For the detection of 241Am at 60 KeV for example, the pulse shape,
electronic dead time, discriminator window, and Compton effect in the
sample are very important (14 and 81).
 The intensities of gamma rays and X-rays in 241Am alpha decay has
been reported by Magnusson (57) detected with a 0.3 cm thick NaI(T1)
scintillator. Presently more accurate decay schemes are available such as
in Lederer et al. (53). A detailed spectrum of 241Am radiation shows
many other peaks beyond the main peak energy of 59.6 KeV. The most
important of these are the 17.5 and 103 KeV energy peaks. When the
spectrum was taken with a NaI(Tl) detector, sometimes a 32 KeV
escape peak and a region of summation were observed. Because of these
unwanted radiation peaks, the window discriminator for the gamma
spectrophotometer must be correctly adjusted. A good rule is to adjust
the energy window with the same thickness as the crystal resolution for
that ..neig\. A thin window decreases the photon counts due to the
scattering provided by the Compton effect in the sample. This is par-
ticularly important if the collimator solid angle is large.
 The Compton effect in the sample is important for low energy pho-
tons, i.e. when E/Eo < 1 where E is the incident photon energy, Eo is
the electron rest energy moC2, and C is the speed of light. For low
energy photons, the Compton effect equation which shows the photon
wave length variation as a fraction of the scattering angle, a, may be
presented as:
 AE E
 (1 cosa). [10]
 E Eo
 This equation states that loss of energy is very small for large values of
 the angle a and the scattered photon energy, E', is approximately the
 same as the incident photon energy E. The angular distribution of the
 Compton effect is not isotropic and has been described with the Klein-
 Nishina equation by Evans (24) and by Heitler (46).
 Ignoring the small influence of multiple scattering, the contribution
 due to the Compton effect is less than 0.5% for collimators with solid
 angles less than 6 on the detector side. Cisler et al. (8) reported the
 influence of the Compton effect upon the counts and Groenevelt et al,
 (40) reported the influence of the Compton effect upon mass attenua-
 tion coefficients measured with IJtlerent collimator geometry. After ex-
 tending the work of Conner et al. (9), Gopal and Sanjeevaiah (38) con-
 cluded that the effect of multiple scattering upon determinations of mass
 attenuation coefficients could be greatly minimized by always maintain-
 ing the product tkx (mass attenuation coefficient and sample thickness)
 as less than one mean free path.
 A finite resolving time in measurements of radiation intensity for the
 garnma ray spectrometer contributes to a coincidence loss or counting
 17