Prototype Setup Research Articles

A new X-ray transmission-reflection scheme for the study of deeply buried interfaces using high-energy microbeams

We present a new experimental scheme for the high-resolution X-ray study of deeply buried interfaces, as they occur in novel functional nanomaterials and in nature. Our experimental approach is based on the preparation and the use of high energy X-ray microbeams and on stable and high-resolution mechanical diffraction stages. We discuss the principle of this technique and demonstrate its future potential for the study of functional interfaces by way of several proof-of-principle experiments which have been carried out at a prototype setup at the European Synchrotron Radiation Facility.

A Location Model for Communicating and Processing of Context

Location is one of the most important elements of context in ubiquitous computing. In this paper we describe a location model, a spatial-aware communication model and an implementation of the models that exploit location for processing and communicating context. The location model presented describes a location tree, which contains human-readable semantic and geometric information about an organisation and a structure to describe the current location of an object or a context. The proposed system is dedicated to work not only on more powerful devices like handhelds, but also on small computer systems that are embedded into everyday artefact (making them a digital artefact). Model and design decisions were made on the basis of experiences from three prototype setups with several applications, which we built from 1998 to 2002. While running these prototypes we collected experiences from designers, implementers and users and formulated them as guidelines in this paper. All the prototype applications heavily use location information for providing their functionality. We found that location is not only of use as information for the application but also important for communicating context. In this paper we introduce the concept of spatial-aware communication where data is communicated based on the relative location of digital artefacts rather than on their identity.

Experimental study of a proximity focusing Cherenkov counter prototype for the AMS experiment

A prototype of Proximity Focussing Ring Imaging Cherenkov counter has been built and tested with several radiator materials and configurations, including a dual radiator configuration, using separately cosmic-ray particles and 12C beam fragmentation products at several energies. Counter prototype and experimental setup are described, and the results of measurements are reported and compared with simulation results. The performances are discussed in the perspective of the final counter design.

Comparison of two current modulation strategies for matrix converters under unbalanced input voltage conditions

In this paper, the input current performance of matrix converters is analyzed, especially with reference to the operating conditions determined by unbalanced supply voltages. The space-vector modulation (SVM) technique is utilized to calculate the duty cycles of the active voltage vectors that must be applied, in each switching cycle period, in order to satisfy the input and output requirements. A detailed theoretical analysis of the input current harmonic content under unbalanced input voltage conditions is presented for two different current modulation strategies. On the basis of numerical simulations as well as measurements on a laboratory prototype setup, the strategies' performance are compared and the validity of the theoretical investigation confirmed. It is concluded that, when the input voltages are unbalanced to a significant extent, a dynamic input current modulation strategy has to be preferred, since a lower harmonic line current distortion will appear.

A multi channel dosimeter based on scintillating fibers for medical applications

Dosimetry with plastic scintillators is an interesting alternative for the measurement of the absorbed dose. A scintillator does barely disturb the radiation field due to its mass absorption coefficients which is water-equivalent in a wide range of energies. Furthermore, plastic scintillation dosimeters provide a fast and direct reading of the measured value combined with a high-spatial resolution. In the set-up described so far, the light produced by the scintillators was transported via light-guides to single-channel or multi-channel photomultipliers to be transformed into an electric current read out by pico-amperemeters. The use of photomultipliers becomes expensive and complicated for a dosimeter system with many parallel channels. For such applications, an image intensifier coupled to a CCD is a simpler approach which can read out some 80 fibers in parallel [M. Garg, Konzeption, Aufbau and Test eines Vielkanal-Dosimeters mit szintillierenden Fasern, WUB–DIS 96–17, Universität Wuppertal, 1996 and I.M. Gregor, Ein Vielkanaldosimeter mit szintillierenden Fasern–Klinische Messungen bei Energien oberhalb 1MeV, WU D 98–14, Universität Wuppertal, 1998]. In this note, the design and the first successful measurements of a prototype set-up are described.

An autostereoscopic display providing comfortable viewing conditions and a high degree of telepresence

Research and development on 3-D displays make great progress and even autostereoscopic 3-D displays are on the verge of being put onto the market. The main market within the near future will be, besides entertainment applications, the field of multimedia desktop displays. The use of autostereoscopic displays makes it possible to watch 3-D images without special glasses. Particularly in communication applications dark spectacles hamper natural face-to-face communication. This paper presents a concept for a realization of a 3-D desktop display which was developed at the Heinrich-Hertz-Institute. In this concept a collimation optic was combined with an autostereoscopic display unit. In the past, collimation optics were usually used in head mounted devices. Only a few realizations of autostereoscopic displays are known, which combine autostereoscopic technologies with collimation optics. Studies performed at NASA's Langley Research Center showed that the usable volume of depth can extend to large values when a collimation optic is integrated in a stereoscopic display. Results of our work showed that a "puppet theater effect" is not perceptible when a collimated display is used. Two autostereoscopic prototype setups suitable for communication applications were realized that avoid the disadvantages of most common stereoscopic displays.

Scope of Capacitive Methods in Solid Propellant Diagnostics

Apparatus for instantaneous regression rate measurements based on a simple plane-capacitor geometry and circuit theory is described, and results from a prototype setup are presented for both metallized and nonmetallized AP composite propellants at po 1 bar. The experiments show the apparatus is potentially effective as an instantaneous burning ratediagnostic only for the nonmetallized composite propellant. Formetallized propellants the technique offers potential as 1) a go/no-go technique and 2) a monitor for the onset of bulk activity inside the gaseous part of the e ame. Some tentative general conclusions about the applicability of electric e eld diagnostics for solid propellants are suggested.

Overview of the HERA-B vertex detector system and first results from prototype runs

An overview of the HERA-B silicon vertex detector system is presented. The system is optimized according to the requirements deduced from the physics goals of HERA-B. Due to the high radiation level it is necessary to exchange the modules carrying the silicon detectors once a year. The system is under construction. Data were taken with two prototype setups. Results are presented and compared with expectation.

Measurement of chromatic dispersion in optical fibers using pairs of correlated photons

Photon pairs generated by spontaneous parametric downconversion are used to implement a novel technique for measuring the chromatic dispersion of optical fibers. The time and energy correlation of the photons of a pair allow a measurement with a high time resolution which is only limited by the detection electronics. The device gives direct access to the differential group delays at several wavelengths around 1.3 μm. Our prototype setup is capable of measuring group delay differences with a resolution of about 5 ps, only limited by the upper delay limit of the time interval analyzer (presently 50 ns).

Real time vision-based hand gesture estimation for a human-computer interface

In this paper we discuss a technique for real-time hand gesture estimation by user interfaces. First, an image processing algorithm for hand gesture estimation is formulated assuming the hand to be a non-rigid body. A method is then proposed for real-time hand gesture estimation using pipelined parallel processing in real-time. With the proposed method, erroneous finger extraction is eliminated using global hand features to ensure stable gesture recognition. The influence exerted by occlusions on hand gesture estimation is examined and it is shown that this influence can be eliminated by an appropriate arrangement of multiple cameras. The efficiency of the proposed method is verified by building a user interface environment incorporating a prototype setup. In so doing, it is made clear that an acceptable interface environment may be implemented even without complete solution of problems related to occlusions or hand orientation. © 1997 Scripta Technica, Inc. Syst Comp Jpn, 28(7): 76–88, 1997

Real time vision‐based hand gesture estimation for a human‐computer interface

In this paper we discuss a technique for real-time hand gesture estimation by user interfaces. First, an image processing algorithm for hand gesture estimation is formulated assuming the hand to be a non-rigid body. A method is then proposed for real-time hand gesture estimation using pipelined parallel processing in real-time. With the proposed method, erroneous finger extraction is eliminated using global hand features to ensure stable gesture recognition. The influence exerted by occlusions on hand gesture estimation is examined and it is shown that this influence can be eliminated by an appropriate arrangement of multiple cameras. The efficiency of the proposed method is verified by building a user interface environment incorporating a prototype setup. In so doing, it is made clear that an acceptable interface environment may be implemented even without complete solution of problems related to occlusions or hand orientation. © 1997 Scripta Technica, Inc. Syst Comp Jpn, 28(7): 76–88, 1997

Ion-extraction polarimetry for polarized internal targets

We discuss ion extraction from an internal target in a storage ring, separation of atomic and molecular species, and subsequent measurement of the polarization of the atomic ions. This technique can be applied to internal targets of polarized hydrogen, deuterium, 3He and other gases. Here, we report on the development of such a device for a tensor polarized deuterium gas target internal to a medium-energy electron storage ring. Ions were extracted from a storage cell using a spherical deflector and transported to a mass analyzer. In a prototype setup, using electrons from a gun to simulate the electron beam from a storage ring, the tensor polarization of the atomic ions was measured using the 3H(d̄, n) α reaction. The data show that the extraction of ions from a storage-cell target, followed by their mass and polarization analysis, allows the determination of the nuclear polarization of the target independent of its spatial and temporal variations.

Performance of an improved perfect crystal neutron storage cavity

An improved version of a cold neutron storage apparatus, (VESTA), consisting of two parallel perfect silicon-crystal mirror plates in precise back reflection, has been installed and tested at the ISIS pulsed neutron source. The first measurements on VESTA and its performance compared to the prototype setup are reported. The neutron storage times were increased by one order of magnitude up to about 2 s. Characteristic features of the storage process and future perspectives are discussed.

A direct current superconducting quantum interference device gradiometer with a digital signal processor controlled flux-locked loop and comparison with a conventional analog feedback scheme

A double-washer dc superconducting quantum interference device (SQUID) gradiometer with a flux-locked loop (FLL) based on a digital signal processor (DSP) has been developed for biomagnetic applications. All of the analog electronics in the conventional FLL are replaced and implemented by the DSP except for the low-noise field-effect transistor preamplifier at the front end of the signal recovery components. The DSP performs the signal demodulation by synchronously sampling the recovered signals and applying the appropriate full wave rectification. The signals are then integrated, filtered, and applied to the output. At 4.2 K, the white flux noise of the gradiometer measured in a DSP FLL mode is about 4μΦ0/√Hz and the noise at 1 Hz is 13 μΦ0/√Hz. The corresponding noise levels in the gradiometer operated by the conventional FLL are 1.8 and 3μΦ0/√Hz. The poorer system performance in the DSP FLL compared to the analog FLL is mainly caused by the ambient field noise and interference signals picked up through the connecting cables. Additional noise is also added to the overall noise floor by the instruments employed in the DSP system in the present prototype setup. Further improvement in the noise characteristics and the dynamic behavior of the DSP SQUID gradiometer is expected when a better configuration of DSP with the associated I/O devices is implemented. Additional improvements of the DSP programs are expected by incorporating higher-order integration, adaptive control, and noise reduction schemes.

Low-noise optical heterodyne spectrum analyzer

A prototype setup for a low-noise, high-resolution, multi-Gigahertz-span optical heterodyne spectrum analyzer is presented. The frequencies of the unknown optical spectrum are converted to zero intermediate frequency by heterodyning with the output from a tunable single-mode local oscillator laser in an optical mixer. The low-frequency beats are rectified, and their strength is recorded while the spectrum is scanned by tuning the local oscillator. Low-noise heterodyning requires double balance (or at least single balance) of the optical mixer. Further optimization of the noise performance can be achieved by adjusting the power levels of the light beams. Successful operation of the analyzer has been demonstrated by recording the output spectrum of a mode-locked dye laser.

Random addressable CMOS image sensor for industrial applications

An X–Y addressable image sensor with a logarithmic pixel response has been developed. The readout is based on direct photocurrent sensing, as opposed to the charge-integrating methods used in charge-coupled devices and other solid-state imagers. For this reason no integration time control is necessary. The pixels have a logarithmic light intensity to voltage response, which results in a large dynamic range. The random pixel access allows subimages to be read out, resulting in a proportional gain in speed. By integrating this imager and a custom analog-digital converter (ADC) on the same chip, a fully digital single-chip camera can be realized. The realized prototype and the basic sensor characteristics are discussed and illustrated with measurements. The prototype set-up for a tracking experiment will be described.

A digitally programmable modulation and lock-in set-up

A modulation and lock-in set-up has been developed as a modular assembly for measuring systems detecting weak and noisy signals providing a synthesizer voltage or current source in order to modulate the quantity to be measured, and a phase-sensitive detecting (PSD) circuit. The amplitude and the frequency of the modulation source, the phase of the PSD square-wave reference, the PSD gain and its low-pass cut-off frequency are digitally programmable. The prototype set-up covers the frequency range from 0.1 Hz to 999 Hz with a resolution of 0.1 Hz, whereas the phase-set increments of the lock-in part are about 2 degrees .

ALLIGATOR−An apparatus for ion beam assisted deposition with a broad-beam ion source

Ion beam assisted deposition is a versatile technique for preparing thin films and coatings for various applications. Up to now a prototype setup for research purposes has been used in our laboratory. Processing of industrial standard workpieces requires a high current ion source with broad beam and high uniformity for homogeneous bombardment. In this contribution a new apparatus for large area samples will be described. It is named ALLIGATOR (German acronym of facility for ion assisted evaporation on transverse movable or rotary targets). In order to have a wide energy range available two ion sources are used. One delivers a beam energy up to 1.3 keV. The other is suitable for energies from 5 keV up to 40 keV. The ‘‘high-energy’’ ion source is a multicusp multiaperture source with 180-mA total current and a beam diameter of 280 mm at the target position.

Detection of superconducting transitions of multi-phase (Bi,Pb)-Sr-Ca-Cu-O ceramics by photothermal deflection technique

Superconducting transitions, believed to correspond to the 2223 phase and the 2212 phases, of high T c multi-phase (Bi,Pb)-Sr-Ca-Cu-O superconductors were observed by the photothermal deflection (PTD) method. The deflection signal Φ was found to change anomalously at transition temperature ranges corresponding to but not exactly equal to those observed by reistance measurements. Using a semi-quantitative analysis of previous theoretical results, and based on our Φ- T data, specific heat jumps are found at relatively well-defined temperatures. Our study indicates that the PDT method is a sensitive way of studying bulk superconductivity properties of ceramics. Improvements to our prototype setup are, however, necessary for higher precision measurements to be made.

The nature of the cosmic radiation

In 1965 it was discovered that cosmic ray air showers emit impulsive radio signals at frequencies below 100 MHz. After a period of intense research in the 1960s and 1970s, however, interest in the detection technique faded almost completely. With the availability of powerful digital signal processing techniques, new attempts at measuring cosmic ray air showers via their radio emission were started at the beginning of the new millennium. Starting with modest, small-scale digital prototype setups, the field has evolved, matured and grown very significantly in the past decade. Today’s second-generation digital radio detection experiments consist of up to hundreds of radio antennas or cover areas of up to 17 km2. We understand the physics of the radio emission in extensive air showers in detail and have developed analysis strategies to accurately derive from radio signals parameters which are related to the astrophysics of the primary cosmic ray particles, in particular their energy, arrival direction and estimators for their mass. In parallel to these successes, limitations inherent in the physics of the radio signals have also become increasingly clear. In this article, we review the progress of the past decade and the current state of the field, discuss the current paradigm of the radio emission physics and present the experimental evidence supporting it. Finally, we discuss the potential for future applications of the radio detection technique to advance the field of cosmic ray physics.