Could Cherenkov radiation be used for general illumination, for example, to replace LEDs, light bulbs etc? I.e. are there, or could there be, methods to produce substantial amount visible light with Cherenkov radiation:
to actually make any sense? What other problems could there be for using Cherenkov radiation for this purpose?
Interesting question!
Cherenkov radiation would definitely be inefficient for illumination. You only get Cherenkov radiation from charged particles moving faster than the local speed of light in a medium. If you have a transparent medium with index of refraction $n=2$ and you're sending fast electrons through it, you'll only get Cherenkov radiation while the electrons have $v>0.5c$, or $$\gamma > \frac{1}{\sqrt{1-0.5^2}} = 1.15.$$
Since the kinetic energy is $T = (\gamma-1)mc^2$, this means the first $79\,\mathrm{keV}$ of electron energy contributes absolutely nothing to the Cherenkov illumination. Seems like a lot of energy to waste.
Furthermore Cherenkov radiation tends to be concentrated in the UV, so you'd need some scintillation process to convert the light to visible.
The most serious complaint to me is that if the transparent material is thin enough that most of the light escapes, it won't be thick enough to stop the radiation that's causing the Cherenkov emission in the first place. I think it'd be hard to commercialize a product which involved either (a) a mass equivalent to many radiation lengths in water or (b) hard radiation leaking out into the illuminated area.
Quite aside from the issue of ionizing radiation, Cerenkov generating particles also lose energy by other processes and that ends up as heat.
Moreover, all the kinetic energy of the particles once they drop below the Cerenkov threshold is lost in non-optical channels (i.e. more heat).
So no, they could never be anywhere near as efficient as diode lighting.
On top of that the spectrum is really cool to look at, but not the one you want in a lamp: it's far too blue.
