Design of a new multi-turn ion optical system 'IRIS' for a time-of-flight mass spectrometer

• Published in: Journal of mass spectrometry. Vol. 44; no. 5; pp. 594 - 604
• Main Authors: Nishiguchi, Masaru, Ueno, Yoshihiro, Toyoda, Michisato, Setou, Mitsutoshi
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.05.2009; Wiley
• Subjects: Computer Simulation; Ejection; Electric potential; Electrodes; Electromagnetic Fields; Equipment Design; Exact sciences and technology; Flight paths; Focusing; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; ion optics; ion trajectory simulation; Ions - analysis; Kinetics; Mass spectrometers; Mass spectrometers and related techniques; Mass Spectrometry - instrumentation; multi-turn time-of-flight mass spectrometer; Optics and Photonics - instrumentation; Physics; Resolution; Simulation; surface charge method; transfer matrix method; Surface charge; surface charge method; Theoretical study; Instrumentation; Time-of-flight method; Mass spectroscopy; Trajectories; multi-turn time-of-flight mass spectrometer; Ion optics; ion trajectory simulation; Design; Transfer matrix method; Mathematical models; Modelling; Multiple reflections
• ISSN: 1076-5174; 1096-9888; 1096-9888
• DOI: 10.1002/jms.1531

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. Copyright © 2008 John Wiley & Sons, Ltd.