Okay, first of all, upon reading this headline, I can't help but think this is a BADidea! If you are going to start mixing matter and antimatter, I think underground is not the best place to do it. I'd much rather see this research conducted at, oh... say, the orbit of Jupiter! ...preferrably on the opposite side of the Sun from Jupiter!
Of course the reality is that this is an underground liquid xenon neutrino observatory. Interesting.