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232 ATOMLAB 500 DOSE CALIBRATOR
The sensitivity curve of the Atomlab detector with respect to photon energy has been
determined by means of measuring NIST calibrated isotopes at a multitude of photon energies.
The isotopes Ga-67, Tc-99m, Mo-99, In-111, I-125, I-131, Xe-133, and TI-201 were provided
from the NIST standard reference materials program. in addition, NIST traceable sources of the
isotopes F-18, Co-57, Co-60, Ba-133, and Cs-137 were measured. all of the NIST SRM
isotopes with the exception of Xe-133 were contained liquid solutions of 5 ml volume, in sealed
borosilicate glass ampoules of wall thickness 0.6 mm. The Xe-133 samples were sealed, mixed with
non-radioactive xenon gas, in borosilicate glass ampoules of wall thickness 1.3 mm. The F-18
source was measured in a 10 ml B-D plastic syringe. The Co-57, Co-60, Ba-133, and Cs-137 sources
were contained within epoxy sealed Type E-vials.
In addition to the isotopes measured, a Monte Carlo simulation of the Atomlab detector has
been created. The Monte Carlo simulation allows better determination of the shape of the
sensitivity curve in the regions between measured data points. The photon sensitivity curve
generated by the Monte Carlo simulation was found to be consistent with the sensitivity curve
generated by the isotope measurements. The Atomlab detector sensitivity curve is plotted
below, with a logarithmic scale for photon energy:
The accuracy for dial value calculation depends upon not only the accuracy of the sensitivity
curve and the photon emission intensity data, but also upon the sample configuration, due to low
energy photon absorption (see Radioisotope container below). The photon sensitivity curve
displayed is for sources with configurations similar to the NIST ampoule configuration noted
above. All Atomlab Dose Calibrators are calibrated with NIST traceable Co-60, Ba-133, Co-57, and
Cs-137 sources. Each dose calibrator is certified to measure the correct activity of the
calibration sources to within the specified accuracy.
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