A fast and precise chemiluminescence ozone detector for eddy flux and airborne application

摘要

A commercially available dry chemiluminescence (CI) instrument for fast and precise measurement of ozone (O_(3)) is specified. The sensitivity is approx9000 counts s~(-1) per ppbv of ozone. Its precision is entirely determined by the number of photons reaching the detector (being a photomultiplier), i.e. is quantum-noise limited. The relative precision ((DELTA)O_(3)/O_(3) in percent) thus follows Poisson statistics and scales with the square root of the measurement frequency f and with the inverse O_(3) mixing ratio: (DELTA)O_(3)/O_(3) (propor. to) f~(0.5) (centre dot) O_(3)~(-0.5). At typical O_(3) mixing ratios between 10 and 100 ppbv (and 1 bar), the precision is 0.3-1.0percent at f velence 10 Hz. The maximum measurement frequency is 50 Hz. The mechanical and electronic setup as well as the instrument performance is described. Recommendations on the adequate inlet tube configuration (inlet tube length, sampling flow) and on the way of calibration at stationary ground-based platforms and onboard aircraft are given.