PHOTOMULTlPLlER TUBES R464, R585 For Photon Counting 5mm 8mm Bialkali Photocathode 51mm(2 lnch) Diameter, Head On Type GENERAL Parameter Spectral Response Wavelength of Maximum Response MateriaI Photocathode Minimum Effective Area Window Material Structure Dynode Number of Stages Base SuitabIe Socket R464 300 to 650 R585 160 to 650 420 Bialkali 5 8 Borosilicate glass Synthetic silica Box and Grid 12 21 pin glass base E678 21A(supplied) Unit nm nm mm MAXIMUM RATINGS (Absolut.