Shinku

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A nude type Bayard-Alpert gauge of high sensitivity and low x-ray residual current is described. This gauge is featured by platinum grid and ceramic-sealed stem. By carrying out the sensitivity measurement in a large chamber as functions of electrode configuration and electrical parameters, an optimum condition of operation is fixed.
The sensitivity for air is 25 Torr^-1 and nearly constant for the pressure range between 10^-3 to 10^-11Torrreduced electron currents. The x-ray residual current corresponds to 1.7× 10^-11 Torr.
TThe sensitivity is influenced by the proximity of metal envelope. When the spacing between grid and metal cylinder wall decreases to 6.5mm, the sensitivity is increased by 50%. Compering this anomaly with Redhead and McNarry's data on the Nottingham type gauge, it can be shown that the effect of metal cylinder of different diameters at zero potential is very. similar to that of shield grid at different negative potentials. The drop of shield potential is interpreted as equivalent to the pnoximity of virtual zero-potential cylinder″. to the grid.
TThe metal envelop has also an effect on the proportionality between ion current and electron current. Experiments show that this proportionality does not hold for the truly nude gauge at the electron currents above lmA, whereas it holds for both the nude gauge in a metal cylinder and normal gauge over the range of electron current from 40μA to 5mA.

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