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The IMS-NGR software can be launched from the Windows Start menu or from a desktop icon (Fig. 8).
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Figure 8- NGR Desktop Icon

At launch, the program begins the following initialization process:

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The NGR system, specifically, is built with one INST module (NGR), one MOTION module, and one DAQ Engine module. 
The IMS Main User Interface (IMS-UI) calls these modules, instructs them to initialize, and provides a user interface to their functionality. 
Each module manages a configuration file that opens the IMS program at the same state it was when previously closed and provides utilities for the user to edit or modify the configuration data and calibration routines.
The five buttons on the IMS-UI window provide access to utilities/editors via dropdown menus as shown in Figure 10.

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Figure 10- IMS Control Panel Drop down menus

Core Delivery System

The core delivery system consists of the M-Drive motor assembly, the NSK actuator, Delrin rails, the titanium core boat, and electronic limit switches.

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Figure 10. Program termination query.

 


  • Click the iSEG High-Voltage Control Icon to open the Main window.
  • Click on the EHQ00 and EHQ01 (or EHS00 and EHS01) modules. A window opens for each module (Fig. 11a and 11b). Check the following items:
    • Vmeas values: verify the actual channel voltages have ramped to near zero (1–3 V is acceptable)
    • Current indicators (i.e., Imeas values) have decreased.
    • Status of all channels is OFF (i.e., no green color in the menu status bars).
  • Close all iSEG windows after checking the channel voltages and current indicators.

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Figure 11b. iSEG Multi-Channel High-Voltage Modules; Ch01.

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  • Turn off the NaI(Tl) detector electronics (right-hand NIM rack next to iSEG crate; Fig. 12). This will turn off the high-voltage supply to all 8 NaI(Tl) detectors. Do not turn off the left-hand NIM rack (marked with a circled X in Figure 12 below) or the main power (blue circle) at this time.
  • Leave all other electronics and fans running to prevent additional condensation from forming.

 

Figure 12. Electronics Crate: Shutdown. 

Full Shutdown Procedure

Notes

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  1. Ensure the fans are plugged in and working.
  2. Turn on the master power button above the middle NIM rack (blue circle in Fig. 13).
  3. Turn on the computer.
  4. 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.
  5. Turn on the fast signal processing electronics (left-hand NIM rack, the left red circle in Fig. 13).
  6. Turn on the iSEG voltage crate power found behind the unit near the power cord.
  7. 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.



  8. 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! 

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    Figure 15. EHS/EHQ 00 and 01 iSEG Multi-Channel HIgh-Voltage Modules Screens; VRamp and IRamp fields are circled in red.

  9. 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!
  10. Click on the Module access menu and click Instructions for all channels > On (ctrl+o) to start ramping up the voltage.
  11. Wait until ramp-up completes (1–2 minutes if proper values are used).
  12. Exit the iSEG program.
  13. Answer No to the prompt when asked to ramp voltages back down. If you answered Yes inadvertently, start again at Step 8.

Initial Instrument Setup

NGR Configuration

Configuration values should be set during initial setup and configuration by the Physical Properties technician or scientist(s). There should be no need to change these values unless the configuration file is corrupted.

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  • DAQ Move: This profile controls moves between measurement positions (leader and trailer measurements included) and the move to the drift 2 position. Set this to a reasonable speed with gradual acceleration and watch out for flux jumps. In addition, when you use the speed reduction feature to control flux jumps, this value is the base value for the reduction.
  • Limit Seek: This profile is used for the following moves:
  • This profile finds the limit switch location. Do not exceed 3 cm/sec.Do not use a large acceleration value, but always use a large deceleration value.
  • Home Final: This profile finds the final location of the home switch. Do not exceed 3 cm/sec.Do not use a large acceleration value, but always use a large deceleration value.
  • Load/Unload: This profile is used for moving the tray in and out of the NGR.
  • Drift 1: This profile is used to move from the drift 1 position to the leader position and to move from the last trailer position to the drift 2 position
  • Drift 2: Unused
  • User Define: This profile is used for testing only in the Motion Utilities (Error! Reference source not found.) program.
    • Click the Open Utilities and Test button to open the Motion Utility (Error! Reference source not found.) window and test the settings.
    • Click Done to save the settings. Click Cancel to return to previous values.

Detector Settings


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Background Measurement

Measure the background periodically, whenever the ship changes latitude by more than 1-2 degrees, and at least twice an expedition. A data file is generated for each NaI(Tl) detector and measurement position, utilizing the titanium boat with an empty core liner to create conditions as close as possible to core measurement. The background measurement is taken for a much longer period of time for a good statistical spectrum. Typical measurement time is 300 seconds; the background is normally done for 21,000 seconds (almost 6 hours per measurement position; 12 hours total).

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  1. Place the aluminum calibration core (source holder) on the titanium boat, making sure that hole #8 is on the NGR chamber end and hole #1 is closer to the catwalk hatch. Place both the 137Cs and 60Co calibration sources in the white PFTE holder and insert it into the hole between #1 and #2 (i.e., hole 2-1) as for the energy calibration procedure above.
  2. Ensure no obstructions are on the track or inside the chamber.
  3. From the main NGRL screen, select the Track Utility dialog box and click “Calibration position” to send the core into the chamber.
  4. Open the ORTEC Maestro program. From the top menu choose Display/Detector/00001 PC to open the signal spectrum for NaI(Tl) detector #1. Clear the previous spectrum, if any.
  5. On the Acquire menu, select MCB Properties and on the properties window, ensure that the gate is set to “anticoincidence” on the ADC tab and that the Live time on the Presets tab is approximately 60 seconds. Close the properties box.
  6. On the Acquire menu, click on Start and allow the spectrum to be collected. It should look like one above (Fig. 25). Bring the Maestro cursor to the middle of the 137Cs peak and check the corresponding channel number on the bottom of the screen. If this number is 224 to 228, a bias voltage correction is not necessary, but could still be performed if desired. (Expected behavior is for the channel number for 137Cs to be 226±2 channels (Fig. 26).)
  7. If the drift is sufficiently large to require an adjustment, or if the spectrum appears compressed or stretched compared to the other detectors, perform a bias voltage tuning.
  8. Use a multimeter. Set it to DC current in the millivolt range. Read the voltage in the bias adjustment box. The multimeter’s black probe goes into the white fitting and the red probe into the appropriate red fitting for the detector being examined (see Fig. 27).
  9. Note the current voltage setting and the position of the pulser channel (if the pulser is used), the 137Cs 662 keV peak position, and the 60Co 1170 and 1330 keV peak positions in the table below (Table 1).

  10. Using the potentiometer screw just above (aft of) the red fitting, gently turn the screw to increase voltage (clockwise rotation) if the 137Cs peak is less than channel 226, or to decrease voltage (counterclockwise rotation) if the 137Cs peak is greater than channel 226. Note that you must rerun the 60-second acquisition (step 6) each time to see the new channel.

  11. Once you have set the 137Cs peak close enough to channel 226, record the new voltage setting and the new positions of the pulser channel, the 137Cs 662 keV peak, and the 60Co 1170 and 1330 keV peaks on the table.

  12. You must now set the software calibration as noted in the “Energy Calibration Procedure” section above. Once you have done this for detectors #1 and #2, repeat for the other detector pairs.


Figure 27. Insert the multimeter probes into the bias detector box to measure the voltage. Black to white. Red to red

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The system is now calibrated sufficiently to perform analysis on a total counts basis. Further calibration with known values of K, U, and Th (KUT) must be performed before KUT abundance can be determined. The scientist must do this reduction for KUT from the spectral data and no automated process exists for this.

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Exact Source Placement

The above procedure presupposes the calibration sources are positioned exactly in the center of the lead separator between each NaI(Tl) detector and on the top of the aluminum standard holder. Any significant error in this positioning (especially if the source is too close vertically to the detector) will introduce systematic errors in the calibration, as the lead shielding will interact with the gamma rays differentially between the two detectors. Systematic errors can be controlled by making measurements placed from both the right and left of detectors #2 through #7. (It is physically impossible to make this determination for detectors 1 and 8 but we can use the systematic error determined from the other six detectors to estimate the error for these detectors.) Calibrations done with manual positioning demonstrate that peak position can shift up to 5–6 channels (~15–18 keV) with a typical value of 2–3 channels (~6–10 keV). It is therefore important that the sources be placed precisely (the normal procedure does this).

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