Dual-energy fast neutron imaging using tunable short-pulse laser-driven sources.

A novel dual-energy fast neutron imaging technique is presented using short-pulse laser-driven neutron sources to leverage their inherent adaptive spectral control to enable 3D volume segmentation and reconstruction. Laser-accelerated ion beams incident onto secondary targets create directional, broadband, MeV-class neutrons. Synthetic radiographs are produced of multi-material objects using ion and neutron spectra derived from analytic and numerical models. It is demonstrated that neutron images generated from small changes to the neutron spectra, controlled by altering the initial laser conditions, are sufficient to isolate materials with differing attenuation coefficients. This is first demonstrated using a simplistic combinatorial isolation method and then by employing more advanced reconstruction algorithms to reduce artifacts and generate a segmentation volume of the constituent materials.

New Directions for dMiCE - a Depth-of-Interaction Detector Design for PET Scanners.

Our laboratory has been developing a depth-of-interaction (DOI) detector design based on light sharing between pairs or quadlets of crystals. Work to date has been utilizing 2×2 mm cross section crystals carefully positioned on a multi-anode PMT. However, there is still significant light sharing in the PMT glass envelope and current PMT designs do not allow one-on-one coupling for arrays of smaller cross section crystals. One-on-one coupling is optimal for implementing the DOI estimator. An alternative to PMTs is to take advantage of progress in fabrication of metal resistive-layer semiconductor photodetectors to provide arrays with one-on-one crystal coupling. We report on our initial tests of one manufacturer's devices. The photodetector (MAPD) and scintillator combination (LFS-3) are both products of Zecotek. The LFS-3 crystal is a variant of LFS that has a better spectral match to the MAPD. Measurements show performance equivalent to or better than that obtained with PMTs and LSO, LFS, or LYSO crystals. For example, 2×2×20 mm crystals are providing 11% energy resolution. The high gain of such devices allow flexibility in designs for both the array and the supporting electronics. We are proceeding with the dMiCE development based on the use of MAPD and LFS-3 arrays.