Neutron Imaging for the Hydrogen Economy Neutrons see material differently than x-rays The fine details of the water in this Asiatic Lily are clear to neutrons even in a lead cask Subtle changes in the water distribution inside a running fuel cell impact performance and durability Neutron Imaging measures these small changes at video frame rate

Radiography X-ray radiograph Photo Neutron Radiographs

Neutrons are an excellent probe for hydrogen in metal since metals can have a much smaller cross section to thermal neutrons than hydrogen does. Comparison of the relative size of the x-ray and thermal neutron scattering cross section for various elements. x-ray cross section HDCOAlSiFe neutron cross section Sample t  N – numerical density of sample atoms per cm 3  I 0 - incident neutrons per second per cm 2   - neutron cross section in ~ cm 2  t - sample thickness Why Neutrons

How an image is acquired Point Source Sample (a small motor in this case Neutron sensitive screen

Neutron scintillator Converts neutrons to light 6 LiF/ZnS:Cu,Al,Au Charged particles from nuclear reaction come to rest in ZnS and cause scintillation of green light Resolution limited to about 0.2 mm New technology has reduced this to mm 6 Li absorbs neutrons, then promptly splits apart into energetic charged particles Neutron absorption cross section for 6 Li is huge (940 barns) Nuclear reaction produces energetic charged particles Charged particles come to rest in 10 – 15 microns in the ZnS ZnS:Cu,Al,Au produces green light Unfortunately light easily propagates through the screen expanding to a 200 micron blob that degrades the spatial resolution 6 Li + n 0  4 He + 3 H MeV Scintillator Neutrons in Green light out 0.3 mm thick 20 % efficient

Real-Time Detector Technology Amorphous silicon Radiation hard High frame rate (30 fps) 127 micron spatial resolution Picture is of water with He bubbling through it No optics – scintillator directly couples to the sensor to optimize light input efficiency Data rate is 42 Megabytes per second (160 gigabytes per hour) Most users opt for lower data rates due to the enormous pressure to download the data during and after the experiment Neutron beam scintillator aSi sensor Side view Readout electronics Scintillator aSi sensor Front view Helium through water at 30 fps

How an image is acquired Point Source Sample (a small motor in this case Neutron sensitive screen

All Slice Reconstructions 3D Reconstruction Tomography Radiographs Slice Reconstruction