F9 – Plateau Plot
Gem-5 User’s Manual 75
The detector location is also indicated by hatch marking on the inset layout diagram.
The number, in small font at the top right of the screen, gives the sequential zone
number assigned to the detector (and section if applicable) that is used on various
information screens and printouts. Use the inset diagram to confirm currently
selected zone. Press PgDn, PgUp, Home or End keys to select the next, previous,
first or last detector, respectively.
The background is always blue (i.e., not color-coded) to indicate that there is only
one high voltage setting per detector. The Collect Date/Time, Gamma
Discriminator setting(s), and Dwell Time in effect at the time of the plot are
indicated at the bottom right, along with data points (High Voltage Set and Read,
DAC set value, and measured Gamma Count Rates). Step through the data points
by changing the High Voltage setting (+/-, Ctrl +/- keys). If the value of HV is not
meant to be changed, it can be restored to its original value before exiting by pressing
Ctrl+F7. Upon opening the screen the high voltages for all detectors are turned on
and stabilized. Messages “Ramping HV” and “Stabilizing Detector” are shown on
top right of graph and the former appears until HV is ramped for all detectors (or 30 s
elapses). The latter appears for 2 s after HV is ramped.
The Plateau Plot test sweeps the detector high voltage through the specified range in
increments of Step Volts and plots the detector count rate (Gamma Counter in green)
at each setting. The current Voltage Set, Voltage Read, DAC set value, and
measured Gamma Count Rate(s) are displayed below the plot (right) as the test
progresses.
NOTE:
The HV is turned off when not collecting.
For best results use a check source capable of producing 500 to 2500 cps. The plot
points are saved in PLAT_###.CSV in the D:\MonitorProgram\DATALOG
directory, where ### is the detector number e.g. PLAT_06.CSV. These CSV files
can be opened by a spreadsheet program such as Microsoft Excel. Some useful hints
for viewing CSV files using Excel are provided in the appendix, Viewing Datalog
Files with Excel, on page 303.
The PLAT_###.CSV files containing the Discriminator Plot data contains the
following:
a. 1
st
row “Plateau Plot” has Collect Time
b. 2
nd
row “Detector” has detector number
c. 3
rd
row “Beta Discriminator” is not used for this detector (set to 0)
d. 4
th
row “Alpha Discriminator” is not used for this detector (set to 0)
e. 5
th
row has Gamma Discriminator
f. 6
th
row has Dwell Time
g. 7
th
row has Maximum HV (supported by board)
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