Performance of Hybrid NbTiN-Al Microwave Kinetic Inductance Detectors as Direct Detectors for Sub-millimeter Astronomy

In the next decades millimeter and sub-mm astronomy requires large format imaging arrays and broad-band spectrometers to complement the high spatial and spectral resolution of the Atacama Large Millimeter/sub-millimeter Array. The desired sensors for these instruments should have a background limited sensitivity and a high optical efficiency and enable arrays thousands of pixels in size. Hybrid microwave kinetic inductance detectors consisting of NbTiN and Al have shown to satisfy these requirements. We present the second generation hybrid NbTiN-Al MKIDs, which are photon noise limited in both phase and amplitude readout for loading levels $P_{850GHz} \geq 10$ fW. Thanks to the increased responsivity, the photon noise level achieved in phase allows us to simultaneously read out approximately 8000 pixels using state-of-the-art electronics. In addition, the choice of superconducting materials and the use of a Si lens in combination with a planar antenna gives these resonators the flexibility to operate within the frequency range $0.09 < \nu < 1.1$ THz. Given these specifications, hybrid NbTiN-Al MKIDs will enable astronomically usable kilopixel arrays for sub-mm imaging and moderate resolution spectroscopy.Comment: 7 pages, 3 figures. Presented at SPIE Astronomical Telescopes and Instrumentation 2014: Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VI

Photon noise limited radiation detection with lens-antenna coupled Microwave Kinetic Inductance Detectors

Microwave Kinetic Inductance Detectors (MKIDs) have shown great potential for sub-mm instrumentation because of the high scalability of the technology. Here we demonstrate for the first time in the sub-mm band (0.1...2 mm) a photon noise limited performance of a small antenna coupled MKID detector array and we describe the relation between photon noise and MKID intrinsic generation-recombination noise. Additionally we use the observed photon noise to measure the optical efficiency of detectors to be 0.8+-0.2.Comment: The following article has been submitted to AP

Conceptual Problems of Fractal Cosmology

This report continues recent Peebles-Turner debate "Is cosmology solved?" and considers the first results for Sandage's program for "Practical cosmology". A review of conceptual problems of modern cosmological models is given, among them: the nature of the space expansion; recession velocities of distant galaxies more than velocity of light; cosmological Friedmann force; continuous creation of gravitating mass in Friedmann's equation; cosmological pressure is not able to produce a work; cosmological gravitational frequency shift; Friedmann-Holtsmark paradox; the problem of the cosmological constant; Einstein's and Mandelbrot's Cosmological Principles; fractality of observed galaxy distribution; Sandage's 21st problem: Hubble - de Vaucouleurs paradox; quantum nature of gravity force.Comment: 17 pages, no Figures, report presented at Gamow Memorial Conference, August 1999, St.-Petersburg, Russi

Digital compensation of the side-band-rejection ratio in a fully analog 2SB sub-millimeter receiver

In observational radio astronomy, sideband-separating receivers are preferred, particularly under high atmospheric noise, which is usually the case in the sub-millimeter range. However, obtaining a good rejection ratio between the two sidebands is difficult since, unavoidably, imbalances in the different analog components appear. We describe a method to correct these imbalances without making any change in the analog part of the sideband-separating receiver, specifically, keeping the intermediate-frequency hybrid in place. This opens the possibility of implementing the method in any existing receiver. We have built hardware to demonstrate the validity of the method and tested it on a fully analog receiver operating between 600 and 720GHz. We have tested the stability of calibration and performance vs time and after full resets of the receiver. We have performed an error analysis to compare the digital compensation in two configurations of analog receivers, with and without intermediate frequency (IF) hybrid. An average compensated sideband rejection ratio of 46dB is obtained. Degradation of the compensated sideband rejection ratio on time and after several resets of the receiver is minimal. A receiver with an IF hybrid is more robust to systematic errors. Moreover, we have shown that the intrinsic random errors in calibration have the same impact for configuration without IF hybrid and for a configuration with IF hybrid with analog rejection ratio better than 10dB. Compensated rejection ratios above 40dB are obtained even in the presence of high analog rejection. The method is robust allowing its use under normal operational conditions at any telescope. We also demonstrate that a full analog receiver is more robust against systematic errors. Finally, the error bars associated to the compensated rejection ratio are almost independent of whether IF hybrid is present or not

Properties of Quasar-Galaxy Associations and Gravitational Mesolensing by Halo Objects

A new catalog of 8382 close quasar-galaxy pairs is presented. The catalog was composed using published catalogs of quasars and active galactic nuclei containing 11358 objects, as well as the LEDA catalog of galaxies, which contains on the order of 100 thousand objects. The search for pairs was carried out in such a way that the linear distance between the galaxy and projected quasar does not exceed 150kpc. Based on these new data, the dependence of the number of pairs on a=z_G/z_Q is analysed, where z_G and z_Q are the redshifts of the galaxy and quasar, respectively, revealing an excess of pairs with a<0.1 and a>0.9. This means that the galaxies in pairs are preferably located close to either the observer or the quasar and avoid intermediate distances along the line of sight to the quasar. Computer simulations demonstrate that it is not possible to explain this number of pairs with the observed distribution in a as the result of chance positional coincidences with a uniform spatial distribution of galaxies. Data on globular clusters show that the excess of pairs with a0.9 is consistent with the hypothesis that we are observing distant compact objects that are strongly gravitationally lensed by transparent lenses with a King mass distribution located in the halos of nearby galaxies. The Hubble diagram for galaxies and quasars is presented. Observational tests of the mesolensing hypothesis are formulated.Comment: 11 pages, 7 figure

Full characterization and analysis of a terahertz heterodyne receiver based on a NbN hot electron bolometer

We present a complete experimental characterization of a quasioptical twin-slot antenna coupled small area (1.0×0.15 µm^2) NbN hot electron bolometer (HEB) mixer compatible with currently available solid state tunable local oscillator (LO) sources. The required LO power absorbed in the HEB is analyzed in detail and equals only 25 nW. Due to the small HEB volume and wide antenna bandwidth, an unwanted direct detection effect is observed which decreases the apparent sensitivity. Correcting for this effect results in a receiver noise temperature of 700 K at 1.46 THz. The intermediate frequency (IF) gain bandwidth is 2.3 GHz and the IF noise bandwidth is 4 GHz. The single channel receiver stability is limited to 0.2–0.3 s in a 50 MHz bandwidth

Unfolded protein response is involved in the pathology of human congenital hypothyroid goiter and rat non-goitrous congenital hypothyroidism

Copyright: Copyright 2008 Elsevier B.V., All rights reserved.The unfolded protein response (UPR) is an intracellular signaling pathway that regulates the protein folding and processing capacity of the endoplasmic reticulum (ER). The UPR is induced by the pharmacological agents that perturb ER functions but is also activated upon excessive accumulation of the mutant secretory proteins that are unable to attain correct three-dimensional structure and are thus retained in the ER. Such defects in intracellular protein transport underlie the development of a number of phenotypically diverse inherited pathologies, termed endoplasmic reticulum storage diseases (ERSD). We have studied UPR development in two similar ERSDs, human congenital goiter caused by the C1264R and C1996S mutations in the thyroglobulin (Tg) gene and non-goitrous congenital hypothyroidism in rdw dwarf rats determined by the G2320R Tg mutation. In both cases, these mutations rendered Tg incapable of leaving the ER. A major ER chaperone immunoglobulin-binding protein (BiP), and a novel putative escort chaperone endoplasmic reticulum protein 29 KDa (ERp29) were found to be associated with Tg, which might be interpreted as the contribution of the quality control machinery to the previously shown retention of Tg in the ER. We have extended our earlier observations of ER chaperone induction with the identification of the additional ER (ERp29, ERp72, calreticulin, protein disulfide isomerase (PDI)), cytoplasmic (heat shock protein (HSP)70, HSP90) and mitochondrial (mtHSP70) upregulated chaperones and folding enzymes. Activation of the transcriptional arm of UPR, as judged by the appearance of the spliced (active) form of X-box binding protein (XBP1) and processed activating transcription factor 6 (ATF6) transcription factors was suggested to contribute to the overexpression of the ER chaperones. The processing of ATF6 was observed in both human and rat tissues with Tg mutations. Whereas, in human tissues, weak splicing of XBP1 mRNA was detected only in the C1264R mutant, all rat thyroids including wild-type contained significant amounts of the spliced form of XBP1 as opposed to human liver and rat brain tissues, implying the existence of a previously unknown tissue-specific regulation of XBP1 processing.publishersversionPeer reviewe

Calibration Scheme for Large Kinetic Inductance Detector Arrays Based on Readout Frequency Response

Microwave kinetic inductance detector (MKID) provides a way to build large ground based sub-mm instruments such as NIKA and A-MKID. For such instruments, therefore, it is important to understand and characterize the response to ensure good linearity and calibration over wide dynamic range. We propose to use the MKID readout frequency response to determine the MKID responsivity to an input optical source power. A signal can be measured in a KID as a change in the phase of the readout signal with respect to the KID resonant circle. Fundamentally, this phase change is due to a shift in the KID resonance frequency, in turn due to a radiation induced change in the quasiparticle number in the superconducting resonator. We show that shift in resonant frequency can be determined from the phase shift by using KID phase versus frequency dependence using a previously measured resonant frequency. Working in this calculated resonant frequency, we gain near linearity and constant calibration to a constant optical signal applied in a wide range of operating points on the resonance and readout powers. This calibration method has three particular advantages: first, it is fast enough to be used to calibrate large arrays, with pixel counts in the thousand of pixels; second, it is based on data that are already necessary to determine KID positions; third, it can be done without applying any optical source in front of the array.Comment: Accepted to Journal of Low Temperature Physics LTD16 Special Issue, Low Temperature Detector 16 Conference Proceedings,manuscript number: #JLTP-D-15-00356R1, 6 pages, 5 figure

Comparing the performance of 850 GHz integrated bias-tee superconductor-insulator-superconductor (SIS) mixers with single- and parallel-junction tuner

We present and compare the design and performance of two 850 GHz radial probe fed superconductor-insulator-superconductor mixers, where the antenna is aligned perpendicular to the E-Plane of the input full-height rectangular waveguide connected to a multiple flare-angles smooth-walled horn. Both designs are comprised of 0.5 µm2 hybrid niobium/aluminium-nitride/niobium-nitride tunnel junction, fabricated on top of a niobium titanium nitride ground plane with an Al wiring layer. The entire superconducting circuit is supported with a 40 µm thick quartz substrate. The major difference between the two designs is the method used to cancel out the parasitic junction capacitance for broadband performance. The first design utilises two identical junctions connected in parallel with a short transmission line to convert the capacitance of one junction into the equivalent inductance of the other junction, commonly known as the twin-junction tuning scheme; whilst the second design employs an end-loaded scheme with only one tunnel junction. We found that both methods offer similar radio frequency performances, with close to 2× the double sideband quantum noise temperature, but the twin-junction design is more resilient to fabrication tolerances. However, the end-loaded design offers a much better intermediate frequency (IF) bandwidth performance, made possible by the sub-micron and high current density tunnel junction technology. The improved IF performance is important for many millimetre (mm) and sub-mm observatories, such as future upgrades of Atacama Large Millimetre/sub-mm Array receivers, as well as forthcoming space-borne far-infrared missions. Therefore, we conclude that the single-junction mixer design is the preferred option for THz applications, as long as the fabrication error can be minimised within a certain limit