イオンを用いた流速測定法

抄録

Superfluid helium is considered as an excellent coolant for superconducting magnets because it has an apparent thermal conductivity about 1, 000 times greater than copper.
It is widely well known that the behavior of superfluid helium is described by a two-fluid model. For example, when a thermal disturbance occurs, the normal fluid component is aliented from the heat source and the superfluid component approaches the heat source. The superfluid component has a nil entropy, only the normal fluid component will contribute the heat transport. So it is very important to know the velocity of the normal fluid component of superfluid helium.
We have developed a new flowmeter with the objective of measuring the normal fluid component' s flow velocity using ions because ions are valuable probes in the study of superfluid helium. It has a construction in which two set of electrodes are fitted inside a glass tube. The fluid is flowed inside this glass tube, and 10kV is impressed on the electrode of the upper stream generates a discharge phenomenon by which a part of the fluid is ionized. A voltage of 5-8kV is impressed on the electrode on the downstream side. In this condition, no discharge will be generated, but a discharge is triggered when the fluid ionized upstream flows down. The fluid's flow velocity is calculated from the difference in the time which these two discharge phenomena are generated. This flowmeter is available for all other kind of fluid except inflammable or explosive fluid.
In this paper this flowmeter has been tested for nitrogen gas and liquid nitrogen and proved to work well. We have also succeeded in measuring the flow velocity of the normal fluid component.