2 acquire a background spectrum, Acquire a background spectrum – BNC SAM 935 Portable Gamma Spectroscopy System User Manual

Page 16

background image


SAM 935™ Instruction Manual

The spectrum being measured will be displayed as it develops, and if everything is connected cor-
rectly, you should be able to watch the spectrum resolve. After each adjustment attempt, a tone
will sound to indicate that the SAM 935 is still adjusting itself. For details about the coarse adjust-
ment, refer to Section 5.6.1.


When the adjustment is complete, the two Cs137 peaks will be highlighted, the unit will beep three
times, the

Adjustment Complete message will appear, and the S


(F4) function key will be avail-

able. At this point, the display should look like the one shown below. If not, press C


(F1) and

check that you have the correct source and retry the operation. If everything is correct, press S


(F4) to save the new hardware parameters in memory.

After you save the coarse calibration adjustment, the SAM 935 will return to the Calibration menu. Con-
tinue with calibration by taking a background spectrum next.

3.2.2 Acquire a Background Spectrum

To get accurate identification results, a background spectrum should be taken frequently, and it must be
collected in the same physical location where the monitoring will occur. The background is very important
because it is the point of reference against measured activities.

A new background spectrum should be acquired whenever the ambient background changes, i.e., if the
instrument is moved to a new location or if a patient having received a radionuclide dose enters or leaves
the vicinity. A background spectrum is also required before doing the more accurate fine energy calibra-
tion. Background spectra can be acquired at any point. After one week, the SAM 935 will require that you
take another background spectrum.


At the Calibration menu, select

Acquire Background and press E


, or just press F4.


A background spectrum may not be taken without a prior coarse adjustment. If this is attempted,
the SAM 935 will ask whether you wish to perform the adjustment first. If so, press F3 to perform
the coarse adjustment.


Remove all sources from the vicinity of the detector.

If you experience difficulty during the coarse calibration, press C


(F1) and then select

Calibrate Area Monitor from the Utilities menu to start over.

Press Save to finish the coarse calibration.

Press F2 (Util) if the coarse calibration is not required.
This will take you to the Utilities menu where you can
choose Calibrate Area Monitor to do the background

Press F3 (Adjust) if you have not performed a coarse cal-
ibration yet. The SAM 935 will complete the coarse
adjustment before resuming acquisition of the back-
ground spectrum.