plutonium core polonium beryllium urchin initiator Raemer Schreiber Philip Morrison neutron reflector Kirtland Army Air Field C-54 320th Troop Carrier Squadron 509th Composite Group North Field Project Alberta Fat Man 393d Bombardment Squadron plutonium
The first plutonium core, along with its polonium-beryllium urchin initiator, was transported in the custody of Project Alberta courier Raemer Schreiber in a magnesium field carrying case designed for the purpose by Philip Morrison. Magnesium was chosen because it does not act as a neutron reflector. The core departed from Kirtland Army Air Field on a C-54 transport aircraft of the 509th Composite Group's 320th Troop Carrier Squadron on 26 July, and arrived at North Field 28 July. Three Fat Man high-explosive pre-assemblies, designated F31, F32, and F33, were picked up at Kirtland on 28 July by three B-29s, two from the 393d Bombardment Squadron plus one from the 216th Army Air Force Base Unit, and transported to North Field, arriving on 2 August.
