Many well-motivated dark matter models predict meV-scale energy deposits in interactions with terrestrial experiments, but this regime is challenging to probe due to a lack of mature single-quantum detectors. Here we report results from QUALIPHIDE (QUAntum LImited PHotons In the Dark Experiment), a cryogenic dark matter search using a 41-pixel array of energy-resolving microwave kinetic inductance detectors with a 13 meV threshold, simultaneously used to look for both conversion photons from THz wavelength hidden photon dark matter and phonons from particle-like light dark matter interactions. The experimental design, with on- and off-focus pixels for the hidden photon search, allows for a data-driven background model, giving the experiment discovery potential. A blind analysis of 22 hours of data shows no significant excess, setting the strongest constraints on the hidden photon kinetic mixing parameter χ over the mass range of 13-90 meV/c^2, reaching 1.5×10^-12 at 50 meV/c^2. These data also yield among the first terrestrial limits on dark matter scattering off nuclei and electrons, down to 5 MeV/c^2 and 20 keV/c^2, respectively. The low threshold also enables future study of the low-energy excess limiting cryogenic detectors and, as we project, will allow for a terahertz-scale QCD axion search with a magnetic field.

We present a method of spatially mapping microwave kinetic inductance detector (MKID) arrays, in a dark setup. MKIDs are superconducting natively multiplexed resonators which enable kilopixel arrays, such as for the proposed probe far-infrared mission for astrophysics (PRIMA). In such telescope applications one must map the spatial location of each MKID with their individual resonance frequencies. Traditional LED arrays or beam-mapping methods become increasingly difficult as pixel spacing decreases, e.g., 900 mu m separated MKIDs in the spectrometer module of PRIMA. Our new mapping technique uses a cryogenic interferometer in reflection mode. As on-resonance signals reflect from an MKID, they accrue a phase proportional to the path-length, exactly corresponding to their physical distance on the feedline. Specifically, we use a superconducting transmission line that has nonlinear kinetic inductance. The slow-wave structure of this nonlinear device is designed to have a signal speed of 0.64% the speed of light, enabling a compact system. Current biasing this line allows for varying the wave speed and ensuring that the phase measured is periodic within a nulling interferometric mode. Using this setup, we measure a length ordering that reflects the bimodal MKID distribution of a 44 pixel array of MKIDs designed for PRIMA, which contains the same spacing as the final kilopixel array design.

The Probe far-Infrared Mission for Astrophysics (PRIMA) will use 8 kilo-pixel kinetic inductance detector (KID) arrays in its spectrometer module. We present an improved resonant frequency to spatial position mapping system designed to preserve each array's mapping after transferring it from the mapping apparatus to the flight housing. Such a mapping is necessary for astronomical observations, and additionally allows us to laser trim the capacitive elements of KIDs to optimize resonance separation in frequency space. This increases the operating yield by eliminating collided resonances, reduces crosstalk, and reduces the sensitivity to frequency drift over time.

Microwave kinetic inductance detectors (MKIDs) are generally read out with microwave readout tones of high enough amplitude to adequately suppress the noise contribution of the first-stage amplifier. At high readout power, the detector's resonant frequency is altered as a result of the dependence of the kinetic inductance on the internally circulating microwave current. With the tone placed below the resonant frequency, the nonlinear frequency shift results in a positive feedback effect that can significantly enhance the responsivity of the detector, to both optical and microwave power. We report a factor of 10 enhancement in optical response by tuning the readout power and frequency to close to the resonator's bifurcation point. A corresponding decrease in the bandwidth of the resonator is observed under these conditions. We show that the strength of the feedback effect can be easily selected by adjusting the excitation, and provide a map of possible operational states to do so. Operation of MKIDs in this mode could be used to improve sensitivity when non-intrinsic noise sources are significant.

The Astro2020 Decadal Survey recommended a new line of astrophysics observatories intermediate in scale between MIDEXs and Flagship-class observatories. In response, NASA created the Astrophysics Probe Explorer class and solicited proposals for the first generation of Probes. With a larger cost cap, Probes can achieve more ambitious science than SMEXs or MIDEXs and be implemented faster than Flagships-as frequently as one per decade. The PRobe far-Infrared Mission for Astrophysics (PRIMA) is one of two Probe concepts selected by NASA for a concept study in 2024/2025, potentially leading to implementation and launch as early as 2031. PRIMA was designed for a broad range of astrophysics, from how planets assemble their atmospheres, to the coevolution of galaxies and black holes, to the evolving properties of dust and galactic metallicity over cosmic time. Seventy-five percent of PRIMA's observing time will be allocated to guest observer observations and 25% allocated to principal investigator science; however, the principal investigator science data will be available promptly for guest investigator usage. The observatory features a 1.8-m diameter telescope cooled to 4.5 K with two science instruments: the Far-InfraRed Enhanced Survey Spectrometer (FIRESS) and the PRIMA imager (PRIMAger). FIRESS provides continuous spectral coverage from 24 to 235 mu m, in two spectral resolution modes (R >= 85 and R=4400(112 mu m/lambda)), with spectral mapping capability and order-of-magnitude sensitivity improvement over previous observatories. PRIMAger delivers similar sensitivity advances and first-of-its-kind far-infrared hyperspectral imaging for astrophysics with R similar to 8 from 25 to 84 mu m, and polarimetry in four broadband filters from 80 to 261 mu m. PRIMA's science and technical motivation is outlined, its overall architecture is described, and its cryogenic payload and instruments, including the kinetic inductance detector arrays, and operations and observing modes, are summarized. (c) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. [DOI: 10.1117/1.JATIS.11.3.031628]

We present a characterization of the mapping from resonant frequency to spatial position for a kilopixel kinetic inductance detector (KID) array developed for the Probe far-Infrared Mission for Astrophysics (PRIMA). This work targets the longest wavelength band of PRIMA's FIRESS spectrometer, which in total spans 24 to 235 mu m. Light emitting diodes arrayed to match repeating unit cells of 16 KIDs first discriminate among unit cells. Within each unit cell, frequencies are widely spaced, so positions are discriminated by theoretical predictions of the relative frequency spacing between detectors based on KID geometries. With this mapping, we analyze board features to improve the accuracy of modeling PRIMA KIDs and inform future fabrication runs.

The PRobe far-Infrared Mission for Astrophysics (PRIMA) is working to develop kinetic inductance detectors (KIDs) that can meet the sensitivity targets of a far-infrared spectrometer on a cryogenically cooled space telescope. An important ingredient for achieving high sensitivity is increasing the fractional-frequency responsivity. Here we present a study of the responsivity of aluminum KIDs fabricated at the Jet Propulsion Laboratory. Specifically, we model the KID's temporal response to pair-breaking excitations in the framework of the Mattis-Bardeen theory, incorporating quasiparticle recombination dynamics and the pair-breaking efficiency. Using a near-IR laser, we measure time-resolved photon pulses and fit them to our model, extracting the time-resolved quasiparticle density and the quasiparticle recombination lifetime. Comparing the fit to the known energy of the laser provides a measurement of the pair-breaking efficiency. In addition to photon-sourced excitations, it is important to understand the KID's response to phonon-sourced excitations from cosmic rays. We measure the rate of secondary cosmic rays detected by our devices, and predict the dead time due to cosmic rays for an array in L2 orbit. This work provides confidence in KIDs' robustness to cosmic ray events in the space environment.

The PRobe far-Infrared Mission for Astrophysics (PRIMA) is a future cryogenic space observatory that will revolutionize study of evolving galaxies and forming planetary systems with highly-sensitive far-infrared (far-IR) imaging and spectroscopy. PRIMA's spectrometer, the Far-InfraRed Enhanced Survey Spectrometer (FIRESS), will deploy kilo-pixel aluminum kinetic inductance detector (KID) arrays covering wavelengths from 24-235 mu m. Here we present optical characterization of a prototype FIRESS array operating at 25 mu m. We employ a blackbody modulation technique to measure the detector responsivity, and discuss methods for reducing 1/f noise from the multi-tone readout electronics. We measure an NEP below 3.5 x 10(-20) W/root Hz at 10 Hz accross the array, which exceeds the requirement to be limited by the astrophysical background limit for PRIMA's FIRESS spectrometer. We discuss limitations of the multi-tone readout and compare results to measurements with a single-tone readout system.

We present a multi-chroic kinetic inductance detector (KID) pixel design integrated with a broadband hierarchical phased-array antenna. Each low-frequency pixel consists of four high-frequency pixels. Four passbands are designed from 125 to 365 GHz according to the atmospheric windows. The lumped element KIDs consist of 100-nm thick AlMn inductors and Nb parallel plate capacitors with hydrogenated amorphous Si dielectric. Two different coupling structures are designed to couple millimeter-wave from microstrip lines to KIDs. The KID designs are optimized for a 10-m-class telescope at a high, dry site, for example, the Leighton Chajnantor Telescope. Preliminary measurement results using Al KIDs are discussed.

We present a design for an array of kinetic inductance detectors (KIDs) integrated with phased array antennas for imaging at 150 GHz under high background conditions. The microstrip geometry KID detectors are projected to achieve photon noise limited sensitivity with larger than 100 pW absorbed optical power. Both the microstrip KIDs and the antenna feed network make use of a low-loss amorphous silicon dielectric. A new aspect of the antenna implementation is the use of a NbTiN microstrip feed network to facilitate impedance matching to the 50 Ohm antenna. The array has 256 pixels on a 6-inch wafer and each pixel has two polarizations with two Al KIDs. The KIDs are designed with a half wavelength microstrip transmission line with parallel plate capacitors at the two ends. The resonance frequency range is 400 to 800 MHz. The readout feedline is also implemented in microstrip and has an impedance transformer from 50 Ohm to 9 Ohm at its input and output.

We report on the development of scalable prototype microwave kinetic inductance detector (MKID) arrays tailored for future multi-kilo-pixel experiments that are designed to simultaneously characterize the polarization properties of both the cosmic microwave background (CMB) and Galactic dust emission. These modular arrays are composed of horn-coupled, polarization-sensitive MKIDs, and each pixel has four detectors: two polarizations in two spectral bands between 125 and 280 GHz. A horn is used to feed each array element, and a planar orthomode transducer, composed of two waveguide probe pairs, separates the incoming light into two linear polarizations. Diplexers composed of resonant-stub band-pass filters separate the radiation into 125 to 170 GHz and 190 to 280 GHz pass bands. The millimeter-wave power is ultimately coupled to a hybrid co-planar waveguide microwave kinetic inductance detector using a novel, broadband circuit developed by our collaboration. Electromagnetic simulations show the expected absorption efficiency of the detector is approximately 90%. Array fabrication will begin in the summer of 2016.

A recent theory predicts that bulk superflow breaks down in a heat flux, Q, through an instability, where the fluctuations of the counterflow velocity diverge. In order to observe this interesting effect a number of obstacles must be overcome. First, it was recently suggested that in an ordinary thermal conductivity cell, the breakdown of superfluidity occurs initially at the hot end plate metal/liquid boundary, and not in the bulk superfluid. Second, the sample can become nonuniform due to a temperature gradient in the superfluid caused by vortices. Third, the sample may become non-uniform due to a pressure gradient induced by gravity. We will present analyses of these adverse effects in the Q-T plane and discuss ways to overcome them. The possibility of using the International Space Station to remove the gravity rounding effect will be elaborated. Introduction Due to the admirable success of the Renormalization Group theory and its extension, the Dynamic Renormalization Group theory, much of static and dynamical phase transition phenomena have been explained to some degree of satisfaction. It is therefore quite surprising that under an applied heat current, the properties of He on the superfluid side of the transition are found to be quite different from what is expected. For example, recent measurements of the heat capacity CQ of He in a constant applied heat flux Q showed that the change in the heat capacity due to Q is much larger than predicted. Aside from this discrepancy, it has been predicted that near the bulk superfluid breakdown temperature Tc (Q), CQ is expected to diverge with a very different exponent. Copyright © 2001 by the American Institute of Aeronautics and Astronautics, Inc. No copyright is asserted in the United States under Title 17, U. S. Code. The U. S. Government has a royalty-free license to exercise all rights under the copyright claimed herein for Governmental Purposes. All other rights are reserved by the copyright owner. At Tc (Q), the fluctuations of the counterflow velocity are also expected to diverge. These predictions are based on very general thermodynamic grounds. Therefore one would expect that near Tc (Q) there is a region rich in interesting new physics. However, reaching TC(Q) has proven to be difficult. The reasons for these difficulties as well as ways to deal with them will be explored in the following sections. Surface Breakdown of Superfluidity Tc (Q) is defined to be the bulk superfluid breakdown temperature under a heat flux. From the point of view of theory, this breakdown point arises from the optimization of the Ginsburg-Landau type free energy with V| | set to zero ( I / / is the order parameter). At Tc (Q), one expects to observe an abrupt change from a uniform state (V|^/j = 0) with no temperature gradient to a non-uniform state with a temperature gradient. However, what was observed on Earth is a gradual evolution of a non-uniform state near the hot end plate of a thermal conductivity cell, to another non-uniform state with a Hel-Hell interface inside the cell. In both of these non-uniform states, i// changes from zero at the boundary or a Hel-Hell interface to a finite value far from the boundary. This change occurs over a distance of a few correlation lengths, resulting in a large V| | value. Therefore the temperature at the Hel-Hell interface first measured by Duncan,, Ahlers and Steinberg (DAS), T} (Q), can be interpreted as resulting from the Ginsburg-Landau type free energy with a dominant V| | term. A temperature gradient in Hell adjacent to solid boundary where conversion of heat into counterflow occurs is generally associated with the singular Kapitza boundary resistance. A model was put forth by Harter et al suggesting that the singular Kapitza temperature profile at the hot endplate evolves into the Hel-Hell interface through an instability at the boundary. This model predicted a temperature that

We describe the motivation and status of a new space flight experiment to test the universality hypothesis as applied to second-order phase transitions. We plan to measure the temperature dependence of the superfluid density of helium in the region very close to the superfluid transition on paths of constant pressure along the lambda line. Recently developed high-resolution second-sound detectors have substantially improved our ability to study the behavior of the superfluid density close to the transition. In order to demonstrate the feasibility of the flight experiment, ground based measurements have been conducted. Second-sound was generated using the nearly reversible magnetic entropy of a paramagnetic material and by the conventional heater method. A superconducting pressure gauge was built to allow nondissipative, precision pressure measurement and control. These systems have been fully integrated to demonstrate the performance needed for flight. Preliminary results of the second-sound measurements are presented which are more consistent with universality than were previous experiments.

A high resolution thermometer (HRT) was developed using a dilute alloy of Mn in Pd as the magnetic sensing element instead of the traditional paramagnetic salt. Use of the alloy material facilitated a significant decrease in the total mass of the device to about 3.5 g. The noise and drift of the device were measured and found to be comparable with that of the larger HRTs used on past flight experiments. The origin of the noise observed in state-of-the-art HRTs and the potential of the new thermometric material for achieving lower noise figures is discussed