Voltage division circuit for a photomultiplier tube

A voltage division circuit for a photomultiplier tube which includes:

• a photocathode which emits photoelectrons in response to light incident thereon;
• a first dynode portion having at least one dynode, said first dynode portion receiving the photoelectrons emitted from said photocathode, multiplying the photoelectrons and emitting multiplied photoelectrons;
• a second dynode portion having at least three dynode, said first dynode portion receiving the multiplied photoelectrons emitted from said first dynode portion, multiplying the multiplied photoelectrons and emitting further multiplied photoelectrons;
• a third dynode portion having two or more dynodes, said third dynode portion receiving the multiplied photoelectrons emitted from said second dynode portion and emitting further multiplied photoelectrons;
• and
• an anode receiving the further multiplied photoelectrons emitted from said third dynode portion,
• the voltage division circuit which supplies relevant voltages to said photocathode, said first dynode portion, said second dynode portion, and said third dynode portion, comprising:
• a first voltage division portion which is applied with a first side potential and a second side potential higher in voltage than the first side potential defining a high voltage and outputs voltages applied to said first dynode portion, said third dynode portion, and more than one predetermined dynodes in said second dynode portion excluding a first-stage dynode and a final-stage dynode in said second dynode portion upon voltage dividing the high voltage at a predetermined voltage division ratio;
• and
• a second voltage division portion which is applied with a voltage output from said first voltage division portion and the second side potential of the high voltage and outputs voltages applied to dynodes in said second dynode portion other than said more than the predetermined dynodes upon voltage dividing the high voltage at a variable voltage division ratio.