Shielding: Getting Rid of All That Junk
Ideally it would be nice to have an interaction that produced just taus and tau neutrinos and nothing else; unfortunately, that is not reality, so this experiment used a total of 36m of shielding to remove as much of the extra products (known as background) as they can. Since neutrinos are charge-less and non-interacting, it is fairly simple to provide effective shielding because you have a low probability of affecting them. Immediately following the beam dump the newly created particles pass through the SELMA magnet, a dipole (magnets that have north and south poles, which exert a positive or negative force on particles according to their charge) which deflects almost all of the charged particles. High velocity muons are more penetrating and are harder to deter, so after SELMA the beam passes through the MuSweep2, a toroidal magnet that "sweeps" these muons out of range of the target. Lastly the beam passes through 17m of steel passive shielding, where any remnant particles should interact with a nucleon along the way. No shielding is perfect, however; DONUT physicists estimate that there are approximately 2 x 104 muons per 1013 pot in the target area.
Last updated: 6/29/01 comments