Help modeling Disintegrate damage

I'm trying to build a model to help optimize Disintegrate damage, but I'm a little stuck. Is it known how to calculate how often Disintegrate actually ticks, and how attack speed affects it? Is the expected value of damage on teach tick just the usual SCRAM number?

I'd appreciate it if anyone had advice for doing this, or for good ways to test the numbers once I have them. I've seen some people test damage on the zombies at the very beginning of the game.