  We present a linearly arrayed, 16-element, superconducting nanowire
single-photon detector with 83.4$\%$ system detection efficiency at 1550 nm and
a mean per-element dead-time of 9.6-ns, enabling counting at 1 giga-count per
second with $>50\%$ System Detection Efficiency. This device was designed and
fabricated in an existing scalable commercial process.
