Capintec CRC-25R - APPENDIX II CALIBRATION NUMBERS; DETERMINING CALIBRATION SETTING NUMBERS; RESPONSE AND SENSITIVITY

CAPINTEC, INC CRC
®
-25R
APPENDIX II
CALIBRATION NUMBERS
DETERMINING CALIBRATION SETTING NUMBERS
A method of determining a calibration setting number is described in this section.
1
Response and Sensitivity
It is very convenient to express the response of the detector to a radioisotope, A, relative to
that of a standard reference material, e.g. Co60.
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
≡
Co60 SRM ofActivity Certified
Co60 SRM todueOutput Detector
A Sample ofActivity
A Sample todueOutput Detector
R
A
(1)
The sensitivity of the detector for a photon of energy E
i
is defined as:
Co60 of Curie one todueOutput Detector
E of Photons 103.7 todueOutput Detector
S
i
10
i
×
≡
(2)
The detector response and the sensitivity have the following relation:
(3)
∑
≡
i
ii
SI
i
R
Where I
i
is the intensity of the photon whose energy is E
i
.
The procedure is to measure the response of the detector to all the available primary
standard samples and to establish the sensitivity of the detector as a function of photon
energy so as to satisfy equation (3) for all standards.
Once the sensitivity curve has been determined, the response of the detector to any
radioisotope may be calculated using equation (3), provided that the decay data are known.
The sensitivity curve for a CRC
®
Ionization Chamber is given in Figure A1-1.
1
See Suzuki, A., Suzuki M.N., and Weis A.M.: Analysis of a Radioisotope Calibrator; Journal of Nuclear Medicine Technology
Dec. 1976 for more detailed discussions.
June 09 APPENDIX II A2 - 1