. To me, it seems premature to market technical folks about the wonders of aneutronic fusion. It’s a tired line modified from a Tom Cruise movie, but show me the data! 🙂 Scientists in the field are generally aware of LPP’s claims and work. People are also aware of Tri-Alpha and their work. If someone asked me for an objective assessment, Tri-Alpha had done a better job of convincing fellow scientists of their approach. They have data to support their claim and they only publish or present when they can back it up. Based upon Tri-Alpha results, new experiments are being discussed at NSTX at Princeton. Tri-Alpha has contributed to advancing our understanding of fusion in the general context. I’ve been asked by a number of people about LPP. An objective characterization of the their results to date is neutral at best. They have done what everyone else has done. They have repeated experiments and generally gotten the same results as others. The scaling law of I^5 is not new. Some have claimed scaling laws at large as I^5.7 with data to back it up. Mr Lerner has spent a great deal of time spreading the “good news” of aneutronic fusion and little time supporting it with hard data. The problems of FoFu-1 were encountered twenty years ago by people working at the 2 MA level in the plasma focus and the remedies are well published. The Z-machine at Sandia deals with currents at the 26 MA level so 2 MA is not a problem in modern pulse power even on a ~$2M budget. I hope in the next year that FoFu-1 will pass other machines and show some hints of plasmoid formation as Lerner’s theory suggests.

The marketing is a good idea for non-technical folks and politicians. I think presenting the aneutronic fusion argument to the general public will help in the long term. My caution is how it is presented. If people want to rewrite a textbook go for it. This was just a warning that can be ignored.

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balsysr wrote: There are no facts in science, only hypotheses that have stood the test of time. What this means to me is that we can never be sure that what we believe is truth. We must always test our assumptions and replicate our data measures, looking for the errors, and the new ways that we can interpret the data. It is only by doing this that real progress in Science can be achieved.

I have an on-going argument about the relationship of Science to Religion. He is starting to convince me they are similar. You seem to state the same thing. You cannot know; you can only believe. I will pass it along to my friend.

I agree that some rethinking needs to be done, but I don’t know that substantially different conclusions will be drawn. Who knows for sure. Einstein was mentioned but it needs to be said he was attacked heavily in his day by those that couldn’t accept his theories. I’m not saying they are 100% correct but many tests have shown his theories are predictive, which is the true test of any theory. GPS would not work if general relativity did not apply. A general relativity correction is made to GPS satellites to keep them accurate. The lifetime of muons is known to be longer when they are traveling near the speed of light consistent with special relativity. Relativity is a complicated theory and I don’t claim to understand it, but I think it generally does well as theories go. Dark matter and other less tested theories need some more time. People are exploring alternatives to dark matter. In fact, one is based upon general relativity. I wouldn’t toss out the old knowledge yet, but I am up for looking at old things in a new light.

Gravity waves, the Higgs Boson and other less proven points demand a change of thinking but I look at the experiments and money as a way to find the right answers. Proving something doesn’t exist can be as important as proving it does exist.

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vansig wrote: The problem with Tungsten or any relatively dense conductor is the x-ray absorption cross-section. Lighter elements, such as beryllium or carbon, would be much more transparent to x-ray. Tungsten, even though it resists high temperature, would absorb too much x-ray and evaporate right away.

How about carbon nanotubes?

Plasma facing is the biggest problem in a plasma focus for the electrodes. The anode is particularly susceptible it. The expanding plasma from the pinch will do far more damage than the x-ray pulse. See published works by Rout et al on anode materials in IEEE Transactions on Plasma Science.

The x-ray spectrum will be a bremsstrahlung spectrum with an endpoint near the pinch voltage. For FoFu-1 at ~3 MA, the pinch voltage is roughly 750 keV. Most of the brems spectrum will be concentrated at 1/3 of the endpoint or 250 keV. I estimate the thinnest part of the anode to be 1 cm thick by looking at the pictures.

Time to compare:

Tungsten is dense. Melting point is 3422 C (Wikipedia). Electrical resistivity is 52.8 nOhm-m. It will absorb 99.9% of the x-rays at 250 keV in a 1 cm thick sheet (Numbers from NIST X-COM Data base). Tungsten absorbs hydrogen but will re-emit it when hot (~100 C). I don’t know of any chemical reactions with boron. Very resistant to plasma facing. Tungsten has a long history of being a robust electrode material in a number of plasma facing applications including plasma focus. It will produce more x-rays than any other common material but it can take the heat of the plasma and the chemistry.

Carbon is a dense. Carbon does not melt under most conditions but it sublimates (goes straight to gas) at 3642C. Electrical resistivity is 2500 nOhm-m. It will absorb 22% of the x-rays at 250 keV. Carbon forms a stable carbide with boron under plasma bombardment. Carbon in the graphite phase (this includes nano-tubes and other carbon compounds) is very susceptible to etching by hydrogen plasma. This is how you can remove graphite from diamond in lab created diamonds. Sorry, diamond is one of the worlds best electrical insulators…

Beryllium is not dense. Melts at 1290 C. Electrical resistivity is 36 nOhm-m. Beryllium will absorb 17% of the x-rays at 250 keV. Comes with a warning from most vendors akin to ‘May cause death’. Known carcinogen as a dust or powder. Not like tobacco either. You get five years at best. Beryllium also has a nasty nuclear side. It will emit neutrons if photons of sufficient energy interact with it. So much for the radiation free system. X-rays become neutrons….

Melting point is directly related to plasma facing tolerance. To vaporize the material you have to supply energy to melt it. Tungsten and carbon beat beryllium by a factor of three. Carbon is damaged by chemical reactions. Carbon is a poor electrical conductor so it will absorb electrical energy needlessly. I know nothing about Beryllium chemistry so it might be fine in the boron-hydrogen environment. Beryllium has a dark side in terms of radiation.

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benf wrote:

asymmertic_implosion – 08 November 2011 09:02 AM
I agree that no issue I mentioned is insurmountable, but it takes time, money and most importantly, data. Data on fusion systems with gain is in short supply at the moment.

I presume you’ve reviewed the monthly reports from LPP, found on the same page I directed you to before, or on their website. The reports over the years have shown the difficulties that are being faced as well as the progress made along the way. There is an array of diagnostic tools being employed to quantify and qualify the results. All this takes time, money and expertise to enable. The funding of the research is vital to keep receiving the data to help guide the way toward future improvements. It’s not only hard data that drives the future, it’s also our ability to make the project known and appreciated. This is a task that can be taken on by those of us with no technical background as well as from the scientific community.

I have reviewed the progress updates and some of the technical data. I appreciate you pointing me to the link. It changes nothing I’ve posted. FoFu-1 may be the best chance to produce fusion energy but it hasn’t yet. It might some time in 2012. Progress has been made. However, the D-D fusion yield is on par with other plasma focus devices at similar current levels. Despite the progress, it hasn’t done anything new in terms of the fusion output. This is not to say it won’t, but for people not aware of the state of art in plasma focus research, FoFu-1 just caught up. Now it has to go ahead of the other machines by leaps and bounds. It is my sincere hope that it will.

I agree that marketing and PR are important but I suggest staying away from textbooks and regulators. FoFu-1 has a great deal to prove before either should be approached. The ‘fusion is ten years away’ claim is already trademarked by so called main stream fusion researchers. I advise staying away from that trap. It will not be warmly received by technical folks. Show fusion gain and people will mutter. Let someone else repeat your experiment and people will talk. Show you can do it day in and day out for a week, people will throw money at you. However, fusion gain is still the dream yet to be achieved. FoFu-1 has to produce roughly 57,000 J of fusion yield to breakeven. According to LPP’s last report, it had a fusion yield of 1 J or less. I remain optimistic that FoFu-1 can do better, but I’m not sold on it yet.

My comment about being zealous was a warning, not a criticism. I think people should be optimistic. Hope is a good thing. Hope is a driving force behind science. However, you can’t go blindly into it. Skepticism is also a driving force of science. To challenge the old you first have to doubt it. When you doubt, you perform experiments in new and different ways that challenge the old. LPP is doing that now. However, they have not proven the old incorrect. The hater says they never will. The optimist says its only a matter of time. The skeptic says I don’t know yet. The zealot says… well read a cold fusion forum and it pretty much explains itself. I consider my self a skeptic. All I ask is show me the data before claiming fusion will change the world. I’ve heard it too many times before. 🙁

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zapkitty wrote: Just a note: you seem to be churning over a variety of things that Lerner-hakase and company have already addressed either in their papers or on the forum… a sort of “best of” list of skeptic talking points.

That is my point. Lerner-Hakase have gone over them in paper. I have no problem with speculation and research. Optimism should be the norm for those working on any new technology. Great potential is the reason to take on new things. However, many research papers are not going to convince regulators. To a regulator, FoFu-1 is a new “thing” that they don’t understand. If they don’t understand something, they don’t let it operate. I’ve been there with them and it’s make you want to pull out your hair. I agree that no issue I mentioned is insurmountable, but it takes time, money and most importantly, data. Data on fusion systems with gain is in short supply at the moment.

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This thread along with many others discuss the potential of fusion. It is worth researching but I agree it cannot be counted on at this time to produce energy. There are several areas that require substantial engineering development. LPP is addressing a physics question about fusion energy. Issues with power supply lifetime, capacitor lifetime, electrode lifetime, “unexpected outcomes” and cost demonstration need to be completed. The back of the envelope calculations completed to will not convince a serious power distributor to buy this technology. The real concern is regulations governing the technology. My guess would be a fight between the Nuclear Regulatory Commission and the EPA would take place. You have intense brems radiation from the pinch and electrodes so that has to be dealt with and regulated. Therefore worker safety and training has to be implemented. These are all problems with solutions, but time and money are required. The few million invested in LPP and other technologies is only scratching the surface of what is needed. Building a 3 GW themal power (1GW electrical) plant is nearly a $1B endeavor. I assure you that even if an FoFu system costs only 10% of that to get 1 GW electrical, engineers and regulators will not be satisfied until long term demos are completed under highly controlled circumstances.

The simple answer is you cannot talk about the impact of fusion on the world energy problem in text books until you have demonstrated fusion gain. No one has done that yet. I like the optimism that permeates this site but it is important not to become zealous. Ask the cold fusion folks how well that worked out.

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The two best UV/X-ray sensors that have fast time response (<1 ns) and are radiation hard are GaAs sensors sold by Nutrek and diamond sensors sold by Diamond detectors limited in the UK and Alameda Applied Sciences Corp in the US. The calibration of each detector varies from unit to unit but both are extremely radiation hard. Nominal values for diamond sensitivity are 1E-4 A/W above the band gap of ~5 eV.

Another thought, if you are using Si, you are saturating your detector. The total charge read out is preserved but the time history is incorrect. If you are working on a yield sensor, your Si might be fine. If you are interested in time response, you need to limit the input aperture or switch to a less sensitive material.

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Thanks.

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Any one know how the magnetic field was measured? 0.4 Gigagauss is extremely large for a pinch device. A typical pinch radius is ~0.5 cm. The current that FF-1 seems to be operating at right now is ~ 1 MA. B=mu_0*I_peak/(2*pi*r) where B is the magnetic field, mu_0 is the permeability of free space and r is the pinch radius. I calculate a B-field behind the pinch of 0.4 mega gauss. I’ve run across filaments in pinch literature that are 1/10 the pinch diameter but that is only 4 megagauss.

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zapkitty wrote: Tungsten is also less than ideal as an electrode material because of the x-ray flux. While FF theory holds that brem will be limited enough to allow net power, the x-rays will still be quite strong. (thus the “onion”)

The most-discussed alternative is beryllium.

The onion?? Are you talking about the first wall around the vacuum chamber or the anode and cathode itself? I was talking about the anode and cathode. Tungsten is a good material for thermal, mechanical and other reasons. I agree that the the brems power is less than ideal, but most of the brems from the electrodes comes from the e-beam generated by the pinch/plasmoid interacting with the electrode. There is some brems at other locations around the electrode after the pinch explodes but that energy is already lost so if it comes off as brems or heat is a fraction of the fusion gain.

If alternative materials to copper are being discussed I would seriously question beryllium. The cost and environment, health and safety issues are substantial. Moly would be be intermediate material. Science Research Lab (SRL) showed a Mo anode that fired over 5 million shots at 50 Hz with 250 kA plasma focus. Papers by Petr et al in Review of Scientific Instruments discuss the anode and how the brems was addressed.

A question for the community, is FF theory on-line somewhere? I’m curious how it differs from conventional pulse power fusion techniques like reverse field and Sandia’s newest concept, MagLif.

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Henning wrote:

There are plenty of PIC codes that can handle the modest densities of a DPF plasmoid (ie around solid density) Inertial confinement simulations have to cope with 1000 times higher.

I meant here, simulations specifically for DPFs. Sure, the big guys have supercomputers where they can handle this, but the science of DPF is much too small for this currently.

That is also not true. Sandia and Livermore are working on PIC modeling of the PF implosion phase. PF-1000 has been subjected to these models with limited success. A PF at Livermore is undergoing modeling using the LSP simulation. The results from Livermore are likely to appear at the American Physical Society Division of Plasma Physics meeting in a couple weeks.

The PF community in the US is larger than you believe. In fact, there are experiments from New Jersey to California at different scales and with very different goals. However, a superior understanding of the basic physics benefits all applications. Folks around the world see potential in PF technology for producing medical radioisotopes, material modification, radiation sources and weapons effect testing. Few people believe that the PF will ever produce net fusion energy for a number of reasons. Honestly, the main reason is a number of engineering problems like material lifetime. The PF has the same problem as ITER and NIF; you generate a hot plasma. That plasma expands and although it cools, it hits the solid materials. The PF electrodes are damaged a little on every shot. Thus, the electrodes have a finite lifetime. The use of copper like that is used on FF-1 is less than ideal. Published literature (Rout et al IEEE Transactions on Plasma Science vol 23. No 6 1995) showed that Tungsten based materials offer higher fusion yields than copper with far longer lifetimes. This is not to say that experiments shouldn’t be conducted. Materials are the limitation of all fusion devices. Materials are also the least funded fusion area in the US. As more and more experiments show promise of breakeven or gain, the more serious engineering challenges will be addressed.

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Capacitors at the level required for a large plasma focus typically have short lifetimes. Over specification of caps is the only solution. Repetition rate operation further stresses the caps due to effective series resistance in the capacitor which leads to heating. Typically, you need caps that are specifically designed to operate a repetition rate. Caps like the ones used on FF-1, Z and other large pulse power systems are not agreeable to high repetition rate operation. The pulse power solution being worked on at Sandia and other labs is called the linear transformer driver (LTD). The LTD is a transformer based high current driver. Currently, 1 MA modules are the norm but 2 MA modules have been designed. There isn’t a theoretical limit on the current output of an LTD. It is practically limited by the size of the transformer core.

The LTD is different because it is a step down transformer. It uses a large number of small capacitors (small caps are easier to build at high voltage levels to allow derating. Check out the General Atomics website as an example) coupled together with a transformer core. The 1 MA modules are already demonstrated at 1 Hz for hours on end in a test load. Sandia has designs for a 100 MA z-pinch driver that operates at 0.1 Hz. The downside to the LTD is the number of capacitors and switches. In a typical module, you have 40-80 caps with 20-40 switches. In the 100 MA design you have 500,000 switches. One of the biggest weaknesses of a pulse power system is the switches. You can’t use switches like Thyratrons or solid state switching for current reasons (Thyratron) and cost (solid state). This is a huge engineering challenge for any pulse power fusion system.

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Another interpretation of Lee’s paper on dynamic impedance is that the electrodes needs to be shaped differently in >2MA machines. In a conventional plasma focus, the electrodes are in a coaxial geometry with right circular cylinders. Higher neutron yields have been realized when the anode, the inner electrode, is made into a cone. The same can be done with the cathode rods.

The dynamic impedance is a velocity effect of the moving plasma sheet in the axial phase of the plasma focus. You cannot slow down the plasma without reducing the yield, however, you can alter the electrodes. The inductance of a coaxial geometry is given as the mu_0/(2*Pi)*ln(r_c/r_a)*z, where r_c is the cathode radius, r_a is the anode radius and z is the axial position and mu_0 is the permeability of free space. If the ratio of r_c to r_a is decreasing with axial position, the effective dynamic impedance can be reduced.

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Impaler wrote: Is their some way in which the results can be graphed along side earlier results and with comparisons to other projects (ITER & NIF) along with a ‘goal’ point to give a more visual sense of the progress?

The typical relationship is a ratio of fusion energy to energy required to drive the fusion events. Based upon the statement by LPP, eight 9 microfarad capacitors were used at a charge voltage of 40 kV or 57.6 kJ. The D-D fusion yield would be ~1 J with a D-D yield of about 1E12 neutrons. This means the conversion efficiency from the cap bank to fusion is 0.001%. JET has reported a physics conversion ratio of 70%. However, this neglects the pumps, magnets and other auxiliary systems that are necessary for fusion to take place. It only takes into account the energy to heat the plasma. In reality, I would guess 25% is a better number but don’t hold me to that. NIF on the other hand is likely to show gain, i.e. conversion greater than 100% in the next few months. However, it will never be a fusion power system. NIF has one purpose despite the advertising and it is NOT to make electricity.

This is a reasonable comparison, but one has to ask about goals. My personal opinion is 3MA is too small to demonstrate a fusion gain. However, the critical physics of a fusion burn in a pulse power system with p-11B might be demonstrated. One should not underestimate the value of this information. It would be a huge advance for fusion in general.

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