Improving the sensitivity of the end-cap reflectron time-of-flight mass spectrometer

A miniaturized time-of-flight (TOF) mass spectrometer utilizes an end-cap reflectron to achieve high kinetic energy focusing and improved mass resolution. However, the coaxial geometry gives rise to considerable losses in sensitivity resulting from reflected ion trajectories close to the center. These trajectories were modeled, using initial ion velocity distributions in the radial direction up to 300 m s(-1), and the portion of the active area of the detector that is utilized was evaluated experimentally using a variable diameter iris diaphragm. The sensitivity was improved by modification of the reflectron by tilting the end-cap electrode 4 degrees and redirecting the ions to a portion of the detector active area. Sensitivity was then measured as 3 fmol of the peptide substance P.