XSCAN in the Core Lab

I. Introduction

This guide describes the standard operating procedures for the X-Ray imager (XSCAN) located in the Core Lab. The system is capable of collecting linescan X-radiographs on whole round and section half cores. Furthermore, the source and detector can be rotated around the core material for linescans with different view angles. A specific region of interest (ROI) on a core section can be imaged separately using the ROI feature.

Theory of Operation

Users should review the X-Ray Methods and Theory Powerpoint from B. LeVay, 2019 for background on X-Ray radiograph acquisition before operating the system.

Hardware

The IODP X-Ray scanner is composed of a 210W, 160 kV, 1.3 mA constant potential X-Ray source and a linescan detector. The source is a Spellman XRBD 160PN210 Monoblock X-Ray generator with a 0.5 mm focal spot. The beam fan angle is 90 x 12 degrees which is distanced approximately 36 cm from the source. The detector is a Hamamatsu C12300-321 composed of a CCD sensor with a ~22 cm field of view utilizing time-delayed integration (TDI) and a resolution of 48 microns per pixel.

Shielding

The shielding consists of several complimentary designs. The primary shield (Figure 1) houses the X-Ray source and detector. It is constructed of 3D-printed ABS plastic with hollow walls that are filled with Tungsten powder. The base of the primary shield (under the detector) is a solid piece of 1-cm thick Tungsten plate to block the primary X-Ray beam. X-Ray scatter is shielded by 2mm lead equivalent leaded vinyl or leaded acrylic panels on the sides, ends, top and bottom of the logger (Figure 2). The leaded acrylic provides a view of the inside of the logger while it operates. The hatches that allow insertion of core material on either end of the logger are also shielded with solid Tungsten plates.

Figure 1: Primary shield top and bottom halves, the latter shows the tungsten powder filling and solid tungsten plate used in the first design of the XSCAN.

Figure 2: Leaded acrylic and leaded vinyl shielding panels

Safety Systems

The XSCAN imager has multiple safety systems in place to ensure a user does not operate the system in a radiologically unsafe manner. Never attempt to operate the X-Ray source without the proper shielding in place! The safety subsystems include:

X-rays ON amber lights on two corners (Figure 3) Note an extra X-rays On amber light is mounted on the aft of the Xscan and indicates when the xrays are on for the spare source.
Colored light status indicators (AKA Patlite tower) (Figure 5)
Shutter position sensors
Door electronic locks (Figure 6)
X-ray source interlock
Emergency Stop Switch (motion and X-ray abort) (Figure 7)
X-rays auto-off after a user-selectable period

These components are wired into one fail safe system controlled by a National Instruments cRIO-9053 unit.

Figure 3: X-Ray emitting lights (lit=ON) on two corners of the XSCAN

Failsafe Circuitry

In order to generate X-Rays, a series of safety switches and shutter positions must be verified to enable the generation of X-Rays. Certain switches or sensors are operated electrically, others use pneumatics.

Figure 4 shows the failsafe circuit and the safety switches involved. All switches must be verified before the software command to generate X-Rays will be performed.

Figure 4: Fail safe circuit schematic.

Visual Indicators

A multi-color tower light mounted horizontally on the top corner of the logger acts as a visual indicator of the safety system and X-Ray status. It has four segments that reflect specific safety subsystems of the logger plus one for the measurement phase at the time (Figure 5).

X-Ray source:
- Amber: source is in use, X-Rays are emitted
- Green: source is ON, but there is no X-ray emission
- Light OFF: source is OFF
Shutter light indicator:
- Amber: shutter is open
- Green: shutter is closed – safe to open doors
- Light OFF: shutter is disabled
Door light indicators:
- Amber: doors are latched and/or unsafe to open
- Green: doors are unlatched, safe to open
IMS measurement operations status colors:
- Purple – initialized
- Green – idle
- Blue – translational move of the camera
- Sky blue – rotational move of the camera
- Amber – image in progress
- Off – IMS software is not open

Figure 5: Multi-section Patlite tower mounted horizontally at the top of the logger. These lights act as visual indicators of measurement operations, door(s), and X-Ray status.

The Table 1 below illustrates the status combinations:

Scenario	X-Ray source	Shutter/E-stop	Forward (FWD) Door	Aft Door	IMS Status
Subsystems powered, doors unlatched, IMS off	Off	Green	Green	Green	Off
IMS at idle, doors unlatched, shutter closed	Green	Green	Green	Green	Purple
Latch doors via IMS menu	Green	Green	Amber	Amber	Purple
Open shutter via IMS menu	Off?	Amber	Green	Green	Purple
X-rays ON, shutter closed, doors unlatched	Amber	Green	Green	Green	Purple
During imaging	Amber	Amber	Amber	Amber	Purple, then Blue at end

Table 1. Different Patlite status indicator combinations

Door Switches

Electronically-controlled safety locks have been installed on both the forward and aft doors. If either of these doors are open at the beginning of imaging, calibration or seasoning the c-RIO will disallow the process and warn the user about it. There are also indicator lights on the door lock electronics (Figure 6). Note that a lit red indicator means that the door is unlocked and can be opened. These switches are always energized and therefore are usually warm to the touch, but this is not an issue.

Figure 6: Electronic safety lock on the logger door

Emergency Stop Switch

There are two main Emergency Stop switches installed on the XSCAN, one for each source.

Main (in use) source (S/N: 135769488-A00001)

An emergency stop (e-stop) switch is located on the port side of the XSCAN along the top rail (Figure 7). When activated, i.e., the user hits the button, the e-stop switch cuts two circuits. One circuit runs straight to the source power supply and one circuit runs through the cRIO with the safety circuit. The e-stop switch opens the interlock on the XRB and the X rays go OFF. It also kills the MDrive and will immediately stop all motion.

Figure 7: X-ray logger Emergency Shut Off Switch.

Spare source (S/N: 132614727-A00001)

The emergency stop for the spare source is located near the spare source on aft end, starboard side near the bottom of the XSCAN. This switch cuts the power circuit to the spare source when pressed.

Figure 8: Emergency Shut Off Switch of the spare source

Thermal Management

The detector (camera) on the XSCAN logger can run warm when it is on. Additionally, the X-Ray source adds heat while producing X-rays: due to the low efficiency of the X-ray tube, most of the power it uses will be expended as heat. Optimally the camera should be operated at temperatures less than 40°C. The IMS software continuously monitors the camera and X-ray source temperatures and displays them on the main acquisition screen (Figure 9). Cooling modifications such as two air conditioners on the cabinet portion of the logger and directed fans on the camera itself help to keep things cool during operations. If the camera temperature exceeds 40°C, the temperature diagram (Figure 9) will flash. The user must stop using the instrument to allow the camera to cool down before resuming scanning. Note the AC units are connected to a drain and container that must be emptied periodically.

Figure 9: IMS temperature monitor sub-window for the source and the camera

Source temperature: A graphical temperature display is provided to monitor the temperature of the X-ray source. The source is usually at room temperature or below 30°C.
Camera temperature: A graphical temperature display is provided to monitor the temperature of the camera. The manufacturer recommends that the camera temperature should not exceed 40°C.

II. Procedures

Getting Started

Turning ON the XSCAN

The cRIO switch is always on, unless troubleshooting the instrument requires the cRIO to be reset. All other switches are off when the XSCAN is off.

If the XSCAN is completely shut down, a series of switches must be activated for the instrument to operate properly. The switches are located on two surge protector panels below the shielded cabinet (Figure 10). The top panel involves equipment running through ship’s power, and the lower panel handles equipment connected to a UPS. They should be turned on in the following order:

Lower Switches (connected to a UPS):

cRIO and Excelsys power supply
X Ray Source & Camera: to turn on the main X-Ray source and the camera
Patlite safety status lights

Upper Switches (connected to ship’s power):

M-drive 23 and 34
Power switch for the spare X-ray source (optional)
Power for the spare source’s safety light
AFT A/C*: to turn on the aft piezo air conditioner
FWD A/C*: to turn on the forward piezo air conditioner
Cab lite = Cabinet light: to turn on the cabinet light (optional)

*Only one A/C is required to be on in most situations. If the lab is warmer or if the XSCAN seems to be heating up, the second unit can be turned on.

Note: The computer and its monitors are plugged directly into the UPS. The computer must be powered down via Windows or the computer’s power button.

Figure 10: Switch board

Launching the IMS X-Ray Imager application

The IMS XSCAN software can be launched from the desktop icon (Figure 11). Before launching the IMS software, make sure that all Patlite sectors (except the one for IMS) are green. If IMS is launched before the instrument is fully on, it may generate communication issues between the IMS software and the cRIO safety system.

Figure 11: XSCAN Desktop Icon

At launch, the program begins the following initialization process:

Testing instrument communications (camera, X-ray source)
Homing the rotational actuator
Homing the linear actuator
Verify connectivity with the c-RIO safety system

After successful initialization, the main IMS-XSCAN window will appear (Figure 12).

If the computer has been restarted, the software will typically give a W-axis error when first opened. Close IMS and reopen the program and this error will clear itself.

Figure 12: XSCAN IMS Main Window

A Quick Introduction to the IMS Program Structure

IMS is a modular program. Individual modules are as follows:

INST plug-in: code for each of the instruments (source and detector)
MOTION plug-in: code for the motion control system
DAQ Engine: code that organizes INST and MOTION plug-ins into a track system

The XSCAN system, specifically, is built with one INST module (I_PI_Hama), one MOTION module (M_PI_M-Drive), and one DAQ Engine module (DAQ_PI_XSCAN).

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 four buttons on the IMS-UI window provide access to utilities/editors via dropdown menus as shown in Figure 13.

Figure 13: IMS Control Panel Drop down Menus

Initial Instrument Setup

XSCAN Configuration

Configuration values should be set during initial setup and by the technician or scientist(s). There should be no need to change these values unless the configuration file is corrupted or the hardware setup is changed. The logger will provide some default values automatically if the configuration file is missing or unreadable at startup.

XSCAN Instrument General Setup

To open the XSCAN instrument setup window (Figure 14), select Instruments > Camera: General Setup from the IMS panel menu (Figure 13). This window displays information about the source and camera hardware, primarily for metadata recording. The Table 2 below gives a description of the different settings. These settings are hard coded and cannot be changed by the user.

Name	Description	Meaning
True Pixel Pitch (μ)	Pixel pitch on the detector	48 µm for C12300-321
SID mm	Distance in mm from the focal spot on the source to the detector’s surface	Used to calculate magnification and blur
SOD mm	Distance in mm from the focal spot to the average height of a SHLF surface or the midplane of a WRND core	Used to calculate magnification and blur
OID mm	Distance in mm from the section half plane or WRND midplane to the detector surface	= SID - SOD
Magnification	Calculated magnification factor	= SID/SOD
Apparent Pixel Pitch (µ)	Pixel pitch corrected for magnification	= SOD/SID x true pixel pitch
Focal Spot Diameter mm	Diameter of the X-ray source’s focal spot in mm	0.5 mm for Spellman XRB
Unsharp Blur mm	Blurring in images are a result of focal spot size and system geometry	= OID/SOD x focal spot diameter
Scale Across px/cm	Across-core scaling	222.2 px/cm on split-core plane
Scale Along px/cm	Down-core scaling	254.1 px/cm on split-core plane

Table 2. XSCAN camera parameters

The shutter should be enabled and the air pressure should be selected for safety reasons: both buttons should be YES (Figure 14).

The user can set the time limit for the X-ray Auto off, i.e., the number of minutes when the X-rays will automatically be ramped down after the instrument is in the idle state with no action from the user. It is recommended to set a time of 15 min.

Click Accept to save the changes and write them to the configuration file. Click Cancel to revert to previous values.

Figure 14: XSCAN Parameters Window

X-Ray Power Settings

Prior to collecting X-Ray radiographs on whole rounds or section halves in the XSCAN, the user must set the imaging X-ray power (voltage and current). These are set during the calibration process.

kV: X-ray tube voltage. Maximum voltage for the source is 160 kV, minimum voltage is 35 kV. Lowering the voltage while maintaining the number of X-rays penetrating the core (longer exposure or higher current) will increase image contrast.
mA: X-ray tube current. The maximum allowable current is 2.1 mA. Maximum power for the source is 210 watts. Therefore, the source is either voltage limited or current limited as seen in Table 3 below. Increasing the current will increase contrast if voltage is kept constant.

Voltage (kVp)	Max Current (mA)	Wattage (calculated)	Power State
160	1.31	210	Voltage-limited
150	1.40	210
140	1.50	210
130	1.62	210
120	1.75	210
110	1.91	210
100	2.10	210	Current-limited
90	2.10	189
80	2.10	168
70	2.10	147
60	2.10	126
50	2.10	105
40	2.10	84

Table 3. X-ray source power ranges

Detector Calibration

Detector calibration should be done at the beginning of the expedition or whenever the power settings are changed. It is a quick and easy process to do.

To calibrate the detector, select Instruments> Camera: Calibrate from the main IMS menu (Figure 13). The calibration utility window will open (Figure 15). The purpose of this utility is to collect White and Dark images that will be used to perform offset and gain corrections for all images acquired with the camera at given power settings.

Figure 15: Detector Calibration user interface window. From this utility a user takes the Dark and White correction measurements after setting the track speed, which dictates the camera’s exposure.

Calibrating the Detector

Make sure the bore is empty and clean before starting a calibration.

Step 1: Dark Image Correction

The DARK image is normally made with the X-rays off to capture the electrical background noise of the detector (Figure 16, A).

To capture the dark image:

Click the Grab button (Figure 16, B) to take twenty Dark grabs, numbered 0 to 19. The “Current Grab Stacked” sub window will display the resulting dark grabs with its characteristic striping (Figure 16, C-1). When it is done, the “DARK Measured” indicator becomes green (Figure 16, C-2).

Figure 16: Taking the Dark correction image. Note the small DARK Measured LED is lit in the lower right corner.

Step 2: White Image Calibration

The WHITE image is taken with the X-rays on and the shutter open. We simulate motion by using the exposure of the camera since everything is stationary (this detector has no internal shutter). Changing the track speed will also update the exposure settings (Figure 17, A). The number of scans is automatically calculated from the chosen speed and exposure.

The WHITE image is used for the gain correction after the offset correction from the dark image is completed.

To capture the WHITE image:

Click “Update X-Ray” (Figure 17, B). A window will open (Figure 18).
Enter the desired power settings (Figure 18, A), and click “Apply Values” (Figure 18, B).

Figure 17: Taking the White Image Calibration. Note the small WHITE Measured LED is lit in the lower right corner.

Figure 18: Modifying X-ray power settings

2. Turn on the X-rays by toggling the X-rays ON button (Figure 17, C-1). The source will ramp up to power (Figure 19).

3. Open the shutter (toggle the Shutter button, Figure 17, C-2)

4. Click the Grab button (Figure 17, D). The WHITE Measured LED will light up (Figure 17, E-2) when the grabs finish. The “Current Grab Stacked” sub window will display the resulting white grabs with its characteristic white to grey pattern (Figure 17, E-1). The grey outside edges are the tube.

Figure 19: X-Rays ramping up for white calibration

5. Once acquisition is completed, check the saturation value (Figure 17, F) and confirm that saturation percentage is in the target range of 94-98%. To get more exposure within the image, the saturation values can be higher (100%). This will clip the data, but can produce a better image in denser materials. Adjust the exposure values (Figure 17, A) and repeat until user is satisfied.

6. Adjust the position of the blue left-hand mask bar if needed; this will be rare. XSCAN uses masking to eliminate the bore walls from our images. By default the mask width is set to 1600 pixels.

7. When you are satisfied with everything then click the Accept Changes button (Figure 17, G). This saves the calibration information to memory and to the configuration file.

Starting Measurements

Prior to imaging cores, especially at the start of an expedition, the user must perform a detector white-dark calibration at the chosen power settings (see Detector Calibration). Once this step is complete, the user may begin imaging.

Entering Sample Information

To take images, the user selects the Start button on the IMS main panel (Figure 13) to open the sample information window (Figure 20). This is where the user enters the imaging method and the sample ID for a section and initiates the measurement.

Figure 20: Section Information Window (default display)

Imaging Method

It is possible to measure either section halves or whole round sections. Select “SHLF-A” or “SHLF-W” in the Section Type box for sections halves, and “SECT” for WRND measurements. The selection will determine which imaging method presets are active. The available presets for the selected sample type on the left are highlighted/activated in light grey. The preset selected for the scan is highlighted in green (Figure 20, A). Note that this selection will affect how the sample id information is parsed and displayed when the user scans or selects a sample from LIMS.

Definition of the presets:

For Archive and Working halves

-Section half: only: Basic X-ray imaging of a full or partial section (angle is 0 degrees, camera is perpendicular to the section’s split surface)

-Section half: thickness: X-ray imaging of a full or partial section at 0 and 90 degrees to estimate the thickness of a section half.

-Section half: CT: the user can do multiple consecutive scans of a section at different evenly spaced angles without cropping the image between scans. It is possible to do CT-like imaging at angles from 0 to 180 degrees, with an angle step as low as 1 degree.

-Section half: custom: The user can do multiple consecutive scans of a section at evenly spaced angles. The user must crop the scanned imaged between each scan.

For Whole Round sections

-Whole Round: only: Basic X-ray imaging of a full or partial section (angle is 0 degrees)

-Whole Round: 0-90: X-ray imaging of a full or partial section at 0 and 90 degrees.

-Whole Round: CT: the user can do multiple consecutive scans of a same section at different angles evenly spaced without cropping the image between scans. It is possible to do CT-like imaging at angles from 0 to 180 degrees, with an angle step as low as 1 degree.

-Whole Round: custom: The user can do multiple consecutive scans of a same section at evenly spaced desired angles and crops the scanned imaged between scans.

Sample Entry Tabs

There are three tabs available on the sample information screen (Figure 20, B). Each provides a different method for entering the sample ID information (Figure 21).

Scanner: Scan the IODP barcode to enter the sample’s Text ID and Label ID values, using either a barcode gun or the barcode camera by the loading door (Figure 21, A).
LIMS: Select expedition, site, hole, core, and section values from a series of list boxes that are populated with data from the LIMS database (Figure 21, B).
Manual: Manually enter the sample’s Text ID and Label ID values and a length (Figure 21, C). The name fields will accept any name, but that does not guarantee the data will upload. The user must be careful to enter the name properly. If the name is incorrect files will be created, but it may not upload properly. The Text ID information must match an actual section in order for the data to upload. Click USE ME to update and validate the entries and enable the SCAN button.

Figure 21: Sample Information Window – A. Scanner (barcode gun or barcode camera) entry, B. LIMS entry, and C. Manual Entry

Scanned Interval Length

It is possible to scan either a full section or a portion of it.

The user can select the desired scan length by clicking on the ROI/FULL SECTION button on the right (Figure 20, C). Select full section to scan a section over its entire length (i.e., LIMS length). A user can scan a specific region of interest (ROI), by selecting the ROI option and setting the measurement interval in centimeters (start and end) to scan.

Positioning sections inside the XSCAN

Section position is important within the XSCAN unit. The unit is intended to only image sections up to 150 cm long.

Sections are loaded into the XSCAN by sliding the section into the aft door, bottom of the section first (Figure 22a). The top of a section should face the user, this is typically a blue end cap and where the label for the section will be. If imaging section halves, ensure that the surface of the core is level, i.e., horizontal while inserting the section. If imaging whole round sections, ensure that the double lines are facing up. This ensures that the XSCAN rotation angle matches that of the IODP orientation frame.

To position the section properly in the XSCAN imager, use the double ended core extraction tool (Figure 22a). Use the round flat end to push the section into the acrylic tube until the round stop contacts the outside edge of the XSCAN unit. The user must also be careful not to push sections to quickly into the XSCAN or they may slide further along the track than intended. The forked end of the extraction tool can also be used to rotate the section half to be normal to the X-ray beam if the section twists while being loaded.

Imaging sections longer than 150 cm

Sections longer than 150 cm require multiple images and adjustments to the sample positioning to capture the entire section. The user must first position the section as they would for sections under 150 cm and take an image. After the first image, the user must pull the section back until the top of the section is flush with the end of the acrylic tube and take a second image.

Retrieving Sections from inside the XSCAN

The fork end of the double ended extraction tool is used to retrieve sections. Insert the fork until you feel it touch the end of the section. A brisk short motion will pop the tines of the fork over the end cap and allow you to pull the section back towards you. If repeated attempts are not successful, rotate the fork 180° and try again. When retrieving section halves, the fork often needs to be rotated from horizontal to properly connect the tines to the end cap.

Short sections can be easily loaded into the XSCAN unit, but can be difficult to retrieve using the typical extraction tool. It can also be difficult to retrieve cores with extender caps. The user may use the U-shaped extractor tool to scoop under or over the top of a section and pull it out (Figure 22b). A string tied to the section can also work well on small sections such as core catchers. Loop the string around the top of the core, tighten the loop, and put the knot under the core so the weight is on the string. When pulling the core out, gently pull the string. If none of these methods work, the user may push the section out from the forward end of the XSCAN.

Figure 22a: Positioning a section inside the XSCAN

Figure 22b: Using the U-shaped extractor

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