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The article contains sections titled: 1. Introduction 2. Biological Principles 2.1. Organisms 2.2. Biocenosis 2.3. Metabolism 3. Basic Biotechnological Considerations 4. Technology and Operation of a Wastewater-Treatment Plant 5. Examples of Industrial Wastewater-Treatment Plants Based on a Variety of Centralized Processes 5.1. Single-Stage and Multistage Activated-Sludge Plants 5.2. Oxygen-Based Facilities 5.3. Treatment Facilities with Selective Carbon and Nitrogen Elimination 5.4. Trickling-Filter Facilities 5.5. Biofilter Systems 5.6. Indirect-Discharge Facilities

For ground-based electromagnetic methods in geophysics dc superconducting quantum interference devices based on high-temperature superconductors are well suited as magnetic field sensors. Therefore, we introduce in this paper an advanced fabrication technology for high-temperature superconducting dc SQUIDs based on step-edge Josephson junctions. The dc SQUIDs are prepared on structured magnesium-oxide substrates. A trilayer of YBa 2 Cu 3 O 7-x /SrTiO 3 /YBa 2 Cu 3 O 7-x is deposited by pulsed laser deposition and structured with ion beam etching. The galvanometer-type design consists of four different dc SQUIDs directly coupled to a pickup loop. They exhibit large I c R n products and a voltage swing of more than 30 μV. The magnetic field noise amounts to about 20 fT/Hz 1/2 and 35 fT/Hz 1/2 for the white noise region as well as 25 fT/Hz 1/2 and 100 fT/Hz 1/2 at 100 Hz for ac-bias and dc-bias SQUID electronics, respectively. The advanced fabrication process thus enables to produce HTS dc SQUIDs intended for the use in geophysical applications with high throughput.

This paper describes the deposition of superconductive Nb-N thin films in a metal-organic plasma-enhanced atomic layer deposition process using (tert-butylimido)-tris (diethylamino)-niobium and hydrogen plasma as precursors. In extension of our previous work, which investigated the possibility to deposit superconducting Nb-N, we systematically investigated the influence of different plasma parameters on superconducting and morphological properties of the niobium nitride thin film formed during the process. An initial increase of the duration of the plasma dose led to higher transitions temperatures and critical current densities, the optimum being a plasma dose time of 50 s. By decreasing plasma pressure, the resistivity at room temperature decreased, while the transition temperature increased. In addition, Nb-N thin films were deposited onto several substrates such as silicon, thermally grown silica, magnesium oxide (MgO), and r-plane sapphire. ${\rm{T}}_{{\rm{C}}}$ values from 6.2 K up to 14 K were achieved independently of the substrate materials. However, films deposited on MgO showed lower ${\rm{T}}_{{\rm{C}}}$ values. X-ray photoelectron spectroscopy measurement revealed the presence of niobium nitride but also of niobium oxide and oxy-nitride components in the films as well as the existence of a high amount of incorporated carbon impurities. X-ray diffraction measurements revealed two significant reflexes, which could be attributed to niobium nitride only. No crystalline niobium oxide or niobium oxynitride was detected. Thus, the films consisted of a matrix of polycrystalline Nb-N and amorphous or microcrystalline grains of different niobium oxide and oxynitride phases. Due to the fact that the deposited material showed superconductivity especially for ultrathin layers with thicknesses in the nanometer range, these films may be suitable for superconducting nanowire single photon detectors.

Fabrication of devices composed of Josephson junctions in trilayer technology is usually compromised by the topography of the subjacent layers. If the structures of subsequent layers traverse steps, several adverse effects arise. Lithography may be impaired because of issues with resist thickness uniformity and focus depth, and the superconducting ampacity of the Nb wiring is reduced. Various methods have been tried to planarize perturbing structures. In this contribution, we address a few of the challenges of chemical mechanical polishing. The proposed improvements are based on the well-established IPHT cross-type junction technology.

Silicon nitride membrane based cryogenic bolometers exhibit high sensitivity and enable ultra-sensitive detector applications. Multi-pixel instruments were already introduced as devices for submillimeter-wave imaging. Nevertheless, the numbers of pixels are limited by the readout process which is typically a time-division multiplexing or code-division multiplexing technique. To overcome this challenge, a replacement of the transition-edge sensor as thermometer by a lumped-element resonance circuit seems to be a promising solution. Therefore, one can benefit from the intrinsic capability of frequency-division multiplexing that allows the readout of large detector arrays simultaneously and in real-time. The number of pixels is then limited by the available readout bandwidth and the quality factors of each individual resonance circuit. We successfully demonstrated, based on our feasibility study, the principal operation of such a device, what we call kinetic-inductance bolometer (KIBO). But the overall performance of the achievable noise-equivalent power (NEP) was limited by implementation and operation temperature of KIBO. Therefore, improved KIBO designs were developed and fabricated with niobium thin-film technology. In this paper, we describe the improvement procedure and estimate the expected NEP value.

Tailoring the physicochemical properties of the metallic multijunction nanolayers is a prerequisite for the development of microelectronics. From this perspective, a desired lower reflectance of infrared radiation was achieved by an electrochemical deposition of porous platinum in nonaqueous media on silver mirror supported nickel-chrome and nickel-titanium metallic films with incremental decreasing thicknesses from 80-10 nm. The electro-assembled architectures were examined by means of scanning electron microscopy and Fourier transform infrared spectroscopy and it was observed that the layer and sublayer thicknesses and resistivities have a substantial effect upon the porous platinum morphology and its optical properties. It is here reported that the augmentation of the metallic layer electrical conductivity determines the electroformation of more compact platinum nanolayers. Moreover, the platinum black coating of metallic nanolayers causes a considerable decrease of the reflectance in the region from 1000-8000 cm-1.

In recent years, body scanner technologies based on millimeter-wave and terahertz technologies have been shown to improve security in areas sensitive to terrorist attacks by detecting hazardous objects hidden underneath the clothing of people. Inevitably, useful devices have to provide an adequate compromise between spatial resolution limited due to diffraction and penetration through clothing. Within this context, the spectral absorption of a wide range of fabric, interference caused by the texture, and the effect of moisture within the fabric have to be considered. We have studied these effects by time-domain and Fourier transformation spectroscopy. The experimental findings are verified using a passive THz security camera operating in two frequency bands at 0.85 and 0.35 THz. The latter band was proven to be of superior use for security checks as it provides useful results even in cases of wet clothes.

Extraordinary optical transmission and perfect absorption are two plasmonic-based optical phenomenona that are both accompanied by high local field enhancements that can be exploited for biological and chemical sensing. Here we merge both phenomenona in a slit array metamaterial perfect absorber consisting of a dielectric layer sandwiched between two metallic layers of which the upper layer is perforated with a periodic array of slits. Period and dimensions of the slits and thickness of the dielectric layer are tuned in a way that virtually all light of a certain wavelength incident on the surface passes through the slits and is subsequently absorbed. As a consequence, light–matter interaction is greatly enhanced in the slits. Thus, already small concentrations of analytes down to a monolayer attached to the sidewalls of the slits can be detected by refractive index sensing and identified by their spectral fingerprints with a standard mid-infrared lab spectrometer.

Cryogenic bolometers based on thin silicon nitride membranes show a very high sensitivity, which makes them ideal for ultrasensitive detector applications, particularly in the field of submillimeter-wave imaging. For that, transition-edge sensors (TESs) have been established as a viable approach toward developing multipixel sensor arrays. However, current multiplexer techniques as time- or code-division multiplexing do not scale well to multiplexing levels of several hundred detectors per channel. To achieve such a scalable readout solution, frequency-division multiplexing (FDM) would be an applicable way. For that, the temperature-sensing element of a bolometer has to be resonant or coupled to a resonance circuit, which changes its microwave behavior with the temperature of the absorber.

Aluminum nitride (AlN) thin films with thicknesses from 20 to 100 nm were deposited on silicon, amorphous silica, silicon nitride, and vitreous carbon by plasma enhanced atomic layer deposition (PE-ALD). Trimethylaluminum (TMA) and a H2/N2 plasma mixture were used as precursors. We investigated the influence of deposition temperature and plasma parameters on the growth characteristics and the film properties of AlN. Stable PE-ALD growth conditions were obtained from 150 °C to the highest tested temperature of 300 °C. The growth rate, refractive index, and thickness homogeneity on 4″ wafers were determined by spectroscopic ellipsometry. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and Rutherford backscattering spectrometry (RBS) were carried out to analyze crystallinity and composition of the films. Furthermore, the thermal conductivity and the film stress were determined. The stress was sufficiently low to fabricate mechanically stable free-standing AlN membranes with lateral dimensions of up to 2.2 × 2.2 mm2. The membranes were patterned with focused ion beam etching. Thus, these AlN membranes qualify as dielectric support material for a variety of potential applications.

Surface-enhanced Raman spectroscopy (SERS) is an attractive tool in the analytical sciences due to its high specificity and sensitivity. Because SERS-active substrates are only available as two-dimensional arrays, the fabrication of three-dimensional (3D) nanostructures allows for an increased number of hot spots in the focus volume, thus further amplifying the SERS signal. Although a great number of fabrication strategies for powerful SERS substrates exist, the generation of 3D nanostructures with high complexity and periodicity is still challenging. For this purpose, we report an easy fabrication technique for 3D nanostructures following a bottom-up preparation protocol. Enzymatically generated silver nanoparticles (EGNPs) are prepared, and the growth of hierarchically-designed 3D flower-like silica-silver composite nanostructures is induced by applying plasma-enhanced atomic layer deposition (PE-ALD) on the EGNPs. The morphology of these nanocomposites can be varied by changes in the PE-ALD cycle number, and a flower height of up to 10 μm is found. Moreover, the metallized (e.g., silver or gold) 3D nanostructures resulting from 135 PE-ALD cycles of silica creation provide highly reproducible SERS signals across the hydrophobic surface. Within this contribution, the morphological studies, optical properties, as well as the SERS response of these metallized silica-silver composite nanostructures applying vitamin B2 as a model analyte are introduced.

This paper is based on data sets acquired by a fast and efficient ground-based measurement system, which is based on superconducting quantum interference device technology and ensures geo-magnetic mapping of large areas. The local variations (gradients) of the Earth’s magnetic field are represented in so-called magnetograms, which typically include a large number of magnetic anomalies with different appearance and shape. Here, elongated anomalies are investigated, which are explainable by a polyhedral source body. These underground structures can be represented by a cross section that is approximately uniform along the main strike extent of the source. After introducing the measurement system, a source description model is developed theoretically and in the following adapted to practical problems. In order to illustrate the utility of this kind of minimization-based inversion and to validate the produced results, an example of archaeological measurements in Mongolia is shown. Results of the field measurements are used for inversion toward a description of possible subsoil situation. Finally, an excavation shows the accuracy of the results.

For spectroscopic and imaging applications in the submillimeter wavelength band, superconducting radiation sensors are widely used. Thereby, sensor arrays with a rising number of pixels require multiplexing techniques in order to reduce the number of wires leading to the cryogenic stage. A current steering switch (CSS) provides the basis for one kind of promising code division multiplexers. It is composed of two identical superconducting quantum interference devices (SQUIDs) in parallel current paths. Switching one of them from the superconducting into the normal state, which is controlled by the applied magnetic flux, alters the signal path; thus, they can act as a polarity switch for analog signals. In this paper, we describe a method that uses rapid single-flux quantum (RSFQ) electronics for controlling these switches. Therefore, their SQUIDs are inductively coupled each to the storing loop of an RSFQ delay flip-flop (DFF); hence, the state of the analog switch can be controlled by means of digital RSFQ signals. As a first step, we show the change in the critical current of the SQUIDs by the coupled operating digital circuit. For a wider operating range of the CSS, we developed a DFF, which is able to store a larger quantity of magnetic flux to make it possible to apply more flux to the coupled SQUID. For further improvements, we tested asymmetric SQUIDs to reduce the required magnetic flux. The results of the simulations and measurements are discussed.

Measurement of magnetic vector or tensor quantities, namely of field or field gradient, delivers more details of the underlying geological setting in geomagnetic prospection than a scalar measurement of a single component or of the scalar total magnetic intensity. Currently, highest measurement resolutions are achievable with superconducting quantum interference device (SQUID)-based systems.Due to technological limitations, it is necessary to suppress the parasitic magnetic field response from the SQUID gradiometer signals, which are a superposition of one tensor component and all three orthogonal magnetic field components. This in turn requires an accurate estimation of the local magnetic field. Such a measurement can itself be achieved via three additional orthogonal SQUID reference magnetometers. It is the calibration of such a SQUID reference vector magnetometer system that is the subject of this paper.A number of vector magnetometer calibration methods are described in the literature. We present two methods that we have implemented and compared, for their suitability of rapid data processing and integration into a full tensor magnetic gradiometry, SQUID-based, system.We conclude that the calibration routines must necessarily model fabrication misalignments, field offset and scale factors, and include comparison with a reference magnetic field. In order to enable fast processing on site, the software must be able to function as a stand-alone toolbox.

The intrinsic relaxation rates of the vector magnetization of cesium vapor enclosed in microfabricated atomic magnetometer cells are investigated. Two methods—the optically detected magnetic resonance and the ground-state Hanle effect—are used to carry out automated measurements in dependence on cell temperature and nitrogen buffer gas pressure. The experimental results are compared with expected contributions of the different relaxation processes and in this way allow the discrimination between them to help further optimization of cell design. The methods are compared in terms of basic features, data quality, and practical applicability.

An optical metamaterial, operating in between the MID/IR and the visible domain, which uses the effect of extreme coupling between closely spaced nanostructured gold metal plates and a planar gold substrate was realized by means of electron beam lithography and lift-off technique. This regime is only accessible by using an ultrathin oxide layer between metal plates and substrate, where the oxide layerisrealized by atomic layer deposition here. The involved fabrication is discussed in detail. The metamaterial shows the predicted effect of perfect absorption with multiple resonances in the spectral range from 100 THz to 600 THz. The plasmonic based resonance frequencies are very sensitive to the plate size of the grating and the spacer thickness.

We present a newly designed high-detectivity thermoelectric linear array, based on an organic membrane for use in the room temperature range. The sensor array has 64 individual readable channels and was designed and developed for IR spectroscopy. This detector may be used to infer the condition of lubricants and coolants within a mechanical system, so that they can be replaced when needs be, e.g. determining the age of technical oils of wind power plants in real time. Thus valuable resources can be saved and costly damage to equipment avoided. In order to achieve a D* greater than 2 × 109 cmHz1/2/W, the sensor was designed and optimized to be operated under vacuum conditions. To minimize the thermal cross talk between individual pixels, the pixels are separated from each other by a 50 μm slit in the self-supporting organic membrane made of SU-8.

Many processes on planetary bodies are driven by their respective surface energy balance, and while planetary climate is influenced by the dynamics of the atmospheric boundary layer, surface radiation drives the Yarkovksy and YORB effects on small airless bodies. In addition, insolation governs cometary activity and drives the dust cycle on Mars. The radiative flux received and emitted at the surface of solar system bodies is thus a fundamental quantity, which is driven by the reception of solar radiation in the visible wavelength band, while re-radiation primarily occurs in the thermal infrared. Knowledge of the relevant radiative fluxes enables studies of thermo-physical surface properties, and radiometers to measure surface brightness temperatures have been payloads on many missions. The HP3-RAD is part of the Heat Flow and Physical Properties Package (HP3) on the InSight mission to Mars. It is a light-weight thermal infrared radiometer with compact design. HP3-RAD measures radiative flux in 3 spectral bands using thermopile detectors. The 120 g device includes integrated front-end electronics as well as a deployable cover that protects the sensors from dust contamination during landing. In addition, the cover is simultaneously used as a calibration target. The instrument concept as well as its implementation will be described, and special emphasis will be put on technological challenges encountered during instrument development. Potential future improvements of the design will be discussed.

We present a detailed experimental and theoretical study on the relaxation of spin coherence due to the spin-exchange mechanism arising in the electronic ground states of alkali-metal vapor atoms. As opposed to the well-explored formation of a stretched state in a longitudinal geometry (magnetic field parallel to the laser propagation direction) we employ adapted hyperfine-selective optical pumping in order to suppress spin-exchange relaxation. By comparing measurements of the intrinsic relaxation rate of the spin coherence in the ground state of cesium atoms with detailed density-matrix simulations we show that the relaxation due to spin-exchange collisions can be reduced substantially even in a tilted magnetic field of geomagnetic strength, the major application case of scalar magnetic surveying. This explains the observed striking improvement in sensitivity and further deepens the understanding of the light- narrowed Mx magnetometer, which was presented recently. Additionally, new avenues for investigating the dynamics in alkali-metal atoms governed by the spin-exchange interaction and interacting with arbitrary external fields open up.

Graphical abstractDisplay Omitted Highlights? Homogenous and sensitive SERS-substrates based on surface metalized resist gratings. ? The approach combines e-beam lithography, atomic layer deposition and silver evaporation. ? The SERS enhancement is 4-5 orders of magnitude compared with the un-patterned film. ? The method enables disposable SERS substrates by using imprint techniques. A method using microfabricated resist masks as highly homogenous and sensitive substrates for surface enhanced Raman spectroscopy (SERS) is introduced. Our approach combines e-beam lithography for a polymer (PMMA) mask preparation, atomic layer deposition of aluminum-oxide as protection layer for the PMMA mask and silver evaporation for the SERS-active metal film. Compared to our former investigations on silver deposited etched quartz SERS-substrates these polymer based SERS substrates are easier to fabricate while showing the same reproducible signal enhancement across the whole grating area. The presented method provides high potential as it uses low-cost imprint techniques to pave the way towards low-cost SERS substrates in the future.

Thermopile detectors are particularly well suited for spectral imaging, space science applications, track recording, presence detection and applications with low energy consumption. The purpose of this work is the fabrication of a surface-micromachined 2-D high detectivity thermopile array using a highly effective BiSb/Sb thermocouple materials combination. The thermoelectric array is built on 8x8 pixels with an active area of [email protected] in square, which are wired directly. Thermopile structure and absorber area are manufactured upon a sacrificial layer based on polyimide, which is removed at the end of the manufacturing process. Thermoelectric layers as well as wiring layers has been patterned almost exclusively by lift-off technique in order to obtain very small structure dimension with high reliability as well as high integration level. The active area of detectors can be equipped with two absorber types for different application, a broadband colloidal silver black layer as well as a quarter wavelength arrangement for the MIR wavelength range from 8 to [email protected] The detectivity of so manufactured FPAs is about 1x10^9 Jones exceeding most of the state-of-the-art thermopile detectors.

A digital SQUID magnetometer measures the magnetic field amplitude by counting integer magnetic flux quanta within its superconducting input loop. Although resolution is limited in comparison to analog SQUID systems, the digital SQUID is able to outrange its analog counterpart with regard to parameters such as slew rate and dynamic range. In this work we evaluate the performance of a digital SQUID based on a three-level logic. Due to this basic principle, we face a combination of two comparator grayzones leading to hysteretic behavior of the sensor that produces a “dead zone” in the signal reversal point. The dependence of the comparator threshold on design parameters is investigated by simulation studies and reconfirmed by experimental results. We were able to reach a total dynamic range of more than 540,000 flux quanta (about 19 bit) with a linearity error of about 5 bit due to the mentioned hysteretic behavior. We discuss the results of our investigations and provide guidelines to extend dynamic range and linearity for future sensor designs.

We present the concept and experimental set-up of a passive submillimeter-wave stand-off imaging system for security applications. Our ambition is the design of an application-ready and user-friendly camera providing high sensitivity and high spatial resolution at video frame rates. As an intermediate step towards this goal, the current prototype already achieves a frame rate of 10 frames per second and a spatial resolution below 2 cm at 8 m distance. The camera is the result of a continuous development and a unique concept that yielded first high-resolution passive submillimeter-wave images provided by cryogenic sensors in May et al. (2007). It is based on an array of 20 superconducting transition-edge sensors operated at a temperature of 450 mK, a closed-cycle cooling system, a Cassegrain-type optics with a 50 cm main mirror, and an opto-mechanical scanner. Its outstanding features are the scanning solution allowing for high frame rates and the compact and integrated system design.

People have a desire for security, especially when they are about to enter an aircraft. Nobody wants to sit next to a terrorist flying 30,000 ft above ground. So, modern technology is expected to provide a solution to screen anybody willing to enter an aircraft for hidden threats. Obviously the actual solution using metal detectors and manual control is secure only to a certain level; moreover it is inefficient and offending. Security screening and respecting privacy at the same time constitute a conflict which cannot be easily solved. Characteristic for that dilemma is the actual public discussion regarding the so called “strip scanner” [1], where a technology with high security standard obviously violates privacy when in a figurative sense it undresses people and even worse illuminates them with arguable radiation (x-ray or millimetre waves). This article describes a possible solution, which respects people‘s privacy and complies with their basic need for security.

A geomagnetic field measurement system for the detection of archaeological signatures in the subsoil is presented based on the superconducting quantum interference device (SQUID). The system provides fast mapping of large areas with high magnetic field gradient resolution as well as lateral precision. The acquired data are geographically referenced and also the altitude profile is given. The properties of the system were tested intensively at the large Neolithic double-ring ditch enclosure of Niederzimmern near Weimar, Germany. Differences of the signal acquisition compared with caesium magnetometers are discussed. In the Niederzimmern double-ring ditch enclosure, with an area of 27 ha, archaeological patterns were found only near the gates. These SQUID measurements, together with accompanying excavations, provide a complex picture of the double-ring ditch enclosure, dated about 5600 years old. Copyright © 2008 John Wiley & Sons, Ltd.

A Josephson arbitrary waveform synthesizer (JAWS) has been used for the synthesis of bipolar waveform voltage signals. The two major changes with respect to earlier work are the use of Josephson arrays consisting of more junctions and the use of a new type of pattern generator. With a multi-branch Josephson array from IPHT, the synthesized sinusoidal voltages have amplitudes up to 9.5 mV zero to peak and frequencies in the range from 100 Hz to 150 kHz. For instance, for a 9.5 mV sine wave of 122 kHz, the spectrum of the synthesized signal shows that higher harmonics are at least 86 dB below the fundamental. Comparable suppression was achieved with a single-branch Josephson array from PTB generating a 17 mV sine wave of 180 Hz. Additionally, with a PTB array, sinusoidal signals with amplitudes up to 57 mV zero to peak are generated with higher harmonics typically 60 dB to 70 dB below the fundamental at frequencies below a few hundred hertz.

Wieviel sicherer waren unsere Flugreisen, wenn die Kontrollbeamten wirklich alle versteckten Bedrohungen finden konnten, die potentielle Terroristen mit an Bord eines Flugzeugs schmuggeln wollen. Auf einem Terahertzbild konnte man Verdachtigen buchstablich unter die Kleidung schauen. Doch bislang gab es noch keine Technologie, eine THz-Videokamera zu bauen. Jenaer Forscher aus dem Institut fur Photonische Technologien konnten das jetzt andern.

A unique system for geomagnetic archaeometry is presented. It uses extremely sensitive superconducting quantum interference devices (SQUIDs) as magnetic field sensors, laid out as intrinsic gradiometers. These sensors are mounted on a non-metallic cart, which guarantees smooth movement even at high speeds. Using a differential global positioning system (GPS) together with an inertial system the measured magnetic field gradient data are located on the mapped area with centimetre resolution and the height profile is also provided using the GPS. All data are stored in a data logger and partially online displayed on a laptop computer. At the time of this report, the system is pushed manually and has been tested on a Neolithic double ring ditch near Weimar, Germany. In a gateway through the rings, remains of palisades and buildings have been well resolved, confirming the high sensitivity of the SQUID-based system. An excavation at the ring ditch showed that material with enhanced susceptibility was the origin of the magnetic field gradient signals. Copyright © 2007 John Wiley & Sons, Ltd.

The aim of this work is to deploy a new SQUID (Superconducting Quantum interference device) based instrument for the measurement of the full magnetic gradient tensor of the Earth’s magnetic field in survey scenarios in a sedimentary basin in Thuringia, a local province in Germany. This task requires developing according processing, inversion, and interpretation techniques for this new instrument. The recent state of the instrument and data processing techniques is presented. The new instrument has several advantages compared to commercially available high-resolution aeromagnetic survey instruments. Besides the fact that weaker magnetic anomalies could be detected, it delivers vector data and thus more detailed information even on remanence of the geologic structures. It is required for more enhanced magnetic anomaly delineation and possibly for the determination of the age of intrusive or alteration structures. As a proof of principle a small-scaled magnetic anomaly on the border of the Thuringian basin was selected. The area was mapped in 2013. The results are presented and preliminary results of the inversion discussed which indicate remanent magnetization of the rocks which cause the magnetic anomaly.

Superconducting quantum interference filters (SQIFs) are arrays of superconducting loops, with Josephson junctions, with different sizes of loops. This produces a delta-like unique peak at zero fields in the voltage–magnetic field characteristics. This paper summarizes the status of the attempts to use SQIFs, realized with high-Tc superconductors, for sensitive magnetometers. Rules are given for how the SQIF itself has to be set up and how high-Tc technology hurdles have to be considered. After revising the most simple layouts of magnetometers, using only one single superconducting layer, a way is shown to exploit the SQIF power in a flip-chip layout with a flux transformer. Such a magnetometer is described. A noise-limited magnetic field resolution of 65 fT Hz−1/2 is achieved. Ways toward further improvement are sketched out.

We report on successful tests of planar LTS SQUID gradiometers on airborne platforms such as helicopter and aircraft. The system works stable and allows profile work without any constraints. In mobile applications the gradient resolution at low frequencies is dominated by motion noise, since the parasitic areas of the SQUID gradiometer lead to strong disturbances if the gradiometer is tilted in the homogenous Earth's magnetic field. The balance can be improved further by software using data of a SQUID magnetometer triple. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

An integrated gradiometer system is presented, consisting of a single-layer high-temperature superconductor dc superconducting quantum interference device (SQUID) and two coils, realized on printed circuit boards. The coils compensate the homogeneous background field, thus allowing the gradiometer to be freely moved in the Earth's magnetic field. The gradiometer signal is not harmed by any additional noise introduced by the homogeneous field compensation. Therefore, a noise-limited magnetic field gradient resolution of 15 pT m−1 Hz−1/2 with a 1/f corner frequency of 2 Hz was achieved. This is preserved even after motion in the Earth's magnetic field. Because of the small dimensions of the compensation coils, the gradiometer system can also be used for non-destructive evaluation. Preliminary measurements were performed by moving the SQUID across a workpiece, without any shielding.

We developed a gradiometer system based on a single-layer high-temperature superconductor dc superconducting quantum interference device (SQUID), which can be freely moved within the Earth's magnetic field during measurement. The problem of circumferential shielding currents in the parallel gradiometer pick-up loop is solved by the use of an appropriately designed magnetometer SQUID integrated on the gradiometer chip. The magnetometer's feedback coil of the flux-locked loop is laid out as a small Helmholtz coil pair, thus keeping the homogeneous magnetic field constant for both the magnetometer and the gradiometer. Therefore, the balance of the directly coupled gradiometer SQUID is enhanced from 100 up to 3800. The noise limited magnetic field gradient resolution of 45 pT m−1 Hz−1/2 is preserved down to frequencies of several Hz even after strong motion in the Earth's magnetic field.

A novel fabrication strategy is introduced for the synthesis of 3D silver–silica hybrid nanostructures by employing the plasma-enhanced atomic layer deposition (PE-ALD) on the templated substrates with enzymatically generated silver nanoparticles (EGNPs). Comparing with the conventional PE-ALD process for the silica deposition (by using the precursors of tri-dimethyl-amino-silane (TDMAS) and oxygen plasma), here the EGNPs play a key role for the formation of 3D hierarchical structures. During the oxygen plasma step, a metastable silver oxide surface is formed, and then thermally decomposes and releases excess oxygen during the next TDMAS step. A side reaction for the deposition of silica occurs with the excess released oxygen. The formation of the metastable silver oxide and its decomposition repeat cyclically during the PE-ALD process, thereby, the side reaction is going on progressively, and finally, the 3D silver–silica hybrid nanostructures are formed with this novel strategy of metastable state assisted atomic layer deposition. Various 3D silver–silica composite nanostructures, such as nanosponges and nanoflowers, can be fabricated easily by tuning the PE-ALD parameters. With each additional ALD cycle, the silver particle size decreases which also further reduces side reactions. The observed growth-effect thus seems to be limited by the amount of silver used.

Cryogenic bolometers are adequate sensing devices for sub-millimeter observations. They are used for instrumentation in radio telescopes like the Atacama Pathfinder Experiment (APEX), which is a 12-m radio telescope in Chile's Atacama desert. Through its thin and dry atmosphere, star formation in the red-shifted early universe can be observed. A suitable bolometer has a high sensitivity and consists of several tens to hundreds of pixels that are combined to an array. To meet these requirements, we use transition edge sensors. They detect radiation by measuring a temperature increase in an appropriate absorber. For highest sensitivity, the absorber is only in weak thermal contact to its surroundings. This is achieved by placing it on a SiN membrane that is structured to further decrease the thermal coupling. A superconductor that is biased at its transition temperature serves as thermometer for the transition edge sensor. We present the fabrication of such devices and discuss encountered difficulties. Further, we briefly describe the incorporation of a sensor chip with an array of 39 pixels into an instrument that currently operates at APEX. For the fall of 2010 the installation of a 300 pixel array is scheduled.

International audience

session 3: Superconductor Circuits and Devices; International audience

The key issue for the implementation of a metamaterial is to demonstrate the existence of collective modes corresponding to coherent oscillations of the meta-atoms. Atoms of natural materials interact with electromagnetic fields as quantum two-level systems. Artificial quantum two-level systems can be made, for example, using superconducting nonlinear resonators cooled down to their ground state. Here we perform an experiment in which 20 of these quantum meta-atoms, so-called flux qubits, are embedded into a microwave resonator. We observe the dispersive shift of the resonator frequency imposed by the qubit metamaterial and the collective resonant coupling of eight qubits. The realized prototype represents a mesoscopic limit of naturally occurring spin ensembles and as such we demonstrate the AC-Zeeman shift of a resonant qubit ensemble. The studied system constitutes the implementation of a basic quantum metamaterial in the sense that many artificial atoms are coupled collectively to the quantized mode of a photon field.

Nowadays detection systems based on superconducting nanowire single-photon detectors (SNSPD) are mainly with a single-pixel detector. Multi-pixel systems would extend the field of possible applications. Therefore, new concepts are required for effective readout of multi-pixel SNSPDs. We give an overview of possible concepts, conditions of operation and dedicated effort to optimize the requirements of different applications in the single-photon regime.

The integration of superconductor digital electronics together with superconducting sensors can enable smart multi-channel sensor arrays. Applications of such sensors range from basic astrophysical research to advanced security screening devices. The main advantage of superconducting sensor interfaces is the very low power consumption in combination with a very low noise level; both are required in order to keep the excellent superconducting sensor performance without distortions. The FLUXONICS Foundry technology has been optimized with respect to electronic interfaces circuits for analogue sensor readout and signal multiplexing. In this work, we describe this new interface technology and present a comparison with our standard RSFQ technology.

Since 2007 we are developing passive submillimeter-wave video cameras for persona l security screening. Incontradiction to established portal-based millimeter-wave scanning techniques, t hese are suitable for stand-o or stealth operation. The cameras operate in the 350GHz band and use arrays of superconducting transition-edge sensors (TES), reector optics, and opto-mechanical scanners. Whereas the basic principl e of these devicesremains unchanged, there has been a continuous development of the technical details, as the detect or array, thescanning scheme, and the readout, as well as system integration and performance. The latest prototype of thiscamera development features a linear array of 128 detectors and a linear scanner capable of 25Hz frame rate.Using di erent types of reector optics, a eld of view of 1 2m 2 and a spatial resolution of 1{2cm is providedat object distances of about 5{25m. We present the concept of this camera and give detai ls on system designand performance. Demonstration videos show its capability for hidden threat detectio n and illustrate possibleapplication scenarios.Keywords: submillimeter-wave, THz, terahertz, camera, imaging, video, bolometer, TES

As manmade space debris in the low earth orbit becomes an increasing risk to space missions, which could even result in total mission loss, it has become even more critical to have detailed knowledge of the properties of these particles like the mass, the velocity and the trajectory. In this paper, we present a newly designed, highly sensitive impact detector array with 16 pixels for space debris analysis. The thermopile sensor array, which was developed in the project, consists of 16 miniaturized multi-junction thermopile sensors made by modern thin-film technology on Si wafers. Each thermopile sensor consists of 100 radially arranged junction pairs formed from evaporated antimony and bismuth thin films. The centrally located active (hot) junctions comprise the active area of 1 mm². The output e.m.f. of the sensor is proportional to the temperature difference between the active and the reference junctions. The thermopile requires no cooling and no bias voltage or current for operation. It generates no 1/f noise but only the thermal resistance (Nyquist) noise. The sensor can be used for DC and low frequency AC measurements. The impact energy of micro sized particles is measured by a calorimetric principle. This means that the kinetic energy of the particle is converted into heat by hitting the absorbing foil, which is glued on the surface of the membrane area. This setup in combination with a preceded velocity detector allows the measurement of the most interesting particle quantities mass, velocity and trajectory.

The mapping of the Earth's magnetic field or field gradient is a proven method in surface exploration and archaeometry. Caesium vapour magnetometers show the best magnetic field resolution of commercial devices, but their sampling frequency is limited to 10 Hz. Using SQUIDs it is possible to achieve the same or even better magnetic field resolution with a sampling frequency as high as 100 Hz or more. This allows significantly shorter acquisition times, which is essential for the mapping of large objects. In this paper we check the performance of our developed systems on a neolithic double-ring ditch enclosure near Weimar, Germany. We compare mappings of this area using an electronic caesium gradiometer, an electronic HTS SQUID gradiometer and an integrated planar LTS SQUID gradiometer. With all three systems the magnetic pattern of the ditch is visible; however, the electronic HTS gradiometer shows disturbances of the same order of magnitude as the gradient signal of the ditch, due to an insufficient common mode rejection whilst being moved. The planar LTS SQUID gradiometer shows superior performance. Its mapping shows a much better contrast and features that are not visible in the mapping of the caesium gradiometer.