this sort of laser uses a relativistic electron beam passing through a series of magnetic feilds to produce coherent light.

 

i'm a little confused as to how it gets into the soft xray spectrum. surely the alternating magnetic feilds would need to be set up at the wavelength of the out put or shorter for the electron to oscillate sufficiently.

 

as far as i can gather, it relies on relativistics to get past the microwave range. can anyone clarify this?

AFAIK the period of oscillation of the magnetic field depends on the original magnet spacing and the electron speed. If you want a higher frequency, you speed up the beam.

sure, but as far as newtonian dynamicas goes, you hit C before the output wavelength exceeds the magnet spacing.

what parts of relativity allow this thing to go into soft xray?

A speculation as I'm not very familiar with this laser type, could the relativistic Doppler shift shift the radiated photons into xray?

it Sounds similar to a Synchrotrons function or a Klystron valve, even a Magnetron (with a linear rather than an angular type cavity resonator).

it may be helpful to look these up

sure, but as far as newtonian dynamicas goes, you hit C before the output wavelength exceeds the magnet spacing.

what parts of relativity allow this thing to go into soft xray?

 

The wavelength dependence on speed is non-Newtonian and nonlinear — it varies inversely with [math]\gamma^2[/math]

 

http://pbpl.physics.ucla.edu/Research/Theory/Free-Electron_Laser/

i didn't realise it could actually be a resonator with such a short wavelength.

the klystron depends on spacing of certian components equal to that of the wavelength but using doppler to boost the frequency makes sense.

 

thanks all