Patent ID: 8664592

Claim:
A time-of-flight mass spectrometer having an energy supplier for giving ions to be analyzed a constant amount of energy to make the ions fly and a time-of-flight mass separator for separating the energy-given ions for each mass-to-charge ratio according to the difference in their flight time, wherein: the mass separator includes a free-flight space in which ions are allowed to fly without being influenced by an electric field, a reflectron having a plurality of electrodes for creating an electric field which acts on the ions flying in the free-flight space to reflect the ions backward, and a voltage supplier for applying a direct-current voltage to each of the electrodes of the reflectron; and the voltage supplier applies the direct-current voltage to each of the electrodes so that: the electrostatic field created by the reflectron is virtually divided into a decelerating region for decelerating ions introduced thereinto and a reflecting region for reflecting backward the ions which have been decelerated through the decelerating region, the two regions being arranged along a traveling direction of the ions; the potential distribution along a central axis of the electrostatic field in the decelerating region is either a potential distribution defined by one kind of function or a combination of potential distributions defined by a plurality of different kinds of functions along the central axis; and the potential distribution along the central axis of the electrostatic field in the reflecting region is one kind of curved potential distribution for which a conditional equation to be satisfied by a flight time T r (E) of the ions in the reflecting region is determined so that a total flight time required for an ion having an initial energy equal to a reference potential U 0 set at a level equal to or lower than a maximal potential value U d in the decelerating region to fly through a round-trip path including the free-flight space, will be equal to a total flight time required for an ion having an initial energy E higher than U d to fly through a round-trip path including the free-flight space, a following equation is used as a relational equation for determining an inverse function x(U) of the curved potential distribution U(x) in the reflecting region realizing the flight time T r (E), and an integral computation in that equation is either an analytic formula using a parameter defining the potential distribution of the electrostatic field in the decelerating field or a numerical solution obtained by a numerical computation: x ⁡ ( U ) = 1 π ⁢ 2 ⁢ m ⁢ ∫ 0 U ⁢ T r ⁡ ( E ) ⁢ ⅆ E U - E where m is a mass of an arbitrary ion of interest.