Comparison of calibration results for an extrapolation chamber obtained with different 90Sr+90Y secondary standard sources.

Two secondary standard systems of beta radiation were used to calibrate a PTW extrapolation chamber Model 23391. Three (90)Sr+(90)Y sources of different activities were used in this calibration procedure. Medium-term stability of the response of the chamber was also studied. The calibration was performed with and without field-flattening filters. The relative standard deviation of the obtained calibration factors was 8.3% for the aluminum collecting electrode and 4.1% for the graphite collecting electrode.