attenuation coefficient in gypsum wallboard

[Douglas Simpkin <dsimpkin@execpc.com>]

Gypsum wallboard is foamed CaSO4 (with various quantities of H2O attached)
with a density of 0.73 g cm-3. For simplicity, let's assume it's just
CaSO4. Then a run of XCOM (cf.
<http://physics.nist.gov/PhysRefData/Xcom/Text/XCOM.html>) yields the
following mass attenuation coefficients at 0.38 MeV:

XCOM: CaSO4 (gypsum wallboard)

Constituents (Atomic Number : Fraction by Weight) 

 Z=16   : 0.235534
 Z=20   : 0.294385
 Z=8    : 0.470081

       PHOTON      SCATTERING      PHOTO-    PAIR PRODUCTION  TOTAL
ATTENUATION
       ENERGY   COHERENT INCOHER. ELECTRIC    IN       IN       WITH   WITHOUT
                                 ABSORPTION NUCLEAR ELECTRON  COHERENT
COHERENT
                                             FIELD    FIELD    SCATT.   SCATT.
        (MeV)    (cm2/g)  (cm2/g)  (cm2/g)  (cm2/g)  (cm2/g)  (cm2/g)  (cm2/g)

       3.800E-01 1.15E-03 9.69E-02 6.22E-04 0.00E+00 0.00E+00 9.86E-02
9.75E-02


Therefore, at first blush, I'd say the linear attenuation coefficient in
gypsum wallboard at 0.38 MeV is close to 9.86E-2 * 0.73 = 0.072 cm-1.

Doug
Douglas J. Simpkin, Ph.D., DABR
St. Luke's Medical Center
2900 West Oklahoma Avenue
Milwaukee, WI 53215
phone: (414)649-6457
fax: (414)649-5061
email: dsimpkin@execpc.com
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