Introduction to Neutron Radiography and Computed Tomography Hassina Bilheux Neutron Imaging Scientist Cellphone #: 865-384-9630 June 19th, 2019 Neutron School Team: Shawn Zhang Jean Bilheux Hassina Bilheux ORNL is managed by UT-Battelle for the US Department of Energy Imaging is a Growing Part of the ORNL Neutron Sciences Program High Flux Isotope Reactor (HFIR) Spallation Neutron Source Intense steady-state neutron flux (SNS) and a high-brightness cold neutron World’s most powerful Techniques such as Bragg- source accelerator-based neutron edge imaging are being source Dedicated Imaging implemented on BL3 SNAP Instrument (CG-1D) diffractometer (VENUS is Steadily improving capabilities the future imaging beamline) Expanded support 2 Bilheux - Imaging Neutrons Measure Structure and Dynamics Neutron Diffraction Neutron Scattering Neutron Microscopy Neutron Imaging You can Fluid interactions in directly see plant- groundwater the structure. systems 50-100 mm routinely available Soil-root SANS used to interface 25 mm available withconstruct trade protein- off in (rhizosphere) kinase A (PKA) field-of-view and acquisition times25 mm Neutron diffraction of D sorption 50 mm Computed 2 tomography in Cu3[Co(CN)6]2 100 mm 200 mm 300 mm Characterization of biological membranes, colloids, In Vivo Study of Embolism Nuclear and electronic density 400 mm Ice/water segregation in in enzymes porosity, etc. Formation permafrost structures Inferred structure (indirect) Direct structure 500 mm 10-11 10-9 10-7 10-5 10-3 Dimension (meters) Spatial 0.1Å 1.0nm 0.1mm 10.0mm resolution1mm is limited! 3 Bilheux - Imaging Neutrons can detect light elements such as H buried in heavy elements such as Fe Neutron Radiograph X-ray Radiograph Isotope Sensitivity Courtesy of E. Lehmann,PSI (important for soft matter studies) [M. Strobl et al., J. Phys. D: Appl. Phys. Neutron Radiograph of Neutron CT of an 42 (2009) 243001] Rose in Lead Flask Inconel Turbine Blade 4 Bilheux - Imaging HFIR CG-1D Imaging has a broad scientific portfolio Soft Matter and Materials for Materials Polymers, 3% infrastructure, 3% degradation, 3% Composites, 3% Biomass and Materials science - Biofuels, 3% General, 17% Porous media, 6% Nuclear Energy materials , materials, 6% 11% Medical applications, 6% Phase Industrial transformations/kin applications , 6% etics, 11% Earth and Fluids , 9% environmental Life science , 9% science, 6% 5 Bilheux - Imaging Neutron imaging supports applied research with academia, industry and government agencies 6 Bilheux - Imaging Game #1: Can you guess what this neutron radiograph represents? 7 Bilheux - Imaging What is imaging? • Imaging is the visual representation of an object: photography, cinematography, medical imaging, X-ray imaging, thermal imaging, molecular imaging, neutron imaging, etc. • Digital Imaging is a field of computer science covering images that can be stored on a computer as bit-mapped 8 imagesManaged by UT-Battelle for the U.S. Department of Energy Image Modalities and Imaging Science & Technology throughout Nobel Prize history • 1901: Roentgen, FIRST Nobel Prize in Physics, Discovery of X-rays • 1932: Chadwick, Nobel Prize in Physics Discovery of Neutrons • 1979: Cormack and Hounsfield, Nobel Prize in Medicine, Computed Tomography (CT) • 1986: Ruska, Binnig, Rohrer, Nobel Prize in Physics, Electron Microscopy • 2003: Lauterbur and Mansfield, Nobel Prize in Medicine, Magnetic Resonance Imaging (MRI) • 2009: Boyle and Smith, Nobel Prize in Physics, Imaging semi-conductor circuit, the CCD* sensor 9 Managed by UT-Battelle • (*)for the Charge U.S. Department-Coupled of Energy Device Early neutron imaging measurements • Neutron Imaging started in the mid 1930’s but only during the past 30 years has it come to the forefront of non-destructive testing Discovery of neutron in 1932 by Chadwick First neutron radiograph in 1935 Left to right: Pressure gauge with metal backplate; fire hydrant and test tubes filled with H2O and D2O imaged with gamma-rays (top) and neutrons (bottom) [ Kallman and Kuhn, Research 1, 254 (1947) ] • Dedicated world class imaging user facilities such as NIST, PSI, HZB, FRM-II, J-PARC and at many worldwide universities • World conferences and workshops being held regularly • Growing worldwide user community 10 Managed by UT-Battelle for the U.S. Department of Energy Multiple scattering and low detector spatial resolution [ J. Anderson et al., Br. J. Radiol. 37, 957 (1964) ] 11 Managed by UT-Battelle for the U.S. Department of Energy Today: Comparison microscopy/microCT and neutron radiography • 92% of the pixel intensities agreement between histological and neutron 12 Managed by UT-Battelle Watkin, K. et al., Neutron Imaging for the U.S. Department of Energy and Applications, Springer, 2009. Quantitative Neutron Imaging Lambert-Beer Law: m is the attenuation coefficient I() − ()m x and x is the thickness of the T == e sample I0 () () is the material’s total N A t ()()= t m cross section for neutrons, is M its density, NA is Avogadro’s number, and M is the molar mass. CCD Camera Aperture I0 I Light Mirror Neutron at 45° Source Neutrons 13 Bilheux - Imaging Sample Scintillator Light-tight Box Data Normalization for Imaging • 2D – Radiography I()()i, -j DF i, j – Normalization I ()i, =j N OB()()i, -j DF i, j Normalized Image 1 - Image Dark Field = 0 Transmission - 14 Managed by UT-Battelle Open Beam Dark Field for the U.S. Department of Energy Computed/Computerized Tomography (CT) • Several techniques: – Filtered Back Projection • Radon transform • Works well with high signal to noise ration measurements • Easy-to-use commercial, semi-automated software available • Quick – Iterative Reconstruction • Direct approach • Less artifacts • Can reconstruct incomplete data • High computation time 15 Managed by UT-Battelle for the U.S. Department of Energy Computed/Computerized Tomography (Filtered Back Projection) Raw Data: Normalized Data: Sinograms: Slices: 3D reconstruction: 2048x2048 pixels, 2048x2048 pixels, 2048x721 pixels, 2048x2048 pixels, 2048x2048x2048 ~800 projections ~800 projections 2048 files 2048 slices voxels Transmission ~910 Counts ~32760 0 1 0 Transmission 1 0 Attenuation ∞ Turbine Blade CT Video 16 Bilheux - Imaging available here Detection of “imaging” neutrons • Scintillator-based techniques such as 6Li(n,α) 3H – Good signal-to-noise (SNR) ratio – Large Field Of View (FOV) and 0.01 to hundreds of seconds images – BUT spatial resolution limited by the dissipation of particles – Can take a lot of neutron flux! CCD 1,1 1,2 1,3 … … 1, ny Lens 2,1 2,2 2,3 Aperture… of … 2, ny Sample of diameter D thickness x 3,1 3,2 … … … 3, ny I I Collimator 0 … … … … … …, Source nx nx, 1 nx, 2 nx, 3 … … nx, Mirror ny L Scintillator Each pixel is coded using n-bit. 17 Bilheux - Imaging 16-bit = pixel value is between 0 and 65535 Detection of “imaging” neutrons (cont’d) • Pixelated detectors – Micro-Channel Plate (MCP) – In the direct path of the beam Courtesy of Prof. A. Tremsin, UC- – Limited FOV for high spatial resolution MCPs Berkeley • 1.4 cm x 1.4 cm at ~ 15 microns – Encodes events at x, y position and time of arrival, at high temporal resolution ~ 1 MHz – Detection efficiency has improved for both cold (~70%) and thermal (~50%) energy range – Absence of readout noise – Not as gamma sensitive – Becoming commercial http://www.novascientific.com/neutron.html – BUT: works in relatively low-signal beam! 18 Bilheux - Imaging CG-1D: Cold Neutron Imaging Beamline at HFIR The CG-1D neutron imaging beamline is designed to probe structural features of length scales between ~ 25-100 µm and a few mm and kinetic changes on time scales between a few µs (repetitive motion events) to hours across a wide variety of subjects (e.g., batteries, engineering components, geological systems, biological systems, archeology and condensed matter). 19 CG-1D Neutron Imaging Facility (HFIR) 2.5E+06 Light Neutrons 2.0E+06 Scintillator 1.5E+06 Neutron Counts Neutron 1.0E+06 Detector Lens 5.0E+05 0.0E+00 0 2 4 6 8 10 Wavelength (Å) CCD Neutron wavelength distribution at CG-1D Detector assembly (side view) 20 Bilheux - Imaging Conventional Neutron Imaging Techniques at Steady-State (HFIR) Sources • Radiography Routinely available at CG-1D • Tomography • Stroboscopic Imaging Available at CG-1D • Imaging of processes that happen fast using the MCP detector • Polarized Neutron Imaging Newly implemented at • Monochromatic Imaging CG-1D • Grating Interferometry (Phase and Dark Field Imaging) – Under development – Increased spatial resolution and different contrast mechanism (less than 20 mm) 21 Bilheux - Imaging Neutron Imaging Techniques at pulsed sources (SNS) • Wavelength-dependent (or Time-of-Flight) imaging – Contrast enhancement Available at SNS SNAP – Bragg edge using the MCP detector – Resonance Imaging/Spectroscopy • Stroboscopic imaging – SNS has a natural clock • Neutron Imaging at energies not accessible at reactor facilities – Mainly bio-medical applications 22 Bilheux - Imaging Resonance imaging allows isotopic mapping at the SNS MCP detector Modular Pb shielding Table supporting the Pb shielding Photograph of the 4-in thick lead shielding and support table at the SNAP beamline 2D resonance imaging measurement of tantalum foil during testing of the lead shielding. The blue data points are the calculated ideal spectrum and with the MCP detector. the red show the measured spectrum. ✓ Measurements performed at SNS with the micro-channel plate (MCP) detector. ✓ Technique works great up to neutron energies of ~ 300 eV (heavier elements). ✓ However,