Design Chart for Trochoidal Vacuum Analyzer

Design charts for trochoidal mass spectrometer as a vacuum analyzer are made for rational determination of the electrode dimension. The fundamental charts, Figs. 3, 4, 5 and 6, are calculated by Eqs. (4), (5), (6) and (7), where notations used are shown in Fig. 2. β is a coefficient defined as β=Vo/Ep, where Vo, E and p represent the accelerating voltage of ion, the strength of electric field and the distance between do and dn (refer to Fig. 2), respectively. The spreads X and Y of ion beam, in x and y directions can be obtained from these figures as functions of β and θ. For example, considering the the conditions Xmax =Ymax and θ≤135°, the relations among (X/a) max (= (Y/a) max), pβ/a and (s/a) min are then given, in Fig. 8. From this figure, optimum value for a (i. e. b) corresponding to any value of Xmax/smin can be odtained. Table 1 shows a typical example of electrode design under the above condition. Use of Figs. 3, 4, 5, and 6 also makes it easy to draw the path of ion beam.