  We demonstrate superconducting nanowire single photon detectors with 76 +/- 4
% system detection efficiency at a wavelength of 315 nm and an operating
temperature of 3.2 K, with a background count rate below 1 count per second at
saturated detection efficiency. We propose integrating these detectors into
planar surface electrode radio-frequency Paul traps for use in trapped ion
quantum information processing. We operate detectors integrated into test ion
trap structures at 3.8 K both with and without typical radio-frequency trapping
electric fields. The trapping fields reduce system detection efficiency by 9 %,
but do not increase background count rates.
