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NIF 1.9e16 Neutron Shot!

Posted: Mon Dec 31, 2018 6:36 am
by Robert Dwyer
I was browsing the internet for some information on x-ray plasma diagnostics, when I came across this article from June from LLNL. NIF achieved a record shot 1.9e16 neutrons from a shot. That's a lot of neutrons!

This outperforms the little reactor at my university, as well as some of the smaller TRIGA reactors at others (running steady-state, that is). Any fusion device capable of these numbers deserves some respect.

They really seemed to pull the big guns out on this one too: A DU Holhraum, a diamond shell, (DT fuel of couse with some He3 added for diagnostic purposes). Apparantly the diamond shell helped with some of the low-mode asymetries the Indirect drive method suffers from.

Regardless of how you view this, the physics is very interesting, and it is a respectable achievement. In a presentation I was given last summer they claimed over 30% of the yield was from alpha heating. Depending on who you ask some, will say this is 'ignition' (in the sense that the energy released from the fusion reaction is heating other fusion reactions), but many consider ignition synonymous with breakeven and don't give credit to the claim.

Below is the article if anyone is interested. This device has fielded a lot of knowledge in radiation and plasma diagnostics which (as someone studying the field of HEDP and plasma physics, am fascinated by and grateful for). ... sion-yield

Re: NIF 1.9e16 Neutron Shot!

Posted: Mon Dec 31, 2018 10:37 pm
by Richard Hull
Fabulous physics, lots o' neutrons, and great work.

No usable energy or path pointing immediately towards it.

NIF was sold to congress only on the idea of being a critical, much needed research tool in the stewardship of our nuclear stockpile with a sweetener of a look at fusion energy. The project started and remained a disaster. Over budget and running late, congress was asked for huge amounts more to complete the project. Congress demanded a GAO report that was a gross embarrassment, when published. Another of those make busy projects that blunders along to an over-budget, super late, finish line. Now, the people manning the project must justify their continued employ by doing cool stuff that impresses all in attendance.

A book could be written about this effort and its people. I followed it from its inception and have a copy of the full GAO report. Unbelievable antics and waste throughout.

It took so long to complete past its finish-by date that work-arounds were developed in the stewardship program. Originally, it was to be solely used for weapons research for the first year or two and then be allowed to do fusion energy research. As the stewardship work-arounds proved successful during the blundering and plodding build, NIF got to do fusion research pretty much from the fitful start.

The horrors, mis-steps and proven wastefulness of many such fusion efforts are often never thrown into the faces of the public who financed them.

Richard Hull

Re: NIF 1.9e16 Neutron Shot!

Posted: Tue Jan 01, 2019 3:35 am
by Robert Dwyer
I've always wondered how much of NIF's overbudget and delay was a lack of understanding of the materials needed (I.E. the short lifetime of the laser glass, building an in-situ cryogenic fill station rated for Tritium), how much of it was bureaucracy, and how much was mismanagement or willfull misinformation.

At least it is being used, and hasn't ended up like many other of the multi-million dollar fusion experiments (Atlas or TFTR), and ended up buried or sitting in some storage unit.

Re: NIF 1.9e16 Neutron Shot!

Posted: Tue Jan 01, 2019 6:12 am
by Richard Hull
True, indeed. In the GAO's report and in some news articles on page B12 in some newspapers, back when some reporter managed to actually read the report....It turned out the science, as presented to Congress, seemed a sure thing. Issues as regards the special Schott neodymium glass laser frequency multipliers arose. Upon GAO pressing Schott on this extremely expensive, yet key aspect of the project, Schott told GAO that they told the project planners, up front, that they were unsure whether the glass of the dimensions they requested could be made uniformly enough. What's more, Schott was unsure that they could warrant the huge glass slabs could absorb, survive and frequency multiply the IR laser powers NIF planners were expecting.

Just one of the many revelations in the thick report.

Richard Hull

Re: NIF 1.9e16 Neutron Shot!

Posted: Tue Jan 01, 2019 8:38 pm
by Dennis P Brown
NIF knowingly selected the wrong laser (they have a 1 micron laser and under 400 nm is the bare minimum.) They did this because it was what they had experience with - glass laser media. They also ignored well know physics and went with a hohlraum (only useful for weapon work) and worse still, asymmetric drive rather than uniform direct drive. Again, well understood at the time that they were doing the worse approach possible for energy fusion but they, as Richard said, were aiming to do mainly weapon work. Using their own numbers, they are five orders of magnitude below break even. As for ignition, they never got close but they continue to try and convince people they are/did/can/might ... well, if a few more billion of dollars are poured into their system - maybe hit some milestone to be named later.

Re: NIF 1.9e16 Neutron Shot!

Posted: Tue Jan 08, 2019 1:35 am
by Frank Sanns
So let's see, a U238 tamper with a capsule with D-T in the middle. Besides the small size, it sounds like the same physics worked out from the original A bomb work. It is astonishing that they are only now looking at what was ultimately successful decades ago. I know the scale is different but symmetry, heavy material tamper ultimately for confinement and neutron multiplication, and short time frame is decades old technology. You would have thought these would have been some of the first experiments.