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Old 09-07-2017, 09:07 PM   #24
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Location: The plutonium rich regions of Washington State
Default Re: [Ultra-Tech] [Spaceships] Weapons that are hard or impossible to miniaturize

Quote:
Originally Posted by Michael Thayne View Post
How likely is it that the size of particle accelerator you'd need for a particle beam weapon is significantly larger/smaller than the one you'd need for an x-ray laser weapon?
Judging by modern facilities, they'll be about the same size.

Quote:
Originally Posted by Michael Thayne View Post
Similarly, am I correct that the accelerator for a graser would likely need to be orders of magnitude larger than the one for an x-ray laser?
Roughly. Unfortunately, "x-ray" and "gamma-ray" are not all that well defined in terms of the photons themselves, but rather in how they were generated. X-rays are usually defined as photons created by core electron transitions in atomic systems; gamma rays are photons made by transitions between nuclear energy states. So the energy range of what is considered an x-ray can overlap with what is considered a gamma ray. Roughly, though, most x-rays that anyone has to deal with are between 10 and 100 keV, gamma rays tend to be between 100 and 2000 keV. So yeah, that's about an order of magnitude difference in energy and thus an order of magnitude difference in accelerator length.

Quote:
Originally Posted by Michael Thayne View Post
Does Compton backscatter present its own issues with miniaturization?
The Compton backscatter sources that people are working on now could easily fit in a van. They won't have enough energy to melt things, of course (mainly they're for detecting contraband nuclear material). The main issue is that the beam spread is likely to be too large for a long range weapon.

Quote:
Originally Posted by Michael Thayne View Post
How does positron annihilation in flight lead to a coherent beam?
You get a beam of positrons and a beam of equal energy electrons and collide them head-on. When you go work out the angular distribution of the resulting annihilation gamma rays, you find out that they are mostly directed along the beam axis. Make the electron and positron energies high enough and you can get fairly narrow beams. Again, like Compton laser backscatter, the beam spread may still be too large for practical offensive applications.

Quote:
Originally Posted by Michael Thayne View Post
So TLDR; if you want to justify a non-tunable x-ray laser you could assume the multiple wigglers was not worth the trouble?
Pretty much, yeah. But keep in mind that for less than an extra 10% mass and volume, you can get a visible light laser of the same power as well. Unless you have wakefield accelerators, which might be so compact that the wigglers are comparable in size to the accelerator - but in that case you already have a high energy laser in the near visible or visible band that you might as well use.

Luke
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