| 摘要 |
<p>The interelectrode gap of an ionography imaging chamber is connected with a variable-volume container which is filled with a high Z gas at atmospheric pressure, and with first and second accumulators which respectively contain high Z gas at a higher and lower superatmospheric pressure. A timer circuit actuates valves in the conduits between the chamber on the one hand and the container and accumulators on the other hand in a given sequence so that, when the pressure of high Z gas in the gap is to be raised to an operating pressure which exceeds the aforementioned higher pressure, the circuit opens a first valve which allows gas to flow from the second accumulator into the chamber and thereafter a second valve which allows gas to flow from the first accumulator into the chamber. The circuit thereupon starts a pump which conveys gas from the container into the chamber whereby the volume of the container decreases. The pumping step is terminated when the pressure in the gap reaches the operating pressure. When the pressure in the gap is to be reduced, the second valve is opened prior to the first valve, and the circuit thereupon opens a third valve which connects the gap with the container so that the container expands until the pressure in the gap drops to atmospheric pressure.</p> |
