Search

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., 6 pages, 4 figures, Journal of Low Temperature Physics

Future instruments employing cryogenic detectors for millimeter and submillimeter astronomy applications can benefit greatly from silicon vacuum windows with broadband antireflection treatment. Silicon is an ideal optical material at these wavelengths due to numerous attractive properties, including low loss, high refractive index, and high strength. However, its high index ($$n=3.4$$) necessitates antireflection (AR) treatment, which has proven a major challenge, especially for the multilayer treatments required for wide spectral bandwidths. We address this challenge by developing a wide-bandwidth integral AR structure for silicon vacuum windows using a novel fabrication technique, tuning the effective refractive index of each AR layer using deep reactive ion etching (DRIE) and using wafer bonding to assemble the structure. We present the progress we have made in designing and fabricating such vacuum windows from 100-mm-diameter silicon wafers. We have previously demonstrated a two-layer AR structure for windows over a 1.6:1 bandwidth and are currently fabricating a four-layer coating designed for a 4:1 bandwidth. We have also converged on a design for a six-layer structure optimized to give − 20 dB reflection between 80 and 420 GHz (5.25:1 bandwidth), which will be useful for future multicolor Sunyaev–Zel’dovich (SZ) observations.

The thermal Sunyaev-Zel'dovich (tSZ) effect is a powerful tool with the potential for constraining directly the properties of the hot gas that dominates dark matter halos because it measures pressure and thus thermal energy density. Studying this hot component of the circumgalactic medium (CGM) is important because it is strongly impacted by star-formation and active galactic nuclei (AGN) activity in galaxies, participating in the feedback loop that regulates star and black hole mass growth in galaxies. We study the tSZ effect across a wide halo mass range using three cosmological hydrodynamical simulations: Illustris-TNG, EAGLE, and FIRE-2. Specifically, we present the scaling relation between tSZ signal and halo mass and radial profiles of gas density, temperature, and pressure for all three simulations. The analysis includes comparisons to Planck tSZ observations and to the thermal pressure profile inferred from the Atacama Cosmology Telescope (ACT) measurements. We compare these tSZ data to the simulations to interpret the measurements in terms of feedback and accretion processes in the CGM. We also identify as-yet unobserved potential signatures of these processes that may be visible in future measurements, which will have the capability of measuring tSZ signals to even lower masses. We also perform internal comparisons between runs with different physical assumptions. We conclude: (1) there is strong evidence for the impact of feedback at $R_{500}$ but that this impact decreases by $5R_{500}$, and (2) the thermodynamic profiles of the CGM are highly dependent on the implemented model, such as cosmic-ray or AGN feedback prescriptions., 21 pages, 10 figures, submitted to ApJ, comments welcome

We use a sample of 14 massive, dynamically relaxed galaxy clusters to constrain the Hubble Constant, $H_0$, by combining X-ray and Sunyaev-Zel'dovich (SZ) effect signals measured with Chandra, Planck and Bolocam. This is the first such analysis to marginalize over an empirical, data-driven prior on the overall accuracy of X-ray temperature measurements, while our restriction to the most relaxed, massive clusters also minimizes astrophysical systematics. For a cosmological-constant model with $\Omega_m = 0.3$ and $\Omega_{\Lambda} = 0.7$, we find $H_0 = 67.3^{+21.3}_{-13.3}$ km/s/Mpc, limited by the temperature calibration uncertainty (compared to the statistically limited constraint of $H_0 = 72.3^{+7.6}_{-7.6}$ km/s/Mpc). The intrinsic scatter in the X-ray/SZ pressure ratio is found to be $13 \pm 4$ per cent ($10 \pm 3$ per cent when two clusters with significant galactic dust emission are removed from the sample), consistent with being primarily due to triaxiality and projection. We discuss the prospects for reducing the dominant systematic limitation to this analysis, with improved X-ray calibration and/or precise measurements of the relativistic SZ effect providing a plausible route to per cent level constraints on $H_0$., Comment: 16 pages, 9 figures, submitted to MNRAS

We report the non-thermal pressure fraction (Pnt/Ptot) obtained from a three-dimensional triaxial analysis of 16 galaxy clusters in the CLASH sample using gravitational lensing (GL) data primarily from Subaru and HST, X-ray spectroscopic imaging from Chandra, and Sunyaev–Zel’dovich effect (SZE) data from Planck and Bolocam. Our results span the approximate radial range 0.015–0.4 R200m (∼35–1000 kpc). At cluster-centric radii smaller than 0.1 R200m the ensemble average Pnt/Ptot is consistent with zero with an upper limit of 9 per cent, indicating that heating from active galactic nuclei and other relevant processes does not produce significant deviations from hydrostatic equilibrium (HSE). The ensemble average Pnt/Ptot increases outside of this radius to approximately 20 per cent at 0.4 R200m, as expected from simulations, due to newly accreted material thermalizing via a series of shocks. Also in agreement with simulations, we find significant cluster-to-cluster variation in Pnt/Ptot and little difference in the ensemble average Pnt/Ptot based on dynamical state. We conclude that on average, even for diverse samples, HSE-derived masses in the very central regions of galaxy clusters require only modest corrections due to non-thermal motions.

In this paper, we will discuss the design, optimization, and measured results of the lumped-element bandpass filter (BPF) network used for submillimeter and millimeter imaging. Careful calculations are required during the filter design process to achieve a filter response that meets our needs. Circuit and layout models are studied to represent the filter transfer function with a physical layout. The measured results exhibit good frequency response and strong agreement with the predicted results. The proposed BPF network was used as part of the multicolor superconducting microresonator imaging array for the Caltech Submillimeter Observatory (CSO).

The LCT project aims to refurbish the CSO telescope, move it from Maunakea to Chajnantor, in Chile, and operate it scientifically for 10 years. The relocation of the telescope involves a variety of changes in the working conditions, which demands in-depth mechanical analysis. To conduct the required studies, an FEM model of the entire telescope has been developed, together with CFD tools. This paper introduces the LCT project, presents the full-FEM model, its validation, and the first steps towards these analyses. Preliminary results of the simulations of the telescope, considering the working conditions at the Plateau, are also shown.

A substantial amount of important scientific information is contained within astronomical data at the submillimeter and far-infrared (FIR) wavelengths, including information regarding dusty galaxies, galaxy clusters, and star-forming regions; however, these wavelengths are among the least-explored fields in astronomy because of the technological difficulties involved in such research. Over the past 20 years, considerable efforts have been devoted to developing submillimeter- and millimeter-wavelength astronomical instruments and telescopes. The number of detectors is an important property of such instruments and is the subject of the current study. Future telescopes will require as many as hundreds of thousands of detectors to meet the necessary requirements in terms of the field of view, scan speed, and resolution. A large pixel count is one benefit of the development of multiplexable detectors that use kinetic inductance detector (KID) technology. This paper presents the development of all aspects of the readout electronics for a KID-based instrument, which enabled one of the largest detector counts achieved to date in submillimeter-/millimeter-wavelength imaging arrays: a total of 2304 detectors. The work presented in this paper had been implemented in the MUltiwave- length Submillimeter Inductance Camera (MUSIC), a instrument for the Caltech Submillimeter Observatory (CSO) during 2013 and 2015.

This article presents an analysis and the resulting limits on light dark matter inelastically scattering off of electrons, and on dark photon and axion-like particle absorption, using a second-generation SuperCDMS high-voltage eV-resolution detector. The 0.93 gram Si detector achieved a 3 eV phonon energy resolution; for a detector bias of 100 V, this corresponds to a charge resolution of 3% of a single electron-hole pair. The energy spectrum is reported from a blind analysis with 1.2 gram-days of exposure acquired in an above-ground laboratory. With charge carrier trapping and impact ionization effects incorporated into the dark matter signal models, the dark matter-electron cross section $\bar{\sigma}_{e}$ is constrained for dark matter masses from 0.5--$10^{4} $MeV$/c^{2}$; in the mass range from 1.2--50 eV$/c^{2}$ the dark photon kinetic mixing parameter $\varepsilon$ and the axioelectric coupling constant $g_{ae}$ are constrained. The minimum 90% confidence-level upper limits within the above mentioned mass ranges are $\bar{\sigma}_{e}\,=\,8.7\times10^{-34}$ cm$^{2}$, $\varepsilon\,=\,3.3\times10^{-14}$, and $g_{ae}\,=\,1.0\times10^{-9}$., Comment: 5 pages + title and references, 3 figures and 1 table

We present an analysis of electron recoils in cryogenic germanium detectors operated during the SuperCDMS Soudan experiment. The data are used to set new constraints on the axioelectric coupling of axionlike particles and the kinetic mixing parameter of dark photons, assuming the respective species constitutes all of the galactic dark matter. This study covers the mass range from 40 eV/c2 to 500 keV/c2 for both candidates, excluding previously untested parameter space for masses below ∼1 keV/c2. For the kinetic mixing of dark photons, values below 10−15 are reached for particle masses around 100 eV/c2; for the axioelectric coupling of axionlike particles, values below 10−12 are reached for particles with masses in the range of a few-hundred eV/c2.

We present limits on spin-independent dark matter-nucleon interactions using a $10.6$ $\mathrm{g}$ Si athermal phonon detector with a baseline energy resolution of $\sigma_E=3.86 \pm 0.04$ $(\mathrm{stat.})^{+0.19}_{-0.00}$ $(\mathrm{syst.})$ $\mathrm{eV}$. This exclusion analysis sets the most stringent dark matter-nucleon scattering cross-section limits achieved by a cryogenic detector for dark matter particle masses from $93$ to $140$ $\mathrm{MeV}/c^2$, with a raw exposure of $9.9$ $\mathrm{g}\cdot\mathrm{d}$ acquired at an above-ground facility. This work illustrates the scientific potential of detectors with athermal phonon sensors with eV-scale energy resolution for future dark matter searches., Comment: 7 pages, 4 figures, this version includes ancillary files from official data release

We present a status update on the development of a phonon-mediated particle detector using kinetic inductance detector (KID). The design is intended for O(1) kg substrate, using O(10^2)KIDs on a single readout line, to image the athermal phonon distribution at 95% inductor current uniformity, using the coplanar waveguide feedline, ground shield, and a new class of KIDs with symmetric coplanar stripline (sCPS) inductor. The multiplexing is designed upon the frequency-geometry relation we develop for the sCPS KIDs. We introduce the fabrications of the Nb RF assessment prototypes and the high phonon collection efficiency Al–Nb devices. We achieve ≲ 0.07% frequency displacement on a 80-KID RF assessment prototype, and the result indicates that we may place more than 180 resonances in our 0.4 GHz readout band with minimal frequency misordering. The coupling quality factors are ∼ 10^5 as designed. Finally, we update our work in progress in fabricating the O(10^2) KID, bi-material, O(1) kg detectors, and the expected position and energy resolutions.

This corrects the article DOI: 10.1103/PhysRevLett.121.051301.

We present the design, simulation, and planned fabrication process of a flat high resistivity silicon gradient index (GRIN) lens for millimeter and submillimeter wavelengths with very low absorption losses. The gradient index is created by subwavelength holes whose size increases with the radius of the lens. The effective refractive index created by the subwavelength holes is constant over a very wide bandwidth, allowing the fabrication of achromatic lenses up to submillimeter wavelengths. The designed GRIN lens was successfully simulated and shows an expected efficiency better than that of a classic silicon plano-concave spherical lens with approximately the same thickness and focal length. Deep reactive ion etching (DRIE) and wafer-bonding of several patterned wafers will be used to realize our first GRIN lens prototype., Comment: J Low Temp Phys (2019)

The Cryogenic Dark Matter Search (CDMS II) experiment aims to detect dark matter particles that elastically scatter from nuclei in semiconductor detectors. The resulting nuclear-recoil energy depositions are detected by ionization and phonon sensors. Neutrons produce a similar spectrum of low-energy nuclear recoils in such detectors, while most other backgrounds produce electron recoils. The absolute energy scale for nuclear recoils is necessary to interpret results correctly. The energy scale can be determined in CDMS II silicon detectors using neutrons incident from a broad-spectrum $^{252}$Cf source, taking advantage of a prominent resonance in the neutron elastic scattering cross section of silicon at a recoil (neutron) energy near 20 (182) keV. Results indicate that the phonon collection efficiency for nuclear recoils is $4.8^{+0.7}_{-0.9}$% lower than for electron recoils of the same energy. Comparisons of the ionization signals for nuclear recoils to those measured previously by other groups at higher electric fields indicate that the ionization collection efficiency for CDMS II silicon detectors operated at $\sim$4 V/cm is consistent with 100% for nuclear recoils below 20 keV and gradually decreases for larger energies to $\sim$75% at 100 keV. The impact of these measurements on previously published CDMS II silicon results is small., Comment: 22 pages, 17 figures, 1 table, 1 appendix

The Super Cryogenic Dark Matter Search experiment (SuperCDMS) at the Soudan Underground Laboratory studied energy loss associated with Frenkel defect formation in germanium crystals at mK temperatures using in situ $^{210}$Pb sources. We examine the spectrum of $^{206}$Pb nuclear recoils near its expected 103 keV endpoint energy and determine an energy loss of $\left(6.08\pm0.18\right)$ %, which we attribute to defect formation. From this result and using TRIM simulations, we extract the first experimentally determined average displacement threshold energy of $\left(19.7^{+0.6}_{-0.5}\right)$ eV for germanium. This has implications for the analysis thresholds of future germanium-based dark matter searches., 4 Figures, Two data files, One data release description file

Many applications in astronomy from tens of GHz to THz frequencies, on the ground and in space, would benefit from silicon optics because silicon's high refractive index and low loss make it an ideal optical material at these frequencies. Silicon can also be used for ambient temperature vacuum windows, however, it's large refractive index necessitates an antireflection coating. Moreover, multilayer antireflection treatments are necessary for wide spectral bandwidths, with wider bandwidths requiring more layers. To this end, we are developing multilayer coatings for silicon by bonding together wafers individually patterned with deep reactive ion etching (DRIE). While a standard approach to antireflection coating is to deposit or laminate dielectric layers of appropriate refractive index, it is difficult (but not impossible) to find low loss dielectrics with the correct refractive index and other properties to match silicon well, especially if more than one layer is required, operation up to THz frequencies is desired, and/or the optic will be used cryogenically. Textured surfaces are an attractive alternative to dielectric antireflection coatings. For millimeter wavelengths, multi-layer antireflection textures with up to 4:1 bandwidths have been cut successfully into silicon lens surfaces with a dicing saw, but this technique becomes unusable at frequencies of 300 GHz and higher given the saw dimensions. Laser machining is being explored but demonstrations are not yet available. DRIE works well on flat surfaces (and has been demonstrated for narrowband windows to THz frequencies), but there are limits to the depth and aspect ratio of the features it can create. Furthermore, etching has not been adapted to large, curved optics. We are pursuing a hybrid approach to this problem: construct a silicon optic by stacking flat patterned wafers. The starting point is a multilayer optical design incorporating both an axial gradient in the refractive index for antireflection and a radial index gradient for focusing. For each optical layer, a hole or post pattern is used to achieve the required effective index of refraction. Using a novel multilayer etching procedure, several layers of the optical structure are fabricated on a flat wafer. Several individually patterned wafers are stacked and bonded together to produce the completed optic. This approach can thus address the aspect ratio limitations of DRIE, and it obviates etching on curved surfaces. We present our results to date, which include simulations, fabrication and measurements of 2- and 4-layer coatings with wafer-bonding, on high resistivity silicon wafers, at 75-330 GHz. The good agreement between the simulations and the test results validates the fabrication and test setup, and allows us to continue the development of larger bandwidth and more efficient coatings. Our near-term goal is to produce a 10-cm lens with a 7-layer coating providing 5.5:1 bandwidth from 75 to 420 GHz, with less than 1% reflection, eventually scaling up to 15-cm, 30-cm, and larger elements.

Future direct searches for low-mass dark matter particles with germanium detectors, such as SuperCDMS SNOLAB, are expected to be limited by backgrounds from radioactive isotopes activated by cosmogenic radiation inside the germanium. There are limited experimental data available to constrain production rates and a large spread of theoretical predictions. We examine the calculation of expected production rates, and analyze data from the second run of the CDMS low ionization threshold experiment (CDMSlite) to estimate the rates for several isotopes. We model the measured CDMSlite spectrum and fit for contributions from tritium and other isotopes. Using the knowledge of the detector history, these results are converted to cosmogenic production rates at sea level. The production rates in atoms/(kg$\cdot$day) are 74$\pm$9 for $^3$H, 1.5$\pm$0.7 for $^{55}$Fe, 17$\pm$5 for $^{65}$Zn, and 30$\pm$18 for $^{68}$Ge., 14 pages, 10 figures, 5 tables. v5 contains the extended data release (and documentation) of the CDMSlite Run 2 data as ancillary files

We present the first limits on inelastic electron-scattering dark matter and dark photon absorption using a prototype SuperCDMS detector having a charge resolution of 0.1 electron-hole pairs (CDMS HVeV, a 0.93 gram CDMS HV device). These electron-recoil limits significantly improve experimental constraints on dark matter particles with masses as low as 1 MeV/$\mathrm{c^2}$. We demonstrate a sensitivity to dark photons competitive with other leading approaches but using substantially less exposure (0.49 gram days). These results demonstrate the scientific potential of phonon-mediated semiconductor detectors that are sensitive to single electronic excitations., 6 pages + title and references, 6 figures, includes erratum submitted to PRL and data release

Although high-resistivity, low-loss silicon is an excellent material for THz transmission optics, its high refractive index necessitates antireflection treatment. We fabricated a wide-bandwidth, two-layer antireflection treatment by cutting subwavelength structures into the silicon surface using multi-depth deep reactive ion etching (DRIE). A wafer with this treatment on both sides has, Comment: Accepted for publication in Applied Optics

We report the result of a blinded search for weakly interacting massive particles (WIMPs) using the majority of the SuperCDMS Soudan data set. With an exposure of 1690 kg d, a single candidate event is observed, consistent with expected backgrounds. This analysis (combined with previous Ge results) sets an upper limit on the spin-independent WIMP–nucleon cross section of 1.4×10−44 (1.0×10−44) cm2 at 46 GeV/c2. These results set the strongest limits for WIMP–germanium-nucleus interactions for masses >12 GeV/c2.

We jointly analyze Bolocam Sunyaev-Zeldovich (SZ) effect and Chandra X-ray data for a set of 45 clusters to derive gas density and temperature profiles without using spectroscopic information. The sample spans the mass and redshift range $3 \times 10^{14} M_{\odot} \le M_{500} \le 25 \times 10^{14} M_{\odot}$ and $0.15\le z \le 0.89$. We define cool-core (CC) and non-cool core (NCC) subsamples based on the central X-ray luminosity, and 17/45 clusters are classified as CC. In general, the profiles derived from our analysis are found to be in good agreement with previous analyses, and profile constraints beyond $r_{500}$ are obtained for 34/45 clusters. In approximately 30% of the CC clusters our analysis shows a central temperature drop with a statistical significance of $>3\sigma$; this modest detection fraction is due mainly to a combination of coarse angular resolution and modest S/N in the SZ data. Most clusters are consistent with an isothermal profile at the largest radii near $r_{500}$, although 9/45 show a significant temperature decrease with increasing radius. The sample mean density profile is in good agreement with previous studies, and shows a minimum intrinsic scatter of approximately 10% near $0.5 \times r_{500}$. The sample mean temperature profile is consistent with isothermal, and has an intrinsic scatter of approximately 50% independent of radius. This scatter is significantly higher compared to earlier X-ray-only studies, which find intrinsic scatters near 10%, likely due to a combination of unaccounted for non-idealities in the SZ noise, projection effects, and sample selection., Comment: 42 pages, 52 figures

Joint thermal conductance testing has been undertaken for bolted copper to copper connections from 60 mK to 26 K. This testing was performed to validate an initial design basis for the SuperCDMS experiment, where a dilution refrigerator will be coupled to a cryostat via multiple bolted connections. Copper used during testing was either gold plated or passivated with citric acid to prevent surface oxidation. Results obtained are well fit by a power law regression of joint thermal conductance to temperature and match well with data collected during a literature review.

SuperCDMS SNOLAB will be a next-generation experiment aimed at directly detecting low-mass (< 10 GeV/c$^2$) particles that may constitute dark matter by using cryogenic detectors of two types (HV and iZIP) and two target materials (germanium and silicon). The experiment is being designed with an initial sensitivity to nuclear recoil cross sections ~ 1 x 10$^{-43}$ cm$^2$ for a dark matter particle mass of 1 GeV/c$^2$, and with capacity to continue exploration to both smaller masses and better sensitivities. The phonon sensitivity of the HV detectors will be sufficient to detect nuclear recoils from sub-GeV dark matter. A detailed calibration of the detector response to low energy recoils will be needed to optimize running conditions of the HV detectors and to interpret their data for dark matter searches. Low-activity shielding, and the depth of SNOLAB, will reduce most backgrounds, but cosmogenically produced $^{3}$H and naturally occurring $^{32}$Si will be present in the detectors at some level. Even if these backgrounds are x10 higher than expected, the science reach of the HV detectors would be over three orders of magnitude beyond current results for a dark matter mass of 1 GeV/c$^2$. The iZIP detectors are relatively insensitive to variations in detector response and backgrounds, and will provide better sensitivity for dark matter particle masses (> 5 GeV/c$^2$). The mix of detector types (HV and iZIP), and targets (germanium and silicon), planned for the experiment, as well as flexibility in how the detectors are operated, will allow us to maximize the low-mass reach, and understand the backgrounds that the experiment will encounter. Upgrades to the experiment, perhaps with a variety of ultra-low-background cryogenic detectors, will extend dark matter sensitivity down to the "neutrino floor", where coherent scatters of solar neutrinos become a limiting background., SuperCDMS SNOLAB Projected sensitivity reach

International audience; We present pressure profiles of galaxy clusters determined from high-resolution Sunyaev–Zel’dovich (SZ) effect observations of 14 clusters, which span the redshift range of $0.25\lt z\lt 0.89$. The procedure simultaneously fits spherical cluster models to MUSTANG and Bolocam data. In this analysis, we adopt the generalized NFW parameterization of pressure profiles to produce our models. Our constraints on ensemble-average pressure profile parameters, in this study γ, C (500), and P (0), are consistent with those in previous studies, but for individual clusters we find discrepancies with the X-ray derived pressure profiles from the ACCEPT2 database. We investigate potential sources of these discrepancies, especially cluster geometry, electron temperature of the intracluster medium, and substructure. We find that the ensemble mean profile for all clusters in our sample is described by the parameters $[\gamma ,{C}_{500},{P}_{0}]=[{0.3}_{-0.1}^{+0.1},{1.3}_{-0.1}^{+0.1},{8.6}_{-2.4}^{+2.4}]$, cool core clusters are described by $[\gamma ,{C}_{500},{P}_{0}]\ =[{0.6}_{-0.1}^{+0.1},{0.9}_{-0.1}^{+0.1},{3.6}_{-1.5}^{+1.5}]$, and disturbed clusters are described by $[\gamma ,{C}_{500},{P}_{0}]=[{0.0}_{-0.0}^{+0.1},{1.5}_{-0.2}^{+0.1},{13.8}_{-1.6}^{+1.6}]$. Of the 14 clusters, 4 have clear substructure in our SZ observations, while an additional 2 clusters exhibit potential substructure.

Silicon optics with broadband antireflective (AR) treatments are being developed for millimeter and submillimeter-wave applications. Combined photolithography and deep reactive ion etching (DRIE) techniques are used to texture the surfaces of high resistivity, low loss silicon wafers. We report on the design, fabrication, and testing at 250 GHz of single and double layer AR treatments on silicon optics.

Kinetic inductance detectors (KIDs) show promise as a competitive technology for astronomical observations over a wide range of wavelengths. We are interested in comparing the fundamental limitations to the sensitivity of KIDs with that of transition edge sensors (TESs) at millimeter wavelengths, specifically over the wavelengths required for studies of the Cosmic Microwave Background (CMB). We calculate the total fundamental noise arising from optical and thermal excitations in TESs and KIDs for a variety of bath temperatures and optical loading scenarios for applications at millimeter wavelengths. Special consideration is given to the case of ground-based observations of 100 GHz radiation with a 100 mK bath temperature, conditions consistent with the planned second module of the QUBIC telescope, a CMB instrument. Under these conditions, a titanium nitride KID with optimized critical temperature pays a few percent noise penalty compared to a typical optimized TES., 6 pages, 2 figures, Proceedings of 15th International Workshop on Low Temperature Detectors (LTD-15, Pasadena, California, June 2013), To be published in the Journal of Low Temperature Physics (JLTP)

We are developing athermal-phonon mediated particle detectors that utilize microwave kinetic inductance detectors (MKIDs) as phonon sensors. MKIDs afford natural frequency domain multiplexing, which allows for massive substrates to be patterned with hundreds of sensors while keeping readout complexity to a minimum. Previously, our 2 cm $$\times $$ 2 cm $$\times $$ 1 mm proof-of-principle device utilized 20 MKIDs and, from the magnitude and timing of their response, we were able to reconstruct the position of a particle interaction to $$

We present measurements of the thermal conductivity between 0.05 and 1 K, and radioactive contamination levels, for some thermally isolating materials. TIMET Ti 15-3-3-3, Mersen grade 2020 graphite, Vespel SP-1, Vespel SP-22, Vespel SCP-5000, Vespel SCP-5050, Graphlite CFRP, and a Kapton/epoxy composite are all investigated. Thermal conductivities were measured using a single-heater longitudinal heat flow method. Material radioactivity was determined for the materials at a low background counting facility using a high-purity gamma detector and GEANT4 Monte Carlo simulations.

Design specifications for the support structures of low temperature instrumentation often call for low thermal conductivity between temperature stages, high stiffness, and specific load bearing capabilities. While overall geometric design plays an important role in both overall stiffness and heat conduction between stages, material selection can affect a structure’s properties significantly. In this contribution, we suggest and compare several alternative materials to the current standard materials for building cryogenic support structures.

We have imaged the Sunyaev–Zel'dovich (SZ) effect signals at 140 and 270 GHz toward 10 galaxy clusters with Bolocam and AzTEC/ASTE. We also used Planck data to constrain the signal at large angular scales, Herschel–SPIRE images to subtract the brightest galaxies that comprise the cosmic infrared background (CIB), Chandra imaging to map the electron temperature T_e of the intra-cluster medium, and Hubble Space Telescope imaging to derive models of each galaxy cluster's mass density. The galaxy clusters gravitationally lens the background CIB, which produced an on-average reduction in brightness toward the galaxy clusters' centers after the brightest galaxies were subtracted. We corrected for this deficit, which was between 5% and 25% of the 270 GHz SZ effect signal within R_(2500). Using the SZ effect measurements, along with the X-ray constraint on T_e , we measured each galaxy cluster's average line of sight (LOS) velocity v_z within R_(2500), with a median per-cluster uncertainty of ±700 km s^(−1). We found an ensemble-mean〈v_z 〉of 430 ± 210 km s^(−1), and an intrinsic cluster-to-cluster scatter σ_(int) of 470 ± 340 km s−1. We also obtained maps of v_z over each galaxy cluster's face with an angular resolution of 70''. All four galaxy clusters previously identified as having a merger oriented along the LOS showed an excess variance in these maps at a significance of ≃2–4σ, indicating an internal v_z rms of ≳1000 km s^(−1). None of the six galaxy clusters previously identified as relaxed or plane-of-sky mergers showed any such excess variance.

A common challenge in low temperature instrumentation is adequately heat sinking signal wires between room temperature and devices at base temperature. Using cryostat space for adequate heat sinking typically comes at the cost of complexity or experimental space. As such, it is useful to know how much heat sinking is adequate given the materials, heat sources and cooling capacities involved. We present a differential equation for modeling the heat flowing out of a flat cable along an interval over which it is adhered to an insulating interface which is bound to a metallic heat sinking surface and numerical results for realistic heat sinks in the Kelvin range. We also present a computational method for solving this differential equation.

Selecting sources with rising flux densities towards longer wavelengths from Herschel/SPIRE maps is an efficient way to produce a catalogue rich in high-redshift (z > 4) dusty star-forming galaxies. The effectiveness of this approach has already been confirmed by spectroscopic follow-up observations, but the previously available catalogues made this way are limited by small survey areas. Here we apply a map-based search method to 274 deg$^2$ of the HerMES Large Mode Survey (HeLMS) and create a catalogue of 477 objects with SPIRE flux densities $S_{500} > S_{350} >S_{250}$ and a $5 ��$ cut-off $S_{500} > $ 52 mJy. From this catalogue we determine that the total number of these "red" sources is at least an order of magnitude higher than predicted by galaxy evolution models. These results are in agreement with previous findings in smaller HerMES fields; however, due to our significantly larger sample size we are also able to investigate the shape of the red source counts for the first time. We have obtained spectroscopic redshift measurements for two of our sources using the Atacama Large Millimeter/submillimeter Array (ALMA). The redshifts z = 5.1 and z = 3.8 confirm that with our selection method we can indeed find high-redshift dusty star-forming galaxies., Accepted by MNRAS

© 2016 American Physical Society. The CDMS low ionization threshold experiment (CDMSlite) uses cryogenic germanium detectors operated at a relatively high bias voltage to amplify the phonon signal in the search for weakly interacting massive particles (WIMPs). Results are presented from the second CDMSlite run with an exposure of 70 kg day, which reached an energy threshold for electron recoils as low as 56 eV. A fiducialization cut reduces backgrounds below those previously reported by CDMSlite. New parameter space for the WIMP-nucleon spin-independent cross section is excluded for WIMP masses between 1.6 and 5.5 GeV/c2.

The Astrophysical Journal 819.1 (2016): 36 reproduced by permission of the AAS, Morphology is often used to infer the state of relaxation of galaxy clusters. The regularity, symmetry, and degree to which a cluster is centrally concentrated inform quantitative measures of cluster morphology. The Cluster Lensing and Supernova survey with Hubble Space Telescope (CLASH) used weak and strong lensing to measure the distribution of matter within a sample of 25 clusters, 20 of which were deemed to be "relaxed" based on their X-ray morphology and alignment of the X-ray emission with the Brightest Cluster Galaxy. Toward a quantitative characterization of this important sample of clusters, we present uniformly estimated X-ray morphological statistics for all 25 CLASH clusters. We compare X-ray morphologies of CLASH clusters with those identically measured for a large sample of simulated clusters from the MUSIC-2 simulations, selected by mass. We confirm a threshold in X-ray surface brightness concentration of C≥0.4 for cool-core clusters, where C is the ratio of X-ray emission inside 100 h70-1 kpc compared to inside 500 h70-1 kpc. We report and compare morphologies of these clusters inferred from Sunyaev-Zeldovich Effect (SZE) maps of the hot gas and in from projected mass maps based on strong and weak lensing. We find a strong agreement in alignments of the orientation of major axes for the lensing, X-ray, and SZE maps of nearly all of the CLASH clusters at radii of 500 kpc (approximately 1/2 R500 for these clusters). We also find a striking alignment of clusters shapes at the 500 kpc scale, as measured with X-ray, SZE, and lensing, with that of the near-infrared stellar light at 10 kpc scales for the 20 "relaxed" clusters. This strong alignment indicates a powerful coupling between the cluster- and galaxy-scale galaxy formation processes, A.B. was partially supported by the same NASA ADAP award NNX13AI41G and a Chandra archive grant SAO AR3-14013X. E.R. was supported by FP7- PEOPLE-2013-IIF (Grant Agreement PIIF-GA-2013-627474) and NSF AST-1210973. S.E. acknowledges the financial contribution from contracts ASI-INAF I/009/10/0 and PRIN-INAF 2012. This work was supported in part by National Science Foundation Grant No. PHYS-1066293 and the hospitality of the Aspen Center for Physics. J.S. was supported by NSF/AST-0838261, NASA/NNX11AB07G, and the Norris Foundation CCAT Postdoctoral Fellowship. G.Y. acknowledges financial support from MINECOʼs grant AYA2012-31101

Measuring the intrinsic shape and orientation of dark matter (DM) and intracluster (IC) gas in galaxy clusters is crucial to constraining their formation and evolution, and for enhancing the use of clusters as more precise cosmological probes. Extending our previous works, we present for the first time results from a triaxial joint analysis of the galaxy cluster Abell 1835, by means of X-ray, strong lensing (SL) and Sunyaev Zel'dovich (SZ) data. We parametrically reconstruct the full three-dimensional structure (triaxial shape and principal axis orientation) of both the DM and the IC gas, and the level of non-thermal pressure of the IC gas. We find that the intermediate-major and minor-major axis ratios of the DM are 0.71+/-0.08 and 0.59+/-0.05, respectively, and the major axis of the DM halo is inclined with respect to the line of sight at 18.3+/-5.2 deg. We present the first observational measurement of the non-thermal pressure out to R_{200}, which has been evaluated to be a few percent of the total energy budget in the internal regions, while reaching approximately 20% in the outer volumes. We discuss the implications of our method for the viability of the CDM scenario, focusing on the concentration parameter C and the inner slope of the DM gamma in order to test the cold dark matter (CDM) paradigm for structure formation: we measure gamma=1.01+/-0.06 and C=4.32+/-0.44, values which are close to the predictions of the CDM model. The combination of X-ray/SL data at high spatial resolution, capable of resolving the cluster core, with the SZ data, which are more sensitive to the cluster outer volume, allows us to characterize the level and the gradient of the gas entropy distribution and non-thermal pressure out to R_{200}, breaking the degeneracy among the physical models describing the thermal history of the ICM.

The Keck array is a new multi-camera Cosmic Microwave Background (CMB) polarimeter. Each camera contains 256 polarization pairs of antenna-coupled transition edge sensor (TES) bolometers. We recently deployed three of five cameras at the geographic South Pole, and plan to deploy the final two cameras in early 2012. This new telescope is an ideal instrument to search for the primordial B-mode polarization signal imprinted in the CMB by inflationary gravitational waves. We will discuss the design of the detectors and receivers, the status of current observations, and report on progress toward upgrading the instrument with the full compliment of polarized receivers.

We report on the recent progress of the Multicolor Submillimeter (kinetic) Inductance Camera, or MUSIC. MUSIC will use antenna-coupled Microwave Kinetic Inductance Detectors to observe in four colors (150 GHz, 230 GHz, 290 GHz and 350 GHz) with 2304 detectors, 576 per band, at the Caltech Submillimeter Observatory. It will deploy in 2012. Here we provide an overview of the instrument, focusing on the array design. We have also used a pathfinder demonstration instrument, DemoCam, to identify problems in advance of the deployment of MUSIC. In particular, we identified two major limiters of our sensitivity: out-of-band light directly coupling to the detectors (i.e. not through the antenna), effectively an excess load, and a large 1/f contribution from our amplifiers and electronics. We discuss the steps taken to mitigate these effects to reach background-limited performance (BLIP) in observation.

Spider, the Keck Array, and BICEP2 are projects to study the polarization of the cosmic microwave background (CMB). All three use large format arrays of antenna-coupled, membrane-isolated, transition edge sensors (TES’s). Although similar, each project requires its own set of device parameters, such as thermal conductance, time constants, and normal state resistances. We have perfected a fabrication process that achieves two primary objectives: (1) high device yields of 95% or greater, and (2) very low spreads in devices parameters. Currently our arrays are taking science data at the South Pole in both the BICEP2 and Keck array telescopes. The focal planes for Spider, a high altitude balloon mission, are on schedule for a 2012 deployment. An overview of fabrication and development is given as well as a snapshot of scientific data.

The Keck Array is a system of cosmic microwave background (CMB) polarimeters, each similar to the BICEP2 experiment. In this paper we report results from the 2012 and 2013 observing seasons, during which the Keck Array consisted of five receivers all operating in the same (150 GHz) frequency band and observing field as BICEP2. We again find an excess of B-mode power over the lensed-$\Lambda$CDM expectation of $> 5 \sigma$ in the range $30 < \ell < 150$ and confirm that this is not due to systematics using jackknife tests and simulations based on detailed calibration measurements. In map difference and spectral difference tests these new data are shown to be consistent with BICEP2. Finally, we combine the maps from the two experiments to produce final Q and U maps which have a depth of 57 nK deg (3.4 $\mu$K arcmin) over an effective area of 400 deg$^2$ for an equivalent survey weight of 250,000 $\mu$K$^{-2}$. The final BB band powers have noise uncertainty a factor of 2.3 times better than the previous results, and a significance of detection of excess power of $> 6\sigma$., Comment: 13 pages, 9 figures

Extensive surveys of galaxy clusters motivate us to assess the likelihood of cluster-cluster lensing (CCL), namely, gravitational-lensing of a background cluster by a foreground cluster. We briefly describe the characteristics of CCLs in optical, X-ray and SZ measurements, and calculate their predicted numbers for $\Lambda$CDM parameters and a viable range of cluster mass functions and their uncertainties. The predicted number of CCLs in the strong-lensing regime varies from several ($

We are developing athermal-phonon mediated particle detectors using microwave kinetic inductance detectors (MKIDs) as the phonon sensing elements. Since MKIDs are easily multiplexed, hundreds of sensors patterned on a single dielectric substrate can be read out simultaneously, leading to a precise, time-resolved measurement of the phonon flux at each point on the detector surface. In addition to providing a high-resolution measurement of the location of the interaction, the energy deposited by the particle can be reconstructed with an expected baseline resolution of tens of eV. The complexity of the cryogenic readout electronics is significantly reduced relative to designs based on multiplexed transition edge sensors (TES). Initial proof-of-principle devices demonstrate energy resolutions as good as 0.7 keV at 30 keV, dominated by the position dependence of the phonon signal. New designs are aimed at improving this resolution by more than an order of magnitude. Such high-resolution phonon mediated detectors would have applications including direct detection of dark matter, hard X-ray/soft gamma-ray astrophysics, neutrinoless double beta decay, and coherent neutrino-nucleus scattering.

The Data Acquisition System for the CDMS II dark matter experiment was designed and built when the experiment moved to its new underground installation at the Soudan Lab. The combination of remote operation and increased data load necessitated a completely new design. Elements of the original LabView system remained as stand-alone diagnostic programs, but the main data processing moved to a VME-based system with custom electronics for signal conditioning, trigger formation and buffering. The data rate was increased 100-fold and the automated cryogenic system was linked to the data acquisition. A modular server framework with associated user interfaces was implemented in Java to allow control and monitoring of the entire experiment remotely.

We present a joint analysis of Chandra X-ray observations, Bolocam thermal Sunyaev-Zel'dovich (SZ) effect observations, Hubble Space Telescope (HST) strong lensing data, and HST and Subaru Suprime-Cam weak lensing data. The multiwavelength dataset is used to constrain parametric models for the distribution of dark and baryonic matter in a sample of six massive galaxy clusters selected from the Cluster Lensing And Supernova survey with Hubble (CLASH). For five of the six clusters, the multiwavelength dataset is well described by a relatively simple model that assumes spherical symmetry, hydrostatic equilibrium, and entirely thermal pressure support. The joint analysis yields considerably better constraints on the total mass and concentration of the cluster compared to analysis of any one dataset individually. The subsample of five galaxy clusters is used to place an upper limit on the fraction of pressure support in the intracluster medium (ICM) due to nonthermal processes, such as turbulence and bulk flow of the gas. We constrain the nonthermal pressure fraction at r500c to be less than 0.11 at 95 percent confidence. This is in tension with state-of-the-art hydrodynamical simulations, which predict a nonthermal pressure fraction of approximately 0.25 at r500c for clusters of similar mass and redshift. This tension may be explained by the sample selection and/or our assumption of spherical symmetry., Comment: 25 pages, 8 figures

We report measurements of the fluctuations in atmospheric emission (atmospheric noise) above Mauna Kea recorded with Bolocam at 143 and 268 GHz from the Caltech Submillimeter Observatory (CSO). The 143 GHz data were collected during a 40 night observing run in late 2003, and the 268 GHz observations were made in early 2004 and early 2005 over a total of 60 nights. Below 0.5 Hz, the data time-streams are dominated by atmospheric noise in all observing conditions. The atmospheric noise data are consistent with a Kolmogorov-Taylor (K-T) turbulence model for a thin wind-driven screen, and the median amplitude of the fluctuations is 280 mK^2 rad^(-5/3) at 143 GHz and 4000 mK^2 rad^(-5/3) at 268 GHz. Comparing our results with previous ACBAR data, we find that the normalization of the power spectrum of the atmospheric noise fluctuations is a factor of 80 larger above Mauna Kea than above the South Pole at millimeter wavelengths. Most of this difference is due to the fact that the atmosphere above the South Pole is much drier than the atmosphere above Mauna Kea. However, the atmosphere above the South Pole is slightly more stable as well: the fractional fluctuations in the column depth of precipitable water vapor are a factor of sqrt(2) smaller at the South Pole compared to Mauna Kea. Based on our atmospheric modeling, we developed several algorithms to remove the atmospheric noise, and the best results were achieved when we described the fluctuations using a low-order polynomial in detector position over the 8 arcmin field of view (FOV). However, even with these algorithms, we were not able to reach photon-background-limited instrument photometer (BLIP) performance at frequencies below 0.5 Hz in any observing conditions., Comment: 48 pages, 16 figures, accepted for publication in ApJ