A subsea apparatus for measuring gamma radiation, comprising: a plurality of detectors, each detector comprising: a scintillating material for emitting light in response to incident radiation, and a photodetector for receiving light emitted by the scintillating material and outputting electrical pulses in response to light received from the scintillating material; and a power supply for supplying power to a plurality of said photodetectors, characterized in that the plurality of photodetectors is connected in parallel to the power supply and a capacitor is connected across terminals of the power supply for stabilising the voltage to the parallel photodetectors, and wherein the apparatus further comprises a data acquisition part configured to relate an amplitude of the electrical pulses to an energy associated with the incident radiation allowing the apparatus to take into account an intrinsic variation in gain between the plurality of photodetectors, wherein the apparatus is further configured to compensate for the intrinsic variation in gain between the plurality of photodetectors connected to the power supply by counting the number of electrical pulses having the amplitude within a specified measurement range and adapting the measurement range of the electrical pulses to a photopeak for each photodetector using a software tool, wherein the subsea apparatus comprises a plurality of said power supplies, wherein each power supply is arranged to supply power to a respective plurality of parallel photodetectors, each power supply having an associated capacitor which is connected across terminals of the associated power supply for stabilising the voltage to the associated plurality of parallel photodetectors. a scintillating material for emitting light in response to incident radiation, and a photodetector for receiving light emitted by the scintillating material and outputting electrical pulses in response to light received from the scintillating material; and a power supply for supplying power to a plurality of said photodetectors, characterized in that the plurality of photodetectors is connected in parallel to the power supply and a capacitor is connected across terminals of the power supply for stabilising the voltage to the parallel photodetectors, and wherein the apparatus further comprises a data acquisition part configured to relate an amplitude of the electrical pulses to an energy associated with the incident radiation allowing the apparatus to take into account an intrinsic variation in gain between the plurality of photodetectors, wherein the apparatus is further configured to compensate for the intrinsic variation in gain between the plurality of photodetectors connected to the power supply by counting the number of electrical pulses having the amplitude within a specified measurement range and adapting the measurement range of the electrical pulses to a photopeak for each photodetector using a software tool, wherein the subsea apparatus comprises a plurality of said power supplies, wherein each power supply is arranged to supply power to a respective plurality of parallel photodetectors, each power supply having an associated capacitor which is connected across terminals of the associated power supply for stabilising the voltage to the associated plurality of parallel photodetectors.