Design of a Compact Type Time-of-Flight Mass Spectrometer

Mass spectrometer (MS) is one of the most important analytical instruments in the fields of life science, environmental science, geological survey and clinical diagnosis, etc. Since its birth in 1946 and its combination with matrix-assisted laser desorption/ionization (MALDI) source in the late 1980s, time-of-flight (TOF) mass analyzer has gradually played an increasingly important role in the MS instruments. Thanks to its advantages in mass accuracy, resolution, sensitivity, mass range, analysis speed, TOF have been widely used in microbial identification, clinical diagnosis, proteomics, and some other fields. The performance such as resolution of modern commercial TOF-MS is getting higher and higher. However, the expensive-price, large-in-size, difficult-to-maintain of TOF-MS confined it in the laboratory and made it difficult to broadly applicate in industrial and medical fields. In this work, a compact type time-of-flight mass spectrometer was developed to study the preparation and detection of nanoscale metal clusters. It mainly included a vacuum system, an ion source, a skimmer, an extraction/acceleration and deflection module, an ion mirror, a detector, a circuit system, and the like. Two turbo pumps provided vacuum of 5×10^-5 Pa. The laser ablation ion source could output stable ion beams for a long time, which was beneficial to the development of the TOF. The ions deflection module and the position/angle-tunable detector extended the mass range of the instrument. Skimmers with different diameters were designed to meet the demand for resolution and signal intensity. The time-of-flight mass analyzer could be taken out of the cavity as a whole, which was beneficial to the maintenance and upgrade of the instrument. Metal-coated ceramic was used as the electrodes of the ion mirror. Compared with conventional 304 stainless steel electrodes, the metalcoated ceramic achieves a high flatness in a thinner plate, which facilitates the resolution improvement and the instrument miniaturization. The size of the instrument is small, the length, width and height are 0.5, 0.5 and 0.7 m, respectively, and the flight tube length is only 0.25 m. The modules were packaged independently according to our modular design, and the maintenance and upgrade of the instrument were easy. Several innovative designs allow the instrument resolution to reach 4200 at m/z 2000, m/z 50-5000, and signal intensity is in the range of 1 to 1000 mV.