What type of wire should I use on the top of my run?

[Finn's Mom]

I have a 15x40ft run, with a 1x2" (is it welded wire? The heavy duty stuff?) 6 foot fence. I have 2x4s across the top every 6 feet to support the wire that would enclose the top. I was going to use 2 inch chicken wire on the top because it's light and and the man at the co-op sounded convincing, but I got to thinking -- can a raccon scale this fence and rip off the chicken wire? Our predators here are owls, hawks, fox, coyote and raccons. I let the girls in and out each day and night but it is going to be hot soon and I want to be able to leave their coop door open. What would you use?

Thanks for your advice!