A new multi-turn ion optical system 'IRIS' has been designed for use with a high-performance time-of-flight (TOF) mass spectrometer, which satisfies the new design concepts of time focusing and phase space stability. It has an elliptical flight path composed of four toroidal electric sectors, with a flight path length for one lap of 0.974 m. Dimensions and voltages of sector electrodes have been optimized to satisfy theoretical requirements by simulations using surface charge method. Generally, multi-turn instruments require an injection and ejection system to inject and eject ions. On the basis of this ion optical study, we have designed an injection and ejection ion optical system, which achieves time focusing for the total system. Furthermore, we have designed novel field-adjusting electrodes (FAEs) for the perforated sectors in the injection and ejection systems, which accurately correct the electric potential around the perforated sector's hole. We have also used simulations to evaluate mass resolving power and ion transmissions for various lap numbers or flight path lengths. Through these we have confirmed that mass resolving powers of over 100,000 can be achieved with reasonable ion transmissions for a given set of initial conditions. Usually a multi-turn TOF mass spectrometer with a closed optic axis has mass range limitations from overtaking ions. To solve this problem, a TOF segmentation method is proposed that identifies all peaks in a TOF spectrum, including those from overtaking ions.
A miniature mass spectrograph was newly designed and constructed as a prototype model for future lunar or planetary explorations. The ion optical system was newly designed based on Mattauch῍Herzog geometry. The mass spectrograph employs a focal plane detector consisting of a microchannel plate (MCP), a phosphor layer, a fiber-optic plate (FOP) and a charge-coupled device (CCD). The 2D and 1D spectra of the residual gases, krypton and neon were observed in preliminary experiments. The mass resolution of 130 was achieved experimentally, and this was in good agreement with the simulation based on the transfer matrix method. The experimental value of the detectable m/z range was also consistent with the calculated version. Moreover, stable isotopes of Kr and Ne were observed without saturation of the detector. A dynamic range of 300 was achieved.
A new miniature double-focusing mass spectrograph has been designed and constructed. The ion optical system was designed based on Mattauch-Herzog geometry. The mass spectrograph employs a focal plane detector consisting of a microchannel plate, a phosphor layer, a fiber-optic plate and a charge-coupled device. For the evaluation of the ion optics of the instrument, the energy and angular focal planes were investigated both experimentally and by simulation. Double focusing was satisfactorily achieved along a straight line over a wide mass range, and the experimental and simulated results were mutually consistent. A second-order element of the transfer matrix was also measured experimentally and proved to be in good agreement with the simulated result.
The ion beam profiles of the multi-turn time-of-flight mass spectrometers "MULTUM" and "MULTUM II" were simulated using the ion trajectory simulation program "TRIO 2.0." These ion optical systems satisfy the "perfect focusing" conditions and are suitable for an imaging mass spectrometer in stigmatic mode. From the simulation, it was clear that the higher order aberration of MULTUM II is smaller than that of MULTUM. A smaller initial lateral angular deviation makes aberration after circulation smaller in both the ion optical systems. In the ion optical system MULTUM II, the ion images should be measured at even numbered cycles, because the second-order coe$cient (x῏xx) will be cancelled after every two cycles.
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