3 ThGEM characteristics: ThGEM type C4: Size = 3 X 3 cm 2 Rim = 100  m Pitch = 0.8 mm thickness = 0.4 mm Top coated by CsI acting as photocathode (over 5  m of Ni and 0.02  m of Au) ( good quantum efficiency for  < 200 nm) CsI is damaged by moisture exposure, then the right procedure is to always keep the CsI layer under vacuum or clean atmosphere (~ < 20 ppm H 2 0 and O 2 ).
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