A detector for an electron multiplier comprising: a substrate (102) comprising a dielectric material, the substrate having a first face (110) and an opposing second face (108); a charge collector (122) provided adjacent the first face (110) of the substrate (102); an anode (104a-d) within the substrate (102), the anode (104a-d) spaced from the first face (110), such that the anode (104a-d) is capacitively coupled to the charge collector (122), so that charge incident on the charge collector (122) generates an image charge on the anode (104a-d); and a conduit contact (106a-d), coupled to the anode (104a-d) and passing through the substrate (102) to the second face (108) of the substrate (108).