Fig. P.5 Cross-sectional drawing of the Y-1561 Fat Man implosion sphere showing major
components. Only one set of 32 lenses, inner charges, and detonators is depicted. Numbers in
parentheses indicate quantity of identical components. Drawing is to scale. Copyright by and used
with kind permission of John Coster-Mullen. A 1773 EBW detonator inserted into brass chimney
sleeve (32). B Comp B component of outer polygonal lens (32). C Cone-shaped Baratol component of outer polygonal lens (32). D Comp B inner polygonal charge (32). E Removable aluminum pusher trap-door plug screwed into upper pusher hemisphere. F 18.5-inch diameter
aluminum pusher hemispheres (2). G 5-inch diameter Tuballoy (U-238) two-piece tamper plug.
H 3.62-inch diameter Pu-239 hemisphere with 2.75-inch diameter jet ring. I 0.5-inch thick cork
lining. J 7-piece Y-1561 Duralumin sphere. K Aluminum cup holding pusher hemispheres
together (4). L 0.8-inch diameter Polonium-beryllium initiator. M 8.75-inch diameter Tuballoy
tamper sphere. N 9-inch diameter boron plastic shell. O Felt padding layer under lenses and inner
charges
Preamble
xvii