After a great deal of pain in the butt (and tinkering around with two different third party programs used together), I've been able to successfully rip a crystal-clear, 720p HD video of the ion cannon from Command & Conquer 3's game DVD. I've uploaded it to rapidshare on behalf of all my fellow movie tinkerers, so feel free to download it if you have any interest in fiddling around with it.
http://rapidshare.com/files/340246595/ion_cannon_hd.avi
This is the best quality you're going to find this video in, and seeing as it's only 35 MB I recommend grabbing it while you can.