Moving top hat heat source

Hello,

I'm trying to create a moving heat source with the energy profile of a top hat.
So far I was able to move a circular heat source with a 'waveform' function. But I only managed to create a gaussian energy profile for the heating spot where I used the following function:
P_heat*gp1(x-wv1(t))*gp1(y)

Do you know how to create a cylindrical top hat profile for the heat source that can be moved with the 'waveform' function?

I am very thankful for every answer!
Thanks a lot.
Paul