English: Magnet formerly used in the Lawrence 27" cyclotron, at the Lawrence Hall of Science. The woman in the image is 5' 3" (160 cm) tall. The bottom part of the black donut shaped magnetic pole pieces is buried under the concrete pad. These are made of iron and direct the path of the exterior magnetic field from one pole to the other. The white portions contained coiled copper conductor carrying direct current electricity to create a constant magnetic field. The black structure between the poles was a receiver for the disk-shaped vacuum chamber that contained the cyclotron's D shaped electrodes (called dees), shown in Image:LawrenceCyclotronDees.jpg. After the cyclotron became obsolete as a nuclear research device it was converted to use as a research medical accelerator for non-invasive treatment of inoperable brain tumors. The medical tasks perfected using this device are now performed using much lower cost specialized instruments.