Development of a Portable, Tileable, Dual-Particle Radiography System

A scalable, portable, multi-particle neutron radiography device has been developed using commercial-off-the-shelf-parts. The IDEAS ROSSPAD readout module was selected for use in developing the radiography panel due to its single-wire Power-over-Ethernet (PoE) connectivity and its tileable form factor. Each ROSSPAD detector is paired with an 8 by 8 array of 6-mm-pitch Sensl J-Series silicon photomultipliers (SiPMs). With both single and multi-ROSSPAD testing, a detection package consisting of a 3-mm-thick sheet of EJ-200 plastic scintillator and a 3-mm-thick sheet of acrylic light spreader was coupled to the SiPM board face. After both quality assurance of the detector packages and the calibration of the raw data from the ROSSPADs, sub-SiPM spatial resolution was achieved. For the single- ROSSPAD setup, modulation transfer functions (MTFs) showed spatial resolutions of 2.32 line pairs per centimeter at 10% MTF for gamma rays and 3.35 line pairs per centimeter at 10% MTF for neutrons. The multi-ROSSPAD setups performed similarly with gammas at 2.09 line pairs per centimeter at 10% MTF, while the neutron images lost some spatial resolution with 10% MTF values ranging from 1.30 to 1.46 line pairs per centimeter. Based on the physical characteristics of the board, the raw board spatial resolution sits at 0.833 line pairs per centimeter, meaning all of the methods developed could resolve an object at a sub-SiPM pitch spatial resolution. Additionally, changes to the cutoff values for the full-panel radiography system showed little change to the spatial resolution of the full-panel images, suggesting that the loss is spatial resolution is external to the data collection outside of the number of events recorded. Overall, this research resulted in the development of a state-of-the-art scalable neutron radiography system.