Nick Gorham wrote

Ian Iveson wrote:

Eeyore said

X-ray emission requires a certain *energy level* that has ZERO to
do with
glowing anodes.
So why do x-ray tubes have rotating tungsten anodes?

Ian

They rotate them to allow them to cool.

Aha.

They get hot because the energy in each electron, and the quantity
of electrons hitting them in a unit time. (P=IV)

They emit x-rays if the electrons hit them with sufficient energy to
generate an x-ray photon.

The energy of the electron is dependent on its velocity

The velocity of the electron is dependent on the electrical
potential that has accelerated it.

So if the velocity of the electron is lower than a given value for
the material of the anode, they will get hot, but not emit x-rays.

If the electrical potential is not sufficient to accelerate them to
required velocity, the anode will get hot, but not emit x-rays.

I'll go along with that, more or less.

Current is equally important. And the ability of the anode to lose
heat, and the distribution of temperature also depends on the focusing
of the beam and how well the anode conducts heat.

Since all electrons arrive at the anode with nearly the same energy,
it must be the case that one with just high enough energy to result in
an x-ray doesn't always do so. Presumably the angle of collision with
atoms of the anode has something to do with it too, so you get a
spectrum of emissions from radio to x-ray. Otherwise x-ray tubes
wouldn't need cooling coz they would be making x-rays, not heat.

Nice amp, btw. Nice to see the mad science element of valvecraft on
usenet again.

cheers, Ian