The Thaumic Reactor is a massive reacting engine designed by Ponder Stibbons to split the thaum and generate massive amounts of magical energy in the process of thaumic fission. It was built on Unseen University's squash court, a place where the walls are designed to teleport incoming objects (such as squash balls) to other walls. Nothing excites a particle like meeting itself coming the other way, and this is something he should have taken into consideration...