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 high-performance robust tracking control system for next-generation optical disc system. The proposed tracking control system consists of robust feedback control system and perfect tracking control system based on error-prediction. The proposed robust feedback control system has a good performance of sudden disturbance suppression for improving a free parameter. Moreover, the periodic-disturbance suppression performance of error-prediction feedforward control system is improved by using zero phase low-pass filter (ZPLPF), in comparison with the conventional control approaches. The experimental results point out that the proposed tracking control system has a precise tracking response against both the periodic disturbance and the sudden disturbance.
In optical recording system, the tracking servo system must follow the track of optical disk against the influence of the track eccentricity and the force disturbance. In tracking servo system, the influence of the track eccentricity becomes periodic disturbance. The influence of force disturbance caused by shaking is treated as sudden disturbance.The several control methods suppressing the periodic disturbance have been proposed. On the other hand, it is difficult to detect the sudden disturbance without force sensor. In the conventional tracking servo system, the influence of sudden disturbance has been suppressed by the feedback controller. This paper proposes a new structure of robust tracking servo system, which detects and suppresses the both periodic disturbance and the sudden disturbance without force sensor. The proposed system estimates the both periodic disturbance and sudden disturbance based on a new sudden disturbance observer and memory of tracking error. Moreover, in order to suppress the periodic disturbance quickly, this paper designs the ZPET feedforward servo system with prediction of tracking error.The experimental results point out that the proposed tracking servo system has a precise tracking response against both periodic disturbance and sudden disturbance.
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