  Localised response of a sensitive light detector, such as Hamamatsu H9500
multi anode photomultiplier tube (MAPMT), is of vital importance for
coded-aperture imaging systems. When coupled with a suitable sensitive detector
(e.g. EJ-299-34 plastic scintillator), output signals of the MAPMT can be
retrieved to infer the interaction location in the pixelated scintillator.
Given the number of anodes in H9500 (256), significant processing power would
be necessary to handle each pulse individually. Therefore, a readout
electronics system was developed, based on resistive network approach, which
reduces the number of output signals to individual X and Y coordinates, and
subsequently allows particle identification. Coordinates retrieved in this
manner can be analysed in real time and used to infer the two-dimensional
location. Particle type can be also exploited by pulse shape discrimination
(PSD) application to the scintillator response. In this study, 169 anodes were
used (due to coded-aperture design rules), and reduced to two X and Y output
signals. These have been digitised using a bespoke FPGA based two channel
14-bit 150 MSPS digitiser. The digital data are transferred to a host
application using UART to USB converter operating at 12 Mbits/s. Promising
results have been observed when the scintillator's response was tested in
single particle field of Cs-137. However, further tests performed in the
mixed-field environment of Cf-252 suggest that faster digitiser may be required
to obtain the required PSD performance.
