Two Hamamatsu Tubes are available with GHz count rates

The following Photomultiplier tubes  have been tested at tube-limited speeds
Tube            Manufacturer        Wavelength     Risetime
R5600-01    Hamamatsu           300-820nm       0.65ns        Module
R3091         Hamamatsu           300-500nm       0.4ns          1" SMA head-on  tube
R928p         Hamamatsu           185-900nm       2.2ns
R647           Hamamatsu           300-650nm       2ns
R7400U-04  Hamamatsu          185-850nm       0.78ns
R7400U-02  Hamamatsu          300-880nm       0.78ns
R1784          Hamamatsu          185-680nm       0.9ns
R2949          Hamamatsu          185-900nm       2.2ns          Low dark count R928  
H6780-02     Hamamatsu          300-880nm       0.78ns        Module R7400U-02
HC123-01    Hamamatsu    Powered socket for 1 1/8" side-on PMTs

                                         Tested at Gigahertz count speed:
H13661            Hamamatsu             300-650nm        0.23ns        0.430 ns width
R10467U-40   Hamamatsu              available            0.4ns          Hybrid 45% QE
H1447              Hamamatsu             available             0.35ns        300-650nm                                                  various high QE cathodes available       

New Product:  DUAL Hamamatsu Hybrid PMT Power Supply