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SUPPRESSION OF AFTERPULSING IN PHOTOMULTIPLIERS BY GATING THE PHOTOCATHODE
Citation:
Bristow, M P. SUPPRESSION OF AFTERPULSING IN PHOTOMULTIPLIERS BY GATING THE PHOTOCATHODE. APPLIED OPTICS 41(27):1-13, (2002).
Impact/Purpose:
The objectives of this task are to:
Assess new remote sensing technology for applicability to landscape characterization; Integrate multiple sensor systems data for improved landscape characterization;
Coordinate future technological needs with other agencies' sensor development programs;
Apply existing remote sensing systems to varied landscape characterization needs; and
Conduct remote sensing applications research for habitat suitability, water resources, and terrestrial condition indicators.
Description:
A number of gating schemes to minimize the long-term afterpulse signal in photomultipliers have been evaluated. Blocking the excitation pulse by gating the photocathode was found to reduce the gate-on afterpulse background by a factor of 230 over that for nongated operation. This afterpulse or signal-induced background (SIB), which is particularly troublesome in stratospheric lidar measurements, appears as a weak exponentially decaying signal extending into the millisecond region after the photomultiplier tube (PMT) is exposed to an intense submicrosecond optical pulse. Photocathode gating is not feasible in PMTs with semitransparent bialkali photocathodes because of their slow gate response time, but is easily implemented in PMTs with opaque bialkali or semitransparent multialkali (S-20)
photocathodes that can be gated with nanosecond response. In those PMTs with semitransparent bialkali photocathodes, a gated ( adjacent) focus. grid (if available) also produces a significant reduction in the SIB. (C) 2002 Optical Society of America. (26 References)