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  • Michael Krakovskiy 12:05 pm on June 14, 2002 Permalink | Reply
    Tags: , Enriched uranium, Fissile, , Nanosecond, Neutron, Nuclear physics, Nuclear technology, Nuclear weapon design, , Shake, Shoo   

    Shake and Bake 

    Q: What is measured in shakes?
    A: Time. 1 shake = 10 nanoseconds.

    This unit of time was definitely created by Manhattan Project scientists, but why it was chosen is not 100% clear.

    Theory # 1 – Too morbid
    source
    A shake is only 10 nanoseconds in time and arises from the theory of the chain reaction where one free neutron causes a fission that creates 2.5 to 3 new neutrons like a huge pyramid scheme and by the time the last layers of fissions occur they produce enough energy to “shake” the earth severely.

    Theory # 2 – Too dry
    source

    I like the term “shake” – 10 nanoseconds. I think it’s roughly the time it
    takes the average 1 Mev neutron to cover a distace of one mean free path (13 cm?) in fissile materials at maximum normal densities

    Theory # 3 – Oralloy? Pu plasma? Shoo – way over my head.
    source

    a shake being roughly 10 ns – the time it takes neutrons in oralloy or Pu plasma to cover their Mean Free Path

    Theory # 4 – Sounds just about right.
    source

    The ‘shake’ is a defined unit of time. Scientists working on the Manhattan project
    (to build the first atomic bomb) found that the detonation cycle for the ‘device’
    lasted 30 billionths of a second, or 30 nanoseconds. A shake was defined as
    10 nanoseconds so the detonation cycle of the atomic bomb could be said to take
    ‘three shakes of a lamb’s tail.’

     
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