Abstract
The power of the gamma-ray beam from a Cs137 teletherapy unit was measured by determining the heat produced by absorption in lead. Comparison with ionization measurements made under identical conditions gave a conversion factor of 2959 [plus or minus] 44 ergs/cm2/roentgen and combining the result with the calculated absorption coefficient for air gave a value for W (work function) of 33.9 [plus or minus] 0.5 ev/ion pair.