We describe the KTeV purr cesium iodide calorimeter and explain the calibra
tion of the detector. The calorimeter has a global energy resolution better
than 0.75% and an energy non-linearity less than 0.5% between 3 and 75 GeV
. We discuss the performance of the calorimeter during the data-taking runs
in 1996 and 1997 and briefly comment on the performance in 1999. (C) 2001
Published by Elsevier Science B.V.