Metal channel PMTs

Fig. 6.2 PMT dynode geometries. Circular dynode arrangement, linear focused, fine mesh, Venetian blind, metal channel type. C Cathode, D dynodes, A anode, F focusing electrode,...

Of special interest for time-correlated single photon counting are the linear fo-cused dynodes, which give fast single electron response and low transit-time jitter, and the fine mesh and metal channel types, which offer position sensitivity when used with an array of anodes. Moreover, PMTs with fine-mesh and metal channel dynodes can be made extremely small, which results in low transit time, low transit-time jitter, and a fast single-electron response. 

Fig. 6.4 Multianode PMT with metal channel dynodes left) and multianode MCP-PMT right)...

The TTS of conventional PMTs and miniature PMTs with metal channel dyn-odes can be measured with satisfactory accuracy using picosecond diode lasers. These lasers deliver pulses as short as 30 to 50 ps FWHM. However, the pulses may have a tail or a shoulder, especially at higher power. The diode driving conditions for clean pulse shape with minimum tail are usually not the same as for shortest FWHM. The TTS of MCP PMTs ean be reasonably measured only by a Ti Sapphire laser or a similar femtoseeond or picosecond laser system. 

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