Search

POLARBEAR-2A is the first receiver for the Simons Array cosmic microwave background polarization experiment. POLARBEAR-2A has transition-edge sensor bolometers on the focal plane. Signals from bolometers are multiplexed and read out by a single SQUID. The receiver was deployed in late 2018 in Atacama, Chile, and operation started in 2019, where rapid confirmation of correspondence between bolometers and multiplexed readout channels was important as an initial step of performance validation. For this purpose, we devised a method using a coherent source that allows us to identify the frequency band and polarization sensitivity angle for each readout channel without detailed bolometer tuning. [ABSTRACT FROM AUTHOR]

CUPID-0 is the first neutrinoless double beta decay (0νββ) experiment based on highly enriched scintillating bolometers. It consists in an array of Zn82Se detectors operated at LNGS since 2017. During the Phase I of data taking, concluded at the end of 2018, the experiment collected an exposure of 9.95 kg·yr of ZnSe. The simultaneous heat-light readout provides a powerful rejection of α-particles and allows us to suppress the background in the region of interest down to 3.5−0.9+1.0×10−3 counts/(keV·kg·y), an unprecedented level for this technique. Thanks to this achievement, we set the most stringent lower limit on the 82Se 0νββ half-life. Moreover, we have developed a full background model, which allows us to identify the origin of the events in the region of interest. The reconstruction of the CUPID-0 spectrum has enabled us to perform the most precise measurement of the 2νββ of 82Se. [ABSTRACT FROM AUTHOR]

The half-life of 100Mo relatively to the 2ν2β decay to the ground state of 100Ru was measured as T1/2 = (6.99±0.15) × 1018 yr with the help of enriched in 100Mo lithium molybdate scintillating bolometers in the EDELWEISS-III low background set-up at the Modane underground laboratory. This is the most accurate value of the 2ν2β half-life of 100Mo. [ABSTRACT FROM AUTHOR]

Enhancement in electrical properties as well as temperature and field coefficient of resistance in Nd0.67Sr0.33Mn1-xRuxO3 (0 ≤ x ≤ 0.10) manganites, prepared by solid state reaction route are studied. The substitution at Mn site by Ru invokes a lower value of TP and also an increment in overall MR. The values obtained for TCR and FCR in compounds Nd0.67Sr0.33Mn1-xRuxO3 (0.05 ≤ x ≤ 0.10) are higher as compared to its parent compound Nd0.67Sr0.33MnO3. For memory devices and bolometer IR detectors with a application point of view, these samples show the maximum magnetoresistance (MR) of 81% at 5 T applied magnetic field, while the temperature coefficient of resistance (TCR) and field coefficient of resistance(FCR) is found to be ∼17% K−1 and ∼30% T-1 approximately. [ABSTRACT FROM AUTHOR]

Enhancement in electrical properties as well as temperature and field coefficient of resistance in Nd0.67Sr0.33Mn1-xRuxO3 (0 ≤ x ≤ 0.10) manganites, prepared by solid state reaction route are studied. The substitution at Mn site by Ru invokes a lower value of TP and also an increment in overall MR. The values obtained for TCR and FCR in compounds Nd0.67Sr0.33Mn1-xRuxO3 (0.05 ≤ x ≤ 0.10) are higher as compared to its parent compound Nd0.67Sr0.33MnO3. For memory devices and bolometer IR detectors with a application point of view, these samples show the maximum magnetoresistance (MR) of 81% at 5 T applied magnetic field, while the temperature coefficient of resistance (TCR) and field coefficient of resistance(FCR) is found to be ∼17% K−1 and ∼30% T-1 approximately. [ABSTRACT FROM AUTHOR]

CALDER is a R&D project for the development of cryogenic light detectors with an active surface of 5x5cm2 and an energy resolution of 20 eV RMS for visible and UV photons. These devices can enhance the sensitivity of next generation large mass bolometric detectors for rare event searches, providing an active background rejection method based on particle discrimination. A CALDER detector is composed by a large area Si absorber substrate with superconducting kinetic inductance detectors (KIDs) deposited on it. The substrate converts the incoming light into athermal phonons, that are then sensed by the KIDs. KID technology combine fabrication simplicity with natural attitude to frequency-domain multiplexing, making it an ideal candidate for a large scale bolometric experiments. We will give an overview of the CALDER project and show the performances obtained with prototype detectors both in terms of energy resolution and efficiency. [ABSTRACT FROM AUTHOR]

The paper gives the result of a numerical calculation of the Maxwell equation by the finite element method for a dielectric particle of spherical shape in the optical and THz ranges with a size 0.375÷0.75 of wavelength. The nature of the electric field distribution inside the sphere is shown in the case of high-order resonance for the optical range. The idea was put forward to use the resonance feature of the dielectric sphere to amplify the current in the conductor whip antenna. It is shown, that the use of such an antenna makes it possible to achieve amplification in the conductor up to 30 dB. [ABSTRACT FROM AUTHOR]

We present the first analysis of photometric observations of two detached binary stars, FW Vel and BB Mon. Their V light curves from the All Sky Automated Survey were solved using Monte Carlo Search Method. The final solutions describe these two systems as Algol-like binary stars with detached configurations. The absolute parameters of the components of the systems were also estimated. [ABSTRACT FROM AUTHOR]

Vanadium oxide (VxOy) multilayer sandwich structures previously studied by our group were found to yield a sensitive thermometer thin film material suitable for microbolometer applications. In this work, we aim to estimate the performance of a proposed air-bridge microbolometer configuration based on VxOy multilayer sandwich structure thermometer thin films. For this purpose, a microbolometer was fabricated on silicon (Si) substrate covered with a silicon nitride (Si3N4) insulating layer using VxOy thermometer thin film material. The fabricated microbolometer was patterned using electron-beam lithography and liftoff techniques and it was characterized in terms of its voltage repsonsivity (Rv), signal to noise ratio (SNR), noise equivalent power (NEP) and detectivity D*. A model was then developed by the aid of numerical optical/thermal simulations and experimentally measured parameters to estimate the performance of the microbolometer when fabricated in an air-bridge configuration. The estimated D* was found to be 1.55×107 cm.vHz/W. [ABSTRACT FROM AUTHOR]

Recently, a lot of attention has been paid to infrared imaging using uncooled microbolometer detectors, primarily because of their low cost, and wide military and civilian applications like disaster rescue, night vision, homing and tracking, ecology and weather forecasting, target acquisition, predictive inspection and maintenance, surveillance, remote temperature sensing and medical diagnostic and treatment. The present work demonstrates the design and simulation of uncooled microbolometer detector using Coventorware tool. Geometrical optimization has been done to minimize the pixel size up to 18×18µm. Simulated values for Different parameters like Thermal conductance, Time constant and change in temperature calculated for the structure are 1.2 × 10-7W/K, 4.44ms and 3.5K. [ABSTRACT FROM AUTHOR]

The CUORE-0 experiment, a 52 bolometer array searching for neutrinoless double beta decay from 130Te, has started taking data in spring 2013 underground at the Laboratori Nazionali del Gran Sasso (LNGS). The excellent results obtained in terms of energy resolution and background level allowed this experiment to reach the sensitivity of Cuoricino in approximately half the runtime. Combining CUORE-0 data (9.8 kg·yr exposure of 130Te) with the 19.75 kg·yr exposure of the Cuoricino experiment, we obtain the most stringent limit to date on the half-life of this isotope (T1/2 > 4.0 × 1024 yr). In this article, we review the results from CUORE-0 and discuss the status and the physics potential of CUORE, a 19 times larger bolometer array that plans to begin operations by end of this year. [ABSTRACT FROM AUTHOR]

The LUMTNEU program aims at performing a pilot experiment on 0ν2β decay of 100Mo using radiopure ZnMoO4 crystals enriched in 100Mo operated as cryogenic scintillating bolometers. Large volume ZnMoO4 crystal scintillators (~0.3 kg) were developed and tested showing high performance in terms of radiopurity, energy resolution and α/β particle discrimination capability. Zinc molybdate crystal scintillators enriched in 100 Mo were grown for the first time by the low-thermal-gradient Czochralski technique with a high crystal yield and an acceptable level of enriched molybdenum irrecoverable losses. A background level of ~ 0.5 counts/(yr keV ton) in the region of interest can be reached in a large detector array thanks to the excellent detectors radiopurity and particle discrimination capability, suppression of randomly coinciding events by pulse-shape analysis, and anticoincidence cut. These results pave the way to future sensitive searches based on the LUMTNEU technology, capable of approachingand exploring the inverted hierarchy region of the neutrino mass pattern. [ABSTRACT FROM AUTHOR]

The development of background-free detectors is essential for experiments searching for rare events. Bolometers, that are among the most competitive devices for the study of neutrino-less double beta decay (0νDBD) and Dark Matter interactions, suffer from the absence of techniques that allow to identify the nature of the interacting particles. This limit can be overcome by coupling the bolometer to an independent device for the measurement of the light emitted by interactions, as the combined read-out of the bolometric and light signals allows to identify and reject particles different from those of interest. CUORE, the most advanced bolometric experiment for 0νDBD searches, could disentangle the electrons produced by 0νDBD from the dangerous background due to α particles, by measuring the (tiny) Cherenkov light emitted by electrons and not by α's. LUCIFER, a project based on ZnSe scintillating bolometers for the study of 82Se 0νDBD, would be competitive also in the search of Dark Matter interactions if equipped with light detectors that allow to distinguish and reject the background due to electrons and γ's. These advances require cryogenic detectors characterized by noise lower than 20 eV, large active area, wide temperature range of operation, high radio-purity and ease in fabricating hundreds of channels. The CALDER collaboration aims to develop such detectors by exploiting the superb energy resolution and natural multiplexed read-out provided by Kinetic Inductance Detectors. [ABSTRACT FROM AUTHOR]

The results of R&D of radiopure zinc molybdate (ZnMoO4) based scintillating bolometers for the LUMINEU (Luminescent Underground Molybdenum Investigation for NEUtrino mass and nature) double-beta decay experiment are presented. A dedicated two-stage molybdenum purification technique (sublimation in vacuum and recrystallization from aqueous solutions) and an advanced directional solidification method (the low-thermal-gradient Czochralski technique) were utilized to produce high optical quality large mass (~1 kg) ZnMoO4 crystal boules and first 100Mo (99.5%) enriched Zn 100MoO4 crystal scintillator (mass of ~0.2 kg). Scintillating bolometers based on ZnMoO4 (≈ 0.33 kg) and Zn 100MoO4 (≈ 0.06 kg) scintillation elements and high purity Ge wafers were tested in the EDELWEISS set-up at the Modane Underground Laboratory (France). Long term low temperature tests demonstrate excellent detectors' performance and effectiveness of the purification and solidification procedures for the achievement of high radiopurity of the material, in particular with a bulk activity of 228Th and 226Ra below 4 µBq/kg. The adopted protocol was used to produce for the first time a large volume Zn 100MoO4 crystal scintillator (mass of ~1.4 kg, 100Mo enrichment is 99.5%) to search for neutrinoless double-beta decay of 100Mo in the framework of the LUMINEU project. [ABSTRACT FROM AUTHOR]

With 741 kg of TeO2 crystals and an excellent energy resolution of 5 keV (0.2%) at the region of interest, the CUORE (Cryogenic Underground Observatory for Rare Events) experiment aims at searching for neutrinoless double beta decay of 130Te with unprecedented sensitivity. Expected to start data taking in 2015, CUORE is currently in an advanced construction phase at LNGS. CUORE projected neutrinoless double beta decay half-life sensitivity is 1.6×1026 y at 1s (9.5×1025 y at the 90 % confidence level), in five years of live time, corresponding to an upper limit on the effective Majorana mass in the range 40-100 meV (50-130 meV). Further background rejection with auxiliary bolometric detectors could improve CUORE sensitivity and competitiveness of bolometric detectors towards a full analysis of the inverted neutrino mass hierarchy. CUORE-0 was built to test and demonstrate the performance of the upcoming CUORE experiment. It consists of a single CUORE tower (52 TeO2 bolometers of 750 g each, arranged in a 13 floor structure) constructed strictly following CUORE recipes both for materials and assembly procedures. An experiment its own, CUORE-0 is expected to reach a sensitivity to the ßß(0v) half-life of 130Te around 3×1024 y in one year of live time. We present an update of the data, corresponding to an exposure of 18.1 kg y. An analysis of the background indicates that the CUORE performance goal is satisfied while the sensitivity goal is within reach. [ABSTRACT FROM AUTHOR]

Microbolometers are the most widely used detectors in long-wave infrared uncooled thermal imagers. An optical cavity is required within a microbolometer structure to increase its optical absorption. In this work we present a detailed study on the design and optimization of a microbolometer optical cavity using Essential-Macleod package. In the simulations, the cavity is considered as thin film multi-layers that form cascaded Fabry-Perot optical cavities. In the design phase, the layers structures are selected including materials and initial thickness. The absorbing layers are chosen to be vanadium-pentoxide (V2O5) and titanium (Ti). In the optimization phase, the designed layer thicknesses are varied to maximize optical absorption within the absorbing layers. The simulations show that Ti layer absorption dominates over V2O5 layer. Also, the optimization proves that the air-gap cavity thickness is not simply quarter-wavelength because of the complex cascaded Fabry-Perot structure. The optimized air-gap thickness here is ≈3.5 µm at 10.6µm wavelength. [ABSTRACT FROM AUTHOR]

doi: Long-pulse discharge with the electron density ne0 of 1 x 1019 m-3, electron temperature Te0 of 2.5 keV, discharge length tdis of 19 minutes and heating power Pinject of 1MW, is demonstrated using the HAS antenna and the PA antenna for ion cyclotron heating (ICH) and increasing in the power of electron cyclotron heating (ECH). The HAS antenna is designed to phase dipole and excite ideal fast wave with parallel electric field kept small, and low impurity generation and accumulation are achieved on the steady-state discharge by weak parasitic heating around antennas. On the long-pulse discharge, the radiation measured by bolometer is kept smaller than 20% for injection power, and the heat load to divertor is approximately 60 % with low energetic particle losses. The heat load ratio to divertor is not as a function of injection power around 1MW, and energy confinement has been kept during the steady-state discharge. [ABSTRACT FROM AUTHOR]

In order to obtain high sensitivity in the study of the neutrino mass it is necessary to design experiments able to optimize all the sensitivity parameters. One of the most promising techniques to achieve this goal is the bolometric technique because of its intrinsic characteristics: high detection efficiency, excellent energy resolution, low intrinsic background and the possibility to study many different compounds. The bolometric technique has already obtained excellent results on the neutrino mass study with Cuoricino. The Cuoricino experiment has also shown that surface contaminations of materials facing the detectors would be the limiting factor for the sensitivity of next generation experiments with bolometers. Mainly for this reason scintillating bolometers have been developed allowing a very efficient discrimination of alpha particles thanks to their double readout. Tests performed on these crystals showed moreover the possibility to discriminate the interacting particles through a pulse shape analysis. This feature is very promising because it allows to reach the same results on the background reduction obtained with the hybrid detectors but without complicating the experimental assembly. [ABSTRACT FROM AUTHOR]

In neutrinoless double-beta decay and dark matter searches, one of the main issues is to increase the experimental sensitivity through careful material selection and production, minimizing the background contributions. In order to achieve the required, extremely low, counting rates, very stringent requirements must be fulfilled in terms of bulk material radiopurity. As the experimental sensitivity increases, the bulk impurities in the detector components decrease, and surface contaminations start to play an increasingly significant role In fully active detectors, like cryogenic particle detectors, surface contaminations are a critical issue (as shown by the CUORICINO experiment). 222Rn is by far the most intense source of airborne radioactivity, and if a radio-pure material is exposed to environment where the Radon concentration is not minimized, 210Pb and 210Po contaminations can occur. The mechanisms and the dynamics of Radon-induced surface contaminations are reviewed, and specific solutions to prevent and to reject the induced background are presented. [ABSTRACT FROM AUTHOR]

Due to a very low event rate expected in direct dark matter search experiments, a good understanding of every background component is crucial. Muon-induced neutrons constitute a prominent background, since neutrons lead to nuclear recoils and thus can mimic a potential dark matter signal. EDELWEISS is a Ge-bolometer experiment searching for WIMP dark matter. It is located in the Laboratoire Souterrain de Modane (LSM, France). We have measured muon-induced neutrons by means of a neutron counter based on Gd-loaded liquid scintillator. Studies of muon-induced neutrons are presented and include development of the appropriate MC model based on Geant4 and analysis of a 1000-days measurement campaign in LSM. We find a good agreement between measured rates of muon-induced neutrons and those predicted by the developed model with full event topology. The impact of the neutron background on current EDELWEISS data-taking as well as for next generation experiments such as EURECA is briefly discussed. [ABSTRACT FROM AUTHOR]

We present a search for β+/EC double beta decay of 120Te performed with the CUORICINO experiment, an array of TeO2 cryogenic bolometers. After collecting 0.0573 kg·y of 120Te, we see no evidence of a signal and therefore set the following limits on the half-life: T1/20ν>1.9·1021 y at 90% C.L. for the 0ν mode and T1/22ν>7.6·1019 y at 90% C.L. for the 2ν mode. These results improve the existing limits by almost three orders of magnitude (four in the case of 0ν mode). [ABSTRACT FROM AUTHOR]

New generation of experiments to search for neutrinoless double beta decay with sensitivity to effective Majorana neutrino mass on the level of ∼3-5 meV is discussed. Possible restrictions in achievement of this sensitivity such as: possibility to produce large amount of enriched isotopes, possibility to reach of a very low level of background, energy resolution and possible cost of experiments are considered. It is shown that for realization of so ambitious project 10 tons (or more) of enriched isotope is required. Background index should be on the level ≤10-5-10-6 c/kg·keV·y. In addition, the energy resolution of the detector should be no worse than 1-2%. It is shown that 130TeO2 low temperature bolometer could be the most realistic candidate for such an experiment. Under certain conditions experiments with 76Ge, 100Mo and 136Xe can be realized too. [ABSTRACT FROM AUTHOR]

We have fitted the complete Swift BAT and XRT light curves of 88 GRBs for which we have a redshift with a total of 331 pulses. For each GRB we also include an afterglow component to fit the plateau phase and the late decay seen in the XRT data. The combination of pulses and afterglow model all the emission detected, prompt plus afterglow, including late X-ray flares detected only in the XRT. Each pulse is described by a simple physical model which includes the spectrum at peak and the temporal characteristics of the pulse. We find that the pulse peak luminosity is correlated with both the mean photon energy in the bolometric band of the pulse spectrum at the peak, referred to as Ezbol, and the temporal parameter Tzf which is a measure of the pulse width. An empirical bivariate luminosity model set up with these parameters provides a good fit to the pulse luminosity. The analysis indicates that prompt pulses and X-ray flares are one and the same and arise from the same physical process and this physical process is responsible for the bivariate nature of the luminosity. [ABSTRACT FROM AUTHOR]

A search for WIMP dark matter has been undertaken with new-generation germanium heat-and-ionization cryogenic detectors in the EDELWEISS-II experiment. The InterDigit bolometers, with an interleaved electrode design, have proven excellent rejection performance against gamma-ray and surface event backgrounds which are limiting germanium bolometer dark matter searches. One year of continuous operation at the Laboratoire Souterrain de Modane has been achieved with an array of ten 400 g detectors. Preliminary resultats for WIMP search are presented with an effective exposure of 322 kg.days, which corresponds to a 5×10-8 pb sensitivity to the spin independant WIMP-nucleon cross-section at 90% C.L. for a WIMP mass of 80 GeV/c2. [ABSTRACT FROM AUTHOR]

The production of crystals needed for rare events physics represent a relatively new, exciting challenge in the field of materials science and engineering. Extremely low concentration of radioactive impurities and very high crystal perfection is required for the crystals to be used in experiments in which the main concerns are the reduction of the background and the use of high sensitivity detectors. A further complication is the fact that for an experiment with a significant discovery potential, relatively large quantities of crystals are needed. The present work makes a review of the general problems related to the production of crystals for rare events physics and gives details related to the production of the TeO2 crystals needed for the major experiment in this field using bolometric technique, namely the CUORE experiment. The potential use of crystals for future double beta decay experiments is also discussed. [ABSTRACT FROM AUTHOR]

ALMA will become fully operational in a few years and open a new window on primordial galaxies. The mm and submm domain is privileged, since the peak of dust emission between 60 and 100 microns is redshifted there for z = 5-10, and the continuum benefits from a negative K-correction. At least 100 times more sources than with present instruments could be discovered, so that more normal galaxies, with lower luminosities than huge starbursts and quasars will be surveyed. The high spatial resolution will suppress the confusion, which plagues single dish bolometer surveys today. Several CO lines detected in broad-band receivers will determine the redshift of objects too obscured to be seen in the optical. With the present instrumentation, only the most massive and gas rich objects have been detected in CO at high z, most of them being ultra-luminous starbursts with an extremely high star formation efficiency. However, selection biases are omni-present in this domain, and ALMA will statistically clarify the evolution of star formation efficiency, being fully complementary to JWST and ELTs. [ABSTRACT FROM AUTHOR]

Semiconductor bolometers and microcalorimeters operating at ultra-low temperatures are used in many applications, such as sub-millimetre and X-ray astronomy, dark matter searches, and double beta decay experiments. Various thermistor materials are used, primarily neutron transmutation doped germanium and ion implanted silicon. These materials both exhibit a similar variation of resistivity with temperature (R(T)), believed to be due to variable range hopping. A theoretically motivated equation provides good fits to the R(T) behaviour, with only two adjustable parameters. However, systematic deviations from these fits have been observed. It would be of practical use to obtain a single equation which could take such deviations into account without adding further adjustable parameters. An equation of this form has been proposed based on measurements on ion-implanted silicon [D. McCammon, in Cryogenic Particle Detection, Springer, Berlin, 2005]. Since this was also found to fit measurements on an NTD germanium thermistor, it was proposed as a general function for both materials. We show that it does not apply to NTD germanium in general, and propose an alternative two-parameter fitting function for this material. This enables greatly improved fits to be carried out compared with the standard function, without the penalty of introducing an extra parameter. [ABSTRACT FROM AUTHOR]

We present measurements of the heat capacity of neutron transmutation doped (NTD) Ge temperature sensors from 100–300 mK. The NTD Ge sensor studied consists of a 30μm×100μm×250μm block of NTD Ge type 18 with the natural isotopic abundance, a doping of n = 5.6×1016 cm-3 and ion implanted and metallized contact pads. Each sensor was mounted on a freestanding silicon nitride (Si-N) pad supported by Si-N legs each with a cross section in the range 5–10 μm2. Two of the Si-N legs were metallized for electrical readout of the NTD Ge sensor. The measured heat capacity of the NTD Ge sensor, which includes the metalization and Si-N pad, when fit to power law C = C0Tγ yields C0 = 4.3pJ/Kγ and γ = 1.6. The thermal conductance, GSi-N, of the Si-N support legs was measured over a larger temperature range 80–800 mK. We find Gsi-N at temperatures >200 mK of all 4 samples is at or below the 1D or quantum of thermal conductance limit. [ABSTRACT FROM AUTHOR]

The Herschel/PACS photometer is the largest bolometer camera in operation for submillimeter astronomy in space. CEA Saclay and LETI have developed these bolometers using innovative techniques, such as silicon micro-machining, resonant absorption or CMOS multiplexing. For the next generation space missions an improvement in sensitivity by 2 orders of magnitude is required. We are considering different options to reach sensitivities as low as 10-20W/Hz1/2. Based on our PACS experience, we are exploring the possibility to use semiconducting sensors at very low temperature (50 mK or below). The TES option is also considered as well as the possibility to couple antennas with very small thermal sensors. We present here preliminary results of simulations and analysis for these solutions. [ABSTRACT FROM AUTHOR]

We present optical data on prototype polarization sensitive Argonne/KICP detectors fabricated at Argonne National Labs which are designed to be installed on the South Pole Telescope and used to measure the polarization of the Cosmic Microwave Background radiation. The detectors are Mo/Au transition edge sensors (TES) suspended on silicon nitride, with radiation coupled to the TES using a gold bar absorber. Two stacked detectors with bars in orthogonal directions will be used to measure both polarizations. We discuss measurements of the optical bandpass, time constants and cross-polarization of the detectors. [ABSTRACT FROM AUTHOR]

A digital frequency multiplexing (DfMUX) system has been developed and used to tune large arrays of transition edge sensor (TES) bolometers read out with SQUID arrays for mm-wavelength cosmology telescopes. The DfMUX system multiplexes the input bias voltages and output currents for several bolometers on a single set of cryogenic wires. Multiplexing reduces the heat load on the camera’s sub-Kelvin cryogenic detector stage. In this paper we describe the algorithms and software used to set up and optimize the operation of the bolometric camera. The algorithms are implemented on soft processors embedded within FPGA devices operating on each backend readout board. The result is a fully parallelized implementation for which the setup time is independent of the array size. [ABSTRACT FROM AUTHOR]

We have obtained the first data on the multiplexed operation of titanium hot-electron bolometers (HEB). Because of their low thermal conductance and small electron heat capacity nanobolometers are particularly interesting as sensors for far-infrared spectroscopy and mid- and near-IR calorimetry. However, the short time constant of these devices (∼μs at 300–400 mK) makes time domain or audio-frequency domain multiplexing impractical. The Microwave SQUID (MSQUID) approach pursued in this work uses dc SQUIDs coupled to X-band microresonators which are, in turn, coupled to a transmission line. We used a 4-element array of Ti HEBs operated at 415 mK in a He3 dewar with an optical fiber access. The microwave signal exhibited 10-MHz wide resonances at individual MSQUD frequencies between 9 GHz and 10 GHz. The resonance depth is modulated by the current through the bolometer via a change of the SQUID flux state. The transmitted signal was amplified by a cryogenic amplifier and downconverted to baseband using an IQ mixer. A 1-dB per Ω0/2 responsivity was sufficient for keeping the system noise at the level of ∼2 pA/Hz1/2. This is more than an order of magnitude smaller than phonon noise in the HEB. The devices were able to detect single near-IR photons (1550 nm) with a time constant of 3.5 μs. Follow-on work will scale the array to larger size and will address the microwave frequency signal generation and processing using a digital transceiver. [ABSTRACT FROM AUTHOR]

We discuss materials characterization and integration considerations for large-format, antenna-coupled, low-noise, cryogenic, bolometer arrays for far-infrared space-based observatories. The suitability of Bi as an antenna termination resistor and annealed gold for microstrip and groundplane, in the context of using each to optimize signal and bandwidth of the receiver is addressed. Bismuth is chosen as a candidate termination resistor material because films can be made with the 10–100 Ω/□ needed to impedance-match the antenna in a compact, stable, and reproducible manner. We characterize both the DC electronic transport and the THz optical properties of thermally evaporated (TE) and ion assisted thermally evaporated (IAE) Bi. It is found that the residual resistance ratio of the IAE Bi is an order of magnitude higher than that of TE Bi in the relevant impedance range. Furthermore, we show that we have produced IAE Bi films with linear response across the THz band. We discuss the possibility of employing other, much lower volume, absorber materials including TiAu and PdAu alloys. A comparison of the expected noise in a standard coupling resistor for each material is made. A technique of fabricating 150 nm gold films having a low temperature resistivity equal to 3.5×10-9 Ωm via thermal annealing is also presented. We model the response of these candidate films in an antenna circuit for THz radiation. [ABSTRACT FROM AUTHOR]

We describe the development of a detector for precise measurements of the cosmic microwave background polarization. The detector employs a waveguide to couple light between a pair of Mo/Au superconducting transition edge sensors (TES) and a feedhorn. Incorporation of an on-chip ortho-mode transducer (OMT) results in high isolation. The OMT is micromachined and bonded to the microstrip and TES circuits in a low temperature wafer bonding process. The wafer bonding process incorporates a buried superconducting niobium layer with a single crystal silicon layer which serves as the leg isolated TES membrane and as the microstrip dielectric. We describe the micromachining and wafer bonding process and report measurement results of the microwave circuitry operating in the 29–45 GHz band along with Johnson noise measurements of the TES membrane structures and development of Mo/Au TES operating under 100 mK. [ABSTRACT FROM AUTHOR]

The Atacama B-mode Search (ABS) experiment is a 145 GHz polarimeter designed to measure the B-mode polarization of the Cosmic Microwave Background (CMB) at large angular scales. The ABS instrument will ship to the Atacama Desert of Chile fully tested and ready to observe in 2010. ABS will image large-angular-scale CMB polarization anisotropies onto a focal plane of 240 feedhorn-coupled, transition-edge sensor (TES) polarimeters, using a cryogenic crossed-Dragone design. The ABS detectors, which are fabricated at NIST, use orthomode transducers to couple orthogonal polarizations of incoming radiation onto separate TES bolometers. The incoming radiation is modulated by an ambient-temperature half-wave plate in front of the vacuum window at an aperture stop. Preliminary detector characterization indicates that the ABS detectors can achieve a sensitivity of [formula] in the field. This paper describes the ABS optical design and detector readout scheme, including feedhorn design and performance, magnetic shielding, focal plane architecture, and cryogenic electronics. [ABSTRACT FROM AUTHOR]

SPTpol will consist of an 850 element polarization sensitive bolometric camera deployed to the South Pole Telescope in late 2011. This camera is optimized for measurement of the polarization of the cosmic microwave background with arcminute resolution. These measurements will be used to constrain neutrino masses and to constrain the amplitude of gravitational waves from inflation. The camera includes two detector architectures that observe in two different frequency bands. At 150 GHz, SPTpol will use 650 feedhorn-coupled TES polarimeters fabricated at NIST. At 90 GHz, it will use 200 absorber-coupled polarimeters developed at Argonne National Lab. The NIST pixels will be coupled to the telescope using a monolithic array of corrugated feeds and the Argonne devices will be coupled with individually machined contoured feeds. The entire focal plane will be readout using a digital frequency-domain multiplexer system. We provide an overview of the project, describe the detectors and discuss the design of this system. [ABSTRACT FROM AUTHOR]

The next generation of cosmic microwave background (CMB) polarization experiments targeting the signatures of inflation will require unprecedented sensitivities in addition to careful control of systematics. With existing detector technologies approaching the photon noise limit, improvements in system sensitivities must come from ever-larger focal plane arrays of millimeter-wave detectors. We report on the design and performance of microfabricated planar orthomode transducer (OMT) coupled TES polarimeters and silicon micromachined platelet feedhorns optimized for scaling to large monolithic arrays. Future versions of these detectors are targeted for deployment in a number of upcoming CMB experiments, including ABS, SPTpol, and ACTpol. [ABSTRACT FROM AUTHOR]

We are developing a Transition-Edge Hot-electron Microbolometer (THM) for use in large detector array applications in millimeter-wave astronomy. This bolometer detector consists of a superconducting bilayer TES with an overlapping thin-film semi-metal absorber. The detector is deposited directly on the substrate and thermal isolation of the bolometer is controlled by electron-phonon scattering within the small volume of the detector. We present measurements characterizing the transition behavior of several micron-sized THM test devices which are optimized for photon-noise-limited observations of the Cosmic Microwave Background (CMB). We interpret these measurements in terms of a lateral proximity effect between the TES and the superconducting Nb TES leads. We discuss possible modifications to the THM design to compensate for this effect while retaining the small detector volume necessary to obtain the desired value of electron-phonon thermal conductivity. [ABSTRACT FROM AUTHOR]

A new design for the Ge bolometers of the EDELWEISS project is described here, based on innovative interleaved charge collection electrodes with high background discrimination capabilities. The measured surface event rejection is compatible with WIMP sensitivity levels down to 10-9 picobarn (pb). Use of interleaved electrodes on the overall surface of the Ge crystal, including its lateral surface, results to a high fiducial volume of the order of 80%. Electronic setup is fairly simple with a total of five JFET based read-out amplifiers, one for the NTD-Ge heat channel and four for the ionization signal. Fabrication process is quite simple and the design is easily scalable to higher mass bolometers (1 kg Ge crystal), making it very appealing for the future 1 ton scale EUREKA Dark Matter experiment. [ABSTRACT FROM AUTHOR]

This paper attempts to summarize the Thirteenth International Workshop on Low Temperature Detectors (LTD-13). It comments on the breadth of frontier science being tackled with these technologies and the evolution of the field. In particular, it highlights the shift towards systems with large numbers of detectors, and outlines several proposed solutions for solving the challenges of this large-scale integration. It also presents some of the impressive progress made on the fundamental understanding of transition edge sensors, kinetic inductance sensors, magnetic calorimeters, and semiconductor microcalorimeters. Several of these are now within a factor of two of their theoretical fundamental limits. [ABSTRACT FROM AUTHOR]

The bolometers (and readout circuitry) in the SPIRE instrument on the Herschel Space Observatory are among the best understood and well characterised of any sub-mm astronomy instrument to date. SPIRE contains five arrays of NTD germanium spiderweb bolometers with up to 139 pixels per array. Their behaviour has been shown to be extremely stable as seen by repeated measurements in the years between initial array level and final instrument level tests, and can be described extremely well by a simple physical model (the ideal bolometer model). Calibration of the bolometers must take into account the non-linear response when viewing bright sources, and the effect of fluctuations in the heat sink temperature. The simple and well-understood behaviour of the detectors, coupled with the stable conditions expected in flight, mean that in contrast to previous sub-mm instruments, physical models can be used to improve or possibly replace empirical calibration methods. We describe how this can be done, and use the large amount of data from ground measurements to show that we can use models to accurately calculate the absolute power detected by the bolometers. [ABSTRACT FROM AUTHOR]

The evolution of the Type Ia SN 2003 hv is followed for a period of over 700 days past maximum light. From its early evolution, this is a normal SN Ia with a rare B-band decline rate of 1.61±0.03. The late-time decline rates in the optical bands are consistent with previous results, but a slow-down is observed after ∼520 days. The near-infrared luminosity shows a drop for the first time but no signs of an Infrared Catastrophe are evident. The decline rate of the quasi-bolometric light curve suggests that the majority of positrons are trapped within the ejecta. During late epochs, the [Fe II] λ8621 line is blue-shifted and exhibits a flat-topped profile. Such a behavior is consistent with previously published near- and mid-infrared spectra. [ABSTRACT FROM AUTHOR]

Adding a wire on the axis of wire arrays significantly affects the x-ray emission of the conical arrays, and much less that of the cylindrical ones. The radiation of the conical wire arrays increases with the thickness of the central wire, surpassing that of the equivalent cylindrical arrays. Significant energy is emitted early on, around the time of the conical shock formation, before the pinch stagnation. [ABSTRACT FROM AUTHOR]

The Cornell University COBRA pulser is a nominal 1 MA machine, capable of driving up to 32 wire cylindrical Z-pinch arrays. COBRA can operate with variable current risetimes ranging from 100 ns to 200 ns (short and long pulse, respectively). Wires are typically strung with a “press” contact to the electrode hardware, where the wire is loosely pulled against the hardware and held there to establish electrical contact. The machine is normally negative, but a bolt-on convolute can be used to modify the current path and effectively produce positive polarity operation at the load. Previous research with single wires on a 1–5 kA pulser [1] has shown that soldering the wire, thereby improving the wire/electrode contact, and operating in positive polarity can improve the energy deposition into the wire and enhance wire core expansion. Negative polarity showed no difference. Previous experiments on the negative polarity, 20 MA, 100 ns Z accelerator [2] have shown that improving the contact improved the x-ray yield. Cornell data were collected on 16-wire Aluminum Z-pinch arrays in negative polarity. Experiments were conducted with both short and long current pulses with soldered and no-soldered wire/electrode contacts. The initiation, ablation, implosion and stagnation phases were compared for these four conditions. Time dependent x-ray signals were measured using diodes and diamond detectors. An inductive voltage monitor was used to infer minimum current radius achieved, as defined by a uniform shell of current moving radially inward, producing a time dependent inductance. Total energy data were collected with a metal-strip bolometer. Self-emission data were collected by an XUV 4-frame camera and an optical streak camera. In negative polarity and with short pulses, soldering appeared to produce a smaller radius pinch and decrease variations in the x-ray pulse shape. The bolometer, laser backlighter, 4-frame and streak cameras showed negligible differences in the initiation ablation and implosion phases. X-ray yield was increased with soldered arrays in negative polarity with long pulses. The bolometer also showed a 50% increase in radial power emitted for soldered arrays. 4-frame images showed soldered arrays have a more pronounced “Christmas Tree” effect originating from the cathode. The inductive voltage monitor showed, with both long and short pulses, that soldered and no-solder arrays reached the same minimum current radius at the same time. However, with long pulses soldered arrays radiate x-rays at the time of minimum current radius while no-solder array x-ray output is delayed by ∼20 ns, resulting in decreased x-ray yield. [ABSTRACT FROM AUTHOR]

Implosions from compact cylindrical wire arrays (CCWA) with mid-Z and low-Z wires were carried out on the 1-MA COBRA generator at Cornell University. In particular, the CCWA used either Brass 310 (70% Cu, 30% Zn) wires or a combination of Brass 310 and Al 5056 (95% Al, 5% Mg) wires arranged in an alternating pattern. A total of 16 wires were used on either a 6 or 4 mm diameter array. The diagnostic suite included a bolometer, fast x-ray detectors, a time-integrated spectrometer, and a streak camera. A higher energy output was observed from bolometer measurements when alternating the brass and Al wires compared to using only the brass wires. This study will focus mainly on the spectroscopy of the brass and alternating brass and Al CCWA by applying the non-LTE kinetic models of Cu and Zn to account for the L-shell radiation. The resulting plasma parameters, electron density and electron temperature, will be discussed and compared for the CCWA with only brass wires and alternating brass and Al wires. The simulations with the novel Wire Ablation Dynamics Model that account for wire ablation will be performed to analyze the differences in implosion dynamics of the uniform and alternating compact cylindrical arrays. [ABSTRACT FROM AUTHOR]

POLARBEAR is a ground-based experiment to measure polarization anisotropy in the Cosmic Microwave Background. It is designed to have a combination of sensitivity, foreground mitigation, and rejection of systematic errors to search for the B-mode signature of Inflationary gravity waves over much of the parameter range suggested by simple power-law Inflation models. POLARBEAR is designed to detect a gravitational-wave signature with a tensor-to-scalar ratio r as low as 0.025 (95% confidence). POLARBEAR will also measure polarized lensing of the Cosmic Microwave Background which will give valuable information on large-scale structure at z>1 and bound the total mass of the neutrinos. POLARBEAR will have a 3.5 meter primary meter giving it an angular resolution of 3.0′ at its main observation frequency band centered at 150 GHz. The 250 mK focal plane design contains 637 dual-polarization pixels (1274 bolometers) that are coupled to the telescope using microlithographed planar antennas. The experiment will be sited in the Atacama Desert in Chile at 5000 meter (16,500 ft) altitude starting in 2009 after a prototype testing stage at Cedar Flats California. The first configuration of the experiment will observe at only one frequency band with the first season at 150 GHz and the second at 220 GHz. The optics will be upgraded to have simultaneous observations in those two bands in the third season of observations. POLARBEAR and QUIET will observe the same sky patches, and together they will have frequency bands at 30, 40, 90, 150, and 220 GHz giving broad coverage of galactic foregrounds and a valuable cross-check by comparison of polarization maps. In POLARBEAR, polarization systematic errors are mitigated by a continuously rotating 50 K half-wave plate and an observation strategy that takes advantage of parallactic angle rotation to rotate the experiment relative to polarization patterns on the sky. [ABSTRACT FROM AUTHOR]

We propose an application of Michelson type bolometric interferometer to cosmic microwave background polarization observations. [ABSTRACT FROM AUTHOR]

The bolometer system planned for W7-X consists mainly of metal (Au) resistive detector arrays. All the detectors are exposed to neutral gas environment. The thin bolometer foil used for detecting the radiated power loss may be sensitive to the neutral gas pressure due to the strain gauge effect. Recently, a prototype of this kind of bolometer camera consisting of 12 channels has been installed on the cylindrical plasma device VINETA in order to investigate the influences of the neutral gas pressure on the bolometer signals. Experiments are carried out for Ar-discharges under different gas pressure conditions. It is found that the pressure effect of the neutral gas can make considerable contributions, thus inducing non-negligible errors of the results in most of the investigated cases. Using the VINETA plasmas (Ar, Te<10 eV, ne<10-19 m-3) as examples, the paper demonstrates and discusses how to minimize the neutral gas effects, especially in the data analysis process. The radiated power and the radiation intensity profile obtained in helicon discharges are presented. [ABSTRACT FROM AUTHOR]

The effect of SiO2 addition on the characteristics of CuFe2O4 ceramics for NTC thermistors has been studied. The ceramics were produced by pressing a homogeneous mixture of CuO, Fe3O4 and SiO2 (0–0.75 w/o) powders in appropriate proportions to produce CuFe2O4 based ceramics and sintering the pressed powder at 1100 °C for 2 hours in air. Electrical characterization was done by measuring electrical resistivity of the ceramics at various temperatures (25 °C–100 °C). Microstructure and structural analyses were also carried out by using optical microscopy and X-ray diffraction (XRD), respectively. The XRD analyses showed that the CuFe2O4 and SiO2 added-CuFe2O4 ceramics have crystal structure of cubic spinel. The presence of second phase could not be identified from the XRD analyses. According to the electrical data, it was known that the SiO2 addition increased the thermistor constant (B) and the room temperature electrical resistivity (ρRT). The value of B and ρRT of the produced CuFe2O4 ceramics namely B = 2548–3308 ° K and ρRT = 291–9400 ohm's, fitted market requirement. [ABSTRACT FROM AUTHOR]

This tutorial gives a brief introduction into passive spectroscopy and describes the working principles of bolometers, a high-resolution grating spectrometer, and a novel X-ray imaging crystal spectrometer, which is also of particular interest for profile measurements of the ion temperature and plasma rotation velocity on ITER and future burning plasma experiments. [ABSTRACT FROM AUTHOR]