| 摘要 |
PURPOSE:To improve the measurement precision for the light element concentra tion by reducing the error due to the flow rate variation by correctly controlling the flow rate of PR gas by supplying the PR gas which contains Ar as main component into a gas flow type proportional counter tube through a mass flow controller. CONSTITUTION:A mass flow controller 11 correctly controls the flow rate of the PR gas supplied from a gas cylinder S for storing PR gas. The PR gas whose flow rate is controlled is supplied from a gas inlet 5 into a gas flow type proportional counter tube 1. The flow rate of the PR gas is displayed in a flow rate display part 12, and the flow rate of the PR gas can be set at an arbitrary value by operating a flow rate operation part 13. Since the PR gas is supplied into the counter tube 1 by the mass controller 11 which can control the flow rate according to the set operation of the operation part 13, the flow rate of the PR gas which flows in the counter tube 1 is prevented from being affected by the of temperature and pressure, and kept constant.
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