Multimodal Advanced Radiography Station
MARS | CG-1D | HFIR
Experiment planning
The following steps should be taken to plan a neutron imaging experiment at MARS and/or VENUS.
- Discuss proposed measurements with instrument scientists at MARS (https://neutrons.ornl.gov/mars/team) and/or VENUS (https://neutrons.ornl.gov/venus/team).
- Choose an imaging modality. Table 1 summarizes the available modalities, common applications, and at which instrument to conduct those measurements.
Technique Principle Example Applications Instrument selection Attenuation-Based Radiography Attenuation contrast Hydrogen mapping, fuel cell operation, cultural heritage, materials screening MARS: highest sensitivity and spatial resolution
VENUS: highest penetration and wavelength discriminationComputed Tomography (CT) 3D reconstruction from projections Corrosion/hydrogen mapping, battery electrode degradation, porous materials MARS: fastest CT or highest spatial resolution
VENUS: hyperspectral CT, higher penetrationBragg-Edge Imaging (BEI) Crystallographic edge absorption Residual stress mapping, phase distribution in metals VENUS only Phase-Contrast Imaging Refractive index differences Soft tissues, low-Z materials, porous foams MARS: qualitative only (under development at VENUS) Polarized Neutron Imaging Spin-dependent scattering Magnetic domain imaging, superconductors MARS only (under development at VENUS) Dark-Field Imaging Small-angle scattering effects Fiber composites, microcrack detection, foams, heterogeneous particle/void distributions MARS: qualitative only (under development at VENUS) Resonance Imaging Nuclear capture in epithermal range Nuclear materials VENUS: 2D only (3D under development) In Situ/Operando Imaging (time-resolved imaging) Controlled environment operation Battery cycling, phase transitions/solubility, fuel cell operation, fluid dynamics MARS: fastest
VENUS: wavelength discrimination, cycling motion, event mode measurementsTable 1. Image modalities - Estimate the total neutron transmission through the sample and its container,
- Use the online transmission calculator: https://neuit.ornl.gov/transmission
- Aim for minimum 20-25% total transmission for CT and 15-20% contrast for best results
- Figure 1 shows the total transmission through common materials encountered at MARS
- Determine the minimum spatial and temporal resolutions required to answer the research question(s).
- Standard setup: ~16 μm pixel size (~45 μm effective resolution under ideal conditions), 8.6 cm x 8.6 cm field of view, 30-to-60s exposure
- Figure 2 summarizes the currently available detector systems
- Table 2 summarizes the detection systems with exposure times
- Total CT time T is a function of sample (effective) diameter D, pixel size d, and exposure time t: T=(π/2 D/d)t where the quantity in parentheses is the number of projections collected at incremental angles.
- Two common sample sizes: (ex. 1) 6 mm diameter and (ex. 2) 25.4 mm diameter
# Detector name Camera model (manufacturer) Max FOV [cm2] Pixel size, d [μm] Best spatial resolution [μm] Typical exposure time, t [s] Max fps @16-bit CT time for ex. 1 [hrs] CT time for ex. 2 [hrs] 1 QHY-S x1 3.6 x 2.4 3.8 10-15 900* 1 622 2631 2 QHY-S x0.5 QHY600 sCMOS (QHYCCD) 5.0 x 5.0 7.6 20-25 300* 1 105 441 3 QHY-L 8.6 x 8.6 16 ~50 30-90* 1 6-16 23-64 4 Marana-6 Andor Marana 4.2B-6 sCMOS (Oxford Instruments) 5.6 x 5.6 28 ~90 30 74 3 13 5 Marana-11 Andor Marana 4.2B-11 sCMOS (Oxford Instruments) 9.0 x 9.0 43 ~120 30 24 2 8 Table 2. Current MARS detectors and their performance. *Add ~2.5 seconds per acquisition for data transfer. Red cells indicate prohibitive CT time, yellow is possible, and green is routine.
- Make note of all materials and equipment that will be within 30cm of the beam and enter them as samples in IPTS. For example, battery cell holders, sample containers/frames, shielding, tubing/lines, power and communication cables. NOTE: once taken into HFIR, all materials (samples, holders, equipment, etc.) require release by radiological control technician (RCT), and anything within 30cm of the beam requires activation calculations along with RCT survey.
- Custom equipment must be discussed with instrument staff well in advance of beam time, and equipment must be inspected and approved by appropriate ORNL safety personnel before use. Be prepared to write a job hazard analysis (JHA) with instrument staff, which includes steps of equipment operation, their associated hazards, and actions to mitigate those hazards.
- Sample & equipment shipping: refer to the online shipping guide for when, how, and where to ship as well as disposition information.
- X-ray imaging/CT (https://neutronimaging.ornl.gov/capabilities/) may be available provided that
- Measurements are feasible, safe, and equipment is operational
- Instrument staff have time and resources to perform measurements
- Samples are shipped well in advance of neutron beam time, coordinated with instrument staff
Running the experiment
Users will be trained to safely operate MARS equipment and will be provided with a list of contacts for any issues. Here are some useful links to control or monitor an experiment remotely.
- Remote beamline controls through https://analysis.sns.gov/:
- Launch Session
- Login using XCAMS credentials
- Go to Applications (top left), Remote Experiments, and then CG-1D MARS
- Login again using XCAMS
- Open a terminal and type css to launch beamline controls (may need to select a layout from the dropdown menu at the top-left)
- Access to the sample environment computer (e.g., to control the Potentiostat) is done within this second instance and going to Applications > Sample Environment. Username and password will be provided by instrument staff.
- Instrument webcam (must be on ORNL visitor network), username and password will be given by instrument staff.
- Online catalogue (OnCaT) with all collected data (public website, requires XCAMS login), wait ~5 minutes for data transfer.
- Beamline monitoring to track process variable (PV) values (public website, requires XCAMS login).
- Communicate with instrument staff primarily using Slack. Please go to https://ornlneutronsciences.slack.com/ in your web browser and login using your XCAMS credentials to be added to the workspace. Provided you are on the proposal with the same email you will be automatically added to the channel once you have joined the workspace.
After the experiment
All materials and equipment that were within 30cm of the neutron beam are considered radioactive materials and will require detailed neutron activation calculations, including complete composition, mass, and exposure time, as well as release by a radiological control technician (RCT). Some materials such as steel will remain activated for months to years.
Shortly after the experiment, all data will be normalized, and CT data will be reconstructed. Instrument staff will update the Slack channel with final data location(s).
- Additional data processing such as image/pixel binning, registration, and other manipulations can be performed by users using the available Jupyter notebooks on the analysis cluster: https://analysis.sns.gov/ and going to Applications > Analysis-imaging > Jupyter Notebooks. Tutorials are available online at https://neutronimaging.ornl.gov/tutorials/imaging-notebooks/
- Additional or customized notebooks may be available upon reasonable request from the Computer Instrument Scientist (CIS): https://neutrons.ornl.gov/mars/team
- Amira/Avizo visualization and segmentation software may be available for limited use, based on availability of licenses.
Note that X-ray imaging/CT after neutron irradiation at MARS is challenging and may not be possible. Discuss these needs with instrument staff.
Publications and reporting requirements
Intent to Publish: As a condition for performing nonproprietary research, the US Department of Energy requires users to publish results from their research. Authorship of publications based on research from these facilities should reflect the normal considerations of recognizing collaborations. It is also important to take into account the considerable efforts of instrument scientists in their role of designing, constructing, and/or operating the instrument and related facilities. Results are typically published in peer-reviewed journals, proceedings, or presentations at technical conferences. Proprietary users are not required to publish.
Credit Line: All publications based on work done in whole, or in part, at the Spallation Neutron Source or the High Flux Isotope Reactor at Oak Ridge National Laboratory should acknowledge the facility (or facilities) with this required statement:
This research [or, A portion of this research] used resources at the High Flux Isotope Reactor [and/or Spallation Neutron Source, as appropriate], a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. [If applicable: The beam time was allocated to [Instrument] on proposal number IPTS-XXXXX.X.]
In addition, users are asked to credit the instrument(s) used in the body of the paper.
Contribute to Our Publication Records: After your results have been published, submit the paper’s citation information via the Publications Portal.
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