| 摘要 |
PROBLEM TO BE SOLVED: To provide a measuring method and an apparatus for measuring breakdown threshold value, by which the breakdown threshold value of fine particles is found precisely, and to provide an apparatus for measuring fine particles in a liquid, which uses them. SOLUTION: The measuring apparatus is constituted of a laser-beam irradiation means 1 which irradiates a sample liquid in a sample cell 4 with a laser beam. It is constituted of an acoustic-wave detecting means 5 which detects breakdown acoustic waves generated by the radiated laser beam. It is constituted of a waveform recording means 6 which records the detected acoustic waves as a waveform. It is constituted of a waveform analytical means 7 by which the peak time T1 of a waveform having a peak value in a shortest time after the irradiation of the laser beam among from a recorded waveform group, the peak time T2 of a waveform having a maximum peak value amoung from the waveform group and the time difference D between the time T1 and the time T2 and found and by which the time difference D is found by the same procedure as before by changing the power density P of the laser beam irradiated at the sample liquid. It is constituted of a threshold-value computing means 9, by which the relational expression of the time difference D with reference to a change in the power density P is found, and by which, the value of the power density P corresponding to a time difference D=0 is found as the breakdown threshold value of tine particles on the basis of the relational expression.
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