Temperature compensation for photomultiplier tube

A method comprising:

• a gamma sensor generating a light signal in response to receiving gamma radiation;
• a photo multiplier tube (PMT) receiving the light signal and generating a PMT signal in response to receiving the light signal;
• supplying a voltage to operate the PMT, wherein a magnitude of the PMT signal depends on a magnitude of the supplied voltage;
• a temperature sensor generating a temperature signal with a magnitude that depends on a temperature sensed by the temperature sensor, wherein the temperature sensed by the temperature sensor is substantially equal to a temperature of the PMT;
• modifying the temperature signal;
• adjusting the magnitude of supply voltage based on a magnitude of the modified temperature signal;
• wherein modifying the temperature signal comprises:
• a first op-amp generating a buffered temperature signal as a function of the temperature signal;
• a second op-amp generating the modified temperature signal as a function of the buffered temperature signal.

An apparatus comprising:

• a gamma sensor configured to generate a light signal in response to receiving gamma radiation;
• a photo multiplier tube (PMT) in optical communication with the gamma sensor, wherein the PMT is configured to receive the light signal and generate a PMT signal in response to receiving the light signal;
• a voltage source coupled to the PMT and configured to provide a supply voltage to the PMT, wherein a magnitude of the PMT signal depends on a magnitude of the supply voltage;
• a temperature sensor positioned near the PMT and configured to generate a temperature signal with a magnitude that varies with a temperature sensed by the temperature sensor, wherein the temperature sensed by the temperature sensor is substantially equal to a temperature of the PMT;
• a signal conditioner configured to modify a magnitude of the temperature signal to create a modified temperature signal;
• a control circuit coupled between the voltage source and the signal conditioner;
• wherein the control circuit is configured to receive the modified temperature signal and generate a control signal for adjusting the magnitude of supply voltage based on the modified temperature signal;
• wherein the control circuit comprises:
• a summing circuit for adding the modified temperature signal and a divided version of the supply voltage to generate an added signal;
• a compare circuit for comparing the added signal to a reference voltage;
• wherein the compare circuit generates the control signal in response to comparing the added signal to the reference voltage.