GAS MEASURING INSTRUMENT AND ISOTOPIC CONCENTRATION RATIO MEASURING INSTRUMENT

摘要

PROBLEM TO BE SOLVED: To perform the measurement of isotopic concentration ratios with high sensitivity by utilizing the absorption of laser beams. SOLUTION: A composite resonator 300 is constituted of a laser medium cell 314 filled up with a<13> CO2 gas, another laser medium cell 316 filled up with a<12> CO2 gas, an absorption cell 320 filled up with a sample gas (the breath of a patient before the patient is dosed with a reagent), and another absorption cell 322 filled up with a reference gas. The two laser medium cells 314 and 316 and two absorption cells 320 and 322 are selected based on the presence/ absence of discharge. A first or second laser beam resonates between mirrors 300a and 300b and the laser beam is absorbed by the gas in either one of the absorption cells 320 and 322. The concentration ratio of<13> CO2 to<12> CO2 in the sample gas is computed based on the absorbed quantities of the first and second laser beams in the reference gas and samples gas. The composite resonator 300 can also be constituted in a waveguide type.