Patent ID: 7667195

Claim:
A time-of-flight mass spectrometer comprising: a. an evacuated ion source housing configured to receive a MALDI sample plate; b. a pulsed ion source located within the ion source housing c. an analyzer vacuum housing; d. a gate valve having an aperture through which a laser beam passes when said gate valve is open and wherein said gate valve is located between and operably connecting said evacuated ion source housing and said analyzer vacuum housing and wherein said gate valve is maintained at or near ground potential; e. a field-free drift region maintained at or near ground potential located within said analyzer vacuum housing and aligned to receive an ion beam from the evacuated ion source housing; f. a two-stage ion mirror located in the end of said analyzer vacuum housing opposite the gate valve; g. a computer-controlled high voltage supply operably connected to each stage of said two-stage mirror h. a baffle adjacent to said two-stage ion mirror, said baffle comprising entrance and exit apertures which act to limit the diameter and location of the ion beam entering or exiting said baffle; and i. an ion detector located within the field free drift region configured to receive ions from the baffle.