Food-SSAFE
Spetrum / Sample Analysis and Food Examination Kit
Operation Manual
Berkeley Nucleonics Corp
2955 Kerner Blvd., San Rafael CA 94901
Tel: 415-453-9955 Fax: 415-453-9956
Email: info@berkeleynucleonics.com
Website: www.berkeleynucleonics.com
b. On the Connection screen confirm that COM 1 is
indicated and tap OK to continue. The screen will close
and after a few moments a message will pop up showing
the serial number of the connected MODEL 970.
Acknowledge that message by tapping OK.
c. Next the Detector Selection screen will be shown.
Confirm that your detector serial number is shown and tap
Use This Detector to continue.
d. The Detector Settings screen is displayed. Tap the OK
button to continue. This screen will disappear for a few
moments (about four seconds) while the application
transmits those settings to the MODEL 970.
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e. When the Main Screen is displayed the system is ready
to operate.
4. Gain Stabilization and Source Check
Note: Prior to measuring samples the software requires that a gain stabilization and source
check be performed. It is possible to bypass or shorten these requirements by using the
manual gain stabilization function instead of the automatic gain stabilization, although
bypassing the automatic gain stabilization is not recommended (discussed later in the
section Bypassing Startup Requirements). For this quick start guide only the automatic
functions are discussed.
It is assumed that the K-40 Marinelli standard and detector are set up as described above in
step 2. Since the same source is used for both gain stabilization and source checking it is
possible
a. From the Util menu, select Auto Gain Stb + Src
Check… A message pops up asking you to confirm that
the K-40 source is on the detector. Tap OK to continue.
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b. The Automatic Gain Stabilization screen will be
displayed. The software will collect a spectrum until a
sufficient number of counts exist to determine a
statistically reliable peak center. If not within a few
channels of the expected location the fine gain will be
adjusted in the appropriate direction and an additional
count started.
Displayed information includes the channel at which the
K-40 peak is expected; the original fine gain setting; the
centroid of the current peak; the current fine gain setting;
the current peak height at the centroid; and the time
elapsed in the current spectrum.
c. Once the software is satisfied with the location of the peak, the Automatic Gain
Stabilization window will close and the K-40 source check will continue on the main
screen. Allow this acquisition to continue until complete.
d. When the source check is complete a message will
display showing the observed count rate for the source,
the limits (±10% by default), and whether the test was
passed or not.
Acknowledge the message by tapping ok and the system
is ready to begin analyzing samples.
e. Use File|Save Spectrum to save a copy of the spectrum
if desired.
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5. Taking a Background Measurement
a. Remove the detector from the shield, take the lid off the
shield, remove the K-40 standard, and recover the
Marinelli spacer from the standard.
b. Place the spacer into a clean, empty Marinelli. Put the
Marinelli into the shield, replace the cover, and put the
detector through the hole in the shield.
c. From the Util menu select Acquire Background…
d. A message will pop up asking for confirm that an empty
Marinelli is on the detector and stating how long the
background acquisition will be for. The default time is
900 seconds.
6. Analyzing a sample
a. Remove the detector from the shield, take the lid off the shield, remove the empty
Marinelli, and recover the Marinelli spacer from the standard.
b. Place the sample to be analyzed in the shield. (If you are analyzing an air sample filter or
wipe sample, insert the wipe/filter spacer first and put the sample into that.)
c. Place the Marinelli spacer into the cavity in the Marinelli.
d. Put the lid on the shield. Stick the detector through the hole and seat it on the spacer.
e. If a spectrum is currently displayed, tap the “X” button along the bottom of the screen (or
use Util|Clear Spectrum) to clear it. If the spectrum hasn’t been saved a warning to that
effect will be displayed, giving you the opportunity to save it if desired.
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f. Tap the green circle “GO” icon (or UTIL|Start
Acquisition) along the bottom of the screen to begin
analyzing a sample. The Sample Data screen will be
displayed. Enter the acquisition time desired (default is
900 seconds or 15 minutes).
Select the appropriate sample matrix--SOIL, WATER, or
FILTER--and the relevant sample geometry—
MARINELLI or DISK.
Note: The Food-SSAFE comes calibrated for water and
soil in a (nominal 500 mL) Marinelli geometry plus a 2”
filter in a disk geometry.
Enter the quantity of the sample and units (e.g.,. 0.7 liters, 0.540 kg, etc.).
Three more fields are available: Location, Description,
and ID. These can be used for whatever purpose makes
sense to your program or the fields can be left blank.
Check the box next to Auto save spectrum file to have
the spectrum automatically saved at the end of the
acquisition.
If a background file has been loaded, the Calculate
Statistics… button can be pressed to determine the MDA
(total Bq) and LLD (activity/quantity, e.g. Bq/liter or
Bq/Kg) to ensure that the sample analysis can meet the
statistical target.
g. Tap the OK button to begin the acquisition. The main
screen will be displayed with the data updated approximately each second.
h. Once the acquisition time has been met (or if the
acquisition is terminated by either tapping the “STOP”
icon, or using Util|Stop Acquisition, along the bottom of
the screen), an analysis of the spectrum will be performed
and the report screen will be opened. Use the scroll bars
to see the complete report. Tap the Save… button to save
to a text file. Reports are not saved unless explicitly
directed.
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Basic Functions of the Main Screen
The Main Screen is divided into three sections. The top
section (colored blue by default) is the Spectrum Display.
a. Colors for the background and spectrum trace (as well
as for other items) can be changed using
View|Preferences.
b. Tapping the Spectrum Display will cause a line to be
displayed at the tapped location. The channel number
and number of counts in that channel will be
displayed. If an energy calibration has been
performed the energy (in keV) will also be displayed.
Tapping in the area beneath the Spectrum Display
will hide the line. Alternately, use View|View
Preferences to set a timed line display where the line
will be hidden after a set number of seconds.
c. An MODEL 970 spectrum (4096 channels) contains
more data than can be displayed, as the PPC screen is
only 240 pixels wide. This means that in normal
(Full Screen) mode, each screen pixel represents the
sum of about 17 channels. To view a section of the
spectrum in the greatest detail (one channel per pixel)
select View|Zoom. If the Spectrum Display has been
tapped the zoomed display will be centered on the
tapped channel. When zoomed, using the scroll bar
on the top of the zoomed display can move the
section being viewed. The display will automatically
scale to the channel with the greatest number of
counts in the displayed region. Return to the normal
view by tapping View|Zoom again to uncheck the item.
d. The spectrum display can also be smoothed by
selecting View|Smoothed Spectrum. Select
View|Smoothed Spectrum again to uncheck the item
and go back to the raw data display.
e. The lower area (gray background by default) contains
information about the current MODEL 970 and
detector as well as sample acquisition information.
The top line contains the total number of counts in the
entire spectrum. The second line is the total elapsed
spectrum acquisition time. The third line is the count
rate (in cpm) from about the most recent 20 seconds
of the acquisition. The fourth, fifth, and sixth lines
contain the MODEL 970 serial number, the detector
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manufacturer, model, serial number, and the detector description. The final line
contains relevant information on acquisition status, background status, etc.
f. The bottom section of the screen contains the menu items and button bar. The menu
items will be discussed in detail in the next section. The button bar consists of a
green circle (grayed out when an acquisition is active), a red circle (grayed out when
not actively acquiring a spectrum), and a black X. Tapping the green circle will begin
an acquisition, the red circle stops an acquisition, and the black X will clear the
spectrum (after giving a warning and opportunity to cancel the deletion).
Menu Items
1. File Menu
The File Menu contains functions generally related to
storage and retrieval of data.
a. File|Save Spectrum allows the current spectrum to be
saved to a standard “.usf” file, compatible with the
MODEL 970 MCA software for the PC.
b. File|Load Spectrum to Live loads a stored spectrum into
the “live” acquisition display. This is especially useful in
offline mode to view and re-analyze stored spectra.
c. File|Load Library File loads a different library file to be
used for analyzing samples for radioactivity.
d. File|Exit will terminate the connection and exit the application (after presenting a
warning and an opportunity to cancel).
2. Util Menu
The Util Menu contains functions generally related to
calibration, detector settings, and analysis.
a. Util|Start Acquisition performs an identical function to
the green circle on the button bar; it begins a sample
acquisition. A checkmark will appear next to this menu
item while an acquisition is active.
b. Util|Stop Acquisition performs an identical function to
the red circle on the button bar; it stops a sample
acquisition. A checkmark will appear next to this menu
item when the MODEL 970 is not actively acquiring data.
c. Util|Clear Spectrum performs an identical function to the black X on the button bar; it
will clear the spectrum (after giving a warning and an opportunity to cancel the deletion).
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d. Util|Detector Settings opens the Detector Settings
screen. The hardware settings (HV, Threshold, Shaping
Time, Input and Polarity, Coarse Gain, and Fine Gain)
can be modified as needed to make the spectrum display
suit your needs and purposes. The proper settings for
these items were set when the initial calibration and
should generally not be altered. This is because changes
to these hardware settings will dramatically affect
detector response, invalidating any calibrations done so
far. The exception to this is the fine gain, which can be
used to compensate for drift in the spectrum caused by
changes in temperature, etc. Note: A separate function
exists for adjusting the fine gain, covered below under
Util|Fine Gain Adjust.
Tap the OK button to load these settings to the MODEL 970 and update the detector
configuration file. Note: If the high voltage has been changed you will need to wait up to
four seconds (while the MODEL 970 ramps the high voltage to the new setting) before
you can begin a new acquisition.
There can only be one set of parameters for any MODEL 970/detector combination; these
settings are loaded following the selection of the detector to use at program startup. You
can force a single detector to have multiple settings by creating a “new” detector and
changing the description, serial number, and/or manufacturer.
Tap the Cancel button to exit the screen without applying any of the changes made.
e. Util|Energy Calibrate opens the Energy Calibration
dialog. The energy calibration has been performed during
the factory setup and calibration. Changing any of these
settings will invalidate that calibration. Instead, use
the fine gain adjustment to compensate for any drift that
has occurred.
In order to perform an energy calibration you should be
displaying a spectrum of a known isotope. The energy
calibration routine involves identifying two or more peaks
and associating the channel numbers with the peak
energies.
To perform an energy calibration check the Allow Edit
box to enable the energy calibration controls.
Next, tap the first peak you know the energy for and a vertical line will appear. Use the
right and left arrow buttons to move the line to the center of the peak—it may also be
helpful to zoom the view. Enter the energy for the peak in the box marked keV:. You
are not limited to whole numbers for energy values.
Use the up arrow to change the energy calibration point to 2. Un-zoom the display by
checking Full and tap the second peak for which you know the energy. Use the left and
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right arrows to adjust the location of the line to the center of the second peak, and then
enter the energy. Repeat this process for up to 12 energy calibration points.
Note: It is not strictly necessary to enter the calibration points in any order. When the
energy calibration is performed the calibration points will be sorted in order of the
channel values, from lowest to highest.
When all energy calibration points have been entered, tap the Do Energy Calibration
button. A summary of the channels and associated energy values will be displayed in the
list box. Review these for accuracy, as out-of-order values will cause strange results in
later analyses.
The energy calibration is not actually stored and made active until the OK button is
tapped. If the Cancel button is tapped any new values entered will be lost.
The Load button can be used to load a stored spectrum into the Spectrum Display.
When Allow Edit is not checked, it is still possible to use the up and down arrow buttons
to scroll through the energy calibration settings.
This screen can, of course, also be used to edit any existing energy calibration. There can
only be one energy calibration for any MODEL 970/detector combination. The energy
calibration is loaded following the selection of the detector to use at program startup.
You can force a single detector to have multiple settings by creating a new detector and
changing the description. When in Offline mode, however, the energy calibration stored
in the detector file (.usf) will be applied each time a new spectrum file is loaded. This
does not occur when not in Offline mode.
f. Util|Manual Fine Gain Adjust opens the Manual Fine
Gain Adjustment screen. An energy calibration must be
performed before this function can be used (see below).
The fine gain adjustment is intended to provide an easier
way to compensate for energy drift in the detector
(typically caused by temperature changes) than using the
Detector Settings screen.
Use the Start, Stop, and Clear buttons as on the Main
Screen. Acquire a spectrum of a known source and select
the isotope from the dropdown list. This will cause the
library energies for that isotope to be displayed on the
spectrum. Checking Full Height will cause the lines to
extend to the full height of the display instead of being
proportional to the abundance. If the energy line does not match up with the peak,
increase or decrease the fine gain control a little bit and tap the Set Fine Gain button.
Then Clear the spectrum and begin another acquisition. Repeat this until the vertical line
and peak line up with one another.
Tap the OK button when the fine gain adjustment is complete or tap Cancel to revert to
the original fine gain.
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