Bomb pumped XRay lasers

kojikun · Post by **kojikun** » 2003-04-22 09:22pm

I was wondering the actual structure fo the laser systems. Wouldn't any lasing system vaporise before the actual lasing occured? I would think that the high energy XRays would totally waste any chamber the instant they hit it.

Or maybe I'm thinking too conventionally. Anyone know how it works?

phongn · Post by **phongn** » 2003-04-22 09:31pm

I doubt that any information on how the bomb-pumped X-ray lasers would work is in the public domain.

That said, they probably figured out some way to get the detonation's X-rays pointed in the same direction (via mirrors - they do exist for the X-ray spectra and used in thermonuclear bombs, for example) - and since the X-rays traveled faster than the blast effects of the bomb, it didn't have to last too long.

As for non-bomb-pumped X-ray lasers, they exist as well, though at much lower power.

kojikun · Post by **kojikun** » 2003-04-22 09:39pm

well, im not so much concerned with the blast destroying the mirror as i am with the mirror being vaporised by the XRays it's reflecting!

phongn · Post by **phongn** » 2003-04-23 12:01am

kojikun wrote:well, im not so much concerned with the blast destroying the mirror as i am with the mirror being vaporised by the XRays it's reflecting!

They only have to survive for a brief moment in time while they are reflecting the X-rays.

kojikun · Post by **kojikun** » 2003-04-23 12:10am

but they have to reflect long enough for lasing to occur. i mean, i guess lasing occurs pertty fast, if its just a burst, but it seems awefully strange that the mirrors would be still intact enough after just a couple of reflections to continue reflecting with any quality.

you have any links to bomb pumped xaser sites or something?

victorhadin · Post by **victorhadin** » 2003-04-23 07:57am

I'd very much like to hear where you found out about this 'mirrors for X-rays' information because as far as I was aware, the wavelength of your common-or-garden X-ray is far too small for an effective mirror or diffraction setup to be built.

Slartibartfast · Post by **Slartibartfast** » 2003-04-23 11:25am

kojikun wrote:but they have to reflect long enough for lasing to occur. i mean, i guess lasing occurs pertty fast, if its just a burst, but it seems awefully strange that the mirrors would be still intact enough after just a couple of reflections to continue reflecting with any quality.

you have any links to bomb pumped xaser sites or something?

X-rays propagate at light speed. Explosions do not. Any amount of time required for the lasing to occur (basically bouncing a few dozen times until they get the angle right) is negligible.

Unless they're travelling planetary distances, the speed of light is pretty much instantaneous.

phongn · Post by **phongn** » 2003-04-23 01:53pm

victorhadin wrote:I'd very much like to hear where you found out about this 'mirrors for X-rays' information because as far as I was aware, the wavelength of your common-or-garden X-ray is far too small for an effective mirror or diffraction setup to be built.

Lemme look. I know that X-ray mirrors are used in the construction of thermonuclear munitions so that they can be used to compress the fission reaction.

kojikun · Post by **kojikun** » 2003-04-23 10:23pm

Well, AFAIK, XRays CAN reflect relatively easilly off of a surface when it strikes it at a very shallow angle. I think the reason XRays tend not to reflect, however, is that the space between atoms or subatomic particles is much larger then the wavelength of the rays. Optical physics says that light cannot reflect off of a meshlike surface (first-surface) where the average spacing between the particles is larger then the wavelength intended to be reflected. That includes metal meshes for reflecting microwaves, etc. But for XRays, a typical wavelength can be so small that even inter/intraatomic spaces are too large.

Freaky shit, no?

Slartibartfast · Post by **Slartibartfast** » 2003-04-24 02:43am

Well the fact is, X-ray lasers (xasers) have been produced, in their nuke and nukeless forms (or at least the nukeless form). Which means that *something* that creates the lasing exists and has been used. All that remains is find out exactly what they use.

Warspite · Post by **Warspite** » 2003-04-24 07:32am

kojikun wrote:Well, AFAIK, XRays CAN reflect relatively easilly off of a surface when it strikes it at a very shallow angle. I think the reason XRays tend not to reflect, however, is that the space between atoms or subatomic particles is much larger then the wavelength of the rays. Optical physics says that light cannot reflect off of a meshlike surface (first-surface) where the average spacing between the particles is larger then the wavelength intended to be reflected. That includes metal meshes for reflecting microwaves, etc. But for XRays, a typical wavelength can be so small that even inter/intraatomic spaces are too large.

Freaky shit, no?

Well, there are several techninques to study crystals that use x-ray diffraction, the wavelenghts produced (between .05 and .25 nanometres) are about equal to the distance between planes of atoms in crystalline solids, think about the graphite, composed by infinite layers, the distance between those layers is equal to the wavelength of x-rays.

Glass Pearl Player · Post by **Glass Pearl Player** » 2003-04-24 07:37am

The X-Ray-Lasers seen in large laboratories (and if I say large, I mean it) are so-called free-electron-lasers, and they do not use mirrors. The X-Ray-Laser pulse takes only one pass through the assembly.
Spektrum der Wissenschaft (the german branch of Scientific American) had a special issue on laser technology. As soon as I have it at hand, I could tell you more on how those toys work.
From memory: High-speed electrons come out of an acellerator into a "undulator", a long linear device in which strong magnetic fields cause the electrons to wiggle around. If done right, the electrons start to emmit laser radiation, frequency depends of velocity and parameters of the magnetic field.

Suggested keywords for Google: "Free Electron Laser Undulator". Should give satisfying results.

PS: A FEL could use mirrors, if one would tune it down to frequencies where mirrors do work.

victorhadin · Post by **victorhadin** » 2003-04-24 07:56am

phongn wrote:
victorhadin wrote:I'd very much like to hear where you found out about this 'mirrors for X-rays' information because as far as I was aware, the wavelength of your common-or-garden X-ray is far too small for an effective mirror or diffraction setup to be built.
Lemme look. I know that X-ray mirrors are used in the construction of thermonuclear munitions so that they can be used to compress the fission reaction.

Well I would very much like some backing for this because as far as I know, it is impossible and X-ray mirrors would not really be necessary in thermonuclear bobms in any case. The requisite pressures and temperatures would occur either way after the initial fission reaction. As for triggering the fission reaction itself, X-rays are not involved.

Lord Edam · Post by **Lord Edam** » 2003-04-24 08:42am

tabletop x-ray lasers

You can't use mirrors in the sense most here seem to be taking them with X-rays. They don't reflect particularly well. You can bend the X-rays a bit if they hit a plate of metal such as nickel at an angle of a few arcminutes, but that's about it. IIRC, nuclear bombs use the mirrors more to direct x-rays that would otherwise just miss the target rather than reflect x-rays going completely the wrong direction back in.

googling on x-ray telescopes and similar astrophysical research would be your best bet for x-ray mirror info, since a lot of the researchers were both astrophysicists and nuclear weapons designers.

It's been a few years since I read it, but maybe Sam's Laser FAQ would have a bit more, or some websites to visit for X-ray lasers.

Warspite · Post by **Warspite** » 2003-04-24 08:51am

victorhadin wrote:
phongn wrote:
victorhadin wrote:I'd very much like to hear where you found out about this 'mirrors for X-rays' information because as far as I was aware, the wavelength of your common-or-garden X-ray is far too small for an effective mirror or diffraction setup to be built.
Lemme look. I know that X-ray mirrors are used in the construction of thermonuclear munitions so that they can be used to compress the fission reaction.
Well I would very much like some backing for this because as far as I know, it is impossible and X-ray mirrors would not really be necessary in thermonuclear bobms in any case. The requisite pressures and temperatures would occur either way after the initial fission reaction. As for triggering the fission reaction itself, X-rays are not involved.

The only mirrors used in nuclear devices, are the explosive lenses that create the compressive shockwave on the fissable material.

Arrow · Post by **Arrow** » 2003-04-24 11:56am

In a military appilication, what advantage would an X-Ray Laser have over an array of IR lasers, with both the X-Ray and the IR Array tranmitting the same power to a point on a target?

The disadvantage of the X-Ray laser seems pretty obivious, in that you either have to find a way to contain and direct a nuclear explosion or in that you have to use an inefficient particle accelerator to energize the electrons used in an FEL; whereas the IR lasers are much more efficient.

Also, if you wanted to block an X-Ray laser, what kind of material would you use? Thick blocks of metal? A tight knit crystaline?

phongn · Post by **phongn** » 2003-04-24 01:17pm

victorhadin wrote:
phongn wrote:
victorhadin wrote:I'd very much like to hear where you found out about this 'mirrors for X-rays' information because as far as I was aware, the wavelength of your common-or-garden X-ray is far too small for an effective mirror or diffraction setup to be built.
Lemme look. I know that X-ray mirrors are used in the construction of thermonuclear munitions so that they can be used to compress the fission reaction.
Well I would very much like some backing for this because as far as I know, it is impossible and X-ray mirrors would not really be necessary in thermonuclear bobms in any case. The requisite pressures and temperatures would occur either way after the initial fission reaction. As for triggering the fission reaction itself, X-rays are not involved.

You misunderstand how thermonuclear bombs work.

The fusion reaction is usually not there to make a Big Boom but rather to increase the efficiency of the fission reaction. The massive X-ray release is used to compress the primary fission sphere (in addition to the chemical explosives), apparently gaining an efficiency of near 100%.

EDIT: Damnit, I had some links but I can't find them...

phongn · Post by **phongn** » 2003-04-24 01:18pm

Warspite wrote:
victorhadin wrote:
phongn wrote: Lemme look. I know that X-ray mirrors are used in the construction of thermonuclear munitions so that they can be used to compress the fission reaction.
Well I would very much like some backing for this because as far as I know, it is impossible and X-ray mirrors would not really be necessary in thermonuclear bobms in any case. The requisite pressures and temperatures would occur either way after the initial fission reaction. As for triggering the fission reaction itself, X-rays are not involved.
The only mirrors used in nuclear devices, are the explosive lenses that create the compressive shockwave on the fissable material.

Are you referring to the chemical-explosive component of nuclear devices?

phongn · Post by **phongn** » 2003-04-24 01:28pm

Well shit, I can't find anything specific about it anymore, so I'll concede. The closest thing I saw was a diagram using a U238 tamper (which could just as easily be lead) to reflect X-Rays.

kojikun · Post by **kojikun** » 2003-04-24 04:02pm

Warspite: Diffraction is not the same as reflection. Diffraction is the alteration of a waves direction after passing over an edge, whereas reflection is the alteration of a waves direction by bouncing off a surface.

Warspite · Post by **Warspite** » 2003-04-24 04:39pm

kojikun wrote:Warspite: Diffraction is not the same as reflection. Diffraction is the alteration of a waves direction after passing over an edge, whereas reflection is the alteration of a waves direction by bouncing off a surface.

OK, sorry, mixed up the words, or for that matter, the physics...

Warspite · Post by **Warspite** » 2003-04-24 04:41pm

phongn wrote:
Warspite wrote: The only mirrors used in nuclear devices, are the explosive lenses that create the compressive shockwave on the fissable material.
Are you referring to the chemical-explosive component of nuclear devices?

Yup, that's an afirmative!

kojikun · Post by **kojikun** » 2003-04-24 05:05pm

Warspite wrote:OK, sorry, mixed up the words, or for that matter, the physics...

Ts'okay. Just to give you an example of diffraction, put some edge (your finger, a book, or a piece of paper all work) up to your eye, and focus on something beyond it. notice how where the objcet blurs out a bit everything is squashed. Moved it a bit and you can see things squash as they move into the area.

Admiral Valdemar · Post by **Admiral Valdemar** » 2003-04-24 06:23pm

A carbon cylinder is what they use, it helps direct the X-rays into a tight beam before being vapourised.

kojikun · Post by **kojikun** » 2003-04-24 07:19pm

carbon cylinders are fine for FOCUSING, but you need multiple passes to lase, so while a cylinder goes reflect, it doesn't reflect properly to cause lasing.