# Homework Help: X-ray tube - Target confusion

1. Aug 24, 2011

Hey,

In an X-ray tube, you know how there is the target where the electrons collide and stuff... and you know how there is the tungsten part and the the copper bit (the tungsten being the one which electrons collide on)... well my book discusses them separately and i am just a bit confused:

1) Are they both anodes? I.e. both are the positive terminal?
2) Which one is referred to as the target? - Is it both or just the tungsten insert?
3) Why is it called the tungsten INSERT? Do we insert it in there or something?
4) Why are they separated? Why cant we just have it all tungsten or all copper?

Thanks

EDIT:

5) Also, why does a lot of heat get generated at the anode? My guess would be because the electrons are hitting the anode... but why does it generate heat when it hits? Why cant all the energy be converted into X-rays? - Apparently over 98% of the energy of the electrons is converted to heat! WHY?

Last edited: Aug 24, 2011
2. Aug 24, 2011

### A.T.

Last edited by a moderator: Apr 26, 2017
3. Aug 24, 2011

### phyzguy

We can't really control things at the subatomic level. We just slam the electrons into the target and take what we get. What we get is that most of the energy gets converted into heat and only a little bit gets emitted as X-Rays. People are working on higher efficiency sources, especially for X-ray lithography. Here is one example, but even this is only about 4% efficient:
http://epsppd.epfl.ch/London/pdf/P4_214.pdf

4. Aug 24, 2011

@A.T.

hahaha, yea sorry i have test tomorrow so i cant really do much research. Thanks btw :)

@phyzguy

Thanks :)

So how about questions 1-3?

5. Aug 24, 2011

### lightgrav

1) what would happen to the electron path, if they collected up a large (-) charge?
2) only the insert is _supposed_ to be hit by the beam
3) in some devices, the insert can be removed, to be replaced with a new one perhaps,
or replaced with an insert made of different material, or with a different shape face.