Photon Counting Performance of Selected Detectors

This seetion gives an overview of the TCSPC performance of a number of deteetors frequently used in TCSPC applications [243]. All IRFs shown below were measured under real-world eonditions with TCSPC modules from Becker Hickl. The IRFs were reeorded with combinations of detector gain and CFD threshold 

The results given below are believed to be representative of the particular detectors or groups of detectors described. However, detector parameters may vary for different specimens of the same type, and will depend on possible changes in the manufacturing process. This is especially the case with parameters that depend on the gain, such as maximum count rate and afterpulsing probability. 

MCP-PMTs [298] are currently the fastest commercially available detectors for TCSPC. A typical representative of this detector type, the Hamamatsu R3809U [211], is described below. The detector is shown in Fig. 6.29. 

The response has a shoulder of about 400 ps duration and about 1% of the peak amplitude. This shoulder seems to be a general property of all MCPs. 

All MCP-PMTs permit only a very small maximum output current. For the Hamamatsu R3809U the specified maximum output current is 100 nA. The permitted output current sets a limit to the count rate that can be obtained from the detector. Operating the MCP at maximum gain is therefore generally not recommended. The count rate for the maximum output current of 100 nA as a function of the supply voltage is shown in Fig. 6.31. 

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