Second generation readout for large format photon counting microwave kinetic inductance detectors
Neelay Fruitwala, Paschal Strader, Gustavo Cancelo, Ted Zmuda, Ken Treptow, Neal Wilcer, Chris Stoughton, Alex B. Walter, Nicholas Zobrist, Giulia Collura, Isabel Lipartito, John I. Bailey, Benjamin A. Mazin
Abstract
We present the development of a second generation digital readout system for photon counting microwave kinetic inductance detector (MKID) arrays operating in the optical and near-infrared wavelength bands. Our system retains much of the core signal processing architecture from the first generation system but with a significantly higher bandwidth, enabling the readout of kilopixel MKID arrays. Each set of readout boards is capable of reading out 1024 MKID pixels multiplexed over 2 GHz of bandwidth; two such units can be placed in parallel to read out a full 2048 pixel microwave feedline over a 4 GHz-8 GHz band. As in the first generation readout, our system is capable of identifying, analyzing, and recording photon detection events in real time with a time resolution of order a few microseconds. Here, we describe the hardware and firmware, and present an analysis of the noise properties of the system. We also present a novel algorithm for efficiently suppressing IQ mixer sidebands to below -30 dBc.