Typically anode of X-ray tube is at angle of ~45 degrees. Many images show that emitted X-rays are mostly perpendicular to electron direction.

Is that correct?

I had an impression that x-rays will be generated isotropically and only partially absorbed by heavy anode when flying in "wrong directions", into the anode.

enter image description here

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    $\begingroup$ Here's a presentation which may be useful. It's got some nice graphics mccc.edu/~kerrs/documents/xrayprod_lec_f12.pdf $\endgroup$ – Carl Witthoft Mar 25 '14 at 15:15
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    $\begingroup$ Funny how every image/source I've come across also shows the x-rays directed in the fashion you indicated, but none explain why. $\endgroup$ – BMS Mar 30 '14 at 3:50

The angular distribution of the x-rays is basically uniform as you indicated, but there are beam restriction devices in use that aren't usually shown in a diagram, as in the typical diagram below.

isotropic x-rays

Here is a more detailed drawing showing the isotropic radiation and a beam restricting device, which is less fancy that it sounds. Perhaps there are other fancier types.

enter image description here

The angled anode target are only angled around 10 degrees (6 to 15 degrees is what the source below tells me). The 45 degrees one often sees in diagrams must be an exaggeration. The angling helps with both heat dissipation and having a selected beam of x-rays be produced from a relatively large surface area on the target. The diagram below shows this better than I can explain it.

enter image description here

More information (and my source): http://en.wikibooks.org/wiki/Basic_Physics_of_Digital_Radiography/The_Source

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