The Gated Photomultiplier Tube (Gated PMT) allows the photocathode of the PMT to be gated on or off for a short period. This is particularly useful when the light source under investigation has a very bright precursor or post cursor. When gating the PMT there are problems associated with the following: 1 The tube gain is slightly dependent on the photocathode to MCP (input face) voltage. 2 The gate pulse can couple to the output signal as unwanted noise. With care this can be subtracted from the output signal after recording of signals. 3 The gate pulse can couple to the MCP directly to cause changes in the gain of the tube. This is not so predictable or so easy to remove. In order to mitigate against this the input and output electrodes of the MCP are decoupled with significant capacitance to each other and to ground. However, the current that charges the photocathode to MCP (input) gap has to flow in the surface coating of these elements. There will be a voltage drop radially while the charging occurs. As the MCP electrode coatings are quite resistive some electric field may enter the MCP and modify the gain. A more conductive coating would be able to reduce this effect by may also change the QE of the MCP detection. The fast gate pulse can cause oscillations to arise in various parts of the system and it may be that the signal is not representative of the input light. This package has been designed to mitigate all of these issues as much as possible without resorting to a specially coated MCP.

The manual is available here.