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Lasers and nuclear proliferation

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LAN_403

Conundrum

Mon May 09 2011, 11:24AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Hi all.

I was reading up on some very interesting work on using lasers for plasma experiments, as it turns out that you could use two or more high power lasers to focus on the centre of a sonoluminescence cell in order to generate a bubble without the use of hazardous isotopes.

Recall a few years back how the now discredited Taleyarkhan claimed to generate fusion using bubbles, but it turned out he was measuring coincidence particles from the isotope he used to generate the seed bubbles.

It seems that there is a potential nuclear proliferation issue with high power laser diodes, because the switching time can be in the nanoseconds due to the small structure.

This effectively means that an array of 600mW 12X BRD's could be a cheap way to set off an implosion warhead by (deleted deleted)

(deleted for very obvious reasons, PM me for this...)

Could be a major problem, as these are easy to get hold of and it means a single skilled individual with access to weapons grade materials and high power diodes could build a nuclear device without the usual hard to find parts such as krytrons, EBWD's etc that normally set off various anti proliferation systems.

Discuss.
-A

ConKbot of Doom

Mon May 09 2011, 01:22PM

Registered Member #509 Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329

Not sure how much this matterrs, but the focus on the 1W nichia diodes is pretty poor, they are multi-mode lasers, and the output when collimated is a rectangular image of the die. Focused at a point will obviously be smaller, however I still think it would be a pain to reduce the image at the focus point to smaller then the die size while still keeping the power level up.

I dont know about the blu-ray diodes however, (I.E if those are single mode or multi-mode)

I'm no expert in glass switching thingys ;p but Ive seen this brought up before, since a krytron is a somewhat refined triggered spark gap, it shouldnt be that much of a hinderance for a motivated nation that wants a hand in the nuclear game. Obviously it takes refinements though, but I could see it being a hinderance for a smaller group upto no good.

I have a feeling we'll hear if the NRC or DHS starts grabbing up all the sanyo(samsung?) projectors that people are pulling the nichia diodes from :o)

Pinky's Brain

Mon May 09 2011, 01:39PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

The peak power you can get out of a laser diode is weak shit.

I don't see how that is of any greater concern to proliferation than the ease with which you can build flash lamp pumped lasers with short pulse times.

Proud Mary

Mon May 09 2011, 05:44PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

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Dr. ISOTOP

Mon May 09 2011, 09:02PM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

@ConKbot of Doom: The projectors are Casios.
Laser fusion is done with peak powers in the terawatts; by comparison, the most powerful QCW diode bars will push 300Wpk.

Sulaiman

Tue May 10 2011, 12:54PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

As far as I know, the only reason a krytron (or similar) is used is so that emp (or microwaves etc.)
cannot set off the warhead, causing a 'chain effect' where multiple nukes are in close proximity.
For a terrorist etc. a spark gap would be adequate.
Export restrictions etc. are to prevent various rogue states having stockpiles of nukes.
It's the fissile material that needs controlling, not the detonation mechanism.

Bored Chemist

Tue May 10 2011, 09:09PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Pinky's Brain wrote ...

The peak power you can get out of a laser diode is weak shit.

I don't see how that is of any greater concern to proliferation than the ease with which you can build flash lamp pumped lasers with short pulse times.

The pulse power you can get is a lot higher; and don't forget that the expected working life of this device is sod all squared before the nuke invalidates the warranty.

The only way to control this risk is to keep the nuclear material under wraps.

James

Tue May 10 2011, 10:21PM

Registered Member #3610 Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506

The peak power from a laser diode is not actually much greater than the continuous output. You end up with catastrophic optical damage, that is the output reaches a point that it cracks or shatters the polished ends of the die.

With early laser diodes, COD was only slightly above the lasing threshold below which there was no beam at all. It's why early laser diodes required such precise current control with closed loop feedback utilizing an internal photodiode.

As someone else said, a flashlamp pumped laser is the way to go if you want high peak power. TEA nitrogen lasers can produce very high peak power as well, although the average power is rarely more than a few milliwatts.

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