The effect of the addition of mercury to a conventional caesium neutralized diode is described. A pronounced Penning effect was found, the mercury 63P1-63D1,, transitions being the most efficient for the volume ionization of caesium atoms. The increased electron scattering due to the introduction of mercury into the diode is to a large extent minimized by the low collision cross section, at 0.17 ev, due to the Ramsauer effect. Consequently, it appears that the performance of the diode operating under arc mode conditions may be significantly improved by the addition of mercury.

This paper proposes a new force sensor-less robust tracking servo system, which detects and suppresses both the periodic disturbance and the sudden disturbance without force sensor. The proposed system estimates both the periodic disturbance and the sudden disturbance by using a new sudden disturbance observer and the memory of tracking error. In the proposed system, the influence of sudden disturbance is suppressed by the proposed sudden disturbance observer. On the other hand, the influence of periodic disturbance is suppressed by means of ZPET feed-forward servo system, respectively. The experimental results point out that the proposed tracking servo system has a precise tracking response against both the periodic disturbance and the sudden disturbance.

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