Patent ID: 7492097

Claim:
An electron multiplier unit comprising: a first support member having an inlet aperture for letting primary electrons in, said first support member being comprised of an insulating material; a second support member located so as to face said first support member, said second support member being comprised of an insulating material; a first dynode held by said first and second support members while being in direct contact with said first and second support members, said first dynode and having a reflection type secondary electron emission surface arranged to emit secondary electrons in response to incidence of the primary electrons having passed through said inlet aperture, into a space between said first and second support members; a second dynode held by said first and second support members while being in direct contact with said first and second support members, said second dynode having a reflection type secondary electron emission surface located so as to face said first dynode and arranged to emit new secondary electrons to a side where said first dynode is located, in response to the secondary electrons coming from said first dynode; and an anode for extracting secondary electrons resulting from successive multiplication in the space between said first and second support members, as a signal, said anode being held by said first and second support members while being in direct contact with said first and second support members, at a position where the secondary electrons emitted from said first dynode do not directly arrive.