Time Response of Photomultiplier Tubes

Dynode chain Circular cage Uoear focused Microdtannei Plate Circular cage 

20-50 ns (Hgure 2.29). The rise time is the time requiied for the PMT anode dgnad to rise from 10% to 90% of its final lev Hie rise time is detennined primarily by the transit fime variafion m the PMT, that is, the scatty around the average transit lime. 

The transit time spread is perhaps the most important determinant of the time resolution available with a given 

Hgui 2.29. Hine response of a Qrpicsl PMT. The date are for a R20S9 head on. Unear focused PMT. Revised fiom Ref. 14. 

The most dramatic advance in U eed PMTs has been the introduction of the MCP PMT. In tins case the photoelectrons are proximity-focused into the MC3 (Bg-ure2.27). Once in tfieMCP, theieis voy litdevaiiatkMiin the electron trajectory. For diis reasrui, MCP PMTs have transit time spreads 10-fold smaHa dian thoseof Auidard PMTsfTAle 2.2). 

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