Laurence Livermore's Latest Lasers

[adam_grif]

Ok so it's actually NIF's lasers, sue me.

World's largest laser sets records for neutron yield and laser energy

LIVERMORE, Calif. -- The National Nuclear Security Administration's National Ignition Facility (NIF) has set world records for neutron yield from laser-driven fusion fuel capsules and laser energy delivered to inertial confinement fusion (ICF) targets. NIF researchers will report on these and other recent experimental results this week at the annual meeting of the American Physical Society Division of Plasma Physics in Chicago.

The neutron yield record was set on Sunday, Oct. 31, when the NIF team fired 121 kilojoules of ultraviolet laser light into a glass target filled with deuterium and tritium (DT) gas. The shot produced approximately 3 x 1014 (300 trillion) neutrons, the highest neutron yield to date by an inertial confinement fusion facility. Neutrons are produced when the nuclei of deuterium and tritium (isotopes of hydrogen) fuse, creating a helium nucleus and releasing a high-energy neutron.

On Tuesday, Nov. 2, the team fired 1.3 megajoules of ultraviolet light into a cryogenically cooled cylinder called a hohlraum containing a surrogate fusion target known as a symmetry capsule, or symcap. This was the highest-energy laser shot and was the first test of hohlraum temperature and capsule symmetry under conditions designed to produce fusion ignition and energy gain. Preliminary analysis indicated that the hohlraum absorbed nearly 90 percent of the laser power and reached a peak radiation temperature of 300 electron volts (about six million degrees Fahrenheit) -- making this the highest X-ray drive energy ever achieved in an indirect drive ignition target.

The experiments followed closely on the heels of NIF's first integrated ignition experiment on Sept. 29, which demonstrated the integration of the complex systems required for an ignition campaign including a target physics design, the laser, target fabrication, cryogenic fuel layering and target positioning, target diagnostics, control and data systems, and tritium handling and personnel and environmental protection systems. In that shot, one megajoule of ultraviolet laser energy was fired into a cryogenically layered capsule filled with a mixture of tritium, hydrogen and deuterium (THD), tailored to enable the most comprehensive physics results.

"The results of all of these experiments are extremely encouraging," said NIF Director Ed Moses, "and they give us great confidence that we will be able to achieve ignition conditions in deuterium-tritium fusion targets."

NIF, the world's largest and highest-energy laser system, is located at Lawrence Livermore National Laboratory (LLNL) in California. NIF researchers are currently conducting a series of "tuning" shots to determine the optimal target design and laser parameters for high-energy ignition experiments with fusion fuel in the coming months.

When NIF's 192 powerful lasers fire, more than one million joules of ultraviolet energy are focused into the ends of the pencil-eraser-sized hohlraum, a technique known as "indirect drive." The laser irradiation generates a uniform bath of X-rays inside the hohlraum that causes the hydrogen fuel in the target capsule to implode symmetrically, resulting in a controlled thermonuclear fusion reaction. The reaction happens so quickly, in just a few billionths of a second, that the fuel's inertia prevents it from blowing apart before fusion "burn" spreads through the capsule -- hence the term inertial confinement fusion. In ignition experiments, more energy will be released than the amount of laser energy required to initiate the reaction, a condition known as energy gain. NIF researchers expect to achieve a self-sustaining fusion burn reaction with energy gain within the next two years.

The experimental program to achieve fusion and energy gain, known as the National Ignition Campaign, is a partnership among LLNL, Los Alamos National Laboratory, the Laboratory for Laser Energetics at the University of Rochester, General Atomics of San Diego, Calif., Sandia National Laboratories, Massachusetts Institute of Technology, and other national and international partners.

In the Oct. 31 "neutron calibration" shot, NIF's lasers were fired directly onto a DT-filled glass target, as opposed to the indirect-drive geometry used in NIF's TD and THD experiments. The purpose of the shot was to calibrate and test the performance of NIF's extensive neutron diagnostic equipment.

The capsule used in the Nov. 2 symcap experiment has the same two-millimeter outer diameter doped shell as an ignition capsule, but replaces the DT fuel layer with an equivalent mass of material from the outer shell to mimic the capsule's hydrodynamic behavior. Achieving a highly symmetrical compression of the fuel capsule is a key requirement for NIF to achieve its goal of fusion ignition.

NIF, a project of the U.S. Department of Energy's National Nuclear Security Administration (NNSA) was built as a part of NNSA's program to ensure the safety, security and effectiveness of the nation's nuclear weapons stockpile without underground testing. With NIF, scientists will be able to evaluate key scientific assumptions in current computer models, obtain previously unavailable data on how materials behave at temperatures and pressures like those in the center of a star, and help validate NNSA's supercomputer simulations by comparing code predictions against observations from laboratory experiments.

Because of its groundbreaking advances in technology, NIF also has the potential to produce breakthroughs in fields beyond stockpile stewardship. NIF experiments have been conducted in support of Department of Defense X-ray testing activities, and NIF experiments in nuclear forensics and other national security areas are planned for the next several years. NIF also will provide unprecedented capabilities in fundamental science, allowing scientists to understand, for example, the makeup of stars in the universe and planets both within and outside our solar system. NIF will also help advance fusion energy technology, which could be an element of making the United States energy independent.

There's gotta be a way we can use this to blow people up. Laser initiated pure fusion weapons perhaps?

[Simon_Jester]

The practical problem with that is that the laser setup is very big, energy-intensive, and has to be just right; you can't make it asymmetric or the plasma just squirts out of the trap instead of being smashed into a much smaller and denser sphere by the lasers.

This is of interest because we want fusion reactors, I think; not because it's weaponizable.

[Gil Hamilton]

A single working practical fusion reactor is worth more than all the weapons grade lasers and bombs on the planet.

[Sarevok]

How do you extract energy from the fusion reaction ? Use some fancy named tech that ultimately drives turbines or something ? Or has someone come up with a more innovative solution ?

[Chardok]

How do you extract energy from the fusion reaction ? Use some fancy named tech that ultimately drives turbines or something ? Or has someone come up with a more innovative solution ?

Man, no, it's always going to be about steam. Unless someone makes a thing that uses lasers to make more lasers that shoot at a paddlewheel of super shiny mirrors utilizing the impact of the photons in the laser to drive the mechanism

[Sea Skimmer]

There's gotta be a way we can use this to blow people up. Laser initiated pure fusion weapons perhaps?

That falls under the vague heading of forth generation nuclear weapons, ones which are purely fusion based. Besides removing serious fallout from the equation such weapons would also be far easier to design to produce fairly directional yields. It’s unlikely such weapons will ever be built because by the time we have sufficiently compact laser or other ignition technology to make the devices compact enough to be useful, we’ll be able to destroy whole nations with fleets of high power laser planes anyway. However this research is very important for understanding how our existing fission-fusion devices work without conducting actual nuclear tests. It also doesn’t violate the Comprehensive Test Ban treaty, which only bans fission testing.

[Veramocor]

How do you extract energy from the fusion reaction ? Use some fancy named tech that ultimately drives turbines or something ? Or has someone come up with a more innovative solution ?

Fusion with a lot of neutron generation would be the thermal route but aneutronic fusion (which is much harder) you can get direct conversion of the energy http://en.wikipedia.org/wiki/Aneutronic_fusion.

[Imperial528]

How do you extract energy from the fusion reaction ? Use some fancy named tech that ultimately drives turbines or something ? Or has someone come up with a more innovative solution ?

The reaction heats water (somehow) to make steam to drive turbines.

If you wanted to you could line the interior with solar cells or some of those heat-to-electricity devices, provided they'd have to be pretty tough, and there's not much space in the interior anyway, unless your laser is fired from one direction into the capsule.

[Kyler]

There's gotta be a way we can use this to blow people up. Laser initiated pure fusion weapons perhaps?

It you want some scientific research that you want to turn into a weapon, read up on NASA's research into anti-matter propulsion technology.

Though I do appreciate the update on the testing at Livermore. I really hope that in few more years that they will get their sustainable fusion reaction. All my life I heard about fusion power, it will be cool to see it finally work.

[Starglider]

It you want some scientific research that you want to turn into a weapon, read up on NASA's research into anti-matter propulsion technology.

Even if we could make antimatter reasonably cheaply, I'm highly dubious about the prospects for making a 99.99999% reliable containment mechanism for (say) 10 grams of antimatter that weighs less than a 500kt nuclear warhead. Plus there's the fact that if one antimatter warhead undergoes premature annihilation, all the other warheads in the immediate area will go up too, causing horrible damage if it was say a bomber on an airbase. This is a manageable problem for say starship propulsion because you can just fuel the thing while it's sitting in Jupiter orbit.

Though I do appreciate the update on the testing at Livermore. I really hope that in few more years that they will get their sustainable fusion reaction.

Strictly no inertial confinement scheme is 'sustainable fusion', they're all pulsed ignition designs with a reaction time measured in nanoseconds. Tokamak designs have fusion pulse times of seconds to minutes (e.g. ITER is targeting five minutes). Stellerator designs can theoretically maintain fusion for hours or even days (e.g. Wendelstein 7-X, an often overlooked but rather awesome fusion experiment).

[adam_grif]

Plus there's the fact that if one antimatter warhead undergoes premature annihilation, all the other warheads in the immediate area will go up too, causing horrible damage if it was say a bomber on an airbase. This is a manageable problem for say starship propulsion because you can just fuel the thing while it's sitting in Jupiter orbit.

Not strictly true. A bomb going off will likely separate the antimatter from it's (no doubt fragile) trigger mechanism before it has a chance to annihilate (or at least break it), such that when the antimatter's containment is breached it's unlikely to ignite the fusion reaction.

AFAIK fratricide in conventional warheads does not cause the fusion stages of the other warheads to go up for similar reasons.

[Purple]

The issue is that with antimatter, fratricide might break the containment of the other antimatter bombs no?
And in that case, would it not just need to contact any molecule of the appropriate matter to annihilate?

Modern nuclear bombs don't nuke out from fratricide because they require a precise application of force from all sides to do so.
Antimatter meanwhile can react with anything it touches (given appropriate matter) and does not need to be focused like that.

So depending on the materials in the environment and the containment area it might not end well even if the antimatter is scattered all over the place.

At least I think so. Correct me if I am wrong.

[darthdavid]

The issue is that with antimatter, fratricide might break the containment of the other antimatter bombs no?
And in that case, would it not just need to contact any molecule of the appropriate matter to annihilate?

Modern nuclear bombs don't nuke out from fratricide because they require a precise application of force from all sides to do so.
Antimatter meanwhile can react with anything it touches (given appropriate matter) and does not need to be focused like that.

So depending on the materials in the environment and the containment area it might not end well even if the antimatter is scattered all over the place.

At least I think so. Correct me if I am wrong.

It's my understanding that any kind of antimatter will react with any kind of matter (so you could say, drop a chunk of anti-iron into a tank of regular air and it would annihilate). So if containment goes in anything but a damn near perfect vacuum shit's blowing the fuck up. But I could be wrong. Is there a physicist in the house?

[adam_grif]

The issue is that with antimatter, fratricide might break the containment of the other antimatter bombs no?
And in that case, would it not just need to contact any molecule of the appropriate matter to annihilate?

Modern nuclear bombs don't nuke out from fratricide because they require a precise application of force from all sides to do so.
Antimatter meanwhile can react with anything it touches (given appropriate matter) and does not need to be focused like that.

So depending on the materials in the environment and the containment area it might not end well even if the antimatter is scattered all over the place.

At least I think so. Correct me if I am wrong.

Of course it will break containment and react with matter, but the antimatter is just being used to set off the fusion reaction in the device. The antimatter triggering the fusion reaction is likely to be something like "injecting antimatter into the deuterium", in which case the containment breach will simply cause a (fairly powerful) conventional explosion, but will not ignite the fusion.

If two bombs go off sufficiently close together though, I assume that the fireball from one may well be able to ignite the fusion products from the other bombs. But you'd have to ask Shep and Co for more details about that because I'm pretty uncertain.