Exp391 X-Ray Tech Report

by Myriam Kars

SUMMARY

Expedition 391 Walvis Ridge Hotspot took place in December 2021-February 2022 in the South Atlantic. Because of Covid outbreak onboard the JR which obliged us to go back to Cape Town, operations started on January 2, 2022 and finished on February 1. The expedition recovered sediments (mostly calcareous ooze) and basement rocks.

XRD analysis on the Aeris XRD was mostly conducted on sediments, and ICP analysis was only carried out on basement rocks. New ICP preparation method was applied during the expedition and constituted of doubling the flux quantity and increasing sample material mass – details are available on Exp391 Chemistry Tech Report. LOI measurements which initially fall under the X-Ray lab tech duty were mainly done by the Chemistry Lab Tech to keep up with the work flow.

TOTALS

Notes: The number of ICP analysis does not include beads re-dos requested by scientist. More ICP measurements were done during X391.

pXRF measurement number includes repeated measurements on section half points and discrete samples.

Fresh and ignited rock standard powders are kept in jars in the X-Ray Lab dessicator. These powders can be reused in next expeditions. Note that the ignition on rock standards during Exp 391 was done at 950ºC for 4 hours.

INSTRUMENTS

BEADMAKER

• Status throughout the expedition: Issue with temperature?

• New issue left open: Temperature shown on the beadmaker screen may not be accurate.

• Details:

At the beginning of the expedition, several beads with “powdery” flux present on the JR and “granular” flux shipped from College Station and delivered during tie-up in Cape Town were made for comparison (Figure 1). Blank powdery flux does not melt properly at 1050 degC (temperature used for making beads for ICP and displayed on the eurotherm) (Figure 2). It is unfortunately not possible to confirm the temperature inside the beadmaker because of heat conductivity. Moreover, it is necessary to leave the beadmaker door/lid open to measure the temperature with the probe available on the JR. As the “granular” flux seemed to be okay, we assumed that it was not a problem with the type of flux used, but more likely the temperature of beadmaker. We therefore increased the temperature by changing the beadmaker settings until the powdery flux melts (Figure 3).

Open

Figure 1. Performed tests (left) and resulting beads (right): Vials 1, 2 and 4 are not melted

Open

Figure 2. Original beadmaker settings for making beads (left) and resulting non-melted powdery flux in Pt crucible (right)

Figure 3. New beadmaker settings (left) leading to melting of powdery flux (right)

After days of transit when the beadmaker could not be used, our Marine Instrumentation Specialist Chris opened the beadmaker, cleaned the inside and tightened some components (December 20, 2021). New bead tests were successful (December 20-21, 2021) (Figure 4).

Figure 4. Beads made after cleaning and checking electronic components

An additional test to check whether it is a temperature issue or a flux issue was conducted with the muffle furnace on January 3, 2022. At the last resort, it is possible to make beads with the muffle furnace located in the Chem lab. See ICP Preparation. Two Pt crucibles (one containing blank powdery flux and one containing powdery flux with ignited powder) were put in the muffle furnace at 1050ºC. They both melted (Figure 5), thereby confirming our hypothesis of a temperature issue with the beadmaker.

Figure 5. Powdery Flux in Pt crucible before (left) and after (right) muffle furnace

Moreover, dark spark/dot "recrystallization" in some beads (Figure 6) while cooling after the crucible is removed from the inside of the beadmaker suggests that some material is not completely melted during fusion or that the beadmaker temperature is actually lower than shown on the screen. After discussion with the shipboard scientists, we changed our protocol for making beads by (i) doubling the flux quantity (800 mg instead of 400 mg) and adding 125 mg of material (instead of 100 mg) and (ii) "increasing" the beadmaker temperature to 1220ºC (Figure 7; see also Exp391 Chemistry Tech Report).

Figure 6. "Recrystallization" in beads during cooling

Figure 7. Beadmaker settings used for making beads during X391

The crucible needs to be close to the beadmaker for the cooling fan to activate.

• Maintenance: On January 15, 2022 the filter for the cooling water was replaced. It would be good to check the filter every 6 months and to replace it every year if the beadmaker is extensively used.

• Suggestion: Buying a new beadmaker. The company of the current beadmaker does no longer exist with difficulty or even impossibility to find spare material and to have technical support. Moreover, the detailed manual is in Japanese.

LABCONCO FREEZE-DRYER

As mentioned in the tech report of X396T, the freeze-dryer of the Thin Section Lab does not hold vacuum. The freeze-dryer of the Chem Lab was used during X391.

AERIS XRD

• Status throughout the expedition: good – standard runs were reproducible

• Old issues still open from previous expeditions: motion errors

• Details:

Motion error continues while the ship is not moving (at berth or on site) as noticed in previous expeditions. Error seems to randomly occur as noticed in the X396 tech report.

• Error on 12/21/21: The Goniometer Omega axis cannot move correctly. Restart the instrument [856384]

• Error on 12/25: The sample changer z axis cannot move correctly. Restart the instrument [960378]

Turn off/on method (Power button on the right side of the Aeris touchscreen) cleared the errors. However, the XRD Data drive on the Aeris computer (i.e., touchscreen) was disconnected. Troubleshooting was needed and XRD Data drive needed to be reconnected to allow the data transfer to the X-Ray lab computer.

These errors are also reported in the Word file “Aeris Issues Log” on the desktop of the X-Ray lab computer.

The motion errors can also be cleared by opening the lid and pushing both detector and source to move them around (see Aeris Advanced User Guide on how to do it safely and video called "Aeris moving detector and source" at T>IODP_Share>XRD>training videos).

• Series of motion errors on 1/23-24:

Error on 1/23: The sample changer z axis cannot move correctly. Restart the instrument [960378]

To clear this error which happened before, the instrument was turned off on 1/24. Unfortunately, when the instrument was restarted two errors happened:

The Goniometer Omega axis cannot move correctly. Restart the instrument [856384] – known error  AND

System error 8501 occurred in the measurement module. Restart the system

Once again, the instrument was turned off and on. However, this method did not clear the System error. The detector and source had to be moved around manually like shown in the video on IODP_Share. This cleared the error system and the last turn off/on technique cleared the goniometer motion error.

• Maintenance: Filled with DI water on December 18, 2021 and January 20, 2022

• Measurement sequence name: X391 4-75deg .25div 18min.xrdmp (in C > XRD Data > XRD data > Exp391). Measurement from 4 to 75 2θ with a 0.25 divergence slit.

Sequence parameters:

start angle: 4 º2θ

end angle: 75 º2θ

step size: 0.0108664 º2θ

time per step: 39.525 s (~40 s)

divergence slit: 1/4º

active length detector: 5.542 º2θ

duration: ~ 18 min (single scan)

• Using the Aeris XRD for the measurements was motivated by the fact that the shorebased scientist in charge of interpreting the XRD diffractograms was familiar with the Aeris and HighScore software.

Raw data file (.xrdml) and .jpg file of diffractograms (screenshots of Data Viewer) were copied to Uservol for quicker access by scientists. Files were also saved via HighScore as .hpf to send to the shorebased scientist and copied to Uservol.

HighScore Software

• Issue: Scientist encountered issues with HighScore software when using the virtual computer access in the Core Lab. Some options were no longer available and at some point, the software completely crashed (personal communication from scientist). Because it is a virtual access, scientist could not have access to other ongoing work on the same "physical" computer.

• Suggestions: It could be nice to have a permanent software license on a computer in the Core Description area of the Core Lab. What about transferring the permanent access to HighScore available on the XRD computer of the X-Ray lab to the Core Lab, and keep a virtual access in the X-Ray Lab (Mettler balance computer has internet access)?

D4 BRUKER XRD

The D4 Bruker XRD was not used for XRD analysis of Exp391 shipboard samples. However, the Bruker was used for comparison tests with the Aeris.

X-PRESS

There is a weak oil leak, known from previous expeditions, from behind the apparatus. It does not prevent the press to work properly.

SHATTERBOX

• Status throughout the expedition: doing its job

• Old issues resolved: loose lever arm was tightened and pins changed

• New issue resolved: Broken "START" and "PAUSE/STOP" buttons were replaced by new 3D-printed buttons (Chris/Clay)

• New issue left open: lid safety switch causing safety error

• Details:

• The lever arm was loose at the beginning of the expedition, as noted previously. Pins inside the lever arm were broken and they were replaced with new ones (Figure 8). The strap around the lever arm to keep it in lower position is used as additional precaution to avoid damaging the lid.

Figure 8. Broken pins (left) and new ones in place (right)

• New "START" and "PAUSE/STOP" buttons for the Shatterbox (Figure 9): the old buttons fell off when the shatterbox was shaking, preventing the shatterbox to work.

Figure 9. New buttons on the shatterbox

It is necessary to press “PAUSE/STOP” button before pressing “START” to start the shatterbox. Safety or misconnection?

• The safety switch of the lid was not activated properly because of repetitive vibrations. Our Marine Instrumentation Specialist, Chris, fixed the issue and warned that it would likely happen again.

HANDHELD pXRF

• Status throughout the expedition: good

• Old issues resolved: new cable connecting the pXRF gun to the computer

• Old issues still open from previous expeditions: communication error between gun and computer when gun interface is used.

• Details:

1. As suggested by X-Ray technicians during X396, touching the gun screen creates some communication error with the computer. If the gun has not been turned off, do not click “Import Data only”, click directly on “Start”. This is included in the updated version of the pXRF user guide.

2. New scanner barcode rules for pXRF measurement for 12-digit text ID (for pXRF discrete sample cups) was created and can be found at T>IODP_Share>XRF>Barcode Rules . Note that the barcode rules between section half and discrete sample (i.e., pXRF cup) are different. Do not forget to change the barcode rules when swtiching from one to the other. The TextID of standards used for QA/QC is read properly with the “section” barcode rules.

3. To upload discrete samples (pXRF cups) on LIMS correctly, make sure that the user writes 0 (zero) in the offset window of the analysis tab of the Innov_X software. The depth is automatically calculated with the information associated with the TextID. If the offset is not computed as zero when doing the pXRF measurement, the final calculated depth will be wrong. This has been noticed by our Database specialist, James, and data had to be deleted from LIMS and uploaded again. For instance, a shipboard sample collected at an offset of 23 cm has a depth of 100 cm (information associated with the TextID in LIMS). If the user puts offset information in the software for pXRF measurements, i.e 23 cm, (like the user must do for section half point measurement), the final calculated depth for this discrete sample in the pXRF data report when uploaded with MUT would be 1.23 m (100 cm + 23 cm). This is not correct, therefore make sure that the offset is zero for pXRF discrete samples.

4. Spectrum data file is limited to 129 runs. Make sure to provide this information to scientists.

5. New 3D-printed tool to dismount pXRF cups (idea by Clay/Chris) to retrieve powder (Figure 10). On X391, powder used in pXRF cups was non-ignited powder (leftover powder of LOI/ICP sample).

Figure 10. New tool to dismantle pXRF cups using a spinning and lever technique

5. pXRF scanner was added in QCViewer for QA/QC. Two rock standards were flagged as pXRF standards: BHVO-2 and BCR-2 (Figure 11). Their respective Text ID for QA/QC are found in the pXRF user guide on Confluence. The pXRF gun user (scientist) is advised to run a standard regularly. For X391, BHVO-2 was chosen.

Figure 11. QAQC Rock Standard BHVO-2 and BCR-2 used to control quality and accuracy of pXRF measurements in QCViewer

• QCViewer for pXRF measurements (Date Order)

• QCViewer for pXRF measurements (Sequence Order)

MISCELLANEOUS

Time in Cape Town and transit was mainly dedicated to lab rearrangement and manual updates on Confluence.

• Manual updates on Confluence and reorganization of contents after Heather’s suggestions. Redundant pages with same information were deleted. The XRD Lab notebook is now better organized with all manuals updated with explanatory figures included.

• Inventory of rock and sediment standards used for ICP available in the Chem Lab. Some standards had no Text_ID. List was provided to Carel, the curator onboard during X391 and TextID was created. Inventory number was added on all rock and sediment standard jars used for ICP. A Confluence page containing tables was created in the Chemistry Lab notebook to keep the rock standard quantity status regularly updated (good, almost empty, etc…):  ICP Rock and Sediment Standards (Status). The original Excel file can be found there as well.

• XRD Diffractograms of mineral standards available in the X-Ray Lab were combined all together (standards were measured by other techs): Conversion of the Aeris file (.xrdml) into .xy (to be read with Eva). Screenshots in Data Viewer to have jpg files of the Aeris diffractograms. One single pdf file was created with all diffractograms of mineral standards measured with the Bruker and the Aeris. The XRD analysis datafile from the Bruker and the Aeris and the corresponding diffractograms can be found in the “XRD STANDARDS” folder on the XRD computer desktop. See XRD Books and Reference Material

• The X-Ray lab library was updated and the list can be found on Confluence at  XRD Books and Reference Material

• Sliding tray for the Aeris keyboard and barcode scanner holder was made by our Marine Instrumentation Specialist, Chris Visser.

• Speaker sound fixed (cable has been changed and speaker B reconnected)

• Sample table for backloading samples of the Bruker - design prototype by Chris (Figure 12)

Figure 12. Prototype Sample Table for backloading sample holders of the Bruker XRD

COMPARISON TESTS BRUKER-AERIS

D4 Bruker: Frontloading vs backloading

At the beginning of the expedition, we performed a comparison test with the two types of sample holders available for the D4 Bruker (Figure 12).

Figure 12. Backloaded samples are shown in blue and green. Regular front loaded samples are in red and black

Question: Is the backloading technique better for clays (i.e., for 2θ < 15º)? There is no difference in higher angles between backloaded and frontloaded samples.

Issue: The backloading sample holder technique suggested by Bruker does not seem ideal. The powder is very fragile to bumping and gets disturbed easily. We therefore thought of a sample table similar to the technique used to prepare backloaded sample with the Aeris (see Figure 12). Try is necessary to seek any improvement.

Comparison test between Bruker and Aeris for clay separations

A pdf document showing all tests and comparison is available here: CLAY SEPARATION COMPARISON.pdf

Preliminary conclusions: The Bruker seems better to measure low angles. Changing hardware in the Aeris does not seem to improve the data.