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Jerry
2012-Jul-27, 10:35 PM
http://www.cnn.com/2012/07/19/tech/innovation/laser-beam-powerful-techland/index.html?iref=obnetwork


another kind of historic event just transpired: a record-shattering laser beam that, in a single shot fired on July 5, 2012, generated more power than the United States does at any single instant...

...
That's what the National Ignition Facility -- home to the world's largest laser -- just did when it pulled the trigger on 192 beams of optically amplified, electromagnetic radiation-emitting light, all fired within a few trillionths of a second of each other, to deliver 500 trillion watts (or terawatts) of "peak power" and 1.85 megajoules of ultraviolet laser light.
I'm a little surprised to read about this; having worked on a hush hush earlier version early in the century, but I guess nothing is secret any more.

If you have seen the move 'Real Genius'; you have an idea of where we were a decade ago. Amazing.

TooMany
2012-Jul-27, 11:53 PM
Can this laser ignite hot fusion? Early in laser fusion (1972) it was thought that a relatively small laser could do the job. It was theorized that 1 kJ could ignite a small sample but 1 MJ would be needed to get a practical return (power generation).

It's been a bit disappointing in that a long series of ever more powerful laser systems have failed to produce expected yields. NIF cost 3.5 billion, with a 2 billion dollar overrun, and appears (at least a year ago (http://www.physicstoday.org/daily_edition/politics_and_policy/1.2657141)) to be falling short of the ignition goal.

The real justification for the facility is the maintenance of our nuclear arsenal. The idea was to be able to build new nuclear weapons without having to test fire them. (Doesn't that seem a bit far fetched?) It's amazing how much money can be spent in pursuit of what appears to be an impractical goal. There have been some rather negative comments (from the Wiki ICF article):

{QUOTE}A retired Sandia manager, Bob Puerifoy, was even more blunt; "NIF is worthless ... it can't be used to maintain the stockpile, period".{/QUOTE}

On the other hand the expense seems to be sold to the public as a step toward development of practical fusion power. The problems that have been encountered are somewhat analogous to problems in magnetic confinement. A high degree of perfection of the beam intensity and shape appears to be required to prevent the energy needed from leaking away too rapidly. New mechanisms of heat loss have emerged.

There is an upcoming NIF deadline in September of some sort, but I don't know the details. The European Union has an ongoing project taking a different approach called "fast ignition". First a big laser shot is used to compress a fuel pellet, then a ultra-short, high-power shot is fired to finish the job. See HiPER.

This is one hard fire to light!

Ara Pacis
2012-Jul-28, 12:47 AM
I don't think there's much chance we can weaponize this.

TooMany
2012-Jul-28, 12:52 AM
I don't think there's much chance we can weaponize this.

Wait, what if we put it on treads like a tank so we can move it around? Then we can lure the enemy in and fry an earlobe.

Solfe
2012-Jul-28, 02:54 AM
I don't think there's much chance we can weaponize this.

The weapon only works when the enemy is holding a pellet. :)

Van Rijn
2012-Jul-28, 04:31 AM
I'm a little surprised to read about this; having worked on a hush hush earlier version early in the century, but I guess nothing is secret any more.

If you have seen the move 'Real Genius'; you have an idea of where we were a decade ago. Amazing.

Real Genius was about a laser that could fit in a plane. It was released in 1985. ICF (Inertial Confinement Fusion) laser arrays are different and development goes back to the '70s. The Nova laser array (the NIF's predecessor) goes back to 1984 (a bit before Real Genius) and it wasn't secret. See:

http://en.wikipedia.org/wiki/Nova_%28laser%29

It was upgraded over time, and with what they learned, they moved onto the NIF. They do play down that part of the reason they built it is to give government nuclear weapons researchers something to do and keep their expertise in weapons physics, but the weapons aspect hasn't been secret. (Some of the results would be, though).

swampyankee
2012-Jul-28, 02:29 PM
The weapon only works when the enemy is holding a pellet. :)

...and has the consideration to stand in the target zone.

Noclevername
2012-Jul-28, 02:41 PM
But just think of all the popcorn you could pop with a laser like this!

swampyankee
2012-Jul-28, 02:53 PM
But just think of all the popcorn you could pop with a laser like this!

This looks like inspiration for a Make project: laser-powered popcorn machine....

trinitree88
2012-Jul-28, 03:02 PM
But just think of all the popcorn you could pop with a laser like this!

Well, countries make treatys to agree not to use stuff on each other, and sometimes they play a bit to find out how to defend against the stuff should some collection of clowns decide to make it anyway. Directed energy weapons and space telescopes looking downwards were kind of cold war banned but emerged anyway. It is a little tricky to shoot stuff with Captain Kirk's/ Captain Picard's "photon torpedoes" because the atmosphere is not homogeneous and you get some refraction. Adaptive optics didn't just emerge to make terrestrial telescope images better....it let's you put the "torpedo" out through the atmosphere,too...if necessary.
In all probability, space battles between satellites, ships, missiles, using space-borne directed energy weapons, where the atmospheric plasmas have less interference will be seen in the next century...including X-ray lasers for Star Wars missile defense, and there hasn't been a whisper of a graser for decades. Thimk. pete

JCoyote
2012-Jul-28, 07:35 PM
It is a little tricky to shoot stuff with Captain Kirk's/ Captain Picard's "photon torpedoes" because the atmosphere is not homogeneous and you get some refraction.

Momentary tangent: "photon torpedoes" were not directed energy weapons, they were projectiles like artillery shells. I think you were looking for "phasers".

And light bending in the atmosphere is not that problematic for targeting unless at very extreme ranges.

Noclevername
2012-Jul-28, 08:31 PM
Could it be used as a launching laser for a beam-rider?

Van Rijn
2012-Jul-28, 10:30 PM
Could it be used as a launching laser for a beam-rider?

A laser array could, but this laser array wouldn't be very good for that. The purpose here is to create a very short, very intense pulse. The array has to cool down after a pulse, so the continuous power output wouldn't be good, you don't need such short pulses, or such a tightly focused beam for laser launch.

Jens
2012-Jul-30, 03:46 AM
I wonder if Pink Floyd could find a use for it. . .

Ara Pacis
2012-Jul-31, 10:56 AM
In all probability, space battles between satellites, ships, missiles, using space-borne directed energy weapons, where the atmospheric plasmas have less interference will be seen in the next century...including X-ray lasers for Star Wars missile defense, and there hasn't been a whisper of a graser for decades. Thimk. pete

Plasmas? The only real plasma weapons on the battlefield are metal vapor jets created by shaped charges, and they are short range in most senses of the word.

Gamma Ray lasers have been mentioned as a potential use for metastable nuclear Isomers, such as Hafnium.

cjameshuff
2012-Jul-31, 05:09 PM
A laser array could, but this laser array wouldn't be very good for that. The purpose here is to create a very short, very intense pulse. The array has to cool down after a pulse, so the continuous power output wouldn't be good, you don't need such short pulses, or such a tightly focused beam for laser launch.

The NIF is in fact trying to get the recovery time down to 4 hours, allowing up to 700 shots a year. That's about 500 watts average power, with overall efficiency below 1%...you'd be better off with an incandescent spotlight.



Plasmas? The only real plasma weapons on the battlefield are metal vapor jets created by shaped charges, and they are short range in most senses of the word.

I don't think trinitree88 is talking about plasma weapons, but about the problems laser weapons have in atmosphere...they ionize the air at high intensities, refracting and scattering the beam. You need very apertures for even short range laser weapons, not because of diffraction limits, but to keep the intensity down for most of the beam path.

Ara Pacis
2012-Jul-31, 06:20 PM
I don't think trinitree88 is talking about plasma weapons, but about the problems laser weapons have in atmosphere...they ionize the air at high intensities, refracting and scattering the beam. You need very apertures for even short range laser weapons, not because of diffraction limits, but to keep the intensity down for most of the beam path.

I seem to recall, from a previous discussion here, that different freqs prefer different air densities, such that one laser might pre-heat/ionize the air for the main event.