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Wednesday, February 26, 2014

Assessing progress on laser fusion

Laser Focus World
February 24, 2014
Assessing progress on laser fusion
Jeff Hecht

Publications from the Wall Street Journal to the Huffington Post hailed the new results from the National Ignition Facility in the February 20, 2014 issue of Nature as a "fusion breakthrough." The progress of the "high foot" experiments at the Lawrence Livermore National Laboratory (Livermore, CA) is welcome good news for inertial confinement fusion. But should it count as a "breakthrough" in the big picture of fusion research?

The "high foot" tests performed last fall illuminate the fusion hohlraum with extra laser power early in the laser pulse in an effort to improve the early stages of fuel compression. An August 2, 2013 test tripled the yield of fusion energy to about 8 kJ, and a test at the end of September did even better.

The Nature paper details results of those two tests and a third in November. As shown in the figure, the September 27 test reached a yield of 14 kJ and the November 19 test yielded 17 kJ. In the August test, the fusion energy yield fell just short of the x-ray energy from the hohlraum coupled to the deuterium-tritium fuel pellet. However, both the September and November tests yielded fusion energy that exceeded the x-ray energy delivered to the target. That's the first report of what a team led by Omar Hurricane calls "fuel gain exceeding unity."

That's a definite sign of progress. So is the increasing fraction of the fusion energy that comes from self-heating rather than from fuel compression, which dominates at lower yields. But NIF was built to demonstrate ignition of a fusion reaction, defined as generating more fusion energy than the 1.8 MJ delivered to the fusion target (i.e., the hohlraum containing the D-T pellet). The new results improved fusion yield by an order of magnitude over earlier D-T experiments, but two orders of magnitude remain to match the 1.8 MJ in the input laser pulse.

The "high foot" tests crucially showed that pulse shaping can reduce instability of the fuel implosion, which has been a crucial problem. But the "high foot" pulses do not scale simply to drive fuel implosions to ignition. "Hohlraum physics is limiting our ability to use the full power capability" of NIF, the authors write in Nature, so they are exploring new strategies. Taming those problems to see a clear path to ignition would be a breakthrough.

Even if NIF itself cannot reach ignition, it provides the experimental facilities we need to learn how to control fusion implosions. The real problem is the scale of the experiments needed to understand the inertial confinement fusion process well enough to control it. NIF cost $3.5 billion and took 15 years to complete, and we likely will need another even more costly testbed to validate what we learn from it. Finding that money will be a challenge.

30 comments:

Anonymous said...

"Finding that money will be a challenge."

Yet it can be done...it can and will be done.

Anonymous said...

NIF cost $3.5 billion and took 15 years to complete. Say what? NIF has already cost in excess of $5.5 B and I'll bet if you add in operational cost of that facility over the last 15 years you'll find they've spent in excess of $10B+ dollars. To do what? Could you imagine if we would have taken that $10B and built solar arrays throughout all the inhabitable lands to run desalination plants to produce water and put power back into the grid, what we could have done for the future, not to mention all the jobs it would have created for decades to come.

Anonymous said...

""Hohlraum physics is limiting our ability to use the full power capability" of NIF, the authors write in Nature"

Boy that's not we were led to believe 15 years ago. Who lied to us !

Anonymous said...

Boy that's not WHAT we were led to believe 15 years ago. Who lied to us !

Anonymous said...

The extra bit of power wouldn't help, they are no where near the "cliff". They know this too, so it's disingenuous to imply it would make a difference.

Anonymous said...

The purpose of NIF was to keep the Phyicists employed to prevent their brains from wondering to a rogue nation. And that is a fact. It is like giving an autistic kid a math problem.

POS

Anonymous said...

@POS: The scientific term for NIF is masterbatorium.

Anonymous said...

"The purpose of NIF was to keep the Phyicists employed to prevent their brains from wondering to a rogue nation. And that is a fact. It is like giving an autistic kid a math problem.

POS

February 28, 2014 at 4:21 PM"

If what are you saying is true that NIF is indeed a very good idea and money well spent.

He POS maybe you are starting to open you eyes and realize that supporting science is a great idea.
Keep it up you are making progress.

Anonymous said...

The purpose of NIF (and I was there) was to sieze an opportunity to build a huge laser facility under the guise of "weapons physics" at a time when nuclear tests were banned (still are). The real weapons physics people had to be dragged to the table, kicking and screaming, and they were forced to get with the program or else be exiled to their isolated closets in 111, picking through the dinosaur bones of old tests. The real program was ICF, hence the name "national ignition facility" and the system requirements that focused on ignition. It can be debated whether or not this was worth the ultimate price that was probably 5 times larger than the initial one, but that's pretty much why it was built. It certainly wasn't to keep weapons physics people from going to work in Iraq or Pakistan or North Korea.

Anonymous said...

Absolutely no one with any scientific knowledge ever believed that NIF was important to weapons physics. Some completely reprehensible and dishonorable scientists pretended otherwise. Unfortunately for the country, a bunch of politicians and bureaucrats bought it (or didn't care as long as the money flowed into their district), and the rest is history. The Big Lie about NIF seems still to have some legs. It boggles the mind.

Anonymous said...

What does Brett "His Highness" Knapp have to say about NIF or does he understand it? Not likely, I'm one of the few who remember Knapp in the early 80's when he was a mediocre engineer at best. He's got folks at the Labs "snookered".

Anonymous said...

NIF will eventually wither away and die because the US cannot afford it. There will be no follow on or upgrade because the country cannot afford it, as any one not living on Mars for the last few years would understand. LLNL has bet the farm on NIF, so the big question is not what will be the future of NIF, but what will be the future of LLNL without NIF.

Anonymous said...

Wishful thinking to hope that NIF will disappear. Don't be surprised when Z and ITER funding get cuts to balance out NIF funding increases.

Anonymous said...

Wishful thinking that there will be any increases. NIF has no significant support, and the fact that a (small) group of CA representatives felt compelled to send a letter to Obama begging for a reprieve suggest the axe is dangling.

Anonymous said...

Ignition Plan B - Polar Direct Drive ! NIF has plenty of UV energy and power for this, since the only real show stopper here is LPI backscatter.

Anonymous said...

Sounds like polar direct drive should have had higher priority from the beginning over indirect drive. Why was the wrong decision made?

Anonymous said...

DD, especially polar DD, was deemed higher-risk based on simulations. Might have been the wrong call, but hindsight is 20/20. There was also an element of designed-and-built-here. Seems certain that DD ignition attempts will also uncover unforseen problems, perhaps different ones, so it would be miraculous if that was an easy path to ignition.

Anonymous said...

Doesn't matter; "Ignition" is not the goal. Sustainable cheap energy production is the goal. "Ignition" would only show that physics works if you have enough energy on target, and are smart enough to fix the "leaks." The goal would still be, as always, "50 years away."

Anonymous said...

Laser fusion is not a path to sustainable cheap energy production. It really never was, never mind the pipe dreams of LIFE and Ed Moses. And the "energy from seawater" blather about fusion in general is ridiculous, since you need tritium and that must be made in a reactor. D-D fusion is orders of magnitude harder than D-T fusion, which is already really really hard. So yes, ignition really is the goal, because there isn't anything after that.

Anonymous said...

So yes, ignition really is the goal, because there isn't anything after that.

March 7, 2014 at 7:01 AM

Just one question: Why spend many millions of dollars, and decades, and the efforts of some of the country's best scientists, pursuing a meaningless, dead-end goal?

Anonymous said...

why indeed? Just a good cover story for NIFs real function -- nuclear weapon research.

Anonymous said...

Just a good cover story for NIFs real function -- nuclear weapon research.

March 7, 2014 at 9:49 AM

No "cover story" was ever needed. Everyone who understood anything about NIF knew that it was intended primarily for weapons research. Unfortunately, it turns out that NIF is a failure at both functions.

Anonymous said...

The "cover story" was needed to bilk the gullible tree hugging taxpayers out of the money for advancing weapons of mass destruction. And it worked, and is still working.

Anonymous said...

The "cover story" was needed to bilk the gullible tree hugging taxpayers out of the money for advancing weapons of mass destruction. And it worked, and is still working.

March 7, 2014 at 5:04 PM

"Weapons of mass destruction" have kept the world from having a WWIII. I guess you'd rather fight Russia's nukes with swords and crossbows? Luddite.

Anonymous said...

""Weapons of mass destruction" have kept the world from having a WWIII. I guess you'd rather fight Russia's nukes with swords and crossbows? Luddite.

March 7, 2014 at 7:19 PM"

If we only had swords and crossbows the world would be safer place and no one would feel threatened by the United States. Sadly it is a only a dream.

Anonymous said...

Russia's posture was defensive from the start. There's no evidence they had any interest in world domination, and they developed nukes because we had them. There was no way they would ever be invaded again, after WWII. The whole cold war myth was a creation to benefit the military-industrial complex Eisenhower spoke frankly about in 1961.

Anonymous said...

And now folks, here's a news flash from Mars:

"Russia's posture was defensive from the start. There's no evidence they had any interest in world domination, and they developed nukes because we had them. There was no way they would ever be invaded again, after WWII. The whole cold war myth was a creation to benefit the military-industrial complex Eisenhower spoke frankly about in 1961.

March 7, 2014 at 10:16 PM"

Anonymous said...

Just one question: Why spend many millions of dollars, and decades, and the efforts of some of the country's best scientists, pursuing a meaningless, dead-end goal?
March 7, 2014 at 9:09 AM

It's many, many billions of dollars. It was pursued because a handful of smart, charismatic people said the right words and showed the right pictures and plots to the right people at the right time, consistently. Eventually the program was too big to kill, forcing DOE to double-down and double-down again despite early problems. That was Moses' real achievement, painting himself as having saved the whole effort from the incompetent 'brainiacs' and establishing the NIF as a cornerstone of the lab. That victory has proven to be pyrrhic.

Anonymous said...

It was pursued because a handful of smart, charismatic people said the right words and showed the right pictures and plots to the right people at the right time, consistently.

March 8, 2014 at 9:07 AM

Perhaps, but that "handful" did not do the work in spite of knowing it was futile and even against the national interest. How do all the rest of those "smart" people get off the hook?

Anonymous said...

Religious fervor perhaps.

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