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 200 is constituted of a laser medium cell 202 filled up with a<13> CO2 gas, another laser medium cell 204 filled up with a<12> CO2 gas, an absorption cell 220 filled up with a sample gas (the breath of a patient before the patient is dosed with a reagent), and another absorption cell 222 filled up with a reference gas. The cells 220 and 220 are used in exchange to each other. In the composite resonator 200, first and second laser beams resonate between mirrors 200a and 200b and a mirror 200c and, when the laser beams resonate, the laser beams are absorbed by the gases. 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 standard gas and sample gas. The composite resonator 200 can also be constituted in a waveguide type.