Correction for nonlinear photon-counting effects in lidar systems

Abstract

A useful analytic model describing the response of a photon-counting (PC) system has been developed. The model describes the nonlinear count loss and apparent count gain arising from the overlap of photomultiplier tube (PMT) pulses, taking into account the distribution in amplitude of the PMT output pulses and the effect of the pulse-height discrimination threshold. Comparisons between the model and Monte Carlo simulations show excellent agreement. The model has been applied to a PC lidar system with favorable results. Application of the model has permitted us to extend the linear operating range of the PC system and to quantify accurately the response of the system in its nonlinear operating regime, thus increasing the useful dynamic range of the system by 1 order of magnitude.

Ground-based water vapor raman lidar measurements up to the upper troposphere and lower stratosphere for long-term monitoring

“…For water vapor retrieval, a simple linear fit with a zero-slope (constant noise) is sufficient as no signal-induced noise is present in any of the Raman channels. At the bottom of the channels' useful range, signal non-linearities (pulse pile-up effect) are corrected either empirically using the method described in Donovan et al (1993), or experimentally using the non-saturated signals from the lower intensity channels. The high intensity pair is optimized to provide water vapor measurements between 8 km and 20 km.…”

Measurements of the dynamical cooling rate associated with the vertical transport of heat by dissipating gravity waves in the mesopause region at the Starfire Optical Range, New Mexico

“…That is, the detected signal was at least 70% of the signal expected in the absence of saturation. Standard techniques were employed during data processing, using the measured counting linearity curves, to remove distortion associated with PMT and discriminator saturation effects [Donovan et al, 1993].…”

Airborne Lidar Measurements of Aerosol and Ozone Above the Canadian Oil Sands Region

“…At high count rates (greater than 10 MHz), the photon counting signal does not respond linearly to the optical power due to overlapping pulses from the detector being counted erroneously as a single pulse. The detection system is unable to count separate individual pulses accurately within a certain 20 time period commonly referred to as dead time t d (Donovan et al, 1993). A dead time correction was applied to the raw photon counting data by calculating the true count rate N T , in terms of the measured count rate N m , as…”