Exploranium GR-135, System Manual, Page: 27 / 80

SAIC Exploranium – GR-135 System Manual page: 27
8.0 STABILIZE
8.1 STABILIZATION - GENERAL
When any spectrometer is turned ON, the internal electronic components exhibit some level of warm-
up drift with time, which may be exacerbated by changes in the ambient temperature. Sodium-
Iodide crystals typically exhibit a +/-15% change over the -10 to +50
o
C temperature range. If
uncorrected, this drift could seriously affect data analysis. For this reason, the GR-135 incorporates a
procedure called STABILIZATION to remove these effects. Stabilization automatically “fine-tunes”
the system to adjust the internal system gain and align the spectrometer correctly.
The GR-135 carries out Stabilization in various ways.
a)
AUTO-STABILIZATION in the DOCKING STATION – AUTOMATIC MODE – see section 8.2
b)
MANUAL-STABILIZATION in the DOCKING STATION – see section 8.3
c)
AUTOMATIC CORRECTION when in USE – see section 8.4
e) MANUAL-STABILIZATION
with no DOCKING STATION – at any time the user can activate
STABILIZE from the Main menu and then use an external Cesium source to carry out the Stabilization
function
8.2 AUTO-STABILIZATION IN THE DOCKING STATION – AUTOMATIC MODE
If the GR-135 unit is set in the AUTOMATIC mode and placed in the DS, the system starts
automatically stabilizing on the very small (0.25uCi) Cesium source embedded in the DS. The display
shows system activity and advises the user when stabilization is complete. During the entire time
the unit spends in the DS, the batteries are continually charged and the system is continually
stabilized. See full details in Appendix A
8.3 MANUAL-STABILIZATION IN THE DOCKING STATION
For normal operation the Docking Station is used (refer to Appendix C
for non-DS operation). From the MAIN MENU select “STABILIZE”
and press ENTER the display shows Fig. 23
This function is usually used with an external source, hence the
display wording. The user can assume that the source in the DS is
positioned correctly - so press ENTER to continue. (Selecting UP
returns to the Main Menu).
Fig. 23
Stabilization will now occur, the system is fully automatic, various
displays will be seen (the word “COMPUTING” may appear as well
as some data are being processed), then finally a beep shows that
the process is complete with the display as shown as in Fig. 24
These data are:
PEAK -
this is the peak channel of the centroid of the
accumulated spectrum. The correct final channel for
CESIUM stabilization is channel 220 (+/- 0.5ch).
Fig. 24
PLACE CS SOURCE
AT THE FACE
OF THE GR-135
PRESS ENTER
TO CONTINUE
OR UP TO EXIT
STABILIZE
STABILIZATION
COMPLETED
REMOVE CS SOURCE AND
PUSH ENTER TO CONTINUE
PEAK: 220.1
FWHM: 6.8%
OLD GAIN : 522
NEW GAIN : 514
STABILIZE