Kiyomi Yoshinari

Theoretical and numerical analysis of the behavior of ions injected into a quadrupole ion trap mass spectrometer

A numerical simulation method has been developed for the analysis of trapping ions injected into an ion trap mass spectrometer. This method was applied to clarify the effects of the following parameters on trapping efficiencies: (1) initial phase of the radio frequency (RF) drive voltage, (2) ion injection energy, and (3) RF peak voltage while injecting ions. The following conclusions were obtained by theoretical and simulation approaches. 1. The second and third dominant oscillations contribute significantly to the trapping mechanism of the injected ions, even for low q values. 2. A formula relating the operating parameters, which gives the maximum trapping efficiency, is derived. 3. Based on the above-mentioned formula, an advanced injection method is proposed, in which the RF peak voltage is decreased while injecting ions. The ability of this method to solve the problem of unequal sensitivity among different ion species is indicated by numerical simulation. Copyright 2000 John Wiley & Sons, Ltd.

Feasibility study for thermal conductivity simulation by coupling between admittance matrix method and finite elemental method

We developed a new method of coupling the finite elemental method (FEM) with the admittance matrix method to simulate the thermal conductivity of large-scale power electronics systems. The feasibility of this method was confirmed from the simulation results that showed the temperature changes differing by 6.5% from those obtained by using the conventional FEM. The accuracy was improved more so that it can be used even if the Y region is divided into several Y blocks. The FEM-Y matrix coupling method also proved to be effective for ensuring there was less calculation time compared to that for the conventional FEM. The FEM-Y matrix coupling method was confirmed to reduce the calculation time by 48% or more when compared to the conventional FEM, based on the number of times the thermal conductivity analysis is iterated.

Axially symmetric electron beam trajectory simulation

An axially symmetric simulator for the Schottky emission gun has been developed using the boundary-fitted coordinate transformation method. The domain decomposition method is successfully employed with multi-layer overlapping, which allows complicated electrode structures to be modeled and the electric potential computation to converge quickly. The angular intensity distribution of Swanson’s Schottky emission gun is analyzed, and good agreement is seen with his experimental data. The simulation results show that angular intensity and virtual source size are remarkably dependent on the real emitter size.

Increase in temperature on the surface of a large iron-based cabinet of a power converter due to generation of eddy current in the cabinet's bus bars

The increase in surface temperature of the large cabinets of power converters, which are typically made of iron materials (with magnetic characteristics), was investigated. For this investigation, a method combining electromagnetic-field analysis and thermal-fluid analysis by using in-house analysis tools was established. According to the investigation results, the calculated temperature rise due to the eddy current was consistent (within an error of 9.2%) with the measured temperature rise.

Computer simulation of charged particle beam trajectories in a quadrupole ion trap mass spectrometer

A numerical simulation method has been developed for the analysis of ion motion in an ion trap mass spectrometer. In this method, ion motion can be simulated with the interaction of ion — bath gas and ion — space charge during mass analysis scan. By applying this method, the influence of the bath gas pressure and the space charge density on mass spectra is clarified. Furthermore, the relationship between the scan speed and the degree of the mass shift is obtained. Based on these relationships, an advanced scanning method is obtained, in which the scan speed is reduced gradually over the scan time. The feasibility of achieving high resolution without mass shift or scan time expansion is also examined.