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In this work, metals were recovered from electronic wastes under optimized conditions. The columnar extraction was used to increase the contact between the leachate solution and solid-state wastes. Industrial metals were recovered by an electrochemical process using a regenerated mild oxidizer under optimized operating parameters to enrich the metal concentrations and reduce waste generation. The maximum recovery rate (1.135 mg·min−1) was recorded under the optimized conditions (160 A·m−2 current density, 7 mL·min−1 leachate flow rate, and 0.8 mol·L–1 ferric concentration). The selective columnar extraction process was employed to extract gold, wherein the highest extraction efficiency (69.39%) was obtained under optimized conditions of 0.7 mol·L−1 thiourea, 0.6 mol·L−1 hydrochloric acid, 0.8 mol·L−1 ferric chloride, 120 min circulation time, and 6 mL·min−1 leachate flow rate. The adsorption process was used for the recovery of gold, which was investigated under the kinetic as well as equilibrium adsorption processes. The adsorption curves conformed to the Langmuir model and followed the first-order kinetics. The adsorption rate decreased with the increasing values of pH, temperature, adsorbent size, while the rate increased with the stirring speed and adsorbent quantity. Finally, acidic extraction under anaerobic and optimal conditions was performed to extract and selectively recover rare-earth elements. The rare-earth elements were initially precipitated in their sulfate forms and subsequently transformed into corresponding hydroxides and oxides. The total recovery efficiencies for cerium and neodymium were found to be 91.7% and 86.7%, respectively.

In this paper, the influence of magnetic fields on the ultraviolet (UV) absorption of water circulated within three different magnetic configurations (inside, outside, and dual Halbach array magnetizers) is presented. Permanent magnets were inserted in the designed magnetizer and magnetic flux densities were varied between 380 and 580 mT. The samples presented evident UV absorption under magnetic fields due to the change of polarization in water molecules. The effectiveness of the magnetic field to remove the scale was investigated by measuring the calcium ion concentration after magnetic treatment. The dual Halbach array configuration enhanced scale removal by 41.4% at a water flow rate of 380 ± 3 mL min

We report on the development of a polarization-sensitive dichroic (150/220 GHz) detector array for the Cosmology Large Angular Scale Surveyor (CLASS) delivered to the telescope site in June 2019. In concert with existing 40 and 90 GHz telescopes, the 150/220 GHz telescope will make observations of the cosmic microwave background over large angular scales aimed at measuring the primordial B-mode signal, the optical depth to reionization, and other fundamental physics and cosmology. The 150/220 GHz focal plane array consists of three detector modules with 1020 transition edge sensor (TES) bolometers in total. Each dual-polarization pixel on the focal plane contains four bolometers to measure the two linear polarization states at 150 and 220 GHz. Light is coupled through a planar orthomode transducer (OMT) fed by a smooth-walled feedhorn array made from an aluminum-silicon alloy (CE7). In this work, we discuss the design, assembly, and in-lab characterization of the 150/220 GHz detector array. The detectors are photon-noise limited, and we estimate the total array noise-equivalent power (NEP) to be 2.5 and 4 aW$\sqrt{\mathrm{s}}$ for 150 and 220 GHz arrays, respectively., Comment: 8 pages, 5 figures, Published in J Low Temp Phys

The design of a two-dimensional spatial beam-combining network employing a parallel-plate superconducting waveguide filled with a monocrystalline silicon dielectric substrate is presented. This component uses arrays of magnetically coupled antenna elements to achieve high coupling efficiency and full sampling of the intensity distribution while avoiding diffractive losses in the multimode waveguide region. These attributes enable the structure’s use in realizing compact far-infrared spectrometers for astrophysical and instrumentation applications. If unterminated, reflections within a finite-sized spatial beam combiner can potentially lead to spurious couplings between elements. A planar meta-material electromagnetic absorber is implemented to control this response within the device. This broadband termination absorbs greater than 0.99 of the power over the 1.7:1 operational band at angles ranging from normal to near-parallel incidence. The design approach, simulations and applications of the spatial power combiner and meta-material termination structure are presented.

Micro-Spec (µ-Spec) is a direct-detection spectrometer which integrates all the components of a diffraction-grating spectrometer onto a $$\sim $$ 10-cm $$^2$$ chip through the use of superconducting microstrip transmission lines on a single-crystal silicon substrate. A second-generation µ-Spec is being designed to operate with a spectral resolution of 512 in the submillimeter (500–1000 µm, 300–600 GHz) wavelength range, a band of interest for several spectroscopic applications in astrophysics. High-altitude balloon missions would provide the first test bed to demonstrate the µ-Spec technology in a space-like environment and would be an economically viable venue for multiple observation campaigns. This work reports on the current status of the instrument design and will provide a brief overview of each instrument subsystem. Particular emphasis will be given to the design of the spectrometer’s two-dimensional diffractive region, through which the light of different wavelengths is focused on the detectors along the focal plane. An optimization process is employed to generate geometrical configurations of the diffractive region that satisfy specific requirements on spectrometer size, operating spectral range, and performance. An optical design optimized for balloon missions will be presented in terms of geometric layout, spectral purity, and efficiency.

This paper studied the different CaCO3 crystal forms between calcite and aragonite under magnetic fields using calcocarbonic solution prepared from dissolving ground natural shell. The experiments were conducted by exposing the solution to magnetic fields. The characteristics of reprecipitated CaCO3 were investigated. The aragonite/calcite ratios were proportional to magnetic flux densities. The physicochemical properties of CaO catalysts from thermal decomposition of CaCO3 depended on polymorphic ratios. The performances of the catalysts for biodiesel reaction were studied. The transesterifications of palm oil and methanol were comparatively performed using CaO catalysts prepared from different CaCO3 polymorphs. The transesterification reacted by CaO prepared from all polymorphic ratios yielded more than 85% of biodiesel under optimal conditions. Some amount of calcium was leached into the reaction medium depending on different polymorphic ratios of precursors. However, the leached calcium did not enhance the biodiesel yield. In addition, CaO-600 mT catalyst is the most promising considering that it is a residual catalyst from shell waste. This green innovation shows major potential of producing biodiesel from plants with environmental and social benefits.

Methylene blue dye can induce negative effects to aquatic life and the environmental system. So, it is important to remove it from water. Although, the photocatalytic degradation of dye solution during magnetic treatment (or static water process) can increase the dye degradation, but it cannot apply for a large wastewater. Therefore, the dynamic fluid system is required. This paper investigated the effect of magnetic fields (MFs) through dynamic fluid magnetization system on the degradation of dye solution. Ultraviolet (UV) irradiation experiments were carried out in the presence of zinc oxide (ZnO) catalyst. The experiment was divided into two parts. First, the dye solution was exposed to MFs multiple times. In the second part, the dye solution was exposed to MFs continuously using a dynamic fluid system. The results indicated that the dye solution degraded faster when the exposure time to MFs under dynamic fluid system was long. At least 60% of the dye solution degraded within 3 min when the MF of strength 600 mT was applied. On the other hand, the dye solution degraded by only 24% in the absence of MFs. The degradation mechanism was observed to fit the pseudo-first-order kinetic reaction. The rate constant of the reaction was higher in the presence of MFs than that in the absence of MFs. This resulted in better degradation performance. Therefore, it can be concluded that the photocatalytic degradation of the dye solution was enhanced when external MFs were applied to magnetize dye solution using dynamic fluid system.

A waveguide split-block fixture used in the characterization of thin-film superconducting planar circuitry at millimeter wavelengths is described in detail. The test fixture is realized from a pair of mode converters, which transition from rectangular-waveguide to on-chip microstrip-line signal propagation via a stepped ridge-guide impedance transformer. The observed performance of the W-band package at 4.2K has a maximum in-band transmission ripple of 2dB between 1.53 and 1.89 times the waveguide cutoff frequency. This metrology approach enables the characterization of superconducting microstrip test structures as a function temperature and frequency. The limitations of the method are discussed and representative data for superconducting Nb and NbTiN thin film microstrip resonators on single-crystal Si dielectric substrates are presented.

The fabrication of low-loss wide-bandwidth superconducting vacuum-gap crossovers for high performance millimeter wave applications are described. In order to reduce ohmic and parasitic losses at millimeter wavelengths a vacuum gap is preferred relative to dielectric spacer. Here, vacuum-gap crossovers were realized by using a sacrificial polymer layer followed by niobium sputter deposition optimized for coating coverage over an underlying niobium signal layer. Both coplanar waveguide and microstrip crossover topologies have been explored in detail. The resulting fabrication process is compatible with a bulk micro-machining process for realizing waveguide coupled detectors, which includes sacrificial wax bonding, and wafer backside deep reactive ion etching for creation of leg isolated silicon membrane structures. Release of the vacuum gap structures along with the wax bonded wafer after DRIE is implemented in the same process step used to complete the detector fabrication.

In the present study, precipitation method was used to synthesize three Mn-doped minerals, namely, dittmarite, struvite, and newberyite, and LiMg0.74Mn0.26PO4 phosphor was prepared through thermal synthesis using each of the afore-mentioned minerals as a precursor. Slight changes in the X-ray diffraction positions in the Mn-dopants validated that the pure-doped phase resulted in the changes in cell volumes and lattice parameters, which demonstrated that the Mn-dopants retained the undoped crystal structures. Photoluminescence (PL) of the phosphors derived from different precursors was examined under various conditions, in terms of physical and luminescent properties. The observed PL was dependent on the surface area, synthesis temperature, particle size, and crystallite size. The energy gap (Eg) value for LiMg0.74Mn0.26PO4 synthesized at 900 ​°C was also determined (5.492 ​eV), and was observed to be slightly decreased compared to the corresponding value for LiMgPO4 (5.60 ​eV). Moreover, the Eg value for LiMg0.74Mn0.26PO4 obtained at 800 ​°C (5.416 ​eV) indicated that higher synthesis temperature resulted in a higher Eg value, from which it could be concluded that Eg restriction could have initiated because of the ratio between the surface areas and the volume of the sample. As expected, the highest PL performance was obtained when Mn-doped newberyite was used as a precursor.

This paper investigates the influence of magnetic fields on the properties of water in both static and dynamic magnetizations by tracking the changes in infrared absorption, Raman scattering, heat capacity and salt solubility. The results indicate the changes in electron distribution, molecular dipole moment and molecular polarization of magnetized water from infrared and Raman results. The thermal property of magnetized water also changed as its heat capacity decreased. The solubility performance of magnetized salt solutions is studied additionally using the electrical conductivity measurement. All the mentioned changes depend on magnetic flux density (B) and magnetic exposure time (te) during the magnetization process. The increase in these two parameters (B and te) will increase the effect and become saturated in static process when B and te approaches 600 mT and 9 min, respectively. The dynamic magnetization shows similar changes in the properties of water. The magnetization with water velocity of 3.18 m s−1 at B of 600 mT at the circulation time of 60 min is the optimal condition for observing the change. It is obvious that static magnetization shows the higher effect than dynamic magnetization.

Plate-like hureaulite is successfully synthesized via a simple precipitation technique, and its vibrational and thermal behaviors are investigated. Its composition stabilizes at up to 165 °C and decomposes to Mn2P2O7 and Mn3(PO4)2 with different morphologies. Three thermal processes correspond to the first and second dehydrations, and polycondensation. However, the second dehydration shows two characteristics, and hence the deconvolution function is employed, which indicates two different water types in the crystal structure. Olivine-structured lithiophilite with nanosize is obtained from the thermal decomposition of the hureaulite precursor. The relationship between thermal and vibrational data is studied and the results are in agreement with each other. The factor-group analysis of hureaulite is also investigated by analyzing [PO3(HO)]2–, PO43−, and H2O. X-ray diffraction is applied for the sample structure determination. The obtained peaks and the corresponding lattice parameters are also found in agreement with the standard databases. The average crystallite sizes of synthesized compounds are determined by using the Scherrer equation, whereas the metal compositions are determined by using atomic spectrophotometers.

Magnesium pyrophosphate catalysts synthesized via the thermal decomposition of dittmarite, struvite, and newberyite precursors were applied for biodiesel production by transesterification. Physicochemical properties of the catalysts and effects of operating transesterification conditions on the biodiesel yield were investigated. Analytical data revealed that the biodiesel yield decreases with increasing crystallite and particle sizes, but it increases with the basic site density and surface area of the catalyst. Further, the results indicate that struvite should be used as the precursor to synthesize the catalyst in order to realize the highest biodiesel yield. Using the struvite-derived catalyst under the optimized transesterification conditions, the highest biodiesel yield was obtained. The transesterification reaction showed pseudo-first-order kinetics. In addition, the activation energy, frequency factor, and rate constant were also determined. The purification step is not needed, resulting in lower biodiesel production cost. Therefore, this catalyst is applicable as a potential transesterification catalyst for industrial plants.

This research studies the influence of static magnetic fields on the structure of calcium carbonate (CaCO3) crystals. Experiments were conducted by exposing Ca2+ and CO32− solutions to magnetic fields. The solutions were then combined to form CaCO3 particles. Three characteristics of CaCO3 formation reaction have been investigated, namely absorbance differentiation, vibrational modes and crystal structure. Absorbances were measured using ultraviolet–visible spectrophotometer, while vibrational modes were measured using Flourier transform (FT) infrared and FT Raman spectroscopies. X-ray diffractometer was used to determine the crystal structure. Experimental results show that the nucleation of CaCO3 crystals was inhibited when starting solutions were exposed to magnetic fields. The effect of magnetic fields was mainly attributed to CO32− solution and remained for more than 144 h after starting solutions were combined. As various magnetic field strengths were applied to the solutions, aragonite was formed, and aragonite/calcite ratios were proportional to magnetic field strengths. Using the X-ray technique, the measured crystal structure indicated that the aragonite/calcite ratio increased from 10 to 82% when the magnetic field strength was increased from 60 to 460 mT for the duration of 8 min.

We present here a study of the use of the SiAl alloy CE7 for the packaging of silicon devices at cryogenic temperatures. We report on the development of baseplates and feedhorn arrays for millimeter wave bolometric detectors for astrophysics. Existing interfaces to such detectors are typically made either of metals, which are easy to machine but mismatched to the thermal contraction profile of Si devices, or of silicon, which avoids the mismatch but is difficult to directly machine. CE7 exhibits properties of both Si and Al, which makes it uniquely well suited for this application. We measure CE7 to a) superconduct below a critical transition temperature, T (sub c), 1.2 K, b) have a thermal contraction profile much closer to Si than metals, which enables simple mating, and c) have a low thermal conductivity which can be improved by Au-plating. Our investigations also demonstrate that CE7 can be machined well enough to fabricate small structures, such as #0-80 threaded holes, to tight tolerances (approximately 25 microns) in contrast with pure silicon and similar substrates. We have fabricated CE7 baseplates being deployed in the 93 gigahertz polarimetric focal planes used in the Cosmology Large Angular Scale Surveyor (CLASS). We also report on the development of smooth-walled feedhorn arrays made of CE7 that will be used in a focal plane of dichroic 150/220 gigahertz detectors for the CLASS High-Frequency camera.

Strategies are explored to reduce the electromagnetic simulation time of electrically large superconducting transmission line structures while retaining model accuracy. The complex surface reactance of an infinite thin-film superconducting sheet is evaluated with the BCS (Bardeen–Cooper—Schrieffer) theory and is used as an input to model the phase velocity and characteristic impedance of finite width transmission line structures. Commercially available electromagnetic simulation software packages are employed for the calculations, and the results are compared with limiting analytic forms from the literature. The influences of line width, metallization thickness, and substrate height on microstrip transmission line propagation are considered in detail, and a scaling approach is presented to compensate for the leading-order effect in numerical simulations. These findings are particularly important near the energy gap of the superconductor due to the influence of the kinetic inductance on the transmission line dispersion.

The Cosmology Large Angular Scale Surveyor (CLASS) aims to detect and characterize the primordial B-mode signal and make a sample-variance-limited measurement of the optical depth to reionization. CLASS is a ground-based, multi-frequency microwave polarimeter that surveys 70% of the microwave sky every day from the Atacama Desert. The focal plane detector arrays of all CLASS telescopes contain smooth-walled feedhorns that couple to transition-edge sensor (TES) bolometers through symmetric planar orthomode transducer (OMT) antennas. These low noise polarization-sensitive detector arrays are fabricated on mono-crystalline silicon wafers to maintain TES uniformity and optimize optical efficiency throughout the wafer. In this paper, we discuss the design and characterization of the first CLASS 93 GHz detector array. We measure the dark parameters, bandpass, and noise spectra of the detectors and report that the detectors are photon-noise limited. With current array yield of 82%, we estimate the total array noise-equivalent power (NEP) to be 2.1 aW$\sqrt[]{\mathrm{s}}$., Comment: 16 pages, 9 figures

The Cosmology Large Angular Scale Surveyor (CLASS) will measure the polarization of the Cosmic Microwave Background to search for and characterize the polarized signature of inflation. CLASS will operate from the Atacama Desert and observe $\sim$70% of the sky. A variable-delay polarization modulator (VPM) modulates the polarization at $\sim$10 Hz to suppress the 1/f noise of the atmosphere and enable the measurement of the large angular scale polarization modes. The measurement of the inflationary signal across angular scales that span both the recombination and reionization features allows a test of the predicted shape of the polarized angular power spectra in addition to a measurement of the energy scale of inflation. CLASS is an array of telescopes covering frequencies of 38, 93, 148, and 217 GHz. These frequencies straddle the foreground minimum and thus allow the extraction of foregrounds from the primordial signal. Each focal plane contains feedhorn-coupled transition-edge sensors that simultaneously detect two orthogonal linear polarizations. The use of single-crystal silicon as the dielectric for the on-chip transmission lines enables both high efficiency and uniformity in fabrication. Integrated band definition has been implemented that both controls the bandpass of the single mode transmission on the chip and prevents stray light from coupling to the detectors., Comment: 7 pages, 5 figures, accepted by the Journal of Low Temperature Physics

We describe feedhorn-coupled polarization-sensitive detector arrays that utilize monocrystalline silicon as the dielectric substrate material. Monocrystalline silicon has a low-loss tangent and repeatable dielectric constant, characteristics that are critical for realizing efficient and uniform superconducting microwave circuits. An additional advantage of this material is its low specific heat. In a detector pixel, two Transition-Edge Sensor (TES) bolometers are antenna-coupled to in-band radiation via a symmetric planar orthomode transducer (OMT). Each orthogonal linear polarization is coupled to a separate superconducting microstrip transmission line circuit. On-chip filtering is employed to both reject out-of-band radiation from the upper band edge to the gap frequency of the niobium superconductor, and to flexibly define the bandwidth for each TES to meet the requirements of the application. The microwave circuit is compatible with multi-chroic operation. Metalized silicon platelets are used to define the backshort for the waveguide probes. This micro-machined structure is also used to mitigate the coupling of out-of-band radiation to the microwave circuit. At 40 GHz, the detectors have a measured efficiency of ∼90%. In this paper, we describe the development of the 90 GHz detector arrays that will be demonstrated using the Cosmology Large Angular Scale Surveyor (CLASS) ground-based telescope.

Micro-Spec is a compact sub-millimeter (approximately 100 GHz--1:1 THz) spectrometer which uses low loss superconducting microstrip transmission lines and a single-crystal silicon dielectric to integrate all of the components of a diffraction grating spectrometer onto a single chip. We have already successfully evaluated the performance of a prototype Micro-Spec, with spectral resolving power, R=64. Here we present our progress towards developing a higher resolution Micro-Spec, which would enable the first science returns in a balloon flight version of this instrument. We describe modifications to the design in scaling from a R=64 to a R=256 instrument, as well as the ultimate performance limits and design concerns when scaling this instrument to higher resolutions.

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors (MKIDs) for the detection of faint astrophysical signatures, as well as for quantum computing applications and materials characterization. In this paper, procedures are presented for the fabrication and characterization of thin-film superconducting microwave resonators. The fabrication methodology allows for the realization of superconducting transmission-line resonators with features on both sides of an atomically smooth single-crystal silicon dielectric. This work describes the procedure for the installation of resonator devices into a cryogenic microwave testbed and for cool-down below the superconducting transition temperature. The set-up of the cryogenic microwave testbed allows one to do careful measurements of the complex microwave transmission of these resonator devices, enabling the extraction of the properties of the superconducting lines and dielectric substrate (e.g., internal quality factors, loss and kinetic inductance fractions), which are important for device design and performance.

Recent measurements of micron-sized Mo/Au bilayer TESs have demonstrated that the TES can behave like an S-S′-S weak link due to the lateral proximity effect from superconducting leads. In this regime the Tc is a function of bias current, and the effective Tc shifts from the bilayer Tc towards the lead Tc. We explore the idea that a micron-sized S-N-S weak link could provide a new method to engineer the TES Tc. This method would be particularly useful when small size requirements for a bilayer TES (such as for a hot-electron microbolometer) lead to undesirable shifts in the bilayer Tc. We present measurements of a variety of micron-sized normal Au ‘TES’ devices with Nb leads. We find no evidence of a superconducting transition in the Au film of these devices, in dramatic contrast to the strong lateral proximity effect seen in micron-sized Mo/Au bilayer devices. The absence of a transition in these devices is also in disagreement with theoretical predictions for S-N-S weak links. We hypothesize that a finite contact resistance between the Nb and Au may be weakening the effect. We conclude that the use of the lateral proximity effect to create a superconducting transition will be difficult given current fabrication procedures.

Observations of the cosmic microwave background (CMB) provide a powerful tool for probing the evolution of the early universe. Specifically, precision measurement of the polarization of the CMB enables a direct test for cosmic inflation. A key technological element on the path to the measurement of this faint signal is the capability to produce large format arrays of background-limited detectors. We describe the electromagnetic design of feedhorn-coupled, TES-based sensors. Each linear orthogonal polarization from the feed horn is coupled to a superconducting microstrip line via a symmetric planar orthomode transducer (OMT). The symmetric OMT design allows for highly-symmetric beams with low cross-polarization over a wide bandwidth. In addition, this architecture enables a single microstrip filter to define the passband for each polarization. Care has been taken in the design to eliminate stray coupling paths to the absorbers. These detectors will be fielded in the Cosmology Large Angular Scale Surveyor (CLASS).

Future ground and space-based astronomy missions in the millimeter and sub-millimeter range will rely upon kilopixel detector arrays. We are developing a superconducting Transition-Edge Hot-Electron Bolometer (THM) for use in these next generation missions. Thermal isolation of the THM is controlled by the hot-electron effect between the electrons and phonons within the small volume of the superconducting detector. To reach noise levels near the photon background noise for observing the Cosmic Microwave Background (CMB) and the submillimeter and far-infrared background the optimal detector size occurs at the micron length scale. We present measurements of the thermal conductance of two micron-sized THM devices which show a hot-electron temperature dependence and predict NEP ≤ 5 × 10-18 W/√{Hz} for CMB loading conditions and NEP ≤ 1 × 10-19 W√{Hz} in the low power loading limit. We also briefly discuss the detector geometry and thermal conductance optimization for CMB loading conditions.

We describe measurements of the properties, at dc, gigahertz, and terahertz frequencies, of thin (10 nm) aluminum films with 10 ohm/{rm square}$ normal state sheet resistance. Such films can be applied to construct microwave kinetic inductance detector arrays for submillimeter and far-infrared astronomical applications in which incident power excites quasiparticles directly in a superconducting resonator that is configured to present a matched-impedance to the high frequency radiation being detected. For films 10 nm thick, we report normal state sheet resistance, resistance-temperature curves for the superconducting transition, quality factor and kinetic inductance fraction for microwave resonators made from patterned films, and terahertz measurements of sheet impedance measured with a Fourier Transform Spectrometer. We compare properties with similar resonators made from niobium 600 nm thick.

We describe a prototype detector system designed for precise measurements of Cosmic Microwave Background polarization. The design combines a quasi-optical polarization modulator, a metal feedhorn, a superconducting planar microwave circuit, and a pair of transition-edge sensor (TES) bolometers operating at

The improved version of a broadband planar magic-T using microstrip-slotline transitions is presented. The design implements a small microstrip-slotline tee junction with minimum size slotline terminations to reduce radiation loss. A multisection impedance transformation network is used to increase the operating bandwidth and minimize the parasitic coupling around the microstrip-slotline tee junction. As a result, the improved magic-T has greater bandwidth and lower phase imbalance at the sum and difference ports than the earlier magic-T design. The experimental results show that the 10-GHz magic-T provides more than 70% of 1-dB operating bandwidth with the average in-band insertion loss of less than 0.6 dB. It also has phase and amplitude imbalance of less than plusmn1deg and plusmn0.25 dB, respectively.

Characterization of the minute cosmic microwave background polarization signature requires multi-frequency, high-throughput precision instrument systems. We have previously described the detector fabrication of a 40 GHz focal plane and now describe the fabrication of detector modules for measurement of the CMB at 90 GHz. The 90 GHz detectors are a scaled version of the 40 GHz architecture where, due to smaller size detectors, we have implemented a modular (wafer level) rather than the chip-level architecture. The new fabrication process utilizes the same design rules with the added challenge of increased wiring density to the 74 TES's as well as a new wafer level hybridization procedure. The hexagonally shaped modules are tile-able, and as such, can be used to form the large focal planes required for a space-based CMB polarimeter. The detectors described here will be deployed in two focal planes with 7 modules each in the Johns Hopkins University led ground-based Cosmology Large Angular Scale Surveyor (CLASS) telescope., 7 pages, 4 figures, Presented at Low Temperature Detectors Conference Grenoble France 2015

A photonic choke joint structure with a wide- stop-band is proposed for use as a waveguide flange interface. The structure consists of arrays of square metal pillars arranged in a periodic pattern to suppress the dominant-mode wave propagation in parallel-plate waveguide over a wide frequency bandwidth. The measurement results at microwave frequencies confirm the structure can provide broadband suppression, more than 56 dB over 6.25 times its operating frequency. Applications at millimeter wavelength are discussed.

A method is proposed and experimentally explored for in-situ calibration of complex transmission data for superconducting microwave resonators. This cryogenic calibration method accounts for the instrumental transmission response between the vector network analyzer reference plane and the device calibration plane. Once calibrated, the observed resonator response is analyzed in detail by two approaches. The first, a phenomenological model based on physically realizable rational functions, enables the extraction of multiple resonance frequencies and widths for coupled resonators without explicit specification of the circuit network. In the second, an ABCD-matrix representation for the distributed transmission line circuit is used to model the observed response from the characteristic impedance and propagation constant. When used in conjunction with electromagnetic simulations, the kinetic inductance fraction can be determined with this method with an accuracy of 2%. Datasets for superconducting microstrip and coplanar-waveguide resonator devices were investigated and a recovery within 1% of the observed complex transmission amplitude was achieved with both analysis approaches. The experimental configuration used in microwave characterization of the devices and self-consistent constraints for the electromagnetic constitutive relations for parameter extraction are also presented., Comment: 12 pages, 4 figures

In this paper, we propose a compact planar bandpass filter design with wide stopband. The double split-end quarter-wave-length (/spl lambda//4) resonator is introduced to reduce the resonator size while providing additional transmission zeros. Optimal split-end length is determined to provide transmission zeros that attenuate the two lowest spurious resonance frequencies. The singly loaded quality factor (Q/sub si/) of the optimal-length /spl lambda//4 stepped-impedance resonator (SIR) is also analytically derived. Using the proposed technique to design an Nth-order filter, N+1 controllable transmission zeros are generated and used to suppress spurious frequency responses. The experimental design shows that the sixth-order filter can provide a very broad stopband of 8.5 times the fundamental frequency with at least 37.8 dB of attenuation using the SIRs with a stepped-impedance ratio (R) of 0.528.

We report on the status and development of polarization-sensitive detectors for millimeter-wave applications. The detectors are fabricated on single-crystal silicon, which functions as a low-loss dielectric substrate for the microwave circuitry as well as the supporting membrane for the Transition-Edge Sensor (TES) bolometers. The orthomode transducer (OMT) is realized as a symmetric structure and on-chip filters are employed to define the detection bandwidth. A hybridized integrated enclosure reduces the high-frequency THz mode set that can couple to the TES bolometers. An implementation of the detector architecture at Q-band achieves 90% efficiency in each polarization. The design is scalable in both frequency coverage, 30-300 GHz, and in number of detectors with uniform characteristics. Hence, the detectors are desirable for ground-based or space-borne instruments that require large arrays of efficient background-limited cryogenic detectors., Comment: 7 pages, 3 figures, Presented at SPIE Astronomical Telescopes and Instrumentation 2014: Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII. To be published in Proceedings of SPIE Volume 9153

The Cosmology Large Angular Scale Surveyor (CLASS) is an experiment to measure the signature of a gravita-tional-wave background from inflation in the polarization of the cosmic microwave background (CMB). CLASS is a multi-frequency array of four telescopes operating from a high-altitude site in the Atacama Desert in Chile. CLASS will survey 70\% of the sky in four frequency bands centered at 38, 93, 148, and 217 GHz, which are chosen to straddle the Galactic-foreground minimum while avoiding strong atmospheric emission lines. This broad frequency coverage ensures that CLASS can distinguish Galactic emission from the CMB. The sky fraction of the CLASS survey will allow the full shape of the primordial B-mode power spectrum to be characterized, including the signal from reionization at low $\ell$. Its unique combination of large sky coverage, control of systematic errors, and high sensitivity will allow CLASS to measure or place upper limits on the tensor-to-scalar ratio at a level of $r=0.01$ and make a cosmic-variance-limited measurement of the optical depth to the surface of last scattering, $\tau$., Comment: 23 pages, 10 figures, Presented at SPIE Astronomical Telescopes and Instrumentation 2014: Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII. To be published in Proceedings of SPIE Volume 9153

We describe the instrument architecture of the Johns Hopkins University-led CLASS instrument, a groundbased cosmic microwave background (CMB) polarimeter that will measure the large-scale polarization of the CMB in several frequency bands to search for evidence of inflation.

The Cosmology Large Angular Scale Surveyor (CLASS) experiment aims to map the polarization of the Cosmic Microwave Background (CMB) at angular scales larger than a few degrees. Operating from Cerro Toco in the Atacama Desert of Chile, it will observe over 65% of the sky at 38, 93, 148, and 217 GHz. In this paper we discuss the design, construction, and characterization of the CLASS 38 GHz detector focal plane, the first ever Q-band bolometric polarimeter array., Comment: 15 pages, 4 figures. Presented at SPIE Astronomical Telescopes and Instrumentation 2014: Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII. To be published in Proceedings of SPIE Volume 9153

We propose a low-loss slotline (SL) stepped circular ring termination for use in a microstrip-to-slotline (MS-to-SL) transition. Not only does this termination achieve broadband characteristics, but it also reduces SL radiation. The experimental results show that, using the proposed technique, the radiation loss around the pass-band frequency is lower than that of the conventional transitions using radial or circular pad terminations

We propose a new type of microstrip half-wavelength (lambda/2) stepped impedance resonator (SIR) for use in bandpass filter (BPF) designs. This lambda/2 SIR has an internal coupling section that can be used to generate a coupling coefficient in the filter design in addition to couplings between SIRs. It also contains additional stepped impedance lines that shift and suppress the lowest even-mode resonance frequencies to more than what can be achieved by conventional lambda/2 SIRs. Moreover, a transmission zero is generated close to its fundamental resonance frequency (f0) which can be used in definition of the filter response. A fourth-order microstrip BPF with 10% bandwidth was constructed using two of the proposed lambda/2 SIRs with a stepped impedance ratio (R) of 0.528. The experimental result shows that the filter can achieve low in-band loss and out-of-band attenuation of 52.6dB up to 3f0. The lowest spurious resonance frequency is shifted to 3f0 as opposed to 2.5f0 in conventional lambda/2 SIRs with the same R value

We report technology development of millimeter/submillimeter polarization modulators that operate by introducing a variable, controlled phase delay between two orthogonal polarization states. The variable-delay polarization modulator (VPM) operates via the introduction of a variable phase delay between two linear orthogonal polarization states, resulting in a variable mapping of a single linear polarization into a combination of that Stokes parameter and circular (Stokes V) polarization. Characterization of a prototype VPM is presented at 350 and 3000 microns. We also describe a modulator in which a variable phase delay is introduced between right- and left- circular polarization states. In this architecture, linear polarization is fully modulated. Each of these devices consists of a polarization diplexer parallel to and in front of a movable mirror. Modulation involves sub-wavelength translations of the mirror that change the magnitude of the phase delay.

We explore a free-space polarization modulator in which a variable phase introduction between right- and left-handed circular polarization components is used to rotate the linear polarization of the outgoing beam relative to that of the incoming beam. In this device, the polarization states are separated by a circular polarizer that consists of a quarter-wave plate in combination with a wire grid. A movable mirror is positioned behind and parallel to the circular polarizer. As the polarizer-mirror distance is separated, an incident linear polarization will be rotated through an angle that is proportional to the introduced phase delay. We demonstrate a prototype device that modulates Stokes Q and U over a 20% bandwidth, from 77 to 94 GHz., Comment: 13 pages, 6 figures, submitted to Applied Optics

The next generation of Cosmic Microwave Background (CMB) experiments probing for signals of inflation and small angular scale polarization anisotropies require higher sensitivity and better control of systematics. We are developing monolithic arrays of orthomode transducer (OMT) coupled transition edge sensor (TES) polarimeters designed for operation at 150 GHz to address these requirements. OMT coupling allows for simultaneous and independent detection of two orthogonal linear polarization states incident on a single pixel. We present measurements of optical efficiencies η op of single pixels with on-chip band-defining filters, with η op = 57±4 stat±9 sys %. We also provide evidence for an out-of-band blue leak and address possible sources as well as mitigation techniques. Additionally, we discuss methods for increasing efficiency being implemented in the next generation of pixels, currently in fabrication. Still under development, these pixels are produced as monolithic polarimeter arrays and are slated for use in the Atacama Cosmology Telescope Polarization (ACTpol) and South Pole Telescope Polarization (SPTpol) experiments, while single-pixel polarimeters are to be deployed in the Atacama B-mode Search (ABS) experiment.

We have fabricated absorber-coupled microwave kinetic inductance detector (MKID) arrays for sub-millimeter and far-infrared astronomy. Each detector array is comprised of lambda/2 stepped impedance resonators, a 1.5 micrometer thick silicon membrane, and 380 micrometer thick silicon walls. The resonators consist of parallel plate aluminum transmission lines coupled to low impedance Nb microstrip traces of variable length, which set the resonant frequency of each resonator. This allows for multiplexed microwave readout and, consequently, good spatial discrimination between pixels in the array. The Al transmission lines simultaneously act to absorb optical power and are designed to have a surface impedance and filling fraction so as to match the impedance of free space. Our novel fabrication techniques demonstrate high fabrication yield of MKID arrays on large single crystal membranes and sub-micron front-to-back alignment of the microstrip circuit.

Photonic choke joint (PCJ) structures for dual-polarization waveguides have been investigated for use in device and component packaging. This interface enables the realization of a high performance non-contacting waveguide joint without degrading the in-band signal propagation properties. The choke properties of two tiling approaches, symmetric square Cartesian and octagonal quasi-crystal lattices of metallic posts, are explored and optimal PCJ design parameters are presented. For each of these schemes, the experimental results for structures with finite tilings demonstrate near ideal transmission and reflection performance over a full waveguide band.