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The vanadium redox flow battery (VRB) is well-suited for applications with renewable energy devices. This paper presents a practical analysis of the VRB for use in a microgrid system. The first part of the paper develops a reduced order circuit model of the VRB and analyzes its experimental performance efficiency during deployment. The model parameters of the various VRB system components were estimated from experimental field data. The parasitic losses of the circulation pumps power consumption were predicted during different operating situations. The second part of the paper addresses the implementation issues of the VRB application in a photovoltaic-based microgrid system. Commercially available chargers designed for lead-acid battery systems were shown to be non-optimal for VRB systems and a new dc–dc converter control was proposed to provide improved charging performance. The system model was validated with field-obtained experimental data.

Maximizing profits through vehicle-to-grid interactions are in conflict with the minimizing battery degradation costs, and thus a major customer concern. A holistic scheduling problem is, therefore, required to consider the impact of the charging power and that of the switching between vehicle-to-grid and grid-to-vehicle modes to account for battery health. In this paper, we propose a mixed-objective approach toward vehicle-to-grid interactions of a residential parking lot complex. The solution makes accommodation for battery health while considering the cost/profit model for the electric vehicles. We discuss the importance of system constraints in achieving both, valley filling and peak shaving. A moving horizon model is used to determine real-time schedules for the vehicles. Customer convenience is the central focus of the proposed methodology.

Vanadium redox batteries (VRBs) have proven to be a viable energy storage technology for portable microgrids due to their rechargeability and high energy density. VRBs exhibit parasitic load loss during operation due to pumping of electrolyte across the membrane during charging and discharging cycles, as well as required temperature control in the form of heating, ventilation and air conditioning. This paper focuses on empirically characterizing VRB efficiency based on known climatic operating conditions and load requirements. A model is created to determine system performance based on known climatic and load data collected and analyzed over an extended time period. A case study is performed using known data for a week time period to characterize system performance, which was compared to actual system performance observed during this same time period. This model allows for appropriate sizing of the PV array and discretionary loads based on required energy density of the system.

A prototype detector based on the inclined boron layer principle is introduced. For typical measurement conditions at the Liquids Reflectometer at the Spallation Neutron Source, its count rate capability is shown to be superior to that of the current detector by nearly two orders of magnitude.

In this paper we compare the performance of grooved and flat ZnS/6LiF scintillators in a wavelength-shifting-fiber (WLSF) detector. Flat ZnS/6LiF scintillators with the thickness L=0.2−0.8 mm were characterized using photon counting and pulse-height analysis and compared to a grooved scintillator of approximately 0.8 mm thick. While a grooved scintillator considerably increases the apparent thickness of the scintillator to neutrons for a given coating thickness, we find that the flat scintillators perform better than the grooved scintillators in terms of both light yield and neutron detection efficiency. The flat 0.8-mm-thick scintillator has the highest light output, and it is 52% higher compared with a grooved scintillator of same thickness. The lower light output of the grooved scintillator as compared to the flat scintillator is consistent with the greater scintillator-WLSF separation and the much larger average emission angle of the grooved scintillator. We also find that the average light cone width, or photon travel-length as measured using time-of-flight powder diffraction of diamond and vanadium, decreases with increasing L in the range of L=0.6−0.8 mm. This result contrasts with the traditional Swank diffusion model for micro-composite scintillators, and could be explained by a decrease in photon diffusion-coefficient or an increase in micro-particle content in the flat scintillator matrix for the thicker scintillators.

Demand response is an important resource that can significantly increase the efficiency of the future power systems. It is a key component of smart grids that can bring a lot of benefits to power system operators and customers. This work assesses potential impacts of demand response on some major attributes of the distribution system such as the network losses, voltage profiles, and maximum power flow through the lines. We considered detailed and practical models of individual residential loads for flexible loads in the system. The flexible load models are various household appliances with different acceptable delay times (ADTs) within which their consumption can be shifted from the normal schedules. With these models, demand response was applied to the 33-bus IEEE test system. In this system, each bus served a specific number of aggregated individual residential loads. The obtained results have shown the great effects of demand response on distribution system attributes.

A prototype neutron scintillation detector has been developed, specifically aimed at the needs of the powder diffractometer POWGEN3 at the Spallation Neutron Source at Oak Ridge National Laboratory. This instrument requires a detector array with large (6 mm×40 mm) pixels and an area of several square meters. The prototype uses a two-dimensional grid of wavelength shifting fibers, with the fiber axes parallel to the scintillator screen, to collect the scintillation photons. The fiber ends for each pixel go to a specific set of four photomultiplier tubes, so that the position of each event can be determined by a 4-tube 2 C n × 2 C n coded coincidence. The observed maximum light yield with a 6 LiF/ZnS:Ag neutron scintillation screen, summed over four tubes, is greater than 200 photons/neutron. This is about 0.13% of the ∼150,000 photons/neutron produced in the scintillator. The light yield is sufficient to allow pulse discrimination between neutron signals and gamma-ray background. Further light collection gains should be achievable using double-clad fiber and green-enhanced photomultiplier tubes. Currently, the shape, structure, and specific composition of the scintillator are being investigated, on the assumption that 6 LiF/ZnS:Ag will be the chosen scintillator material.

With one of the highest intrinsic magnetic moments $(10.6\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{B}/\mathrm{atom})$ among the heavy rare-earth elements, dysprosium exhibits a rich magnetic phase diagram, including several modulated magnetic phases. Aided by the Ruderman-Kittel-Kasuya-Yosida interaction, the magnetic modulations propagate coherently over a long range. Neutron diffraction experiments were performed to determine the microscopic magnetic origin of the field induced phases in bulk Dy as a function of temperature, covering regions of the well-known ferromagnetic, helical antiferromagnetic, fan phases, and several possible new phases suggested by previous studies. A short-range ordered fan phase was identified as the intermediate state between ferromagnetism and long-range ordered fan. In a field of 1 T applied along the $a$ axis, the temperature range of a coexisting helix/fan phase was determined. The magnetic phase diagram of Dy was thus refined to include the detailed magnetic origin and the associated phase boundaries. Based on the period of the magnetic modulation and the average magnetization, the evolution of the spin arrangement upon heating was derived quantitatively for the modulated magnetic phases.

The vanadium redox flow battery is well-suited for renewable energy applications. This paper studies VRB use within a microgrid system from a practical perspective. A reduced order circuit model of the VRB was introduced. Experimental field data are collected to estimate the key parameters of the VRB system. Methods of predicting major parasitic losses are proposed. Loss models include the circulation pumps and the HVAC system that regulates the environment of the VRB enclosure. The HVAC system can draw a significant amount of the VRB power considerably impacting its overall efficiency, but this is usually ignored by other theoretical models.

A ferromagnetic ${\mathrm{Pd}}_{97.5}{\mathrm{Mn}}_{2.5}$ alloy single crystal was studied by neutron scattering and susceptibility measurements. The diffuse satellite peaks along the [1 0 0] axis were observed for the ferromagnetic alloy. The diffuse satellite peaks, however, disappeared under a magnetic field of 5 T applied along the [0 0 1] direction perpendicular to the (0 0 1) scattering plane. Combined with the susceptibility data, we discuss several models for the ferromagnetic state of the dilute PdMn alloy.

We have developed a concept for an ultracold neutron (UCN) turbine source based on a long-pulse spallation source. Using a single reflection from a receding blade, the turbine converts cold neutrons from the primary moderator to UCN. The UCN pulse length is spread out in time and is comparable to the primary pulse interval, producing a quasi-continuous UCN source. The principal parameters for such a design are the primary source pulse length, the flight path distance, and the velocity acceptance interval of the reflector. Taking advantage of recent advances in multilayer reflector preparation, we propose W11B4C multilayer reflectors with a high-reflectivity plateau in the velocity range of 80±5 m/s. We have simulated a multilayer turbine which converts 160±5 m/s neutrons from a 1 ms primary source with a 2.5 m incident flight path to UCN with an efficiency, in terms of phase space density, of about 4.4%. For a ∼1 MW long-pulse spallation source with 1 ms pulse length and 60 Hz frequency, and a time average flux in a liquid hydrogen moderator of 1 × 1014 n/cm2 s, this corresponds to a UCN source flux of 1.9 × 105 n/cm2 s, a total UCN current of 3.3 × 107 n/s, and a UCN density (for velocity ≤6.2 m/s) of 500 n/cm3.

We study the surface and interface roughness of a two-liquid film system using neutron reflectometry. The middle phase and bottom phase are extracted from a three-phase microemulsion containing 2 wt% non-ionic surfactant C 10 E 4 , 81 wt% D 2 O and 17 wt% octane (C 8 H 18 ). The system is formed by spreading a few drops of the middle phase of the microemulsion on the bottom phase of the microemulsion. The middle phase does not wet the bottom phase, but demixes to form a top octane—water mixture layer with a thickness of ∼ 580 A. The mean surface roughness of the system is found to be 7 A but the data are insensitive to interface roughness. An extended capillary wave model for a two-liquid-film system is derived to account for the coupling between the surface and interface. The dispersion relation yields two fundamental modes. In a calculation of mean-square roughness (〈 ζ 2 〉 1/2 ) a high- k -cutoff is needed to account for non-linear terms in the Navier—Stokes equation. A low- k cutoff is also needed to avoid a “slip phenomenon” at the interface, which characterizes one of the modes. It turns out that for the parameters of our experiment the narrowing of k region is so significant that the mode causing the slip is strongly suppressed. As a consequence, the calculated interface roughness is much smaller than that derived from ordinary capillary wave theory.

Wavelength-shifting (WLS) fiber scintillator neutron detectors were developed for two time-of-flight (TOF) neutron powder diffractometers (POWGEN, VULCAN) at Spallation Neutron Source (SNS). In a recent module (v3.0), however, there are 32 l-inchdiameter photomultiplier tubes (PMTs), which are bulky and expensive. We built a new detector module (v3.1) based on four multi-anode (MA) PMTs, and tested its performance including detection efficiency, count rate capability, spatial resolution, ghosting properties, and gamma-ray sensitivity. The v3.1 module was compared with two prior v3.0 modules, and 3He tu be detectors.

This paper reports efforts towards establishing a parallel numerical algorithm known as Waveform Relaxation (WR) for simulating large systems of differential/algebraic equations. The WR algorithm was established as a relaxation based iterative method for the numerical integration of systems of ODEs over a finite time interval. In the WR approach, the system is broken into subsystems which are solved independently, with each subsystem using the previous iterate waveform as ''guesses'' about the behavior of the state variables in other subsystems. Waveforms are then exchanged between subsystems, and the subsystems are then resolved repeatedly with this improved information about the other subsystems until convergence is achieved. In this paper, a WR algorithm is introduced for the simulation of generalized high-index DAE systems. As with ODEs, DAE systems often exhibit a multirate behavior in which the states vary as differing speeds. This can be exploited by partitioning the system into subsystems as in the WR for ODEs. One additional benefit of partitioning the DAE system into subsystems is that some of the resulting subsystems may be of lower index and, therefore, do not suffer from the numerical complications that high-index systems do. These lower index subsystems may therefore be solved by less specialized simulations. This increases the efficiency of the simulation since only a portion of the problem must be solved with specially tailored code. In addition, this paper established solvability requirements and convergence theorems for varying index DAE systems for WR simulation.

We have developed a wavelength-Shifting-fiber Scintillator Detector (SSD) with a 0.3 m2 area per module. Each module has 154 × 7 pixels and a 5 mm × 50 mm pixel size. Our goal is to design a large area neutron detector offering higher detection efficiency and higher count-rate capability for Time-Of-Flight (TOF) neutron diffraction in the Spallation Neutron Source (SNS). A ZnS/6LiF scintillator combined with a novel fiber encoding scheme (v.3) was used to record the neutron events. A Cross-fiber Read-Out-Card (CROC) based digital-signal processing electronics and position-determination algorithm was applied for neutron imaging. Neutron-gamma discrimination was carried out using Pulse-Shape Discrimination (PSD). A sandwiched flat scintillator detector can have a detection efficiency close to He-3 tubes (about 10 atm). A single layer and sandwiched flat scintillator detectors have count rate capabilities of about 6,000 and 35,000 cps/cm2, respectively, which can satisfy the count rate requirement of powder diffractometers at SNS. Detectors with v.3 fiber encoding have better image quality and higher spatial resolution than those with previous v.2 fiber encoding.

The dynamic performance of dc-dc power electronic converters is mainly determined by the output filtering capacitor and inductor, control loop(s) compensator(s), and the voltage conversion ratio. Normally, a larger capacitance and/or a smaller inductance are not recommended because of the extra cost and size of the capacitor and/or the increment of the inductor current ripple. The capacitor current feedforward method has gained popularity due its fast dynamic response, simpler structure, and less sensing losses. In applications where a large voltage conversion ratio is needed, dynamic response for a load step-down scenario is worse than that of a load step-up condition. In order to alleviate this situation, a buck derived dc-dc converter is chosen. By combing the capacitor current feed-forward control and the buck derived converter topology, a novel control scheme is proposed in this paper. Simulation results containing the voltage overshoot and settling time are presented. The proposed approach is a high performance, simple structure, and low cost/volume strategy for load step-down dynamic improvements.

This paper presents the development of a FACTS interaction laboratory (FIL) to interface a real-time power system simulator with multiple FACTS/UPFC devices via hardware-in-loop (HIL) to study their dynamic responses and test control approaches. The HIL line includes a synchronous machine, a UPFC device and a load device to simulate the dynamics of the UPFC sub-network. The practical feasibility of the proposed HIL scheme has been demonstrated by implementation on a PC-DSP-based UPFC platform. A detailed design of the HIL distributed control system including synchronous machine, UPFC and load is presented.

Neutron depolarization measurements on an epitaxial thin film of YBaCuO superconducting material are reported and interpreted on the basis of formation of an Abrikosov flux lattice by field cooling. The temperature and field dependences of this effect have been measured and suggest that the technique may be useful in obtaining information on flux lattice stability and pinning forces.

A prototype detector based on the inclined absorber layer principle is introduced. For the Liquids Reflectometer at the Spallation Neutron Source, it is shown to be a significant improvement over its current detector, which imposes an instantaneous count rate limitation of 50 kcps.

Powder and sintered samples of La0.9MnO3 (LMO) and La0.62Y0.07Ca0.31MnO3 (LYCMO) are used in this study. The two initial calcined in air powders have almost identical ferromagnetic properties with Tc≈250 K, and saturation magnetization of σ≈90 emu/gm corresponding to Mn4+(0.3)/Mn3+(0.7). Heating the calcined powders in argon to high temperatures lowers Tc to ≈120 K; however, subsequent oxygen annealing brings back the high Tc form. The LYCMO remains ferromagnetic with σ≈90 emu/gm in both heat treatments but only has a colossal magnetoresistance (MR) for Tc≈120 K. In contrast the LMO with Tc≈120 K has σ reduced to one-half its ferromagnetic value and the MR is almost zero. Neutron diffraction shows only the ferromagnetic structure below Tc for LYCMO but the low magnetization of LMO is best interpreted as a mixed ferro–antiferromagnetic structure rather than a canted one.

Natural mica crystals have been characterized for use as reflectors for an ultracold neutron source using Bragg scattering of cold (400 m/s) neutrons from a moving mica reflector, recently installed at the Los Alamos neutron science center (LANSCE). In particular, the triotahedral Mg-rich mica phlogopite has been obtained in large sheets. The structure factor for the first-order Bragg reflection is a factor of four larger than for muscovite, the first variety of mica examined. The observed peak reflectivity for a phlogopite of 0.25 mm thickness is about 8.2% at 1.9 A, with a mosaic spread of about 0.3° FWHM, in good agreement with the ideally imperfect crystal model. This can be extrapolated to a reflectivity of about 63% at the 17.4 A operating wavelength of the ultracold neutron source. Improvements are possible by obtaining Fe-rich mica, which should be almost as effective as the alternative approach of using synthetic perfluorinated mica.

The structural changes occurring in oil layers during condensation of deuterated octane (C 8 D 18 ) on the surface of a solid (single-crystal silicon) and a liquid (water solution with low (0.08 wt%) concentration of a non-ionic surfactant (C 10 E 4 ) have been studied by neutron reflectometry. The results demonstrate the presence of pseudo-partial wetting during condensation. The van der Waals attractive potential stabilizes a thin oil film coexisting with the residual droplet. We report a study of the growth dynamics of the residual droplet.

A moving diffractor changes the energy of elastically diffracted neutrons by the Doppler effect. Depth-graded multilayers can diffract neutrons over a large band of energy. Using a pulsed neutron source, such a depth-graded multilayer, decelerating synchronously with the incident neutron pulse, can shift the reflected neutrons into a compressed energy window. This focusing in energy is associated with a broadening of the pulse in time, but the process does not involve a significant decrease in the neutron phase-space density. The proposed method can be used to design long pulse or quasi-continuous sources of cold, very cold or ultra cold neutrons (UCN). The analysis concentrates on enhanced production of UCN at pulsed neutron sources.

The magnetism of antiferromagnetic ${\mathrm{Fe}}_{x}{\mathrm{Pt}}_{1\ensuremath{-}x}$ thin films $(x=0.27$ and 0.30) epitaxially grown onto MgO (110) and a-axis sapphire $(\ensuremath{\alpha}{\ensuremath{-}\mathrm{A}\mathrm{l}}_{2}{\mathrm{O}}_{3})$ substrates has been studied by elastic neutron and x-ray scattering. Bulk chemically ordered ${\mathrm{FePt}}_{3}$ exhibits an antiferromagnetic spin structure with a wave vector ${Q}_{1}=2\ensuremath{\pi}/a(\frac{1}{2}\frac{1}{2}0)$ below ${T}_{N1}\ensuremath{\sim}160\mathrm{K}.$ For slightly Fe-rich alloys $(x\ensuremath{\gtrsim}0.26)$ a spin-reorientation transition to a second antiferromagnetic phase with a wave vector ${Q}_{2}=2\ensuremath{\pi}/a(\frac{1}{2}00)$ occurs below ${T}_{N2}\ensuremath{\sim}100\mathrm{K}$ at the expense of ${Q}_{1}.$ For increased Fe content $(x\ensuremath{\sim}0.30)$ the ${Q}_{1}$ phase is strongly suppressed with a dominant ${Q}_{2}$ phase. For (111)-oriented films grown on a-axis sapphire the spin structure is the same as that found in the bulk. The $x=0.27$ film exhibits transitions at ${T}_{N1}$ and ${T}_{N2}.$ The film with $x=0.30$ exhibits an almost completely suppressed ${Q}_{1}$ phase and a dominant ${Q}_{2}$ phase with an enhanced ordering temperature of ${T}_{N2}\ensuremath{\sim}140\mathrm{K}.$ In contrast ${\mathrm{FePt}}_{3}$ (110) films grown onto MgO (110) exhibit only the ${Q}_{1}$ phase for both compositions $x=0.27$ and $x=0.30$ with the onset of the ${Q}_{2}$ phase suppressed. The distinct behavior of the films grown onto MgO from those grown onto a-axis sapphire and bulk ${\mathrm{FePt}}_{3}$ may be explained by higher strain and defect densities incorporated in the films grown onto MgO.

The local atomic environments of homogeneous Si-rich Si-Ge single crystals were studied using x-ray and neutron diffuse scattering. No evidence of either chemical short-range order or clustering was observed. Static atomic displacements, however, were clearly present and are consistent with an expansion of the lattice in the vicinity of the Ge atoms. The dispersion of the acoustic phonons was also measured using inelastic neutron scattering. The acoustic modes of the Si-Ge alloy were found to lie nearer those of pure Si than expected from the homologous relationship found between pure Si and pure Ge.

We report evidence for an ordered flux line lattice in a 2‐μm epitaxial film of YBaCuO from both neutron depolarization and diffraction measurements. Depolarization occurred when field cooling was done normal to the film plane but not within it; this is consistent with frozen‐in vortices. Evidence for ordering of the flux lines comes from intensity maxima observed in difference patterns between field cooled and zero field cooled conditions.

The depolarization of a neutron beam passing through a sample of the high‐Tc superconductor YBa2Cu3O7−δ has been measured as a function of temperature and applied field. The difference in behavior between field‐cooled and zero‐field‐cooled states, the observation of hysteresis correlated with Hc1, and the disappearance of the effect near 55 K (below Tc) suggest an explanation in terms of vortex line lattice formation with possible connection to recently proposed flux line entanglement and melting.

The interfacial characteristics of an oil-water-surfactant sample were studied using the thermal neutron reflectometer at the Rhode Island Nuclear Science Center (RINSC). The sample was a mixture of deuterated octane with H2O and non-ionic surfactant (C10E4), spread onto an H2O substrate. A mixture of low surfactant concentration was used so that it could demix into a lamellar oil-water structure, stabilized by a monolayer of surfactant intervening at each oil-water interface. The reflectivity data showed a clearly visible difference between 25.2° C and 30.2°C, indicating that the significant increase of interfacial tension between these two temperatures induced a structural transition.

We report a simple analytic form for the convolution integral in transmission Moessbauer spectroscopy allowing accurate representation of the line shape even for very thick absorbers (t = 10), and permitting easy fitting to the true line-shape function. This representation permits the accurate determination of all Moessbauer-effect (ME) parameters, including position, width, cross section, and interference. This analytic method can be applied to deconvolute accurately information contained in either source or absorber, and an explicit analytic form for the emission and absorption Fourier transforms is given. We show that from the asymptotics of the line shape, it is possible to determine all line-shape parameters, and that line-shape asymptotics can circumvent short-ranged hyperfine or instrumental broadening contributions to the observed spectrum. A formula for the correction to the line shape caused by source self-absorption is given, and it is shown that when there is significant source resonance self-absorption a ''good'' fit to data, judged by a chi-squared analysis, can yield completely wrong ME line-shape parameters. We find an equation for the dependence of the area under the absorption curve and the resonance peak height, and give its explicit dependence on the interference parameter and source broadening parameters. Although these effects havemore » been neglected in earlier work, their contribution may be of order 10% in many cases of interest.« less

The Debye-Waller factor of sodium has been measured as a function of temperature from 80 to 295 K using Moessbauer ..gamma..-ray scattering. The high energy resolution provided by this technique allowed experimental separation of the elastic scattering from the inelastic thermal diffuse scattering. The results were compared with the harmonic model using integrations over dispersion curves from the neutron-scattering measurements of Woods et al. and the lattice-dynamics calculations of Glyde and Taylor. The Debye-Waller exponent was shown to exceed the harmonic prediction by 23% at room temperature. This difference is attributed to anharmonic terms in the interatomic potential.

The Mossbauer diffraction instrument at the Missouri University Research Reactor has been used to measure the elastic and inelastic contributions to the 444 Bragg reflection in dynamic silicon at room temperature. These measurements used the 46.5-keV gamma rays from high intensity183Ta sources cooled to liquid nitrogen temperature. The main feature of this study compared to similar measurements on silicon is the significantly improved momentum space resolution. ΔQ values of 0.011 A−1 and 0.11 A−1 were measured for the transverse and longitudinal directions, respectively.

A Mossbauer gamma-ray diffraction instrument has been developed which utilizes high intensity sources produced by neutron irradiation. Most of the early work has used 70 Ci, 5.1 d 183Ta sources produced by double neutron capture which yield 12 × 1010 photons/s for the 46.5 keV Mossbauer transition in 183W. A dewar is enclosed in the shielding cask which allows sources to be cooled to 77 K. Samples are located approximately midway between source and detector, which are separated by 155 cm. Collimators in front of the sample and detector commonly limit the beam to 3 mm wide by 25 mm high. A 27% minimum is seen in the velocity spectrum for the 46.5 keV photons scattered from the 200 Bragg reflection in LiF taken in transmission. Enriched, room temperature absorbers mounted on a rotor can be Doppler-shifted up to 17 meV. Q-space resolution of 0.01 A−1 is significantly better than that reported by other groups using Mossbauer scattering. When a microfoil internal conversion electron (MICE) detector is used, the instrument has the potential for directly measuring the energy transferred by the inelastically scattered photons, especially for low energy excitations in solids which require high energy resolution.

Using exceptionally high intensity Mossbauer sources (∼ 1–100 Ci) of182Ta and183Ta, we have measured the Mossbauer effect for the 46.5 and 99.1 keV transitions of183W and the 100.1 keV transition of182W. Using a microfoil internal conversion electron (MICE) /1/ detector capable of operation at low temperatures, and a LiF crystal monochromator, we obtain effects of nearly 600% for the 46.5 keV transition and 3 1/2% and 6% for the other two cases, while standard transmission measurements typically yield much smaller signal-to-background ratios. With this technique we have measured the asymmetry term in the conversion electron spectra. To our present level of accuracy the results are in agreement with theoretical calculations of interference parameters /2/. Our results do not agree with earlier measurements /3/ on this transition, which are grossly at variance with theoretical calculations of the interference parameter.

Using 100 Ci183Ta and 5 Ci182Ta sources, with LiF and NaCl crystal monochromating filters, we have measured the lineshape parameters for the 46.5 keV and 99.1 keV Mossbauer effect (ME) transitions of183W and the 100.1 keV transition of182W. Using an analytic representation of the convolution integral and utilizing asymptotic analyses of the lineshape, we find, for both transmission and microfoil internal conversion (MICE) experiments, accurate values of all ME parameters including width, position, cross section, and interference. This new approach allows deconvolution of source and absorber spectra and gives a simple analytic expression for both as well as their Fourier transforms. The line widths for the 46.5, 99.1, and 100.1 keV transitions are 3.10(10), 0.369(18), and 0.195(12) cm/s, respectively. The interference parameters are −0.00257(9), −0.0093(12), and −0.0107(12) in the same respective order. The agreement between transmission and MICE /1,2/ measurements for the above lineshape parameters is within the experimental errors. We believe these measurements are the first having sufficient precision to allow a quantitative comparison with dispersion theory /3,4/ and they indicate interference parameters 10 to 20% smaller than predicted. Our measured line widths are less than earlier reported values. This is because our analysis of the true lineshape and the study of line asymptotics permits a quantitative determination of the isomer lifetimes rather than the usual lower bound found in earlier ME experiments.

We have recently reported[l] neutron depolarization measurements on an YBa2Cu3O7−δ composition exhibiting a transition from a low temperature state which caused depolarization (P=0.76+−.02) to one at high temperatures (T=55K) where depolarization was absent. Since this temperature is well below the measured superconducting transition at 86K, we speculated that the transition was a dynamic one corresponding to flux lattice melting[2] or to formation of a glassy state[3]. We have now extended these depolarization measurements to two specimens of Bi2.2Sr1.7CaCu2O8+δ' prepared and characterized[4] at IBM, which showed superconducting transitions at 80K with weak tails extending to 110K. The two samples have critical current densities, as determined by the Bean expression[5], that differ by 50%.