QCYK Reference material - CalibrationsHome Page | Examples | 0 to 200 keV | 200 to 700 keV | 700 to 1200 keV | 1200 to 2000 keV
Energy calibrationThis is a straightforward energy calibration using the 13 major gamma-rays of the 12 nuclides available, with the exception of the 514 keV gamma-ray of 85Sr. The latter is is overlapped by the annihilation peak and, unless the analysis software recognizes its Doppler broadening, deconvolution will be in error.
For reasons known only to ORTEC, GammaVision can only fit a quadratic to energy calibration data. In this particular calibration the root-mean-square difference between measured and fitted energies is 0.024 keV.
FWHM (width) calibrationThis calibration was performed simultaneously with the above energy calibration. Again GammaVision insists on a quadratic fit. As I demonstrate in Chapter 6, a square root quadratic fit would be more accurate. The root-mean-square difference between measured and fitted peak widths is 0.016 keV. Note, however, that these points were derived from very well defined peaks. Even so, there is more scatter about the best fit line than was the case with the energy calibration. The uncertainty on the FWHM of poorly defined peaks would be much larger.
FEP Efficiency calibrationThis calibration, performed by GammaVision using a linear function above and quadratic below the knee, set at 150 keV. In this calibration, the 136.47 keV peak of 57Co is included to assist with fitting below the knee. In this diagram the red line is the fitted function, the blue line is a linear regression using only the nuclides not subject to true coincindence summing (TCS). This can be taken as the true efficiency fit. Although 54Mn and 65Zn are both electron capture nuclides and are expected to sum, their low energy X-rays are absorbed before reaching the active region of the detector. 109Cd and 113In are again electron capture nuclides, but their gamma-rays are emitted by isomeric daughter states some time after the decay itself. Once again, they show no summing.
The following features are notable:
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