EXO is a double beta decay experiment that is housed in six clean rooms coupled together underground in a tunnel at the Waste Isolation Pilot Plant (WIPP) near Carlsbad, NM. WIPP is a Department of Energy salt mine where relatively low level radioactive waste is being interred, but a couple of the tunnels in the mine are dedicated to research. The salt mine is a good place to do this kind of experiment because the salt has a low background level of radiation. The cleanliness required of this experiment is a constant burden. The double beta decay of the Xenon 136 atom that EXO is looking for is a very rare radioactive decay. That signal would be easily swamped if the apparatus were built from normal materials. Every piece of material near the central detector has to be screened for radio-cleanliness. If you've never worked on an ultra-clean experiment, it's hard to conceive of all the trouble you have to go through to eliminate the uranium and thorium daughter elements that are all around us in minute quantities on the surface of the earth (mostly thanks to the atmospheric testing of atomic bombs in the '60s). For example, the copper that the cryostat is made from comes from Europe where the cleanest copper is made by a company in Switzerland. Nobody really knows why their copper is as low-background as it is. If this copper is left on the surface of the earth for too long, however, cosmic rays will cause enough of the copper atoms to become radioactive that the material would be useless for the experiment. We have to keep the copper shielded by several meters of concrete at all times to preserve its cleanliness. Only when it gets installed underground at WIPP can we stop worrying about its increasing activation.

Bartoszek Engineering has done many sub-projects leading up to the EXO 200 prototype. The projects include the design of the cart that rolled the cryostat into the clean room for the first time. We designed a special lifting and rolling fixture that allowed the inner cryostat to be removed from the outer cryostat for cleaning. We designed a steel pallet to allow the large forklift at WIPP to carry the clean rooms from the mine shaft to their final assembly place in the tunnel. One of the biggest jobs was to design an adjustable foundation system to allow the clean rooms to be leveled as the salt below them shifts over time. We are designing the copper vessel to hold the enriched xenon in the EXO 200 kg prototype detector. Some of the projects for 2008 will be the design of the welding fixturing necessary to electron beam weld the copper vessel together. We will also design the installation jig that will precisely position the liquid xenon copper chamber into the surrounding cryostat. The purpose of these pages is to communicate with the experimenters and vendors and to show the status of the various sub-projects.

You are welcome to download any of the images. If they are used for other than private viewing, credit to the EXO collaboration and Bartoszek Engineering would be appreciated.