Sunday, July 13, 2008

The Nucleus - Laws

Law of radioactive decay

N = N0e- λ t

N = number of active nuclei at time t

N0 = number of active nuclei at t = 0.

λ = decay constant

-dN/dt = λN

-dN/dt give the number of decays per unit time and is called the activity (A) of the sample

A = λN

A = A0e- λ t

Lawson criterion for fusion reactor

In order to get an energy output greater than the energy input, a fusion reactor should achive

n τ >10^14 s/cm³

n = the density of the interacting particles

τ = confinement time

the quantity n τ in s/cm³ is called Lawson number

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