Thermal emission at submillimeter wavelengths carries unique information for many astronomical applications, ranging from disks and planet formation around young stars to galaxy evolution studies at cosmological distances. Advancing the mapping speed to detect this faint emission in ground-based astronomy has been a technical challenge for decades. The APEX Microwave Kinetic Inductance Detector (AMKID) camera was designed to accomplish this task. The instrument is a wide field-of-view camera based on kinetic inductance detectors. It is installed on the 12-meter APEX telescope in Chile at 5100 meters above sea level. The instrument operates in dual color, covering the 350 and 850 GHz atmospheric windows simultaneously. It has a large field of view of 15.3′ × 15.3′ and an unprecedented number of pixels: 13 952 detectors in the high-frequency band and 3520 detectors in the low-frequency band. Here we present a complete description of the instrument design and construction, together with results from the successful low-frequency-array (LFA) commissioning campaign executed over the last year. The LFA performance is in good agreement with design parameters, with detector sensitivity of 2.2 mK s and diffraction-limited beam sizes of 17.0″. On-sky measurements demonstrate a sensitivity of 70–90 mJy s per detector under good atmospheric conditions (PWV below 1.0 mm). With this performance the LFA regularly achieves a mapping sensitivity of 25 mJy when mapping a square degree in one hour. AMKID on APEX with its dual-color observing capabilities, high sensitivity, large field of view, and high angular resolution promises to open new scientific opportunities with the APEX telescope. ... Read more

Far infra-red, mm and sub-mm astronomy requires very large arrays of detectors for future wide field cameras and spectrometers. We present an array of lens-antenna coupled Microwave Kinetic Inductance Detectors (MKID) for a wide field camera at 350 GHz. We discuss the optimization to maximize the usable detector yield and matching the array to the readout to enable array performance close to the background limit. We overview the optical characterization techniques required to have confidence in the instrument performance prior to on telescope integration, finally giving measured optical performance for an optimized array. ... Read more

For astronomical instruments, accurate knowledge of the optical pointing and coupling is essential to characterize the alignment and performance of (sub-)systems prior to integration and deployment. Ideally, this requires the phase response of the optical system, which for direct (phase insensitive) detectors was not previously accessible. Here, we show development of the phase-sensitive complex beam pattern technique using a dual optical source heterodyne technique for a large-field-of-view microwave kinetic inductance detector camera at 350 GHz. We show here how you can analyze the measured data with Fourier optics, which allows integration into a telescope model to calculate the on-sky beam pattern and telescope aperture efficiency prior to deployment at a telescope. ... Read more

Aims. Future astrophysics and cosmic microwave background space missions operating in the far-infrared to millimetre part of the spectrum will require very large arrays of ultra-sensitive detectors in combination with high multiplexing factors and efficient low-noise and low-power readout systems. We have developed a demonstrator system suitable for such applications. Methods. The system combines a 961 pixel imaging array based upon Microwave Kinetic Inductance Detectors (MKIDs) with a readout system capable of reading out all pixels simultaneously with only one readout cable pair and a single cryogenic amplifier. We evaluate, in a representative environment, the system performance in terms of sensitivity, dynamic range, optical efficiency, cosmic ray rejection, pixel-pixel crosstalk and overall yield at an observation centre frequency of 850 GHz and 20% fractional bandwidth. Results. The overall system has an excellent sensitivity, with an average detector sensitivity (NEPdet) =3 × 10-19 W/Hz measured using a thermal calibration source. At a loading power per pixel of 50 fW we demonstrate white, photon noise limited detector noise down to 300 mHz. The dynamic range would allow the detection of ~1 Jy bright sources within the field of view without tuning the readout of the detectors. The expected dead time due to cosmic ray interactions, when operated in an L2 or a similar far-Earth orbit, is found to be <4%. Additionally, the achieved pixel yield is 83% and the crosstalk between the pixels is <-30 dB. Conclusions. This demonstrates that MKID technology can provide multiplexing ratios on the order of a 1000 with state-of-the-art single pixel performance, and that the technology is now mature enough to be considered for future space based observatories and experiments. ... Read more