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Immiscible liquid–liquid displacement is a fundamental problem in fluid mechanics and has many applications like, for instance, enhanced oil recovery. One of the most valuable methods to increase oil recovery is injecting a fluid into the reservoir to displace the oil, and the primary motivation of this work is to evaluate the liquid–liquid displacement in homogeneous and heterogeneous porous media. We carried out a direct numerical simulation of liquid–liquid displacement in three different porous media: medium I, II, and III. The medium I is homogeneous. Medium II is heterogeneous, in which the diameter of the spheres reduces from the bottom to the top boundary. Finally, in medium III, the diameter of the spheres is randomly distributed all over the domain. The three media were composed of spheres and had the same mean porosity. We tracked the liquid interface front over time until the breakthrough to compute the mass entrapped as a function of viscosity ratio and capillary number. The sweep efficiency increases when the displacing liquid viscosity also increases. The role played by the capillary number is more complex. In medias I and II, the entrapped mass rises with the capillary number. For a specific condition in medium III, when the displacing liquid is more viscous than the displaced one, the opposite can occur, i.e., the entrapped mass decreases with the capillary number. Beyond the capillary number and viscosity ratio, the sweep efficiency strongly depends on the kind of medium. Mainly, the entrapped liquid is smaller in the homogeneous medium. [ABSTRACT FROM AUTHOR]

An improvement for the vacuum system of the multidriver radio frequency (RF) prototype negative ion source SPIDER has been developed, to allow operating at high RF power, while minimizing the breakdown probability on the outside of the plasma source. A first-of-its-kind large nonevaporable getter (NEG) pump, based on a modular design of 384 cartridges totaling about 350 kg of ZAO® alloy (composed by Zr-Ti-V-Al) with an installed pumping speed at a room temperature of 330 m3/s for hydrogen, will complement the existing pumping system, based on eight cryogenic pumps and four turbomolecular pumps totaling about 90 m3/s in hydrogen. The vessel pressure during absorption is expected to be between 20 and 40 mPa, while during the getter regeneration, the peak operating pressure will be around 2 Pa. The NEG pump will use an additional vessel module, with integrated thermal shields to protect the in-vessel components during activation and regeneration of the pump, to be carried out at temperatures in the range of 550–600 °C. Integrated thermal analyses were carried out to verify the low heat load on pre-existing in-vessel components with a low limit of acceptable temperature, and to provide boundary conditions for the mechanical verifications of the pump structure. The scenario of cyclic hydrogen load was calculated considering the SPIDER operation modes, the expected gas throughput, and the cumulated load to the pump, to determine the regeneration temperature and auxiliary pumping necessary to make the regeneration duration compatible with the high availability of the system. The upgrade of the auxiliary pumping system is also described, as well as the mitigation of air or water exposure risk during regeneration of the NEG pump. [ABSTRACT FROM AUTHOR]

In this paper, a pioneer partial discharge (PD) loop antenna sensor is presented and examined. It is made of a 70-turn square planar inductor with a side length of 1.8 mm, which is fabricated on top of a silicon substrate in complementary metal oxide semiconductor technology. The microsensor ability to detect corona PD is demonstrated once connected in series with a 60 dB gain amplifier. The behavior is studied at different separation distances from the line through which the PD pulses flow. At 5 cm away, a damped sinusoidal induced voltage with an amplitude of about 100 mV has been measured. The output signal spectrum is highly concentrated around a central resonance frequency of ∼5 MHz. The microsensor response is compared with those of other industrial sensors from Techimp, i.e., horn antennas and high-frequency current transformer sensors. The presented on-chip sensor can be considered a non-intrusive competing solution compared with other heavy and expensive commercial sensors due to its lightweight, compact size, and low cost. In addition, it shows an acceptable signal to noise ratio compared with other commercial electromagnetic wave-based sensors. [ABSTRACT FROM AUTHOR]

P-wave conversion to slow diffusion (Biot) modes at mesoscopic (small-scale) inhomogeneities in porous media is believed to be the most important attenuation mechanisms at seismic frequencies. This study considers three periodic thin layers saturated with gas, oil, and water, respectively, a realistic scenario in hydrocarbon reservoirs, and perform finite-element numerical simulations to obtain the wave velocities and quality factors along the direction perpendicular to layering. The results are validated by comparison to the Norris-Cavallini analytical solution, constituting a cross-check for both theory and numerical simulations. The approach is not restricted to partial saturation but also applies to relevant properties in reservoir geophysics, such as porosity and permeability heterogeneities. This paper considers two cases, namely, the same rock skeleton and different fluids, and the same fluid and different dry-rock properties. Unlike the two-layer case (two fluids), the results show two relaxation peaks and the agreement between numerical and analytical solutions is excellent. [ABSTRACT FROM AUTHOR]

Optically induced electronic transitions in nitride based polar heterostructures have been investigated by absorption and emission spectroscopy. Surface photovoltage (SPV), photocurrent (PC), and photo luminescence spectroscopy have been applied to high quality InAlN/AlN/GaN structures to study the optical properties of two dimensional electron gas. Energy levels within the two dimensional electron gas (2DEG) well at the interface between the GaN and AlN have been directly observed by SPV and PC. Moreover, a strong enhancement of the photoluminescence intensity due to holes recombining with electrons at the Fermi Energy, known as fermi energy singularity, has been observed. These analyses have been carried out on InAlN/AlN/GaN heterojunctions with the InAlN barrier layer having different In content, a parameter which affects the energy levels within the 2DEG well as well as the optical signal intensity. The measured energy values are in a very good agreement with the ones obtained by Schrödinger-Poisson simulations. [ABSTRACT FROM AUTHOR]

High resistivity CdTe can be achieved by introducing impurities that create deep levels which, in turn, control the electronic transport properties of the material via a compensation process. We have characterized the effects of thermal annealing of high resistivity CdTe:Ge under either Te- or Cd-rich atmosphere to understand how modifications in the structure of Ge-related defective states and their electrical activity affect the material transport properties. We have investigated the transport properties with current-voltage analyses, the electrically active deep traps by photo-induced current transient spectroscopy and the local environment of Ge atoms by x-ray absorption spectroscopy. By correlating the modifications observed, we determined the occurrence of Ge clustering effects and associated them to the formation of electrically active deep donor traps, one located at EC-0.31 eV and the other one at midgap, with an activation energy of 0.82 eV. [ABSTRACT FROM AUTHOR]

Hydrogenated nanocrystalline silicon (nc-Si:H) is a multiphase, heterogeneous material, composed of Si nanocrystals embedded in an amorphous matrix. It has been intensively studied recently due to very promising photovoltaic and optoelectronics applications. The present paper aims to study electronic transitions in nc-Si:H grown by Low Energy Plasma Enhanced Chemical Vapor Deposition by Surface Photovoltage Spectroscopy. The study of several thin films grown at different conditions and the comparison with recently published computational studies allowed us to advance a hypothesis on the defect structure responsible for electronic transitions in nc-Si:H. [ABSTRACT FROM AUTHOR]

The electrical properties of high-purity 4H–SiC epitaxial layers are investigated. The current density versus applied voltage curves shows that some specimens have space charge limited transport behavior. Lampert–Mark model for trap-controlled electron transport in semi-insulating materials demonstrated the presence of an intragap state at 0.26 eV below the conduction band. Photodeep level transient spectroscopy has confirmed the presence of a deep level at about 0.3 eV below the conduction band only in samples with non-Ohmic behavior. Cathodoluminescence imaging has revealed the presence of high luminescent areas related to stacking faults (SFs) under the devices showing non-Ohmic behavior. The presence of single-layer SFs was detected by cathodoluminescence spectroscopy due to the typical emission at 2.95 eV. Thus, we demonstrated that the SFs modified the charge transport from Ohmic conduction to space charge limited conduction of the affected samples. [ABSTRACT FROM AUTHOR]

CdZnTe-based detectors possess unique properties as room-temperature x- and gamma-ray detectors. We report on the effects of x-ray irradiation on CdZnTe and CdTe:Cl detectors with increasing x-ray doses. We correlate the “macroscopic” performance of the detectors, investigated by gamma-ray spectroscopy to the “microscopic” effects induced by the impinging radiation, i.e., the defective states introduced in the crystal lattice. The electrical activity of the defects and their activation energy have been investigated by photo induced current transient spectroscopy and by space charge limited current analyses. We identify the x-ray dose that induces a significant degradation in the detector performance, and by cross-correlating the results obtained, we achieve a reliable estimate of the actual concentration of electrically active deep states and assess the potentiality of these experimental methods as tools for quantitative analyses of high resistivity materials. [ABSTRACT FROM AUTHOR]

The electrical compensation processes of high resistivity CdTe is controlled by deep levels. We have characterized the electrical activity of deep traps by means of three different and complementary spectroscopic methods: photoinduced current transient spectroscopy, surface photovoltage spectroscopy, and space charge limited current analyses. The aim is twofold: to achieve a thorough characterization of the deep trap properties and to assess the potentiality and limitations of the three experimental techniques by a cross correlation of the results obtained with each one of them. We have obtained a direct quantitative estimate of the major deep trap concentration, and we have assessed the sensitivity limit in deep-level detection for surface photovoltage spectroscopy. [ABSTRACT FROM AUTHOR]

The potential energy curves of the ground state and of some excited states of the manganese dimer have been calculated over a wide range of internuclear distances using the second order n-electron valence state perturbation theory applied to a complete active space self-consistent field reference wave function. The ground state of Mn2, for which also the third order NEVPT has been used, is calculated to be a singlet belonging to the Σg+ symmetry, characterized by a large equilibrium internuclear distance Re of 3.7–3.8 Å, by a low dissociation energy De of 0.07–0.08 eV, and by a small harmonic frequency ωe of 43 cm-1. The experimental evidence that Mn2 is a van der Waals molecule is thus confirmed. Among the excited states, 11Πu, which is usually indicated as the ground state by density functional theory studies, appears as a low-lying state with Re=2.50 Å, De=1.35 eV, and ωe=246 cm-1. [ABSTRACT FROM AUTHOR]

This paper analyzes the thermal degradation of GaN-based light emitting diodes with hydrogen-rich passivation layer by combined capacitance and current measurements. The decrease of optical power arising during thermal treatment at T=250 °C is well related to a decrease in the high-frequency capacitance and to the generation of a further peak in the conductance/frequency curves. Deep level transient spectroscopy measurements excluded the role of further deep levels introduced/generated in the p-n junction region. Transmission line method analysis showed that stress induces nonlinearity of the characteristics of the contacts, related to the increase of Ohmic contact resistivity. All these modifications are explained using a small-signal model in which a parasitic impedance arises as a consequence of stress in the portion of metal/(p-GaN) interface exposed to diffusion of hydrogen from the passivation layer. Therefore, degradation is shown to be related to the worsening of the properties of the metal/semiconductor interface at the p side of the diode, due to the interaction between the hydrogen-rich passivation layer and the acceptor dopant. This interaction is well confined to the immediate proximity of the interface, leaving the activated acceptor concentration in the bulk almost unaffected. [ABSTRACT FROM AUTHOR]

Cd1-xZnxTe alloys have been studied by surface photovoltage spectroscopy (SPS) and energy dispersive spectroscopy (EDS). The analyses of surface photovoltage spectra have been perfomed at near and above band gap energies. Surface recombination effects on the surface photovoltage have been investigated. SPS analyses of Cd1-xZnxTe alloys with different surface conditions have shown that the surface recombination velocity significantly affects the SPS determination of the material band gap. Accounting for this and preparing the surfaces accordingly, SPS spectra of Cd1-xZnxTe samples have allowed an accurate determination of the optical band gap as a function of the Zn concentration, determined via EDS analyses. The local increases in the density of states associated with band structure features in Cd1-xZnxTe alloys have been investigated by SPS spectra in the above band gap energy range. [ABSTRACT FROM AUTHOR]

Defects in freestanding gallium nitride were examined in this work. Electron beam induced current mapping evidence a low density of dislocations in the first microns from the upper Ga-terminated surface; correspondingly, deep levels detected by junction spectroscopy exhibit point-like characteristics. Spectral photoconductivity measurements in the poorly dislocated region show the characteristic red, yellow, green, and blue bands, which shift toward higher energies with decreasing temperatures according to Varshni’s law. Spectral photoconductivity measurements carried out in depth evidenced, instead, the quenching of the defect-related yellow band and the prevalence of the green band when temperature increases. This behavior suggests a dislocation-assisted connection between the yellow and green bands, in agreement with theoretical models on their common origin involving complexes VGa-ON. [ABSTRACT FROM AUTHOR]

The potential energy curves of the molecules Mo2, W2, and CrMo have been studied ab initio using large basis sets and the “n-electron valence state perturbation theory” up to the third order in the energy. The third order results for Mo2 and W2 reproduce the equilibrium distances re and the harmonic frequencies ωe in fairly good accordance with the experimental values but tend to underestimate the dissociation energy. The CrMo molecule, for which experimental dissociation energy data do not exist yet, is predicted to have a value for De of ≈2.5 eV. [ABSTRACT FROM AUTHOR]

We studied a GaN epitaxial wafer grown by metal organic chemical vapor deposition, in which a lateral variation in the density of dislocations and associated defects was induced by a special preparation of the GaN buffer layer. Electron beam induced current and photocurrent measurements reveal lateral variations in the electrical properties of the GaN epilayer corresponding to the gradient in the defect density. The photocurrent spectra show four well distinct peaks separating the well known defect related yellow band in a blue, a green, a yellow, and a red component. In particular, we observe a strong dependence of the green component on the density of the a-type threading dislocations. There is evidence that the green and the yellow components are also significantly influenced by point defects. [ABSTRACT FROM AUTHOR]

This work describes an experiment on degradation mechanisms of InGaN light-emitting diode (LED) test structures which do not fulfill the requirements of longlife products. We present a combined capacitance-voltage (C-V), deep level transient spectroscopy (DLTS), electroluminescence (EL), and cathodoluminescence (CL) study of short-term instabilities of InGaN/GaN LEDs submitted to low current aging tests at room temperature. In the early stages of the aging tests, the EL and CL characterizations showed an optical power decrease, more prominent at low current levels. The C-V profiles indicated that the stress induced an apparent charge increase, well related to the deep level changes detected by DLTS and to the optical power decrease. It is supposed that the main cause of the degradation is the generation of nonradiative paths, due to the generation/propagation of defects activated by carrier transport. [ABSTRACT FROM AUTHOR]

A formulation of the n-electron valence state perturbation theory (NEVPT) at the third order of perturbation is presented. The present implementation concerns the so-called strongly contracted variant of NEVPT, where only a subspace of the first-order interacting space is taken into account. The resulting strongly contracted NEVPT3 approach is discussed in three test cases: (a) the energy difference between the 3B1 and 1A1 states of the methylene molecule, (b) the potential-energy curve of the N2 molecule ground state, and (c) the chromium dimer (Cr2) ground-state potential-energy profile. Particular attention is devoted to the last case where large basis sets comprising also h orbitals are adopted and where remarkable differences between the second- and third-order results show up. [ABSTRACT FROM AUTHOR]

The effects of low-temperature annealing in 8.2 MeV electron-irradiated 4H-SiC Schottky diodes were investigated. Deep-level transient spectroscopy and minority-carrier diffusion length (Ld) measurements were carried out on not-irradiated samples and on irradiated samples before and after thermal treatments up to T=450 °C. We found that several deep levels in the upper half band gap (S1 with enthalpy ET=0.27 eV, S2 with ET=0.35 eV, S4 with ET=0.71 eV, and S5 with ET=0.96 eV) anneal out or modify at temperature values lower or equal to T=450 °C, whereby their progressive annealing out is accompanied by a net increase of Ld, up to 50% of the value in the as-irradiated sample. We drew some conclusions regarding the microscopic nature of the defects related to the deep levels, according to their annealing behavior. [ABSTRACT FROM AUTHOR]

The effects on 4H-silicon carbide epilayers of irradiation with protons and electrons having particle energies, respectively, of 6.5 and 8.2 MeV were carefully studied and critically compared. In detail, the electronic levels associated with the irradiation-induced defects were analyzed by current-voltage characteristics and deep-level transient spectroscopy (DLTS) measurements up to 550 K. In the same temperature range the apparent free-carrier concentration was measured by capacitance-voltage characteristics in order to monitor compensation effects due to the deep levels associated with the induced defects. Introduction rate, enthalpy, and capture cross section of such deep levels were compared. We found that a set of deep levels (at ET=0.39 eV, ET=0.65 eV, and ET=0.75 eV) is the same in both cases of proton and electron irradiations, whereas two other pairs of levels (S1, ET=0.20 eV and S1*, ET=0.23 eV; S5, ET=1.09 eV and S5*, ET=0.89 eV) appearing in the same temperature range within the DLTS spectra should be associated with different defect complexes according to the irradiation type. Some conclusions regarding the microscopic nature of the defects related to the deep levels have been drawn. [ABSTRACT FROM AUTHOR]

The distribution of the electric field and its spatial extent are key predictors of the charge collection efficiency of particle detectors. The electric field is strictly related to the electrically active defects, which are significantly modified by irradiation. In this paper we analyze the native and radiation-induced defects and infer the mechanisms controlling the electrical properties of semi-insulating GaAs Schottky diodes. The correlation between the electric-field distribution and deep levels confirms that the compensation mechanisms are mainly due to the donorlike centers and to their enhanced neutralization, which occurs for moderately high electric fields. Moreover, taking into account the charge balance among native and irradiation-induced defects, the active region extent is predicted. [ABSTRACT FROM AUTHOR]

The electronic recombination properties of Mg-doped GaN have been investigated by steady state and time-resolved cathodoluminescence (TRCL) in the scanning electron microscope, photocurrent (PC) spectroscopy, and optical beam induced current (OBIC). CL and OBIC maps reveal an inhomogeneous recombination activity in the investigated material. Deep levels giving rise to level-to-band transitions were detected by PC spectroscopy. A large PC quenching observed upon illumination with light of (2.65–2.85) eV is tentatively attributed to metastable traps within the band gap. CL spectra reveal the existence of emission bands centered at 85 K at 3.29, 3.20, 3.15, and 3.01 eV, respectively. Both time-resolved and steady-state CL measurements carried out under different excitation conditions indicate that the 3.15 and 3.01 eV emissions are likely related to donor-acceptor pair transitions. TRCL measurements also reveal different recombination kinetics for these bands and suggest that deep donors are involved in the mechanism responsible for the 3.01 eV emission. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The features of current deep level transient spectroscopy (I-DLTS) spectra are investigated in AlGaAs/GaAs heterostructure field-effect transistors both through experiments and two-dimensional numerical device simulations. Differently from electron traps located in the n-type semiconductor bulk, which can only be detected in emission-mode by I-DLTS, deep levels located at the ungated device surface are shown to be revealed both in emission and capture transients by I-DLTS. Experimental and simulation results indicate that this behavior originates from inherent physical properties of surface deep levels interacting with holes attracted at the ungated surface by the negative charge associated with ionized traps. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We present a study of the effects of high and low energy neutron irradiation on CdTe and CdZnTe high resistivity detector grade material. The evolution of the defect states under increasing irradiation fluence has been monitored by means of photoinduced current transient spectroscopy analyses. Particular attention is placed on the comparison and correlation between the results from the two materials under the two different neutron irradiation energies. The behavior of the observed deep traps associated with defect states allowed us to attribute an origin to most of them and to understand the role they play in the charge carrier collection process and in the degradation of material spectroscopic capabilities. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Time-resolved cathodoluminescence (TRCL) and photocurrent (PC) spectroscopies have been applied to the study of the yellow band of Si-doped GaN. Measurements carried out combining both techniques unambiguously reveal the complex nature of this broad emission and confirm that different deep defect levels are involved in the observed luminescence. Five emission bands centered at 1.89, 2.03, 2.16, 2.29, and 2.38 eV were found by steady state and time-resolved CL investigations, while PC spectra showed four transitions at about 2.01, 2.14, 2.28, and 2.43 eV. The behavior of the deep-level emissions intensity as a function of the excitation pulse width as well as their decay times were investigated by TRCL. A decay time of 245 μs was measured for the 2.29 eV emission band, while longer decay times of 315 and 340 μs were found, respectively, for the 2.16 and 2.38 eV bands, in agreement with TRCL spectra. The appearance of the 2.03, 2.16, 2.29 eV and 2.38-2.43 eV peaks both in PC and CL spectra suggests that these bands are related to deep acceptor to band transitions, as supported by the single exponential character of the corresponding decay transients. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) and deep level transient spectroscopy (DLTS) measurements were used to study the origin of optical emissions in the 0.8-1.0 eV region of selected oxygen precipitated and dislocated silicon samples. It was shown that the D1 band, present in both types of samples, is the convolution of different sub-bands, narrowly spaced between 0.802 and 0.820 eV. The emission at 0.807 eV, assigned in the literature to dislocations, was found only in samples where dislocations were intentionally generated by plastic deformation or induced by the clustering of self-interstitials generated during the growth of oxide precipitates. A comparison of the results of PL, DLTS, and optical DLTS measurements allows the assignment of levels involved in the radiative recombination processes. [ABSTRACT FROM AUTHOR]

This article concerns the existence of a double-junction effect in proton-irradiated silicon p[sup +] υ-n[sup +] (pin) diodes demonstrated by surface potential and optical-beam-induced current (OBIC) investigations. By increasing the diode biasing, the junctions existing at both ends in the irradiated devices move towards each other up to join, hence, causing a full depletion of the diodes. Due to the inhomogeneity of the electric field, however, the charge-carrier collection is strongly dependent on the position. The extent of the diode depletion layers at both ends and the shape of the electric field within the p[sup +]-υ-n[sup +] diodes are determined as a function of the bias applied. Three-dimensional photocurrent maps obtained by OBIC profiles allow for imaging the double junction. The deep level analysis evidences the presence of irradiation-induced defects, which are responsible for the double-junction effect. [ABSTRACT FROM AUTHOR]

Presents information on the study which investigated the electrical and optical characteristics of Erbium-doped silicon by liquid phase epitaxy. Experimental details; Results and discussion; Conclusions.

Presents an experiment which investigated the levels which are present in semiconducting Cadiminum/Tellurium (Cd/Te) and semi-insulating Cd/Te:Chlorine and (Cd0.8Zn0.2Te) by means of cathodoluminescence. Indepth look at the experiment; What the results showed.

Presents a study that investigated the EL2 trap in highly doped gallium arsenide:tellurium. Method of the study; Results and discussion; Conclusion.

Presents a study which investigated the distribution in liquid-encapsulated-Czochralski GaAs:Te wafers of point and complex defects together with their influence on the minority-carrier diffusion length. Characteristics of the wafers of liquid-encapsulated-Czochralski gallium arsenide tellurium doped; Methods used; Results of the study.

Investigates the defective states induced in floating zone silicon by the heavy diffusion of dopants by means of the electron beam-induced current (EBIC) method. Evolution of the electrical and morphological properties of the induced defects; Role of aluminum in the electrical activity of bulk defective states; Sample mounting geometries utilized for EBIC analyses.

Presents information on a study that determined the diffusion length and surface recombination velocity of the minority carriers from electron beam induced current profiles on a semiconductor containing a barrier perpendicular to the scanned surface. Methodology of the study; Results and discussion on the study.

Presents a study which obtained the diffusion length of minority in n-type floating-zone silicon samples with the electron-beam-induced current technique in planar configuration. Background on the moment method; Experimental procedures; Results of the study.

We developed a 375-channel, whole-head magnetoencephalography (MEG) system ("BabyMEG") for studying the electrophysiological development of human brain during the first years of life. The helmet accommodates heads up to 95% of 36-month old boys in the USA. The unique two-layer sensor array consists of: (1) 270 magnetometers (10 mm diameter, ~15 mm coil-to-coil spacing) in the inner layer, (2) thirty-five three-axis magnetometers (20 mm × 20 mm) in the outer layer 4 cm away from the inner layer. Additionally, there are three three-axis reference magnetometers. With the help of a remotely operated position adjustment mechanism, the sensor array can be positioned to provide a uniform short spacing (mean 8.5 mm) between the sensor array and room temperature surface of the dewar. The sensors are connected to superconducting quantum interference devices (SQUIDs) operating at 4.2 K with median sensitivity levels of 7.5 fT/√Hz for the inner and 4 fT/√Hz for the outer layer sensors. SQUID outputs are digitized by a 24-bit acquisition system. A closed-cycle helium recycler provides maintenance-free continuous operation, eliminating the need for helium, with no interruption needed during MEG measurements. BabyMEG with the recycler has been fully operational from March, 2015. Ongoing spontaneous brain activity can be monitored in real time without interference from external magnetic noise sources including the recycler, using a combination of a lightly shielded two-layer magnetically shielded room, an external active shielding, a signal-space projection method, and a synthetic gradiometer approach. Evoked responses in the cortex can be clearly detected without averaging. These new design features and capabilities represent several advances in MEG, increasing the utility of this technique in basic neuroscience as well as in clinical research and patient studies. [ABSTRACT FROM AUTHOR]