Gated photomultiplier response characterization for DIAL measurements

Abstract

The characteristics of various detector responses are studied to understand the cause of various systematic biases and to minimize these undesirable effects in measurements of transient signals with large dynamic range. We quantitatively evaluated signal induced bias, gain variation, and the linearity of commonly used gated photomultipliers in the current integrating mode. Analysis of the results indicates that impurity ions inside the photomultiplier tube are the source of the signal induced bias and gain variation. Two different photomultiplier tubes used in this study show significant differences in the magnitude and decay behavior of signal induced bias. We found it can be minimized by using an external amplifier to reduce PMT gain, and by applying a low potential between the cathode and first dynode. The linearity of a photomultiplier tube is also studied over a large dynamic range of input intensities employing a new technique which does not require an absolute calibration. The result of this study shows that the photomultiplier response is linear only for a limited input intensity range below a certain anode current.

Comparisons of airborne lidar measurements of ozone with airborne in situ measurements during the 1995 Southern Oxidants Study

“…Since PMT-SIBs are known to have exponential decay profiles with the decay constant depending on PMT voltage [e.g.,Lee et al, 1990], we fitted an exponential of the form A x exp(-B x R), with R being range away from the lidar, to the SIB tail and then subtracted the exponential from the lidar signal. Since the SIB level changes with the magnitude of the large near-field signal and the exponential decay constant B varies with PMT voltage (which was periodically adjusted during the lidar measurements), we determined the SIB fit parameters were recorded during an aircraft turn have not been used for retrieval since we do not record aircraft attitude data to correct the slant lidar path altitudes.…”

Raman lidar calibration for the DMSP SSM/T-2 microwave water vapor sensor

“…Signals were collected with varying attenuation in order to minimize photomultiplier and photon-counting nonlinearities [11]. The lidar was equipped with a beam director periscope that scanned over a hemisphere.…”

Alternative method for determining the constant offset in lidar signal

“…Generally, the laser discharge originates electromagnetic noise in a wide spectrum, which is superimposed on the signal offset. Typically, the electromagnetic noise is a slowly decaying ringing voltage induced after triggering the light pulse [2][3][4][5][6][7]. Accordingly, the backscatter signal after the subtraction of the pretriggered signal may have some remaining constant or variable shift.…”