State Detectors Research Articles

Ab initio study for molecular-scale adsorption, decomposition and desorption on AlN surfaces during MOCVD growth

Since AlGaN offers new opportunities for the development of the solid state ultraviolet (UV) luminescence, detectors and high-power electronic devices, the growth of AlN buffer substrate is concerned. However, the growth of AlN buffer substrate during MOCVD is regulated by an intricate interplay of gas-phase and surface reactions that are beyond the resolution of experimental techniques, especially the surface growth process. We used density-functional ab initio calculations to analyze the adsorption, decomposition and desorption of group-III and group-V sources on AlN surfaces during MOCVD growth in molecular-scale. For AlCH3 molecule the group-III source, the results indicate that AlCH3 is more easily adsorbed on AlN (0001) than (000overline{1}) surface on the top site. For the group-V source decomposition we found that NH2 molecule is the most favorable adsorption source and adsorbed on the top site. We investigated the adsorption of group-III source on the reconstructed AlN (0001) surface which demonstrates that NH2-rich condition has a repulsion effect to it. Furthermore, the desorption path of group-III and group-V radicals has been proposed. Our study explained the molecular-scale surface reaction mechanism of AlN during MOCVD and established the surface growth model on AlN (0001) surface.

Noninvasive Electroencephalogram Based Control of a Robotic Arm for Writing Task Using Hybrid BCI System.

A novel hybrid brain-computer interface (BCI) based on the electroencephalogram (EEG) signal which consists of a motor imagery- (MI-) based online interactive brain-controlled switch, “teeth clenching” state detector, and a steady-state visual evoked potential- (SSVEP-) based BCI was proposed to provide multidimensional BCI control. MI-based BCI was used as single-pole double throw brain switch (SPDTBS). By combining the SPDTBS with 4-class SSEVP-based BCI, movement of robotic arm was controlled in three-dimensional (3D) space. In addition, muscle artifact (EMG) of “teeth clenching” condition recorded from EEG signal was detected and employed as interrupter, which can initialize the statement of SPDTBS. Real-time writing task was implemented to verify the reliability of the proposed noninvasive hybrid EEG-EMG-BCI. Eight subjects participated in this study and succeeded to manipulate a robotic arm in 3D space to write some English letters. The mean decoding accuracy of writing task was 0.93 ± 0.03. Four subjects achieved the optimal criteria of writing the word “HI” which is the minimum movement of robotic arm directions (15 steps). Other subjects had needed to take from 2 to 4 additional steps to finish the whole process. These results suggested that our proposed hybrid noninvasive EEG-EMG-BCI was robust and efficient for real-time multidimensional robotic arm control.

FPGA Implementation of a Real-Time Weak Signal Detector Using a Duffing Oscillator

This paper presents an implementation of a weak signal detector using a Duffing oscillator on field programmable arrays (FPGAs) for the real-time detection of weak signals in noisy environments. The proposed implementation has combined the efficiency of weak signal detection by chaotic oscillators in noisy environments with the advantages of hardware implementation to achieve an efficient weak signal detector. To optimize the performance versus area, we have used VHDL. A novel state detector, phase trajectory autocorrelation, has been introduced for the state detection of the Duffing oscillator. As an experiment, the Duffing oscillator has been implemented on a Cyclone IV GX FPGA. In this paper, in addition to the structure and resource utilization of the design, experimental results are presented to demonstrate the effectiveness of the proposed implementation.

Tracking with Straw Tubes in the PANDA Experiment

The PANDA spectrometer will be built at the FAIR facility at Darmstadt (Ger- many) to perform accurate tests of the strong interaction through ¯ pp andannihilation studies. The charged particle tracking at PANDA will be done using both solid state and gaseous detectors. Among the latter, two straw tube detector systems will be built (1). The cylindrical, central straw tube tracker features a high spatial and momentum resolu- tion for a wide range of particle momenta from about 8 GeV/c down to a few 100 MeV/c, together with particle identification in the momentum region below about 1 GeV/c by measuring the specific energy-loss. A new technique, based on self-supporting straw double layers with intrinsic wire tension developed for the COSY-TOF straw tracker (2), has been adopted for the PANDA trackers. The development of the readout electronics for the straw tubes is ongoing. Prototypes have been produced and used to instrument straw tube modules that have been tested with cosmic rays and proton beams. Design issues of the PANDA straw tubes, together with the results of the prototype tests are presented. The PANDA experiment (3) is one of four experiments planned for the future Facility for Antiproton and Ion Research (FAIR) (4) in Darmstadt, Germany. The scientific program of the PANDA Collaboration is oriented towards precise studies of strong interaction in the QCD transi- tion region between asymptotically free quarks and hadronic matter. The maximum available center of mass total energy in the PANDA experiment ( √ s= 5.46 GeV/c 2 ) will allow hadronic structures involving the charm quark degrees of freedom to be investigated. The PANDA detector will be in- stalled around the internal target of the High Energy Storage Ring (HESR), which will accumulate, accelerate and cool up to 10 11 antiprotons. In the experiment, the annihilation of antiprotons with

Applications Outside HEP

Abstract High energy and particle physics has considerable acquired knowledge, expertise and resources that can, when transferred in a realistic way, significantly impact the practice of medical imaging for diagnosis and therapy. This overview introductory talk “from basic science to the clinical reality” intends to show how successful technology transfer between fundamental research in particle physics and medical imaging can be achieved using some specific examples. Using as input, the recent advance of HEP state of the art techniques and tools in detectors developments such as solid state and gaseous detectors, calorimeters, photodetectors, read-out electronics and simulations, some direct applications in medical and molecular imaging will be presented like Positron Emission Tomography (PET) and particle therapy.

Corrugated quantum well infrared photodetectors for far infrared detection

We have extended our investigation of corrugated quantum well infrared photodetector focal plane arrays (FPAs) into the far infrared regime. Specifically, we are developing the detectors for the thermal infrared sensor (TIRS) used in the Landsat Data Continuity Mission. To maintain a low dark current, we adopted a low doping density of 0.6×1018 cm−3 and a bound-to-bound state detector. The internal absorption quantum efficiency (QE) is calculated to be 25.4%. With a pixel fill factor of 80% and a substrate transmission of 70.9%, the external QE is 14.4%. To yield the theoretical conversion efficiency (CE), the photoconductive gain was measured and is 0.25 at 5 V, from which CE is predicted to be 3.6%. This value is in agreement with the 3.5% from the FPA measurement. Meanwhile, the dark current is measured to be 2.1×10−6 A/cm2 at 43 K. For regular infrared imaging above 8 μm, the FPA will have an noise equivalent temperature difference (NETD) of 16 mK at 2 ms integration time in the presence of 260 read noise electrons. The highest operability of the tested FPAs is 99.967%. With the CE agreement, we project the FPA performance in the far infrared regime up to 30 μm cutoff.

C-QWIPs for space exploration

We have extended our investigation of corrugated quantum well infrared photodetector focal plane arrays (C-QWIP FPAs) into the far infrared regime. Specifically, we are developing the detectors for the thermal infrared sensor (TIRS) used in the NASA Landsat Data Continuity Mission. This mission requires infrared detection cutoff at 12.5 μm and FPAs operated at ∼43 K. To maintain a low dark current in these extended wavelengths, we adopted a low doping density of 0.6 × 10 18 cm −3 and a bound-to-bound state detector in one of the designs. The internal absorption quantum efficiency η is calculated to be 25.4% for a pixel pitch of 25 μm and 60 periods of QWs. With a pixel fill factor of 80% and a substrate transmission of 70.9%, the external η is 14.4%. To yield the theoretical conversion efficiency CE, the photoconductive gain was measured and is 0.25 at 5 V, from which CE is predicted to be 3.6%. This value is in agreement with the 3.5% from the FPA measurement. Meanwhile, the dark current is measured to be 2.1 × 10 −6 A/cm 2 at 43 K. For regular infrared imaging above 8 μm, the FPA will have a noise equivalent temperature difference (NETD) of 16 mK at 2 ms integration time in the presence of 260 read noise electrons, and it increases to 22 mK at 51 K. The highest operability of the tested FPAs is 99.967%. With the CE agreement, we project the FPA performance in the far infrared regime up to 30-μm cutoff, which will be useful for the Jupiter-Europa deep space exploration. In this work, we also investigated the C-QWIP optical coupling when the detector substrate is thinned.

Weak continuous measurements of multiqubits systems

In this review we summarize our recent experiments on the investigation on superconducting qubits. Instead of strong projective measurement used by other groups in their first pioneering experiments we have proposed and realized a weak continuous readout which belongs to the class of quantum non-demolition measurements. Moreover, our scheme enables to measure a superconducting qubit at the so called sweet (or magic) point where a qubit is in a superposition of two classical states and its sensitivity to external noise is minimized. In this scheme, which is widely used nowadays, the superconducting oscillator coupled to superconducting qubit is used as a detector of the qubit's state. Such system is analogue to a system of a single atom interacting with photons in a cavity, which allows to study quantum electrodynamics in artificial macroscopic systems. Pushing this analogy we demonstrate Sisyphus cooling and amplification caused by energy exchange between an oscillator and a flux qubit. Using the Sisyphus effect we show consistency between the adiabatic weak continuous measurement in the ground state and the spectroscopic measurement. This allows us to characterize the more complicated system of coupled qubits by making use of the same method. We have realized and studied fixed ferromagnetic, antiferromagnetic as well as tunable qubit---qubit coupling. We argue that ground state measurements can be used for characterization of entangled states in coupled flux qubits.

Soil Gas Radon Spectra and Earthquakes

Continuous soil gas radon monitoring in real time with improved solid- state detector is carried out in south-central and southern Taiwan. The time series register spike-like anomalies which could be precursors of earthquakes. Monitoring stations located in a brecciated zone of active fault at Taiwan 3 and faults at Taiwan 1 showed drastic variations of radon when the terrain is stressed before the onset of earthquake. In contrast, the spectrum recorded at a station sited on a craton Akron 1 which is sited on a craton shows no significant radon variations. To actually prove that the variation of the time series is related to stress, a fourth station was anchored in a sand column (209 L) with exactly the same type of radon detector system. The time series recorded in this manner shows higher background level and spikes of high radon counts as it is stressed. Temperature and moisture variations are not affecting radon counts.

지능형 에이전트의 환경 적응성 및 확장성

To live autonomously, intelligent agents such as robots or virtual characters need ability that recognizes given environment, and learns and chooses adaptive actions. So, we propose an action selection/learning mechanism in intelligent agents. The proposed mechanism employs a hybrid system which integrates a behavior-based method using the reinforcement learning and a cognitive-based method using the symbolic learning. The characteristics of our mechanism are as follows. First, because it learns adaptive actions about environment using reinforcement learning, our agents have flexibility about environmental changes. Second, because it learns environmental factors for the agent`s goals using inductive machine learning and association rules, the agent learns and selects appropriate actions faster in given surrounding and more efficiently in extended surroundings. Third, in implementing the intelligent agents, we considers only the recognized states which are found by a state detector rather than by all states. Because this method consider only necessary states, we can reduce the space of memory. And because it represents and processes new states dynamically, we can cope with the change of environment spontaneously.

The beam splitter as a state and entanglement detector

In this article we propose a very simple scheme for detecting the state and the degree of entanglement of two modes of radiation using a beam splitter. We find that using this device we can tell whether the state coming out of a certain apparatus is maximally entangled, by measuring the intensity of the radiation of one of the modes. This result is independent of the transmittivity of the beam splitter. In some cases it is also possible to determine the state exactly, by measuring the dispersion of one of the modes.

TWO-BAND MAGNETO-OPTICAL ELEMENTS FOR SOFT X-RAY POLARIZATION ANALYSIS AT THE Fe, Co 2p AND Gd 3d EDGES

We present angle-, energy- and polarization-dependent magneto-optical properties of Gd/Fe and Gd/Co multilayers with periods of the order of 1 nm for the photon energy range of 700–1230 eV. In the vicinity of the 2p absorption edge of transition metals (TM) and the 3d edge of the rare earth elements (RE), the X ray magnetic circular dichroism (XMCD) was measured in transmission and the X ray resonant magnetic scattering (XRMS) was investigated in L-MOKE geometry. The magnetic state of Gd could be realized at room temperature. Based on these data a calibrated detector of the polarization state of synchrotron radiation has been developed.

State detection for hands-free telephone sets by means of fuzzy LVQ and SOM

The step gain of adaptive algorithms for acoustic echo cancellation should vary with time in dependence of the far-end signal, the local signal, and the adaptation quality. It can be described as state-dependent, which is also the case for the control parameters of other algorithms in a hands-free telephone set, such as adaptive loss control or noise reduction. Most of the known state detection methods can only distinguish between subsets of the states, and are unreliable for certain state transitions, so that they should be combined for improved reliability of the state detection. In this contribution, state detection is performed by a fuzzy learning vector quantization/self-organizing map approach to combine several state detectors. The step gain is inferred from state information using fuzzy logic concepts. Finally, adaptation results are compared to the best conventional step-gain control method used in the complete structure.

Compton-scattering study of the electronic properties of the transition-metal alloys FeAl, CoAl, and NiAl.

Directional Compton profiles of the transition-metal alloys FeAl, CoAl, and NiAl have been measured. Both a conventional technique (resolution 0.55 a.u. of momentum), based on a 59.3-keV x-ray source with a solid- state detector, and a high-resolution spectrometer (0.15 a.u. of momentum) with 50-keV x rays from a synchrotron source have been used. The results are interpreted using a theory based on a full-potential linearized augmented-plane-wave method. The agreement between the experimental and the theoretical momentum density anisotropy is very good. It is shown that the anisotropies at low momenta are heavily influenced by the particular shape of the Fermi surface. \textcopyright{} 1996 The American Physical Society.

Particle Tracks, Events and Quantum Theory

The law of track formation in cloud chambers is derived from the Liouville equation with a simple Lindblad's type generator that describes coupling between a quantum particle and a classical, continuous, medium of two--state detectors. Piecewise deterministic random process (PDP) corresponding to the Liouville equation is derived. The process consists of pairs (classical event,quantum jump), interspersed with random periods of continuous (in general, non--linear) Schroedinger's--type evolution. The classical events are flips of the detectors -- they account for tracks. Quantum jumps are shown, in the simplest, homogeneous case, to be identical to those in the early spontaneous localization model of Ghirardi, Rimini and Weber (GRW). The methods and results of the present paper allow for an elementary derivation and numerical simulation of particle track formation and provide an additional perspective on GRW's proposal

Bounded-input—bounded-output stabilization of nonlinear systems using state detectors

This paper is devoted to the study of relations between Lyapunov stabilization and bounded-input—bounded-output (BIBO) stabilization of nonlinear systems when the state is not available for measurement and various state detectors are employed for implementing feedback control. It is found that with some constraints imposed on the detectors, Lyapunov stabilization implies BIBO stabilization. A feedback control scheme for achieving BIBO stability is presented.

Design and evaluation of an echelle grating optical system for ICP-OES

An echelle polychromator for inductively coupled plasma optical emission spectroscopy (ICP-OE9) was designed for use with the multichannel solid- state detector described in the companion article. The optical system has separate output sections for the UV and visible wavelength ranges, which permit high spectral resolution and high optical throughput nahile covering the spectral range from 167 to 782 nm. A novel component in the UV section corrects spherical aberration, cross-disperses the spectrum, and separates the UV and risible beams. A large-area echelle grating has been ruled for this system which has high diffraction efficiency and constant blaze angle across the spectrum and low stray light

Resonant Raman scattering with gamma rays

Abstract Resonant Raman scattering has been observed in the spectra of 241Am 59·5 keV gamma rays scattered from an ytterbium target (K-binding energy 61·3 keV). The KL (1s, 2p) and KM (1s, 3p) contributions are clearly identified and the detailed KM line shape studied for the first time. The KM line has been measured with a solid- state detector and the line shape, after subtraction of the Compton scattering background, was found to be in very good agreement with the predictions of semi- classical radiation theory within the dipole approximation, even at these photon energies.

Collisional angular-momentum mixing of Na Rydberg states with Xe

The collisional angular-momentum mixing of the $\mathrm{Na}\mathrm{nd}$ Rydberg states into states of higher angular momentum with Xe as the collisional partner has been studied in zero field and in the presence of a small electric field. The collisional $l$-mixing cross section in zero field has been measured for $9\ensuremath{\le}n\ensuremath{\le}23$ using a vapor-cell-fluorescence method and a crossed-beam technique with a selective-field-ionization (SFI) scheme as the state detector. Using the $|{m}_{l}|$ selectivity of the SFI, we have also investigated the final-$|{m}_{l}|$-state distribution of the collisionally populated states of $l>2$. Our measurements suggest that the collisionally populated states have predominantly low $|{m}_{l}|$ values ($|{m}_{l}|\ensuremath{\le}2$). An application of a low electric field (\ensuremath{\sim} 50 V/cm) substantially reduces the collisional population of the low-$|{m}_{l}|$ states, thus reducing the total cross section as well.

Phase-angle determination by anomalous X-ray scattering with a four-circle SSD diffractometer

By the use of a four-circle diffractometer with a solid- state detector, the integrated Bragg reflexion intensities from hemimorphite [Zn4Si2O7(OH)2.H2O] have been measured by energy-dispersive diffractometry at three energy values, including the region very near the Zn Kα absorption edge. The anomalous difference Patterson map obtained indicated Zn-Zn peaks. By the use of the anomalous-scattering effect to the maximum extent, the phases of one hundred reflexions have been deter- mined with a mean error of 15.4°