| 摘要 |
An ion optical system to form a loop orbit is provided to sufficiently ensure required performance such as ion transmission efficiency while making it easy to design the system by alleviating a space-focusing condition. The loop orbit of the ion optical system is realized so as to satisfy (t|x)=(t|α)=(t|δ)=0 as the time-focusing condition and to satisfy −2<(x|x)+(α|α)<2, and −2<(y|y)+(&bgr;|&bgr;)<2 as the space-focusing condition. (x|x) and other similar terms are constants determined by the elements indicated in the parenthesis in a general expression format of the ion optical system. The conditions are substantially alleviated as opposed to the conventional space-focusing condition where each of (x|x), (α|α), (y|y) and (&bgr;|&bgr;) needs to be ±1. Thus, the parameters to decide the shape of electrodes by which the ion optical system is configured have higher degree of freedom.
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