  A mini-PET style detector system is being developed for a plant imaging
application with a compact array of silicon photomultipliers (SiPM) replacing
position sensitive photomultipliers (PSPMT). In addition to compactness, the
use of SiPMs will allow imaging setups involving high strength MRI-type
magnetic fields. The latter will allow for better position resolution of the
initial positron annihilations in the plant tissue. In the present work,
prototype arrays are tested for the uniformity of their response as it is known
that PSPMTs require significant gain compensation on the individual channels to
achieve an improved uniformity in response. The initial tests indicate a high
likelihood that the SiPM arrays can be used without any gain compensation.
