Orthogonal acceleration time-of-flight mass spectrometer

An orthogonal acceleration time-of-flight mass spectrometer comprising:

• a vacuum chamber in which an internal space is partitioned into a first vacuum chamber and a second vacuum chamber;
• an insulating spacer member disposed in and between the first vacuum chamber and the second vacuum chamber;
• a former-stage-side ring electrode fixed to a side of the insulating spacer member on the first vacuum chamber;
• a plurality of subsequent-stage-side ring electrodes fixed to a side of the insulating spacer member on the second vacuum chamber and connected to each other via a connecting member having an insulation property;
• a first fixation member configured to position the insulating spacer member with respect to a predetermined position in the second vacuum chamber, the first fixation member including a first displacement member configured to displace a central axis of the former-stage-side ring electrode and the subsequent-stage-side ring electrodes in a predetermined direction orthogonal to the central axis by thermal expansion;
• and
• a second fixation member configured to position one of the plurality of subsequent-stage-side ring electrodes with respect to the predetermined position, the second fixation member including a second displacement member configured to displace the central axis in the predetermined direction orthogonal to the central axis by thermal expansion, a difference between a thermal expansion amount of the first displacement member per unit temperature and a thermal expansion amount of the second displacement member per unit temperature being 30% or less of the thermal expansion amount of the first displacement member.