A conductor assembly and method for constructing an assembly of the type which, when conducting current, generates a magnetic field or which, in the presence of a changing magnetic field, induces a voltage. The first optical amplifier receives a light and amplifies the received light. A flow path along a preferred flow path through a deflector lens permits passage of the ions from the source to the detector while inhibiting a sightline from the detector to the source in a direction parallel to the central longitudinal axis of the deflector lens.