We found that no significant difference in the ratio of the NTF to FTF signals occurred because of the filter. The x-rays were acting as if the 3 mm copper was transparent.
This could only be the case if the x-rays were produced by electrons that had an average energy of at least 400 keV. We will keen to analyze in even greater detail results relative to the electron temperature, which is crucial for in turn heating the ions and thus overall fusion yield.
I take it 400-keV electrons is a good thing, but is there a significant difference between 400-keV electrons and, say, 100-keV ions, as reported a year ago?
Anyway, best wishes for the coming year and the move beyond deuterium.
In most plasmas that I’m familiar with, electrons are consistently much hotter than ions.
That depends on the heating mechanism. For example, resistive heating is only significant for electrons, so they can get to a higher temperature this way. But this heating mechanism is only capable of getting plasmas to a few keV not >100keV (since resistivity falls with temperature).
Alternatively, as in tokamaks, ion cyclotron resonant heating (ICRH) can be used to specifically heat just the ions.
In the case of DPF, I see the 400keV electron temperature as a bad thing since it leads to excessive bremsstrahlung radiation losses. The key will be if the proportion of energy going to raise the electron temperature can be limited enough with the switch to p-B11 fuel.
In the case of DPF, I see the 400keV electron temperature as a bad thing since it leads to excessive bremsstrahlung radiation losses. The key will be if the proportion of energy going to raise the electron temperature can be limited enough with the switch to p-B11 fuel.
actually, seeing these 400 keV electrons represents a good opportunity to test and quantify the magnetic field effect. gigagauss fields should suppress them. so just how powerful is the effect?
So sometimes when we get data posts, the quantity of data leaves me feeling a bit skittish. I know how long it can sometimes take a rig to get up and running, but when things are working properly, how much time passes between shots?
Its not about quantity. Quality is what matters. LPP, being a private commercial enterprise, are not going to just upload all their raw data. It has to be analysed and interpreted. There will be many series of shots testing and calibrating diagnostics, coming up with new combinations of timing, voltage, pressure and other adjustments before each set of actual ‘optimised’ experimental shots to gather proper data.
If you watch some of the videos posted previously it only takes a few minutes to setup and fire a shot, so I’d think they could do a couple an hour. If it has been opened up for cleaning or other adjustments though it would take a day or two to get back to operating conditions.
James is on the mark at a few shots an hour. Regarding the quantity of data, though, you are wise to keep in mind that monthly update findings should in general be treated as preliminary, relative to future publication. We do hope to make 2010 and earlier data available in full soon, there has been some discussion of a public repository also shared with other DPF groups, so need to get cracking there. Fourteen shots today, FYI ;-D
I acknowledge their rights regarding what data they do or do not release, but I also want to make clear, they’re shooting for an industrial result. Quantity is exactly the quality they are looking for. If they can genuinely get an excess of 1, 5 or 10 megajoules a shot, but each shot takes a week of set up, the method and device won’t be very practical. It will provide a giant flag for where to investigate next though. Which will be nice, since I’ll be in need of a thesis subject by about that time.
on the subject of ungainly radiation, i’ve been reading up on nuclear isomers a lot lately. I wonder if the wavelength of the x-rays could be tuned to stimulate nuclear excitations. You could have a nice little complex with a power generating DPF keeping the x-ray generating DPF’s going and recharging atomic batteries.
Wow, great result on the high energy x-rays. I agree that quality is important but quantity is a big deal as well. The result of 5 shots of repeatability was nice but it’s a far cry from what I would call statistically significant. A hundred or thousand shots would be far better. I know this requires a great deal of engineering on the pulse power and other components but that is the long term goal right; operating at ~10 Hz all the time. It sounds like the physics is being sorted out nicely so when is the engineering of the pulse power going to begin?
One questions: where are the x-rays coming from? Are they generated in the pinch itself via brems or are they coming from the anode brems? I thought LPP had a diagnostic for hard x-ray imaging develop by Dr. Murali. I’d love to see the pics if they exist. I find the HXR images more telling than visible images.
A billion shots would be even better, but there is reality to consider. This is a purely scientifc project at the moment. No one can do engineering with our staff and budget, and we will not try. The engineering phase comes later, after we have demonstrated scientifc feasibility and raised $30-50 million.
With this machine, we aim to fire 200 shots per MONTH and we have not yet been able to do so, due to various technical problems. So we have to budget our shots carefully. For a paper about repeatability we may do 20 shots at the same conditions. But five shots are statistically signigicant in the sense that if your real variability is 15% there is only a one in 14,000 chance that by accident you get five shots in a row that vary by only 3%. We demonstrated that it can be done. Considering that msot DPFs have something like 50% variability with the same conditions, that is worth reporting.
Also, we know the x-rays are coming from the plasmoid because the line of sight to the anode is blocked for the time-of-flight detectors by two inches of lead. We don’t have x-ray images yet, but hope to soon when we get bigger x-ray yields. These willbe images of the x-rays emitted at much lower energies—30 keV—because the 400 keV x-rays will go through our imaging foil with no trouble.
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