How thin do the electron emitters in the onion have to be?
I can imagine a heavy metal layer deposited or plated super thin on a substrate.
Will the electrons go only in the direction of the x-rays, or will both sides of the emitter film need to be exposed?
A substrate below a fragile super thin film could be etched away in a pattern leaving a mostly open but thick mesh for strength.
I don’t think the electron collectors have to be that thin also? Instead of a film the collectors could be a layer of carbon tubes with coolant in them?
Would a metal like gold or tungsten be used in all the layers or could they vaporize in the inner most intense layers of the onion, instead requiring medium z metals that would not absorb as many x rays per layer?
thickness of an aluminum layer would determine its conductivity, and xrays will scatter as they knock electrons off. the electrons will get thrown in the general direction of the xray’s momentum. i suppose this scattering through several layers could be simulated.