Time-of-flight mass spectrometer

A time-of-flight mass spectrometer in which a mass separation unit forming a flight space designed for ions to fly through, an accelerating electrode for initially accelerating the ions and a detector for detecting the ions are provided within an evacuated vacuum container, where the ions that are initially accelerated by the accelerating electrode and temporally separated according to their mass by flying through the flight space are detected by the detector and a mass spectrum having a mass axis and an intensity axis is created from a detection signal of the ion detector, which is characterized by comprising:

• a) a first temperature detecting means for detecting a temperature of the vacuum container;
• b) a second temperature detecting means for detecting a temperature of a power unit for applying a voltage to the accelerating electrode;
• c) a first memory means for storing information based on a result of a previous measurement relating to a transfer function from a temperature change of the vacuum container and a shift of the mass axis due to a temperature change of the mass separation unit;
• d) a second memory means for storing information based on a result of a previous measurement relating to a transfer function from a temperature change of the power unit and a shift of the mass axis due to a temperature characteristic of an output of the power unit;
• and
• e) an estimating operation means for estimating a current shift length of the mass axis by using current temperatures of the vacuum chamber and the power unit obtained with the first temperature detecting means and the second temperature detecting means as well as information relating to the transfer functions stored in the first memory means and the second memory means, respectively.