How to Build a Laser Death Ray
Everyone knows x-rays are highly penetrating, right? Not necessarily. As the graph below shows, the low energy x-rays (so called soft x-rays) can't even go through a meter of air without being attenuated away. |
They are also rapidly absorbed by all other matter.
It is difficult to focus soft x-rays. Since they will not pass through matter, you can't use lenses. Mirrors will only work at grazing angles, so you need complicated grazing incidence mirrors. Furthermore, to get diffraction limited performance, the mirrors will need to be smooth and perfectly shaped down to about 1/3 of a wavelength. This means you would need to have a mirror without any imperfactions larger than about 1 to 10 atoms across (depending on the wavelength). If you can get these, however, soft x-rays would make an excellent wavelength for space combat, since they could be focused to high intensities at very long ranges.
Conventional lasers can generate soft x-rays, but with extremely low efficiencies. You need to turn a bit of matter ito a highly ionized plasma with a powerful laser pulse in order to get a weak x-ray beam out. However, there are free elelctron lasers that generate beams of soft x-rays for scientifc research. These beams are produced in extremely powerful pulses. Scientists love the high brighness, but get annoyed because a single pulse will vaporize their sample. As death ray designers, however, this is exactly what we want. X-ray free electron lasers may be the weapons of choice for future spacecraft.