A-3 APPENDIX A
NOTE: A tuberculin syringe is not suitable in this procedure. Hamilton microliter syringe, model 701-N, has a
capacity of 10 ul with 0.2 ul resolution and will provide the necessary precision. Hamilton Co., P.O. Box
10030, Reno, Nevada, 89520. Phone: 800-648-5950.
After the source preparation, the efficiency can be measured by counting the source in the Administration
Mode “Isotope Efficiency” page of the Atomlab 950.
D. Efficiency Measurement
1. Make sure the Atomlab 950 has a current Cs-137 calibration.
2.
Then
go
to
the
“Isotope
Efficiency”
page.
Use
the
arrow
keys
<previous>
or
<next>
to
display
the
isotope you wish to set the efficiency for.
3. Set the Geometric Efficiency using the buttons near the top right of the display. (See Administration
Mode in manual for directions.)
4. At the top left of the screen is an isotope activity calculator. Enter the source calibration time and
activity. If you press <Show Current Activity> button, the unit displays the calculated decayed
activity of the standard you created.
5. Now near the bottom of the display screen, click the mouse on the <well>.
6. Perform an automatic 100 second background count with an empty well by clicking on the <Calculate
Efficiency> button to the right of the displayed detector efficiency values.
7. When the background count is completed, if you wish to manually calculate detector efficiency,
record the counts in the ROI as (B). The display will direct you to place the standard into the well and
press
<Adjust>.
The
system
will
now
perform
an
automatic
100
second
count
on
your
prepared
standard. The system displays the spectrum as it counts.
NOTE: The A950 system will automatically record and calculate for you.
8. If you wish to manually calculate the efficiency, record the counts in the ROI as (S). (Proceed with
step 10 for Manual Calculation.)
9. Click the mouse on Accept and the system will automatically calculate and display the isotope
detector efficiency.
NOTE: Total efficiency is a combination of the geometric and detector efficiencies.
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