NIF finally manages to do some real fusion

Reflections on fusion history, current events, and predictions for the 'fusion powered future.
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Dennis P Brown
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NIF finally manages to do some real fusion

Post by Dennis P Brown » Thu Aug 19, 2021 12:13 am

While NIF has the wrong wavelength laser, a terrible non-uniform illumination methodology, and worst of all - holmes they finally managed some real fusion. They achieved (for inertial) a record neutron yield of about 10^+19 neutrons!

This does demonstrate that near ignition can be achieved and considering they used indirect drive (which is inferior to direct drive) and even with frequency tripling still have too long a wavelength laser source (more prone to creating pellet collapse instabilities), and also, with not very good drive uniformity (holmes effects) - they almost achieved true ignition. They released about 10 mega-joules of energy (please try to ignore that silly wattage they used in the NYT article - while true, it is extremely misleading - dividing by an extremely tiny number in the denominator certainly blows up the numerator and looks impressive without being impressive when you realize that trick); while certainly not break-even, still, the largest production of controlled thermonuclear fusion energy ever achieved for that time period of burn. With ignition one would, in principle, far exceed net energy cost and they did have partial burn over into the fuel - hence, getting a lot closer to that "holy grail".

Since they use holmes, injection of targets is impossible for their design - energy production would require pellets to be injected at five per second. The interesting thing is that just such an injection system is easy to build (been done), as is making sufficiently uniform pellets at low cost (about $0.25/pellet filled with deuterium and tritium ice/gas. And said pellets have sub-micron spherical uniformity.) Add to that that there are far better and more efficient lasers (KrF and better still, ArF) and finally, by using direct drive one can achieve far better on target illuminating uniformity, this semi-milestone certainly points the way and gives the best support today that laser fusion isn't as difficult as previously believed.

A NYT article has some of the details: https://www.nytimes.com/2021/08/17/scie ... earth.html

In any case, fusion is, with the success of the German test bed stellarator, and now some critical success with NIF, starting to look more doable. I will say the former system (magnetic) is going be very expensive and difficult to maintain for a real thermonuclear burn, and the later system (inertial) is likely less expensive and far easier to maintain (esp. relative to the neutron flux for real target ignition.) Bottom-line, still no breakthrough but certainly a major step (for both systems) and things no longer look as impossible as once thought.

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Richard Hull
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Re: NIF finally manages to do some real fusion

Post by Richard Hull » Thu Aug 19, 2021 2:51 am

Still putt-putt boat fusion. Capturing lightning bolts...Actually small thermonuclear, H-bomb explosions. Five chargings of the huge capacitor bank for the laser per second makes for a very heavy pulsed load on the grid. I would love to see the net joule energy lost in the charging and discharging cycles, to light from the laser and losses in the tripplers or conversely the total joule energy in to joule energy out in distributable electricity. Remember there is no direct conversion here of the neutrons to electricity. Gotta' put on the kettle, as always with its attendant losses, (steam to juice).

That 10e19 neutrons is not flux and the source of the energy is a point source. Gotta' reach an efficient neutron absorber at some safe thermonuclear blast distance to heat that kettle to make that steam to turn those turbines.

The bean counters at the power companies rule and not the scientists nor the engineers when it comes to putting the juice out of the outlets in homes.

In the end, not real soon now. Not in 20 or 30 years either.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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