Abstract: A channel secondary electron multiplier has a mechanically sturdy body made of metal or ceramic material. The body forms an internal multiplier channel having a curved, e.g. helical main portion and a funnel shaped entrance end. A resistive layer forming a secondary electron emissive surface is provided on the inner wall of said channel inclusive that entrance end. The secondary electron emissive resistive layer in said funnel shaped entrance end has the form of a spiral-shaped band or stripe having a width which is preferably at least approximately equal to the circumferential dimension of the main portion of said channel. The body has a thermal coefficient of expansion which is at least 15% larger than the thermal coefficient of expansion of said layer, to maintain said layer under compression.