This part is a kind of semiconductor called S8559.

Function of this product has Si photodiode Detector.

Manufacturers : Hamamatsu Corporation

Image and pinout :

Some of the text within the PDF file :

PHOTODIODE Si photodiode S8559 Detector for X-ray monitor Features Applications l Si photodiode coupled to low cost CsI scintillator l Ideal for detection of X-ray energy below 100 keV l X-ray detection l X-ray monitors s Absolute maximum ratings (Ta=25 °C) Parameter Reverse voltage Operating temperature Storage temperature s Electrical and Symbol VR Max. Topr Tstg Value 5 -10 to +60 -20 to +70 Unit V °C °C optical characteristics (without scintillator, Ta=25 °C) Symbol λ λp S ID Ct Condition Min. Typ. 190 to 1000 720 0.26 2 950 Max. 50 Unit nm nm A/W pA pF Parameter Spectral response range Peak sensitivity wavelength Photo sensitivity Dark current Terminal capacitance λ=500 nm VR=10 mV VR=0 V, f=10 kHz s X-ray sensitivity (reference value, tube curre [ ... ]

S8559 PDF Datasheet Download