  Crystal Calorimetry is widely used in high energy physics because of its
precision. Recent development in crystal technology identified two key issues
to reach and maintain crystal precision: light response uniformity and
calibration in situ. Crystal radiation damage is understood. While the damage
in alkali halides is found to be caused by the oxygen/hydroxyl contamination,
it is the structure defects, such as oxygen vacancies, cause damage in oxides.
