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234 ATOMLAB 500 DOSE CALIBRATOR
Once the new dial value has been calculated, a new isotope name should be created on the
display for the isotope, with the dial value as calculated above. Then, the source should be
measured again and compared with its known time-decayed activity, in order to verify that the
calculation is correct. It may be necessary to adjust the dial value very slightly in order to
match the known activity - if necessary, do so at this time.
Once the dial value has been determined by means of comparison to a source of known activity, it
should not be changed unless access to a source with an activity known to higher accuracy allows
determination of a more accurate dial value. Dial values should never be adjusted daily to make a
source match daily isotope measurements. The dial value should only be determined with a
calibrated isotope source of known accuracy.
Biodex supplies dial values for many isotopes. Many of these dial values are calculated using a
Monte Carlo simulation corrected by actual measurements. If a source is available which has
calibrated accuracy better than the uncertainty listed in the table in Appendix E, then this
source can be used to modify the dial value for an existing isotope.
Biodex is interested in users’ measurements which have better accuracy than the uncertainty
listed in the dial value table. If you have a more accurate dial value for an isotope listed in the
table, please contact us and supply documentation including the measurements, isotope
calibration (and independent measurement method), measurement geometry and source
container, and calculation, so that we may share this information with other users.
References
1. National Nuclear Data Center, Nudat 2.2 Database, Upton, NY: Brookhaven National
Laboratory, 2007
2. Browne, Edgardo, and Richard B. Firestone, Table of Radioactive Isotopes, New York:
John Wiley and Sons, Inc., 1986
3. David C. Rayburn, Determination of The Response Characteristics of The Atomlab Re-Entrant
Ionization Detector, Melbourne, FL: Florida Institute of Technology, 2007
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