The magnitude of the anode current of a photomultiplier tube is influenced by various factors,
Cathode integral sensitivity:
Definition: Cathode integral sensitivity refers to the magnitude of the cathode current caused by white light shining on a photocathode per unit luminous flux, commonly expressed in mA/Lm.
Correlation: The cathode integral sensitivity directly determines the response ability of the photomultiplier tube to light signals. The higher the integral sensitivity, the greater the current generated by the photocathode under the same lighting conditions, which in turn affects the magnitude of the anode current.



Magnification factor:
Mechanism: The photomultiplier tube achieves electron amplification through a multiplier electrode. The multiplier will emit more secondary electrons entering and exiting, and after the incident electrons are multiplied by an N-th order, the photoelectrons will be amplified by an N-th power.
Impact: The magnitude of the amplification factor directly determines the degree to which the photomultiplier tube amplifies the photoelectrons, thereby affecting the magnitude of the anode current. The higher the magnification, the greater the anode current.

Anode voltage:
Function: Anode voltage is an important parameter that affects the working state of photomultiplier tubes. It determines the electric field strength between the doubling poles, which in turn affects the electron doubling process.
Correlation: The higher the anode voltage, the stronger the electric field between the doubling electrodes, the more significant the electron multiplication effect, and the greater the anode current. However, excessive anode voltage may lead to unstable anode current and even damage the photomultiplier tube.
Dark current:
Definition: Dark current refers to the small current that still exists on the anode of a photomultiplier tube in the absence of light. It mainly consists of the leakage current between the photocathode and each secondary electron emitter and anode, as well as the thermal current formed by the hot electron emission from the photocathode and each secondary electron emitter.
Impact: Although the dark current itself is small, it will superimpose on the anode current, affecting the measurement of the anode current. Therefore, when measuring anode current, the influence of dark current needs to be considered.



Load of external circuits:
Mechanism: The anode current output of the photomultiplier tube needs to be connected to an external circuit for subsequent processing. The load characteristics of external circuits can affect the magnitude of anode current.
Correlation: Reasonable circuit design and load matching can ensure stable anode current output of photomultiplier tubes. If the load is not matched or the circuit design is unreasonable, it may cause instability or distortion of the anode current.

The magnitude of the anode current of a photomultiplier tube is influenced by various factors such as cathode integral sensitivity, amplification factor, anode voltage, dark current, and external circuit load. In practical applications, it is necessary to comprehensively consider these factors based on specific requirements and environmental conditions to optimize the performance of photomultiplier tubes.