Michel Jullian writes. > > Ingenious! (Faraday cup and saucer, indeed ;) > Very British for tea, what? :-) > > For electrons slow enough not to produce secondary emission I would have > thought a simpler collecting device, not a hollow one, would work: a grid > surrounding a solid conductor, the latter positive wrt the former. > In vacuum tubes (if you are old enough to remember them) they call that the suppressor grid, usually tied internally to the cathode. > > For the ultra-low energy emitter photo-emission should work better than > thermo-emission as it will give more homogeneous energies (precisely > controlled by incident light wavelength aren't they?) > I think an LED/or laser could cause low energy-low velocity electron emission from a low work function photo-emissive material.
One of Walter Fendt's applets for materials: http://www.walter-fendt.de/ph14e/photoeffect.htm Measuring the time-of-flight of the electrons from flash to detection at the top/electrometer to determine/prove gravity repulsion might be a chore Fred > > Michel >
