Unformatted text preview: 74 Radiation Interactions Chap.7 6. Calculate the linear interaction coefficients in pure air at 20°C and 1 atm pressure for a IMeV photon and a thermal neutron (2200 m SI). Assume that air has the composition 75.3%nitrogen, 23.2%oxygen, and 1.4% argon by mass. Use the following data: Element Nitrogen Oxygen Argon Solution:
The density of dry air at standard conditions is Pair = 0.0012 gfcm3, The atom density of the elementscomprising air are
Ni = Wi PairNa 0.0636
0.0636 11.9
4.2 2.2 0.0574 A (P7.1) where Wi is the mags fraction of the ith element (i = N, 0, Ar). Photons: Use the gammaray data in Ap. C to obtain = 0.0012[(0.153)(0.0636) (0.232)(0.0636)+ (0.014)(0.0514)] + = 7.61 X 105 cml. Neutrons: obtain
. L = .i iO't Use the neutrons cross section data in Ap. C and Eq. (P7.1) to
f i J.tn
a~r i
= N~O'tPairNa L :.A~ ~
[ (0.753)(11.9) 14.007 + (0.232)(4.2) 15.9994 + (0.014)(2.2) 39.948 ] (0.0012)(0.6022) = 5.07 X 104 cm July 24, 2002 ...
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This note was uploaded on 02/01/2010 for the course ECE 4130 taught by Professor Cady during the Spring '06 term at Cornell.
 Spring '06
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