I was looking at various superweapons in Gundam, and recently came across a Gamma-Ray Weapon in Gundam SEED known as the GENESIS.

Here is a description of how it works:

"GENESIS is a huge gamma ray cannon that uses nuclear explosions to produce a massive burst of gamma radiation, which is reflected back by an external alignment mirror and focused by a second mirror on the cannon to create a laser beam. The nuclear explosions are possible due to the use of the Neutron Jammer Canceller technology. The laser fired by GENESIS is sufficiently powerful that if it were to hit Earth, it would wipe out half the life on the planet. It causes human bodies closest to the shot to inflate and explode. The external mirror is severely damaged in the blast and must be replaced for another shot to be fired."

Before I ask about its feasibility, I should place my own assumptions:

  • The nuclear weapons used can be of any necessary yield, even above the TSAR Bomba. Antimatter, necessary Catalysts to boost fusion, all is fine.
  • The surrounding materials (such as the mirrors) can withstand the high energies and temperatures (some nuke-proof Unobtainium, it is fine here).

With that, I ask if the mechanics of how the Gamma Ray Laser works here is feasible, the radiation reflected and focused between two mirrors to produce the laser. I need not have the big world-ending effects for the weapon work, just the mechanics of creating this Gamma Ray Beam, with the aforementioned assumptions.

If it does not work, then feel free to bring forth corrections, or what will be needed to make it work.

  • $\begingroup$ if you detonated every nuclear bomb on earth it could not wipe out half the life on earth. $\endgroup$ – John Apr 16 at 15:13
  • $\begingroup$ @john no, if it was spread out and properly done you could kill all of earth it would also create a nuclear winter to finish the job $\endgroup$ – Topcode Apr 16 at 20:11
  • $\begingroup$ @Topcode no you really can't people underestimate how big the earth is and how much energy it releases on daily basis, one earthquake puts out more energy than all the nuclear weapons put together. $\endgroup$ – John Apr 17 at 3:05
  • $\begingroup$ @john, its not about pure energy output, a bullet dosent have tat much energy compared to many things that wont kill you but a bullet will kill you $\endgroup$ – Topcode Apr 17 at 3:12

Forget the mirrors, in gamma ray range you will need a matter made exclusively from nuclear particles - something like neutronium or even quark matter - which won't be stable outside humongous gravitational forces and in small but still macroscopic quantities (letting aside that 1cm3 of neutronium would weight 4×1011kg - 400 megatons, that is).

However, pulsed gamma lasers may be possible, the same way a nitrogen TEA lasers work - no resonant cavity, just a single pass of the lasing ray through the medium (which does mean low efficiency).

You will need to pump the nuclei (and not the electrons) on metastable energy states. Of course you will need nuclear explosion to do this and you will need a careful choice of the isotopes you "dope" the "explosive" with.

For some info on what you can choose, see metastable nuclear isomers or even nearly stable isomers.

Some further information, see also graser - gamma ray laser and induced gamma ray emission - seem impossible at current level of technology, but not impossible theoretically.

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  • $\begingroup$ The "single pass" through the medium was actually how the Excalibur X-Ray laser of the SDI program was supposed to work, long rods of a dense metal energized by a nuclear explosion. I suspect a much more complex material will need to be energized to generate gamma ray lasers. $\endgroup$ – Thucydides Apr 16 at 15:56

I ask if the mechanics of how the Gamma Ray Laser works here is feasible, the radiation reflected and focused between two mirrors to produce the laser.

No, it's not feasible.

a massive burst of gamma radiation, which is reflected back by an external alignment mirror and focused by a second mirror on the cannon to create a laser beam.

This is where anybody with a tad of knowledge in lasers starts to shiver before banging his/her head against the wall, crying "why? why? why?".

There are 3 founding elements in a laser:

  1. a resonating cavity, usually constituted by two mirrors (present)
  2. an active medium which emits the laser radiation (missing)
  3. a pumping mechanism that feeds energy into the system (present if you consider the nuke to be it)

The way a laser works is as follows:

  • the pumping mechanism induce population inversion in the active medium (that is, more excited species than relaxed ones)
  • the resonating cavity selects only few frequencies allowed in the cavity
  • a photon induces stimulated emission in the inverted population, increasing the population of photons within the cavity

If you miss one or more of those 3, you don't have a laser.

If you have only the pump and the active medium but no cavity, you have just an optical amplifier.

If you have the cavity and nothing else, you have only a resonator doing frequency selection. This is what that description is giving: only a resonator.

Moreover, laser cavities to be truly selective need to be long as an integer multiple of the wavelength of the light they are emitting. The less wavelengths the cavity is long, the more spectral pure is the emission. This means that for a laser in the visible spectrum, you want a cavity to be a few hundreds of nanometers long. To have a laser at 540 nm, you want to have a cavity which is of a comparable length. The longer the cavity, the more you are spreading the emission on several modes. A 1 cm long cavity would have about 2000 wavelengths at 540 nm, and would be really hard to distinguish from a continuous emission.

Gamma radiation is even worse, because it has a way shorter wavelength, less than 0.1 nm: to make a gamma laser with decent spectral purity, you want the mirror to be that close. No way you can fit a nuke in such a narrow space. To make thing worse, gamma rays are emitted only by nuclear transitions, not by electron transitions. We know no physics which can stimulate nuclear transitions, else we would have solved the problem of processing nuclear wastes.

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  • 2
    $\begingroup$ Not to mention the difficulty of making a mirror able to reflect gamma rays... $\endgroup$ – AlexP Apr 16 at 13:51
  • $\begingroup$ a resonating cavity, usually constituted by two mirrors - you don't actually need them, you only need an "optical path" long enough to get a decent gain (may be short if the density of population inversion is high enough). For example, see TEA lasers; you can build one yourself at home with impressive success rates $\endgroup$ – Adrian Colomitchi Apr 16 at 14:47
  • $\begingroup$ Yup; there's a reason grasers and gravity manipulation / artificial gravity usually go hand in hand. You can reliably shape the course of gamma rays with gravity, but that's about all that can achieve this feat. I'm not aware that it is possible to reflect gamma rays using physical materials. $\endgroup$ – Matthew Apr 16 at 17:17

Sounds impractical, if you're using a nuclear device to trigger a gamma detonate, why not just use the nuke. Converting gamma waves into a laser, requires focusing an apparatus, saturating with radiation would require enormous amounts of heavy shielding or you'll kill the operators. Also gamma saturation would downgrade into lower energy states producing infrared and other energies. Gamma rays can not be reflected off a mirror and their wavelengths are so small that they will pass between atoms in a detector. This means that gamma rays’ detectors often contain densely packed diamonds. Building a gamma concentrator would be more expensive than building an entire stockpile of nuclear weapons.

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  • $\begingroup$ Because Coordinators don't use nuclear missiles like filthy naturals. $\endgroup$ – DKNguyen Jun 21 at 6:53

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