6.3.1.5. Example Background. ORTEC A66-BW GammaVision

783620H / 1013 6. ANALYSIS METHODS

3-point average as the background point (assuming the 5-point and 3-point tests have failed).

This method has advantages in close peaks with good counting statistics.

If in doubt as to which method should be used, use the Auto selection, except when the spectrum has a low number of counts per channel and the peak width (in channels) is more than about 6.

In this case, use the 5-point method.

6.3.1.5. Example Background

An example is shown in Fig. 235, with the spectrum printout in Table 5. The report section for this peak is shown in Fig. 236.

Fig. 235. Example Peak Background Calculation.

The FWHM for this peak is 6.85 channels. The centroid is at channel 2292.16. The background search width is from channel 2271 to 2313. The 5-point averages are shown in Table 5, and the minima are 11.8 at channel 2276 and 12.2 at channel 2311. The background slope is +0.0114

and the offset is

!14.4.

241

GammaVision

®

v7 (A66-BW) 783620H / 1013

PEAK

CHANNEL

2292.16

CENTROID

ENERGY

569.78

BACKGROUND NET AREA

COUNTS COUNTS

432.

UNIDENTIFIED PEAK SUMMARY

17711.

INTENSITY

CTS/SEC

59.04

UNCERT

1 SIGMA %

.81

s Peak fails shape tests.

Fig. 236. Peak Results for Previous Peak.

Table 5. Spectrum and Five-Point Smooth.

FWHM keV

1.734

SUSPECTED

NUCLIDE

Bi-207

Fig. 237 shows an example of the differences among the four methods for determining the

242