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The Track Utility display also provides a Home position (loading position) as well as manual fine controls.
PC and UPS System
The PC is used solely for running the NGRL and reviewing data. It must never be connected to the internet or any devices which may interfere with the proper functioning of the instrument and its software. Users should also avoid using the PC for any other purpose while a measurement is running.
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Inexperienced operators should only the LabVIEW application and MUT. Maestro has many features and controls and can alter the detectors’ settings and care should be taken when using it.
Laboratory Apparatus
The titanium core boat has a 3.5 cm diameter with welded ends, attached to a Delrin rod that connects it to the NSK actuator. The inherent radioactivity of the boat and the rod are very low and do not affect core measurement.
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- Ensure the fans are plugged in and working.
- Turn on the master power button above the middle NIM rack (blue circle in Fig. 13).
- Turn on the computer.
- Turn on the NaI(Tl) detector electronics (right-hand NIM rack next to iSEG crate, the right red circle in Fig. 13), only after ensuring that the fan under it is working.
- Turn on the fast signal processing electronics (left-hand NIM rack, the left red circle in Fig. 13).
- Turn on the iSEG voltage crate power found behind the unit near the power cord.
- Launch the iSEG control software at the NGR computer (Fig. 14).
Figure 14. iSEG Hard ware Setup and Main screen. The controller cards may be the EHS or EHQ model and are labeled accordingly.
- Make sure the voltages (Vset) for ESQ00/EHS00 and EHQ01/EHS01 are set (Fig. 15). Modify the Vset fields as follows:
- Channel 0 = 0 (unused and available for spare channel)
- Channels 1 and 7 = 1100 V (plastic scintillators in the doors)
- All other channels = 1300 V (shell-shaped plastic scintillators)
- If one of the channels on the EHS/EHQ modules has failed, Channel 0 may be in use—be sure you understand which scintillators are connected to which channels, because the door and hoop PMTs require different operating voltages!
Figure 15. EHS/EHQ 00 and 01 iSEG Multi-Channel HIgh-Voltage Modules Screens; VRamp and IRamp fields are circled in red. - Make sure voltage ramp (VRamp) is 5% or lower and the current ramp (IRamp) is 50% or lower. The iSEG software does not remember these values between sessions!
- Click on the Module access menu and click Instructions for all channels > On (ctrl+o) to start ramping up the voltage.
- Wait until ramp-up completes (1–2 minutes if proper values are used).
- Exit the iSEG program.
- Answer No to the prompt when asked to ramp voltages back down. If you answered Yes inadvertently, start again at Step 8.
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- Place the calibration core on the core boat so the round holes face upward. The highest-numbered end (#8) should be closest to the NGR chamber opening (starboard) and the #1 end should be closest to the catwalk hatch.
- Insert calibration source holder containing both the 60Co and 137Cs sources into the hole marked 2-1 (Fig. 18). Match up the red marks on the calibration source holder with the marks on the calibration core so that the plastic holder lies flush into its position and will not strike the edge of the NGR chamber opening.
Figure 18. Calibration Source Holder.
- Make sure the track pathway is free from obstacles. Prepare Bias Voltage Calibration Worksheet (see NGR Log black binder – a blank sheet is attached at the end of this Chapter) to record initial readings.
- Advance the core boat into the calibration position by using NGR Core Analyzer software, “Track Utility” tab, “Calibration Position”, “Move In button.”
- Start Maestro. From the Maestro tool bar (Fig. 19) choose the detectors of interest (starting with #1 and #2) and close any other detector windows; your Maestro window should show two channels (Fig. 20). Record initial readings on Worksheet.
Figure 19. Maestro Aquire menu showing the “MCB Properties” selection.
Figure 20. Maestro window showing NaI #1 and NaI #2 detector responses - Clear any results for both windows (right-click in the dark blue area and select “Clear” from the drop-down mouse menu.
- From the Maestro tool bar open the “Acquire” drop-down menu (Fig. 19) and open “MCB Properties;” this should be the last item on the menu as shown.
Figure 21. Maestro MCB Properties dialog window.
- For each detector window, In the MCB Properties dialog window (Fig. 21), make sure the Gate setting in the “ADC” tab is set to Anticoincidence. In the “Presets” tab, enter the Live time; exact Live time is not important so long as the Cs and Co peaks are sharp. For a new 1 µCi standard, 60 seconds is sufficient; as the standard ages (esp. the 60Co source with its short half-life), it will be necessary to use a longer Live time.
- For each detector window, right-click in the dark blue area and select “Start” from the mouse window. The progress for the spectra can be observed in the “Pulse Ht Analysis” box on the right side of the Maestro window. Clicking the left mouse button on the spectrum will activate the detector window of interest (Fig. 22.)
Figure 22. Detectors #7 and #8 after acquiring signal from the 137Cs and 60Co sources; the lower window, detector #8.
- Click with the left mouse button in the middle of the left (first) peak; this is the 137Cs line. Use the zoom functions if it will help see the peak. Go to the tool bar menu, choose the “Calculate,” then “Calibration” commands. A small dialog window will show up (Fig. 23) by peak. Fill the “Calibration (Energy)” field with 662.0, then click OK. Confirm that the calibration units are in keV (not MeV) in the subsequent pop-up window. Peak in channel should be at 226 (+/- 2).
Figure 23. Calibrate dialog window to set a peak’s energy
- Repeat this operation for the right (third) peak; this is the higher-energy 60Co line (448 +/- 2). When the Calibrate dialog window appears, enter 1330.0 in the “Calibration (Energy)” field.
- Check the calibration by clicking on the top of the middle (second) peak; this is the lower-energy 60Co line (394 +/- 2). Go to the Calculate/Calibration dialog window to see if the value in the “Calibration (Energy)” field is close to 1172. If the observed value for the second peak is within +/- 3 keV, you may click OK and proceed to the save step. If the value is outside of this range, click the “Destroy Calibration” button and return to step 11 until in-range values are obtained. It may be necessary to adjust voltage, see following section on Tuning the NGRL Voltage Settings.
- Save the energy calibration file by clicking the in the detector window and choosing File: Save. Save the calibration file in C:\data\ngr\.config\calibration\[expedition]\date folder (you may have to create this folder, where [expedition] is the current expedition number). Ensure the detector number in the file name matches the actual detector number in the title bar above the spectrum.
- Retract the core boat to the loading position (Click “Find Home” in the NGR Core Analyzer Software)
- Remove the source holder from the current position and place it in the next position.
- Repeat steps 2–8 until all four positions (2-1, 4-3, 6-5, and 8-7) and all eight detectors have been calibrated.
- After all eight detectors are calibrated and each calibration file is properly saved, close the Maestro window. Make sure to update the NGR’s NGR_configuration/Folders_and_Files dialog window with the correct location of the most recent calibration files. When done, close the configuration window.
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- Place the core section in the tray and ensure the top of the section is against the top of the boat.
Note: the PMTs for the door plastic scintillators are visible (and exposed to potential damage) so significant care must be taken during core section movement to avoid the possibility of damaging the detector or PMTs. - Place the core section in the titanium boat on the NGR delivery system loading track. Ensure the blue end of the core section is against the leading edge of the boat (closest to the NGR door
- Open NGR Core Analyzer (Fig. 30), which is usually found on the NGR’s workstation desktop. If the configuration files are corrupted or missing, load them from the Main control menu by choosing Configuration.
- Press the Scan button (Fig. 30, #1) on the NGR Core Analyzer screen to initiate a run. The Sample Information dialog window will appear (Fig. 30, #2).
Important! Ensure that the cursor bar is blinking in the Text ID box before scanning the section’s barcode. The NGRL can be set to run without a sample identifier if no Text ID is present and this will waste time. - Ensure the barcode reader has read the sample identification and the Text ID and Sample Name, fields
- fields have been completed on the Sample Information screen. Sample length is very important for proper edge correction and must be entered manually. (Text ID and Sample Name fields can also be entered manually if the barcode won’t scan.)
Note: the - the “Run the Experiment” button will not activate unless a length >0.0 cm is entered in the Sample Length field. The user must click elsewhere, tab out of the field, or click press enter (user’s choice) in order for the software to register the entered value and enable the “Run the Experiment” button.
Figure 30. NGRL Core Analyzer Screen, Ready to Start Scan.
- After all necessary lines are filled click “Run the Experiment” in the Sample Information window and the boat will begin moving. The boat will proceed automatically into the chamber without further intervention, so be sure the track is clear of obstructions!
- As soon as the sample reaches measurement position I, the measurement will begin. Eight channels will collect gamma ray counts from measurement points along the core section in Position #1 for a user-defined time period.
- The core will move automatically forward 10 cm into Position #2 and again collect data for another eight positions (for a total of 16 measurement positions every 10 cm).
- As the sensors take measurements, counts are plotted vs. sensor number on the mainscreen. Hit the Detail/Summary button at the upper right of the screen to switch between the histogram vs. binned mode displays. The button name changes from Summary to Detail, depending on which view is selected (Fig. 31 and 32).
Figure 31. Core Analyzer Screen Showing Histogram.
Figure 32. Core Analyzer Screen in Binned Mode Display.
- Elapsed time (on the left side of window) during normal run (e.g., with 10 min acquisition time per position should go up to 21–22 min).
- After data acquisition finishes, the boat will retract from the NGR chamber automatically. It is therefore important not to have anything blocking the actuator’s path!
- The analysis is now complete.
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