The Manhattan Project
Page 14
R Decay rate [2.6]; general radius of bomb core during explosion [3.3]
Rbare Threshold critical radius of untamped bomb core
Rcore Initial radius of bomb core
RMBq Decay rate in millions of Becquerels in analysis of radioactivity exposure [6.4]
Rshut Radius of core at second criticality
Rtamp Outer radius of tamper
Rα Rate of alpha-decays
Rn Rate of emission of neutrons from (α, n) reactions [2.6]
S Number of stages in gaseous diffusion analysis [4.2]
T Temperature
U Energy density
Vacc Accelerating potential in analysis of electromagnetic enrichment [4.1]
Vf Final gas volume in adiabatic expansion of gun-bomb triggering [5.2]
V0 Initial gas volume in adiabatic expansion of gun-bomb triggering [5.2]
Y Weapon yield or fractional yield
Z Atomic number
a Angle in analysis of neutron scattering [6.3]
aC Coulomb energy parameter [2.1]
aS Surface area energy parameter [2.1]
b Brightness in analysis of bomb fireball with subscripts F for fireball and S for Sun [6.1]; angle in analysis of neutron scattering [6.3];
d Distance; characteristic core dimension [3.1]
k Boltzmann’s constant
kt Kiloton (4.2 × 1012 J)
mheavy Mass of heavy-isotope species in gaseous diffusion analysis [4.2]
mlight Mass of light-isotope species in gaseous diffusion analysis [4.2]
n Nuclear number density of core material [3.1]
nfissile Nuclear number density of fissile material in analysis of (α, n) reactions [2.6]
nheavy Number density of heavy isotope in gaseous diffusion analysis [4.2]
nimpurity Nuclear number density of impurity material in analysis of (α, n) reactions [2.6]
nlight Number density of light isotope in gaseous diffusion analysis [4.2]
t Time
tcore Time to complete core assembly following first criticality
thr Exposure time in hours in analysis of radioactivity exposure [6.4]
tsec Exposure time in seconds in analysis of radioactivity exposure [6.4]
t1/2 Half-life
y Reaction yield; usually in sense of (α, n) reaction [2.6]
vneut Average neutron speed
α Parameter in analysis of fission energy [2.1]; parameter in analysis of efficiency [3.4] and pre-detonation probability [5.1]
β Parameter in analysis of fission energy [2.1]
ε Parameter in analysis of tamped criticality [3.3]
γ Adiabatic index in gun-bomb triggering [5.2]
η Parameter in criticality analysis [3.1]
Δ Mass excess [2.1]
λ in analysis of tamped criticality [3.3]
λfiss Mean free path for neutron fission
λtrans Also . Transport mean free path for neutrons in fissile material
Transport mean free path for neutrons in tamper material
σelas Elastic scattering cross-section
σfiss Fission cross-section
σtrans Neutron transport cross-section
v Number of secondary neutrons per fission
ρ Mass density
ρ0 Initial mass density of bomb core; usually the ‘normal’ density of the fissile material
τ Travel time for neutron to cause fission; atmospheric transmittance in analysis of radiant energy in a nuclear explosion [6.1]
ω Number of collisions sustained by neutron to be slowed to a specific energy [6.3]