Simulations of a Scintillator Compton Gamma Imager for Safety and Security

Silicon Photomultiplier-Based Compton Telescope for Safety and Security (SCoTSS)

“…THE IMAGER An extensive design phase has been conducted to determine the optimal imager materials and geometry [18], [19]. We considered the following parameters: 1) Total Size: The imager total weight and exterior volume were constrained by the requirement that teams composed of one or two people should be able to lift the imager from a transport container into a survey vehicle or platform, without machine assistance.…”

“…Despite the large initial-state electron effects on image resolution of high-Z scintillator materials, materials like NaI(Tl), CsI(Tl) and LaBr 3 (Ce) still perform better than organic scintillator due to their much superior energy resolution [19]. The SensL SiPM which we use has a peak light sensitivity at 480 nm, and therefore CsI(Tl), with its relatively high peak wavelength of emission, was chosen for the material of the scatter detector.…”

“…The mobile survey workhorse, NaI(Tl), which is well matched in peak wavelength of light emission to standard PMTs, was selected for the rear detector. Our aim has been to develop a prototype for eventual commercialization and adoption by nuclear emergency response teams and therefore, although an earlier study had determined that its performance was optimal [19], LaBr 3 (Ce) was ruled out for either component due to price constraints.…”

“…We have optimized the total thickness of the scatter detector by choosing the thickness which maximizes the probability for an incoming gamma ray of energy around 1 MeV to scatter once, and then exit the scatter detector, according to the approach described in [19].…”

“…We used EGSnrc [21], [22] simulation studies to balance the conflicting requirements of high absorption probability and good position precision by choosing the depth of the absorber detector which gives the desired image precision in the shortest time [19].…”