  Positrons are accumulated within a Penning trap designed to make more precise
measurements of the positron and electron magnetic moments. The retractable
radioactive source used is weak enough to require no license for handling
radioactive material and the radiation dosage one meter from the source gives
an exposure several times smaller than the average radiation dose on the
earth's surface. The 100 mK trap is mechanically aligned with the 4.2 K
superconducting solenoid that produces a 6 tesla magnetic trapping field with a
direct mechanical coupling.
