Fluke Biomedical 90-12 - Manual (Page 7)

Introduction
Photon Energy Response
1
1-3
Figure 1-1. Photon Energy Response
The energy response curve represents data taken below a rate of 200 mR/hr. Changes in the actual
curve could occur at rates over 200 mR/hr.
1.6 Beta Sensitivity, Slide Open
Table 1-2 shows the beta sensitivity of the 90-12 probe to a variety of sources.
Table 1-2. Beta Sensitivity
Nuclide Particle Energy Max (MeV)
90-12 Sensitivity
CPM/Ci
90 Sr Beta 2.245/.544 362,000
137 Cs Beta/Gamma 1.176/0.662 45,662
36 Cl Beta 0.714 92,827
99 Tc Beta 0.295 560
14 C Beta 0.158 0
These data were taken with the beta shield moved to expose the open window. For these measurements,
one of the two windows was pointed directly at the source.
1.7 Beta Shield Response
The beta shield has a total average attenuation of 1890 mg/cm 2 . This rejects all alpha particles, beta rays
with an energy of 2.5 MeV or less, and non-penetrating x-rays when the slide covers the GM tube. See
the energy response curves for open and closed slide positions.
Figure 1-2. General View