I know that at higher speeds the de Broglie wavelength decreases so the electrons diffract less, but does the fact electrons repel affect it in any other way?
What I was thinking was that since electrons now reach the screen in less time because of the greater speed, they have less time to repel and thus repel less so rings are closer together. Is this a correct reason and does this relate in any way to the wavelength reason?
These images are from Electron diffraction.
A beam of electrons is accelerated in an electron gun to a potential of between 3500 V and 5000 V and then allowed to fall on a very thin sheet of graphite (see diagram above). The electrons diffract from the carbon atoms and the resulting circular pattern on the screen (see diagrams below) is very good evidence for the wave nature of the electrons.
The diffraction pattern observed on the screen is a series of concentric rings. This is due to the regular spacing of the carbon atoms in different layers in the graphite. However since the graphite layers overlay each other in an irregular way the resulting diffraction pattern is circular. It is an example of Bragg scattering.