Research Facilities--Guide to NIST

This facility is a vibration-isolated, shell-within-shell structure that is one of the quietest and best acoustically characterized rooms in the world. The inner room is supported by 52 coil springs and has walls 0.3 meter thick. All interior surfaces are covered with custom-designed wedges that protrude into the room about 1.8 meters. The inner room is 6.7 meters wide, 10 meters long (wedge tip to wedge tip), and 6.7 meters high. The walls are designed to be 99.9 percent sound-absorptive for frequencies above 45 hertz. The ambient noise in the chamber is so low it cannot be measured above a few hundred hertz with the best quality laboratory microphones.

Applications:
Acoustical measurements under free-field conditions are performed in the chamber. Research done in the chamber supports standards development, improved measurement methods, and sensor development. Measurement services are provided to a broad range of industries and government agencies. In addition, the chamber has been used to support the development of a wide range of transducers, including advanced loudspeakers and hearing aids, micro-machined silicon microphones, and sonar arrays prior to sea trials.

Contact: Victor Nedzelnitsky

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Building Integrated Photovoltaic Testbed

NIST measures the long-term performance of building integrated photovoltaic panels in-situ using the Building Integrated Photovoltaic Testbed. The facility provides comparison between different building integrated photovoltaic panels when exposed to identical meteorological conditions. Up to nine panels can be evaluated simultaneously.

We can compare energy production, operating temperature, heat flux, and characteristic current versus voltage curve traces. This testbed consists of crystalline, polycrystalline, amorphous, and silicon film building integrated photovoltaic products. Two identical panels of each photovoltaic cell technology, one insulated and one un-insulated, are currently installed.

Meteorological instrumentation includes two precision spectral pyranometers, one precision infrared radiometer, and two radiatively shielded type-T thermocouples. An ultrasonic wind sensor is used to measure the magnitude and direction of air movement in a vertical plane.

Two systems are used to monitor the Building Integrated Photovoltaic testbed. A testbed data acquisition system is used to measure the output signals of the outdoor meteorological instruments, the heat flux transducers, the panel temperature sensors, and two radiatively shielded indoor ambient temperature sensors. This data acquisition system scans the sensors and records the data every five minutes. The second data acquisition system is a custom built photovoltaic measurement system, referred to as a multi-tracer. The multitracer simultaneously loads and collects electrical performance data on multiple photovoltaic panels. The multi-tracer can operate with a maximum of 14 panels.

Capabilities: The testbed is capable of evaluating up to nine building integrated photovoltaic panels simultaneously. The size of the panels can vary up to a maximum of 1.38 meters by 2.36 meters. The multi-tracer can dissipate up to 2,400 watts. User selectable load options include: peak power tracking, fixed voltage operation, user specific voltage profile, and unloaded or open circuit.

Availability: This testbed may be available for use by those outside NIST, but it must be operated by BFRL staff. Collaborative programs may be arranged on a cost-reimbursable basis.

Contact: A. Hunter Fanney

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Calculable Capacitor Lab, The

The U.S. legal system of electrical units is tied to the International System of Units with smaller uncertainties than those of any other nation and provides the United States with a very solid basis for the measurement of electrical quantities. The central facility is the NIST calculable capacitor, with which the measurement of capacitance is effectively achieved through a measurement of length. Both the calculable capacitor and the chain of high precision measurements that transfers the SI unit to the calibration laboratories must be maintained and improved. We also conduct international comparisons with other national metrology laboratories to ensure measurement consistency.

Capabilities: This facility provides the realization of the farad at both 1000 and 1592 Hz, traceable to the SI meter, at uncertainty levels of parts in 10⁸.

Applications: Measurements made in this lab link the calculable capacitor to the quantum Hall resistance representation of the ohm. Traceability is provided for the NIST calibration services for impedance (capacitance and inductance).

Availability: By special arrangements only.

Contact: Gerald J. Fitzpatrick

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Center for Theoretical and Computational Materials Science

The NIST Center for Theoretical and Computational Materials Science (CTCMS) is a research program addressing industry's needs for theory and modeling tools for materials design and processing. Founded in 1995, the CTCMS is a center of expertise in computational materials research that develops tools and techniques and fosters collaborations. CTCMS goals are to investigate important industrial problems in materials theory and modeling with novel computational approaches, create innovative and productive opportunities for collaboration in materials theory and modeling, develop powerful new tools for materials theory and modeling, and accelerate their integration into industrial research.

Capabilities: To use the nation's resources more effectively, the CTCMS integrates ongoing research at various institutions by forming multidisciplinary and multi-institutional research teams as required to attack key materials issues. The CTCMS has three principal activities, all operating interactively: planning, research, and technology transfer. Workshops are held as the first step in defining technical research areas with significant technological impact, identifying team members, and building the infrastructure for collaborative research. The CTCMS provides an infrastructure and support for its members, including an interactive World Wide Web information server (www.ctcms.nist.gov) and modern computing and workshop facilities.

Applications: Current research areas include theory and simulation of phase transformation kinetics and morphology, micromagnetics, composite materials, foams, microstructure and dynamics of disordered and partially ordered materials, complex fluids, materials reliability, reactive wetting, pattern formation, crystal growth, sintering, and solidification. Simulation techniques include finite element, finite difference, Lattice Boltzmann, molecular dynamics, Monte Carlo, phase field and cellular automata methods. Current CTCMS working groups include:

Phase field modeling tools: The phase field method has become one of the most flexible and powerful methods for predicting the evolution of materials microstructure. We are focusing on the development of both new applications for this method and tools enabling the solution of the complex equations which emerge from these models.
Matinformatics: With the advent of combinatorial materials science, huge amounts of data are being generated, and this information needs to be both accessible and interpreted. This effort is bringing cutting-edge information technology together with experts in data-mining to develop the tools and techniques needed to manage the ever-increasing volume of materials information.
WWW tools for scientific collaboration: We are working with information science specialists to develop Web-based tools for scientific collaboration.
First principle methods in phase diagrams: Using a fundamental, quantum-mechanical, description to derive the properties of matter, is the ultimate goal of materials modeling. This effort uses electronic structure calculations to derive the phase stability of alloys, with particular focus on ferroelectrics.
Object-oriented finite element modeling of composite materials. We are developing a set of object-oriented finite element modeling tools to improve the characterization and property prediction of composite materials. Public domain software tools are available at www.ctcms.nist.gov.
Structure-property relations in polymer nanocomposites: This working group is exploiting molecular simulation methods to characterize structure in composite materials, and to relate structure to the ultimate material properties and functionality.
Microstructure and dynamics of frustrated materials. This working group is applying new computational capabilities to characterize the relationship between microstructure and dynamics in glasses, plastics, and other amorphous materials and developing a new set of measurement standards.
Tools for neutron scattering measurements. While neutron scattering has become a critical tool for the probing of matters properties, interpreting the results of the experiment present a host of challenges for the scientist. This effort is attempting to develop a better theoretical framework for the interpretation of such experiments, bringing together some of the Green's function library. This team of researchers is developing an interactive, electronic library tool of Green's function and boundary element solutions to reduce the time and cost of industrial component design.

The CTCMS also hosts Web pages with resources and tools in the following areas:

Micromagnetic materials: This working group is addressing the need for accurate, standardized micromagnetics modeling tools. Software tools developed by the group and selected sample geometries may be found at www.ctcms.nist.gov.
Solder interconnect design: The solder interconnect design team is developing public-domain software tools to improve electronic packaging processes. Tools developed by the solder group that model standard solder interconnect geometries are available at www.ctcms.nist.gov

Availability: The CTCMS facilitates numerous interactions between industry, academia, NIST, and other government and national labs to apply materials theory and modeling to solve U.S. industrial problems in materials design and processing. Researchers interested in joining existing efforts or starting new ones are encouraged to contact the CTCMS. The center welcomes proposals for focused workshops in materials theory and modeling at any time. Proposals will be funded on the basis of scientific merit and availability of funds. Computing and workshop facilities are available to U.S. industry, other government agencies, and academia for collaborative research projects. The CTCMS participates in the National Research Council postdoctoral fellowship program and hosts short-term and long-term visitors.

Contact: James Warren

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Combinatorial Methods

New, more complex materials are increasingly in demand for applications in areas such as biotechnology, microelectronics and nanotechnology. The use of combinatorial methods—which comprise a special set of tools and techniques—enables scientists to rapidly explore a wide range of material characteristics in parallel and on a miniaturized scale. The Combinatorial Methods Program at NIST (see www.nist.gov/combi) was initiated to develop this methodology to learn more about materials and their structure, properties, and processing, data that can help manufacturers accelerate the development of new materials.

The program has demonstrated the ability to successfully develop novel combinatorial methods for polymer "library" preparation and characterization, and validation of combinatorial measurements through well-defined problems in polymer materials science such as mapping phase boundary, stability and wettability of thin films, co-polymer morphology, crystallization, and demonstrated new knowledge discovery in the process. State-of-the-art on-line data analysis tools, process control methodology, and data archival methods are being developed. The program works closely to address issues of the multiphase materials, electronic materials, and biomaterials for their structure and properties characterization. A multitier consortium directly serves the needs of industrial customers.

Researchers in the Polymers Division have developed novel combinatorial methods for polymer "library" design and characterization. These include gradient flow coating with elevated temperature control, automated interferometric mapping of film thickness and refractive index, composition gradient library preparation, UV and wet etch for gradient surface hydrophobicity modification of inorganic and polymer surfaces, infrared spectroscopic composition mapping, temperature gradient processing stage, automated optical reflection and transmission microscopy with polarization and process control programming, automated multi-solvent contact angle instrument, high throughput opto-adhesion methodology, and state of the art on-line data analysis tools for image and pattern processing.

Combinatorial and high-throughput measurement techniques available in the facility include:

gradient flow coating method
multilens JKR (Johnson-Kendall-Roberts) for quantitative adhesion measurements
mechanical properties—copper-grid multiple crazing and film fracture technique, and modulus of gradient polymer coatings
UV methods for surface energy gradients, gradient cross-linking and curing, chemical and topographically multiply patterned substrates
IR imaging for automated chemical mapping of coatings
automated optical microscopy with gradient hot stage for in-situ crystallization, curing, phase separation, film drying, film wettability
confocal microscopy for florescence studies of gradient samples (e.g., polymer curing on gradient temperature stage)
molecular probes and optical detection for high-throughput transport studies in polymeric membranes (with NIST Boulder)
gradient composition extrusion of nanocomposites (for flammability studies with NIST fire researchers) and micro hot-plates for calorimetry
gradient composition polymer films from heated polymer solution

Contact: Alamgir Karim

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Controlled Background Radiometric Facility

Infrared radiometry has an important role in space-based civilian, defense, and industrial applications. A facility to maintain an infrared scale for specialized applications was developed with funding from NIST, the National Aeronautics and Space Administration, and the Department of Defense. In particular, the capability for measurements on large-area, vacuum-operational, blackbody sources operated from 200 K to about 400 K is being established. These measurements will be traceable to NIST via infrared radiometry through the radiance temperature of the source. An alternative scheme that is directly traceable to an absolute cryogenic radiometer using laser-illuminated sphere sources and transfer detectors is also under development. An example of the type of scientific activity that this facility supports is the use of satellites for the determination of temperature, based on radiance measurements, for the Earth's surface and atmosphere. These measurements are the basis for the study of global warming. A goal of the facility will be the development of infrared radiometers, which will be used for intercomparisons of large-area blackbody sources used by contractors for NASA's Earth Science Enterprise Project.

Contact: Carol Johnson

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Electromagnetic Anechoic Chamber

The electromagnetic (EM) anechoic chamber at NIST is a facility for generating standard, well-characterized electromagnetic fields. Such fields are fundamental to the research, development, and evaluation of antennas, field probes, and EM material properties.

Capabilities: EM fields up to 100 volts per meter can be established in the chamber over the broad frequency range from 200 megahertz to 40 gigahertz and up to 200 volts per meter for certain bands above one gigahertz. A majority of the individual components are computer-controlled, including a robotic positioner, thus enhancing statistical control of the measurements. The chamber measures 8.5 meters by 6.7 meters by 4.9 meters.

Applications: The EM chamber is used in areas such as:

research, development, and evaluation of new EM-field-generation and measurement methods;
calibration of field measurement instruments;
immunity testing of electronic equipment;
shielding effectiveness and material parameter studies; and
special tests for industry, government agencies, and universities.

Availability: This facility is used heavily in performing calibrations for industry and other governmental agencies. It is available for independent or collaborative work with NIST.

Contact: Dennis Camell

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Electronic Kilogram Facility, The

The equivalence of electrical and mechanical power provides a convenient route to the measurement of mass in terms of other quantum mechanically defined measurement units. The apparatus at our electronic kilogram facility is a balance that compares both kinds of power in a virtual measurement that is unaffected by the dissipative forces of friction and electromagnetic heating. The experimental observables are length, time, voltage, and resistance. We measure these quantities with respect to fundamental and invariant quantum phenomena: atomic clocks, laser wavelengths, the Josephson effect, and the quantum Hall effect, respectively.

Capabilities: The goal is to establish long-term stability of alignment, data acquisition, and reference standards for the repeatability of watt data at an uncertainty of 0.1 ppm. Further optimization of the system will permit regular monitoring of the kilogram at an uncertainty of 0.01 ppm.

Contact: Michael H. Kelley

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Electron Paramagnetic Resonance Facility

NIST is leading a national and international effort in electron paramagnetic resonance (EPR) dosimetry for measuring ionizing radiation. Paramagnetic centers (molecules or atoms with unpaired electrons) are produced by the action of radiation on materials. In the EPR measurement, irradiated materials are placed in a magnetic field and electron spin transitions are induced by an electromagnetic field of the appropriate frequency, typically in the gigahertz range. EPR is used as a non-destructive probe of the structure and concentration of paramagnetic centers. The centers created by ionizing radiation are proportional to the absorbed dose and provide a sensitive and versatile measurement method.

Capabilities: The EPR dosimetry facility is supported by three state-of-the-art X-band EPR spectrometers capable of measuring radiation effects on a wide range of materials from inorganic semiconductors to biological tissues. The data acquisition system provides full computer control of all spectrometer functions, including real-time spectral display and rapid acquisition scan to analyze rapidly decaying signals. The data acquisition system is interfaced with an advanced data analysis station for data manipulation and is capable of simulating and deconvoluting multicomponent spectra.

Applications: EPR dosimetry is operable over many orders of magnitude in absorbed dose (10^-2 Gy to 10⁵ Gy) and impacts many facets of society and industry:

Radiation accident dosimetry. Using biological tissues (bone, tooth enamel) or inanimate materials (clothing), retrospective dose assessment and mapping can be accomplished.

Clinical radiology. Ionizing radiation doses administered in cancer therapy can be measured for external beam therapy using dosimeters of crystalline alanine (an amino acid) or validated for internally delivered bone-seeking radiopharmaceuticals using bone biopsies.

Industrial radiation processing. Routine and transfer dosimetry for industrial radiation facilities can be performed using alanine dosimeters as well as post-irradiation monitoring of radiation-processed meats, shellfish, and fruits using bone, shell, or seed. The EPR facility also serves as a fully functional materials research facility for analyzing radiation effects on semiconductors, optical fibers, functional polymers, and composites.

Availability: The EPR facility is available for collaborative research by researchers from industry, academia, and other government agencies under the supervision of NIST staff.

Contact: Marc F. Desrosiers

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EM Reverberation Chambers

We have designed and constructed reverberation chambers to measure radiated electromagnetic (EM) emission, immunity of electronic equipment, and shielding effectiveness of materials and cable/connector assemblies. A reverberation or mode-stirred chamber is an electrically large (in terms of wavelength), high-quality cavity whose boundary conditions are varied by means of a rotating conductive tuner.

Capabilities: The mode-stirred chamber simulates far-field conditions for tests at frequencies from 200 megahertz to 40 gigahertz. Equipment as large as 1.5 meters by 2.0 meters by 3.0 meters can be tested in high-level test fields up to 1000 volts per meter.

Applications: The range of reverberation chamber tests includes:

radiated emission and radiated immunity testing,
high field level testing (> 200 MHz),
shielding effectiveness of materials (e.g., advanced composites),
shielding effectiveness of gasketing, cables, printed circuit boards, and connectors, and
biological effects.

Availability: Two chambers are available. NIST staff are available for collaborative programs or to advise and interpret measurement results.

Contact: Galen Koepke

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Environmental Chambers

NIST operates several environmental chambers capable of simulating a variety of temperature conditions. The largest chamber, referred to as the large truck chamber, measures 14.6 meters by 7.3 meters by 4.2 meters with a 3.6-meter by 3.6-meter access door. The heat pump chambers are located in adjacent rooms.

Capabilities: The large truck chamber is capable of maintaining steady and dynamic temperature profiles from -45 to 65 degrees Celsius. Cooling and heating tests may be performed with dry-bulb and dew-point temperature control of ±0.1 degree Celsius. A maximum of 35 kilowatts of heat may be removed from this chamber at 35 degrees Celsius and 50 percent relative humidity. The heat pump chambers are designed for testing systems at standard cooling and heating conditions. The indoor chamber can maintain steady dry-bulb and dew-point conditions from 10 to 60 degrees Celsius, and the outdoor chamber can maintain temperatures from -18 to 60 degrees Celsius. The maximum capacity system for these chambers is 35 kilowatts. The appliance chamber may be controlled from -18 to 65 degrees Celsius with relative humidity controlled within ±2 percent. Maximum heat removal from this chamber is 12 kilowatts.

Applications: Testing of large equipment and special structures can be carried out in the large truck chamber. It has been used to test the performance of engines, vehicles, and special structures under extreme heat and cold. The heat pump chambers are used to test residential heat pump and air-conditioning equipment. The appliance chamber is used to test appliances and small heating and cooling equipment such as radiators, heat exchangers, water coolers, and control devices.

Availability: These facilities are available to investigators from industry and universities, but must be operated by NIST staff. Collaborative research programs and proprietary research can be arranged.

Contact: Piotr A. Domanski

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Flat-Panel Display Lab, The

Well-defined methods for specifying and verifying display quality are necessary to enable worldwide commerce of electronic displays. In the Flat-Panel Display Lab, we are developing methods for characterizing the components of reflection (Lambertian, specular, and haze) associated with displays. The refinement of measurement procedures is being pursued in support of display metrology and the application of these to national and international standards for characterizing flat panel displays.

Capabilities: The Display Measurement Assessment Transfer Standard (DMATS) is a portable unit that is available for determining unambiguous color measurements in round-robin testing. A narrow-frustum stray light elimination tube (SLET) apparatus can be used to minimize the effects of stray light in making small-area measurements on displays, particularly important in rendering high-contrast detail.

Applications: This work has led to the second public version of the VESA Flat Panel Display Measurements Standard (FPDM2). DMATS and SLET capabilities are being used to determine the readability of automotive displays under high ambient light conditions.

Availability: By special arrangements only.

Contact: Kevin G. Brady

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Ground-Screen Antenna Range

The ground-screen antenna range is an open-area electromagnetic field test site.

Capabilities: The ground screen consists of 6.35-millimeter mesh galvanized hardware cloth stretched over a level concrete slab. There is a center section of 20-meter-by-30-meter stainless-steel sheets. The screen is 30.5 meters by 61 meters and permits far-field measurements in the high-frequency portion of the spectrum. The mesh dimension provides for an efficient ground plane well into the ultrahigh frequency part of the electromagnetic spectrum.

Applications: The range can be used for the following applications:

antenna calibrations,
antenna patterns at any polarization,
electromagnetic immunity measurements,
electromagnetic radiated emission measurements,
calibration of field intensity meters, and
wave propagation studies.

Availability: This facility is used heavily in performing calibrations for industry and other governmental agencies. It is available for independent or collaborative work.

Contact: Dennis Camell

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High-Resolution UV and Optical Spectroscopy Facility

Accurate atomic data for neutral atoms and ions are required in support of high-technology products and manufacturing processes as well as advanced scientific applications. The primary source of such data is high-resolution optical spectroscopy. Spectrometers in NIST's High-Resolution Ultraviolet and Optical Spectroscopy Facility are the most powerful in the world for observations of emission and absorption spectra in the soft X-ray to near infrared regions. The 10.7-meter grazing-incidence and normal-incidence vacuum spectrographs permit observations from 3 nm to 600 nm with resolving powers of 70,000 to 400,000 and wavelength uncertainties as low as 0.0002 nanometer. In the visible and near-infrared region, an echelle spectrograph provides resolving powers exceeding 1,000,000. NIST's new high-resolution Fourier transform spectrometer will be capable of observations from 300 nm to 6 mm with unmatched resolution and wavelength accuracy. A variety of discharge sources are used to excite spectra of neutral atoms and ions stripped of up to 20 electrons. Species up to 40 times ionized are observed in plasmas created by ablating samples with a high-power laser. Our current research includes observations of transitions in highly ionized atoms for diagnostics of plasma conditions in tokamaks and stars, precision measurements of rare gas spectra in the infrared, laser spectroscopy of Rydberg states in alkali atoms, and Fourier transform spectroscopy of rare earth elements for application to development of more efficient commercial lighting.

Contact: Joseph Reader

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Integrated Circuit Fabrication Laboratory

NIST maintains a complete fabrication laboratory for superconducting integrated circuits. Devices employing both low- and high-temperature superconductors are supported. Demonstrated capabilities include the fabrication of 32,000-junction Josephson 10-volt array standards using niobium trilayer technology. The laboratory is housed in an M2.5/3.5 (Class 100/1000) clean room. Individual facilities include a digital pattern generator, submicrometer waferstepper, precision contact aligner, laboratory-scale electron-beam lithography system, pulsed laser deposition system, metal and insulator thin-film deposition and etching systems, and requisite accompanying processing tools. Silicon wafer processing facilities for microelectromechanical system (MEMS) fabrication include furnaces for oxidations, diffusion, silicon nitride growth, polysilicon growth, and low-temperature doped oxide growth. Etching tools for MEMS work include a XeF₂ system and a special deep reactive ion etcher capable of etching deep trenches with vertical walls. These facilities are available on a limited basis in support of collaborative research with NIST.

Contact: James A. Beall

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Large Fire Facility

NIST recently opened its newly renovated Large Fire Facility for measuring and quantifying the response of basic materials, assembled products, and structures in fires up to 10 megawatts peak heat release. These measurements will be used to validate the predictions of practical and scientific fire models and to serve the unique fire research needs of industry, standards making bodies and other government agencies. Laboratory services include protected areas for safely burning materials and objects without releasing smoke to the environment; state of the art heat release rate measurements with documented uncertainty; a Labview-based data system that acquires and displays, in close to real time, the exhaust flow, heat release history, and critical temperatures in the area of the fire; video records of the experiments synchronized to the heat release measurement; and communications among a range of standard and specialized instruments to meet the objectives of a particular experiment (e.g., smoke meter, mass loss from burning object, radiation distribution, local heat flux, velocity field around fire, extractive and in situ gas and particulate measurements, suppressant flow and droplet characterization).

The facility has a large 27- by 5-meter open area designed to accommodate a wide variety of structures. Four exhaust hoods ranging in size from 1 to 80 square meters are equipped with heat-release-rate calorimeters to cover fires from a small single burning object to a fully flashed-over room. We plan to add the capability to examine wind-aided fires. A standard ISO 9705 burn room or a custom structure can be constructed.

The full-scale performance of fire detection and suppression systems can be measured in the Large Fire Facility or in unique smaller scale laboratories. Our fire-emulator/detector-evaluator has been specially designed to enable the development of new fire detection systems and to measure their performance against alternative technologies. A suite of nuisance sources (e.g., organic aerosols, cigarette smoke, inorganic dust, cooking foods, steam, gases) have been quantified to see how well a particular design can discriminate a flaming or smoldering fire from a non-fire event. We have developed fire suppression screening devices to evaluate the performance of non-traditional halon alternatives.

Our dispersed liquid agent fire suppression screening apparatus can compare the effectiveness of a firefighting agent that exists in liquid phase at room temperature to that of halon 1301, providing a performance measure for liquid agents that is equivalent to cup burner performance measures for gaseous agents. We have developed the transient application recirculating pool fire apparatus to examine the performance of solid-propellant gas generators and enable manufacturers and users of this technology to evaluate proposed improvements in propellant composition or discharge design.

Heat flux transducers used for determining convective and/or radiative heat transfer are a critical part of any measurement of the response of a material to fire. We have developed a special Convective Heat Flux Facility for characterizing transducers by subjecting them to a purely conductive or convective flow traceable to the NIST radiometric source.

Availability: Industry, university, and government representatives are encouraged to contact NIST regarding the use these fire measurement facilities in a collaborative or independent basis.

Contact: William Grosshandler

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Large-Scale Structural Testing Facility

The NIST large-scale structural testing facility consists of a universal testing machine (UTM) that may be used in combination with a 13.7-meter tall reaction buttress and horizontal hydraulic ram to apply tension or compression and lateral forces to large-scale specimens.

Capabilities: The UTM portion of the facility is a servo-controlled, hydraulically operated machine. With a capacity of 53.4 meganewtons and a height of 23.7 meters, it is one of the largest in the world. It can be programmed by function generator or computer to create any desired loading function using force, strain, or displacement as the variable. It tests large structural components and subassemblies and applies the forces needed to calibrate large capacity force-measuring devices. It can apply two-compression forces to test sections up to 18 meters in height. The reaction buttress can resist horizontal forces up to 4.5 meganewtons from floor level to a height of 12.2 meters. Tension specimens may be subjected to forces up to 26 meganewtons. A 2-meter-thick test floor may be used to hold specimens in place.

Applications: A research program was conducted to evaluate the performance of concrete columns 1.5 meter in diameter and up to 9.1 meters in height. Another study evaluated fracture propagation in 1-meter-wide steel plates with thickness of 100 millimeters and 150 millimeters. A third project used the servo-control system to apply repeated loads to fiber-reinforced composite specimens.

We can use this facility for low-cycle fatigue tests, destructive or proof load testing, earthquake simulation in two dimensions, and complex loading of components. Servo operation of this machine creates a unique potential for applying precisely controlled, large forces to test components.

Availability: This facility, which NIST staff must operate, is available for cooperative or independent research. Tests should be arranged as far in advance as possible as special hardware may be needed for attaching specimens.

Contact: Shyam Sunder

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Line Heat-Source Guarded Hot Plate

The 1-meter guarded hot-plate apparatus measures thermal conductivity of building insulation. This facility provides for absolute measurement of thermal resistance of thick and low-density test specimens used as transfer standards. These standards are used to calibrate heat-flow-meter apparatus or verify guarded-hot-plate apparatus. This facility is the only one of its kind in the world that will permit low-density thick insulation to be measured with an expanded uncertainty of less 1 percent.

Capabilities: Laboratory services for thermal resistance measurements and related thermal properties are provided for thermal insulation and building materials having thermal conductivities of 0.02 to 0.15 watt per meter kelvin. In general, the highest accuracy is obtained for homogeneous specimens. The preferred size for the test specimen is 1,016 millimeters in diameter; the minimum size, 610 millimeters square. Customers can supply their own material for specimens, or request NIST to select specimens from an in-house inventory of fibrous-glass material. All tests are performed at an ambient atmospheric pressure of approximately 100 ± 20 kilopascals (site pressure at Gaithersburg, Md.). Services at ambient pressures outside these limits or with other gases are not provided. A dry-air purge is available to reduce the relative humidity to less than 15 percent.

Availability: This apparatus is available for use by those outside NIST, but it must be operated by BFRL staff. Collaborative programs may be arranged on a cost reimbursable basis.

Contact: Robert R. Zarr

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Low-Background Infrared Radiation Facility

In the NIST Low-Background Infrared Radiation Facility, radiant background noise levels less than a few nanowatts are attained in two large (60 cm diameter × 152 cm long) vacuum chambers by cooling internal cryoshields to temperatures less than 20 kelvin using a closed-cycle helium refrigerator system. These chambers, the broadband chamber and the spectral chamber, are equipped with absolute cryogenic radiometers (ACR) of the electrical substitution type that operate at 2 K to 4 K .

Capabilities: The ACR is a broadband detector with a flat response from the visible to the long wavelength infrared spectral region. The ACR in the broadband chamber can measure power levels of 20 nW to 100 W at its 3 cm diameter aperture within an uncertainty of less than 1 percent. The spectral chamber is equipped with a prism grating infrared spectrometer that covers the spectral range of 2 micrometers to 30 micrometers with a spectral resolution of 2 percent. The spectral chamber ACR is more sensitive and can measure power levels of few nanowatts at its 2-cm aperture within an uncertainty of less than 1 percent. Both radiometers have a resolution of 1 nW, and their time constants are about 20 seconds.

Applications: This unique facility can be used to measure total radiant power from sources such as cryogenic blackbodies to deduce their radiant temperatures. The spectral chamber allows the measurement of the spectral distribution of radiation from sources and characterization of infrared detectors and optical components.

Availability: The facility is operated by NIST staff in support of user infrared calibrations. It is available for collaborative research by NIST and outside scientists in areas of mutual interest.

Contact: Steven Lorentz

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Magnetic Engineering Research Facility

Capabilities: This facility is specifically designed for advancing key enabling technologies in the field of ultrahigh-density data storage. Films can be deposited both by the methods preferred in basic research (molecular beam epitaxy) and by the methods of industrial manufacturing (magnetron sputtering). Numerous in-situ structural characterization techniques are available, including scanning tunneling microscopy, X-ray photoelectron spectroscopy, Auger electron spectroscopy, ion scattering spectroscopy, low-energy electron diffraction, reflection high-energy electron diffraction, and mass spectrometry. For in-situ magnetic measurements, both a superconducting magnet and an electromagnet are built into the instrumentation and are equipped for magnetoresistance and magneto-optical Kerr effect measurements.

This array of in-situ instrumentation allows measurements to be made on samples at every step of fabrication with the most modern surface, interface, and magnetic diagnostics. Properties that can be investigated include elemental composition, thickness, atomic structure, roughness, and magnetic and magnetoresistive properties. These measurements allow researchers to establish the correlations between the film structure and properties and to use the resulting insights to help industry establish a scientific basis for their manufacturing processes.

Applications: This facility is used to prepare magnetic spin valves possessing giant magnetoresistance (GMR) effects and to study the science underlying their fabrication. These devices, which are partially comprised of 1- to 2-nanometer-thick alternating layers of Co and Cu, are being used in all current computer hard disk read-heads and may form the basis for a new generation of non-volatile memory chips to compete with dynamic random access memory. For the past three years in this highly competitive area, Magnetic Engineering Research Facility (MERF) activities have led the world in devices possessing the largest GMR values with the switching fields small enough for devices. Through close association with the National Storage Industry Consortium, which comprises the leading magnetic recording companies, NIST has provided the MERF results to the recording industry on a continuous basis. Fierce competition is under way to dominate this key technology of the information storage industry. The introduction of GMR heads means that only eight years elapsed between the discovery of the GMR effect and its introduction into commercial products. The MERF facility is used to support U.S. industry in the competition by making measurements that industry is not equipped to make. This approach is leading to the development of improved GMR read-heads to help keep U.S. industry competitive in world markets.

Availability: The MERF is open to all qualified U.S. researchers who are interested in collaborative research. Scientists from industry particularly are encouraged to take advantage of the opportunities for collaborative research of interest to their companies. Several such collaborations presently are under way. However, facility time can be made available for new collaborations if the proposed research is designed to promote the agenda of our customers.

Contacts: William F. Egelhoff, Jr. and Robert D. Shull

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Magnetic Forensics Laboratory

We use magnetoresistive sensors and arrays to image damaged or partially erased magnetic recording tape and magnetic fields from currents in integrated circuits.

Contact: David Pappas

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Magnetic Thin-Film Fabrication Laboratory

In our laboratory we vacuum deposit layered magnetic thin films—including materials that exhibit giant magnetoresistance—by sputtering, thermal evaporation, and laser ablation. We make specialized magnetic devices, such as magnetoresistive spin-valves, and measure their switching dynamics. We fabricate experimental structures for spintronics.

Contact: Stephen Russek

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Magnetometer Laboratory

The laboratory has several instruments for magnetic characterization, including a superconducting quantum interference device (SQUID) magnetometer (0-7 T, 2-400 K, 0-5000 Hz), a vibrating sample magnetometer (VSM) (0-1 T, 300 K), an alternating gradient field magnetometer (AGM) (0-1 T, 300 K), and induction-field (B-H) looper (0-0.1 T, 10-1000 Hz, 300 K), an ac demagnetizer, a magneto-optical Kerr effect (MOKE) magnetometer, and a second-harmonic magneto-optical Kerr effect (SH-MOKE) magnetometer.

Contact: Ron Goldfarb

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Mass Standards Facility

Dedicated to mass research and development, this facility consists of a class 1,000 clean room with temperature control to within 0.1 degree Celsius in the range of 20 degrees Celsius to 22 degrees Celsius, temperature gradients of less than 0.1 degree Celsius per meter, and relative humidity control to within ± 2 percent in the range of 45 percent to 50 percent. With this and other environmentally controlled laboratories, NIST provides mass measurements in the range 1 milligram to 27,200 kilograms.

Applications: Research and development activities include the characterization of physical and chemical properties of artifact mass standards and support of research efforts aimed at monitoring the mass unit by means of fundamental constants. Mass measurement services also are provided.

Contact: Zeina Jabbour

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Materials Science Synchrotron X-Ray Beamlines

Synchrotron radiation sources provide intense beams of X-rays for leading-edge research in a broad range of scientific disciplines. The Synchrotron Beam Line Operation and Development project in MSEL's Ceramics Division includes the operation of experimental stations at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory, and at the Advanced Photon Source (APS) at Argonne National Laboratory. The Advanced Photon Source is one of three hard X-ray third-generation synchrotron radiation light sources in the world—the brightest sources of X-ray beams available. NIST is a partner at the APS with University of Illinois at Urbana/Champaign, Oak Ridge National Lab, and UOP, in a collaboration called UNICAT. At the UNICAT facility, scientists can examine the microstructure of metals, ceramics, polymers and biomaterials, in detail not possible before. The emphasis at both facilities is on microstructure characterization. Scientists from NIST, industry, universities, and other government laboratories, come to the UNICAT beam lines at the APS and the NIST advanced materials characterization beam lines at the NSLS to perform state-of-the-art measurements. Use of the NIST facilities at the APS and the NSLS are open to all qualified researchers in the scientific community.

The experiments available at the APS include high-resolution X-ray diffraction, ultra-small-angle X-ray scattering (USAXS), surface and interface scattering, X-ray diffraction imaging, X-ray absorption fine structure (XAFS) spectroscopy, diffuse scattering, X-ray microbeam diffraction and fluorescence, and coherent X-ray scattering. Experimental techniques available at the NSLS include XAFS, standing wave X-ray measurements, and ultra-soft-X-ray absorption measurements.

The USAXS instrument offers continuously tunable optics for anomalous USAXS, 1,000 times the intensity of earlier USAXS instruments, high sensitivity and high resolution at low scattering vector, and a scattering vector range from below 0.00012 Å-1 to above 0.5 Å-1. As one of the few small-angle X-ray scattering instruments in the world for which a primary absolute calibration is available, the data from the NIST instrument serves an important role in setting scattering standards. In an optional configuration of this instrument, side-reflection optics enables USAXS measurements of anisotropic as well as isotropic materials.

The high-resolution, monochromatic X-ray diffraction imaging camera at the APS is the only dedicated monochromatic facility of its type in this country, and is the only instrument able to support experiments at the highest resolution. It supports a range of imaging studies such as imaging of semiconductor crystals, photonic materials, and biological crystals.

At the U7A beam line at the NSLS, the NIST/Dow Materials Science end station receives photons in the soft-X-ray energy range from ~ 150 eV to 1000 eV, covering the K-edges of boron, carbon, nitrogen, oxygen and fluorine. It uses a unique focusing multiplayer mirror system for soft X-ray absorption spectroscopy and a new non-destructive photon-in photon-out detector system, which allows the in-situ observation of the chemical species under real reaction conditions. The end station can make direct comparisons between the surface and bulk of a sample by measuring simultaneous electron yield (5 nm depth sensitivity) and fluorescence yield (200 nm) spectra.

Availability: Beam time is available to qualified scientists provided safety requirements are met and scheduling arrangements can be made. Proposals for collaborative use of the facility are reviewed at NIST; proposals for independent use of the NIST facilities should be submitted to directly to the Independent Investigator Program at the APS or the General User Program at the NSLS.

Contact: Gabrielle G. Long

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Medical-Industrial Radiation Facility

NIST operates an electron accelerator as the heart of a new user facility for the medical and industrial radiation communities. The Medical-Industrial Radiation Facility (MIRF) is based on an rf-powered, traveling-wave electron linac donated by the Radiation Therapy Center of the Yale University New Haven Hospital. This reconfigured accelerator provides electron energies from 7 MeV to 32 MeV at average beam currents of up to 0.1 mA. In addition to the original beam-steering system and medical-therapy scanner/collimator head, three additional beam ports and a switching magnet have been added at NIST. The flexibility afforded by access to these four beam lines allows NIST to address issues in radiation metrology, radiation effects, and the uses of electron and high-energy photon beams.

Capabilities: The medical beam line can provide electron doses of up to 5 Gy/min at the patient location and is equipped with a target to produce a 25 MeV bremsstrahlung beam as used in high-energy photon therapy. On other beam lines, dose rates in excess of 1 kGy/s over a small area have been achieved with electrons, and exposure rates of about 2,500 R/min can be attained with suitable bremsstrahlung convertors to produce high-energy photon beams used in industrial radiography.

Applications: MIRF offers unique opportunities for medical and industrial research. At the facility, a number of organizations are collaborating on a variety of projects:

Medical dosimetry. Medical linacs are used for treating approximately 500,000 cancer patients annually at some 1,300 treatment facilities in the United States. Among the medical dosimetry applications of MIRF are the development and testing of instruments and dosimetry systems for use in clinical facilities as well as investigations into shielding requirements for the radiation scattered from the patient.

Radionuclide production. Through photonuclear reactions, radioisotopes can be produced with high-energy electron accelerators as an alternative to the use of nuclear reactors. Applications on MIRF include production tests of radionuclides for use in nuclear medicine.

Radiography. The facility provides for studies pertinent to industrial radiography and computed tomography. In addition, ongoing development on one of the beam lines is aimed at producing quasi-monoenergetic photon beams of channeling radiation and coherent bremsstrahlung suitable for use in digital-subtraction angiography.

Radiation effects and processing. Current applications include electron-beam treatment of waste water, curing of polymer composites, and radiation effects on electronics.

Availability: MIRF is available for collaborative research by researchers from industry, academia, and other government agencies under the supervision of NIST staff.

Contact: Stephen M. Seltzer

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Microfabrication Process Facility

As integrated circuit (IC) sizes increase to more than one square centimeter and feature sizes within the circuits decrease to less than 1 micrometer, critical demands are placed on the measurement capability required to control and monitor IC fabrication successfully. To meet the demand, we are developing state-of-the-art measurement procedures for microelectronics manufacturing.

The Microfabrication Process Facility provides a quality physical environment for a variety of research projects in semiconductor microelectronics as well as in other areas of physics, chemistry, and materials research. The laboratory facilities are used for projects addressing many areas of semiconductor materials and processes, including process control and metrology, materials characterization, and the use of integrated circuit materials and processes for novel applications.

The laboratory complex occupies about 5,200 square feet, approximately half of which is composed of Class 1000 clean room space. Within the clean room, work areas are maintained at class 30. The facility is designed so the work areas can be modified easily to accommodate frequent equipment and other changes required by research.

Capabilities: The facility has a complete capability for IC fabrication. Principal processing and analytical equipment is listed below.

The newest additions to the Microfabrication Facility are two dedicated thin-film deposition and etch systems for R&D applications. The plasma enhanced chemical vapor deposition system (PECVD) can provide low temperature (< 300 C) thin film dielectrics like SiO₂, Si_xN_x, and SiON. The other platform is set up as a plasma etching tool, capable of providing anisotropic and isotropic etching of dielectrics, thin films and other materials used in the semiconductor fabrication industry.
The NIST Microfabrication Facility offers a mask aligner with backside alignment capability and is also wafer to wafer bonding upgradeable. This photolithographic tool can provide resolution in the sub-micron regime (0.35-0.75 micron) for G-line and I-line exposures. With its 1000 watt lamp, processing can be performed using thick resist with full field exposure. This tool is flexible enough to handle small samples (6-25 mm) up to 6-inch wafers.
A surface profilometer is utilized for determining the stress and/or topology of a thermally applied film or etched surface. This system is a contact stylus type with the capability to resolve features as large as 2mm with the extended range option beneficial for MEMS and Microfluidics research. Step heights of an etched feature can be measured with the sensitivity below 10 Angstroms. This model includes a 6.5" stage and 50mm scans with up to 8000 data points. The system uses Windows software and has a color video monitor with video capture.

Applications: We can produce small quantities of specialized semiconductor test specimens, experimental samples, prototype devices, and processed materials. The processes and processing equipment can be monitored during operation to study the process chemistry and physics. The effects of variations in operating conditions and process gases and chemical purities can be investigated. Research is performed under well-controlled conditions. A research-oriented facility, the laboratory is not designed to produce large-scale ICs or similar complex structures. Rather, the laboratory emphasizes breadth and flexibility to support a wide variety of projects.

Our current research projects address many aspects of microelectronic processing steps and materials as well as silicon micromachining. Examples include: metal-oxide-semiconductor measurements; metal-semiconductor-specific contact resistivity; uniformity of resistivity, ion-implanted dopant density, surface potential, and interface state density; characterization of deposited insulating films on silicon carbide; ionization and activation of ion-implanted species in semiconductors as a function of annealing temperature; electrical techniques for dopant profiling and leakage current measurements; and processing effects on silicon-on-insulator materials. A simple CMOS process has been established. Recent work has also begun in the field of molecular electronics.

Availability: We welcome collaborative research projects consistent with the research goals of the NIST semiconductor program. Work is performed in cooperation with the technical staff of the laboratory.

The most productive arrangements begin with development of a research plan with specific goals. The commitment of knowledgeable researchers to work closely with our staff and the provision of equipment and other needed resources are required. Because hazardous materials are present, laboratory staff must supervise all research activities.

Contacts: Russell Hajdaj, Eric S. Johnson, Loren Linholm

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Mobile Solar Tracker Facility

NIST's mobile solar tracking facility is used to characterize the electrical performance of photovoltaic panels. It incorporates meteorological instruments, a solar spectroradiometer, a data acquisition system, and a single-channel photovoltaic curve tracer. Precision spectral pyranometers are used to measure total (beam plus diffuse) solar radiation. We use two instruments to provide redundant measurements. We use a pyrheliometer to measure the beam component of solar radiation and measure long-wave radiation, greater than 3 micrometers, using a precision infrared radiometer. A three-cup anemometer assembly measures wind speed.

We measure the ambient temperature using a thermocouple sensor enclosed in a naturally ventilated multiplate radiation shield.

The solar tracker's photovoltaic array tester measures and records the current and voltage characteristics of the panels under evaluation. The array tester is capable of measuring panels or groups of panels with power outputs ranging from 10 watts to 36 kilowatts. We record and use irradiance and temperature loads from a reference cell and thermocouple probe to normalize the data to user-selected loads of irradiance and temperature. In addition to sweeping the panel I-V curve and storing the measured values, the curve tracer calculates the values of maximum output power, open circuit voltage, closed circuit current, and fill factor. The data acquisition system can accommodate up to 60 transducers.

Capabilities: The mobile solar tracking facility can be operated in the following tracking modes:

azimuth and elevation tracking
azimuth tracking
elevation tracking
azimuth tracking with user selected offset
elevation tracking with user selected offset
fixed position

Up to four photovoltaic modules can be mounted on the facility simultaneously. The facility can be operated over an azimuth range of ± 135° and over an elevation range from horizontal to vertical.

Availability: This apparatus may be available for use by those outside NIST, but it must be operated by BFRL staff. Collaborative programs may be arranged on a cost reimbursable basis.

Contact: A. Hunter Fanney

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Mobile Transient Reception/Transmission Systems

Several broadband antennas are available for transmission and reception of transient signals. By combining these antennas, broadband transient generators, high-speed transient digitizers, and sophisticated signal processing, a variety of measurements are possible.

Capabilities: The capabilities are related closely to the desired application. With existing antennas, it is possible to transmit transient signals with spectral components from 25 megahertz up to 14 gigahertz and field amplitudes of greater than 200 volts per meter. Receiving antennas have similar frequency restrictions and sensitivities determined by the receiving equipment. Sensitivities of better than 500 volts per meter are typical.

Applications: Test applications include:

in-situ shielding effectiveness measurements on large test objects (e.g., autos, aircraft);
non-invasive evaluation of the electrical properties of materials;
reflectivity of dissipative macrostructures (e.g., RF absorber, ferrite tiles);
evaluation of reverberation chamber and anechoic chamber performance; and
electrostatic discharge radiated fields.

Availability: This system is readily available for interesting applications. Higher frequencies, amplitudes, and greater sensitivities are possible but require fabrication of special antennas.

Contact: Robert Johnk

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Near-Field Scanning Facilities for Antenna Measurements

These automated facilities are designed to measure the near-zone phase and amplitude distributions of the fields radiated from an antenna test. Mathematical transformations are used to calculate the desired antenna characteristics.

Capabilities: Near-field data can be obtained over planar, cylindrical, and spherical surfaces; the planar technique is the most popular. Efficient computer programs are available for processing the large quantities of data required. When operated in the planar mode, the facility is capable of measuring over a 4.5-meter-square area with probe position errors of less than ± 0.01 centimeter. Improved position accuracy is possible with further alignment, especially over smaller areas. Antennas with apertures up to about 3 meters in diameter can be measured with a single scan. The facility has been used successfully over the frequency range 750 megahertz to 75 gigahertz. It incorporates provisions for scanning larger antennas in segments.

Applications: Primary applications include:

antenna characteristics,
antenna diagnostics, and
probe calibrations.

Antenna Characteristics: The facility is used primarily for determining the gain, pattern, and polarization of antennas. Accuracies are typically ± 0.15 decibel for absolute gain and ± 0.10 decibel/decibel for polarization axial ratio. Patterns can be obtained down to the -50 decibels to -60 decibels levels with side lobe accuracy typically about ± 1.0 decibel at the 40 decibel level. (The exact uncertainties depend on the frequency, type, size of antenna, and other factors.) Near-field data also can be used to compute near-field interactions (such as mutual coupling) of antennas and radiated field distributions in the near zone.

Antenna Diagnostics. Near-field scanning is also a valuable tool for identifying problems and for achieving optimal performance of various types of antenna systems. It has been used to advantage in locating faulty elements in phased-array antennas and for adjusting feed systems to obtain the proper illumination function at the main reflector. Phase contour plots of the near-field data also can be used to determine surface imperfections in reflectors used for antennas or compact ranges.

Probe Calibrations. A spherical probe calibration facility serves as a far-field range for measuring the receiving characteristics of probes used to obtain near-field data. These measurements are required to determine the probe coefficients, which, in turn, are used to calculate accurate, probe-corrected, far-field gain and pattern characteristics of an antenna.

Availability: Two kinds of arrangements can be made to use this facility. NIST staff can perform specified tests or measurements on a reimbursable basis. In this case, the customer has no direct use of the facility; all measurements are performed by NIST staff, and the customer is issued a test report. As an alternative, work may be performed on a cooperative basis with NIST staff. This arrangement permits the user the advantage of developing firsthand knowledge of the measurement processes, and the user is responsible in large part for the accuracy of test results. In either case, arrangements need to be made well in advance, and reimbursement is required for the facility use and time of NIST staff involved.

Contact: Katherine MacReynolds

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Neutron Interferometer and Optics Facility

The Neutron Interferometry and Optics Facility (NIOF) located at the NIST Center for Neutron Research is one of the world's premier user facilities for neutron interferometry and related neutron optical measurements. A neutron interferometer splits and then recombines neutron waves. This gives the interferometer its unique ability to access experimentally the phase of neutron waves. Phase measurements are used to study the magnetic, nuclear, and structural properties of materials as well as fundamental questions in quantum physics. Related, innovative neutron optical techniques for use in condensed matter and materials science research are being developed.

Capabilities: Neutrons are extracted from a dual-crystal parallel-tracking monochromator system, providing neutron energies in a range of 4 meV to 20 meV. Neutrons are counted with integrating ³He detectors or by high-resolution position-sensitive detectors with a resolution better than 50 µm. The sensitivity of the apparatus is enhanced greatly by state-of-the-art thermal, acoustical, and vibration isolation systems. To reduce vibration, the NIOF is built on its own foundation, separate from the rest of the building. The position of the interferometer is maintained to high precision by a computer-controlled servo system. The result is a neutron interferometer facility with exceptional phase stability (5 × 10^-3 rad/day)and fringe visibility (70 percent). The vibration isolation is -7 g; the positional stability, 2 µm in translation and 1 µrad in rotation; and the temperature stability, 0.1 K/day.

Applications: NIOF applications include neutron phase contrast imaging, neutron tomography, neutron Fourier spectroscopy for surface studies, determination of hydrogen content in materials, measurement of bound coherent scattering lengths, small-angle neutron scattering studies with perfect crystals, tests and demonstrations of quantum principles with matter waves, measurement of the neutron-electron scattering length, and phase transition studies.

Availability: Beam time on the NIOF is available to qualified scientists from the United States and abroad, subject to approval and scheduling by the facility oversight committee.

Contact: Muhammad Arif

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NIST Beowulf System

The NIST Beowulf System (NBS) is a 128-processor parallel computing cluster. Its nodes consist of industry-standard personal computers, which were originally purchased by the Bureau of the Census for processing the 2000 Census and transferred to NIST in the autumn of 2000. The nodes are linked in groups of 16, communicate via fast Ethernet, and implement the Beowulf clustering system originally developed at NASA. The NBS cluster is used for computational simulation of Bose-Einstein condensation and coherent matter-wave systems, quantum information processing devices, electronic and optical properties of materials, and electromagnetic wave propagation. We welcome proposals for collaborative research that explore the use of parallel computing in such problems.

Contact: Charles Clark

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NIST Center for Neutron Research (NCNR)

The NIST Center for Neutron Research (NCNR) is a national center for the application of neutron methods to a variety of problems of national concern. A major component of the center is the cold neutron source and guide hall, the first major facility in the United States devoted to cold neutron research. The cold source offers modern cold neutron instrumentation unique in this country. A wide range of internal and external research and measurement programs have benefited from the broad range of capabilities at the NCNR available to researchers from industry, universities, and government laboratories.

The NCNR operates as a national facility open to all qualified researchers. Under the general user program, the available time is allocated by a program advisory committee on the basis of scientific merit of written proposals. Participating research teams—which constitute another mode of utilization—are responsible for design, construction, and maintenance of the facilities in return for collaborative access to a fraction of the available time. Annually more than 1,700 researchers from government organizations, U.S. industrial and university laboratories, and foreign laboratories participated in research at the facilities, either collaboratively with NIST staff or on a proprietary basis. For further information, visit www.ncnr.nist.gov.

Crystallography and Microstructure

BT-1 high-resolution neutron powder diffractometer. This instrument is used to obtain neutron powder diffraction data for crystallographic analysis by the Rietveld method or for other characterization purposes. It is a 32-detector instrument that can be used with three different monochromators and two different incident Soller collimators to tailor the instrument response to the needs of the experiment. Diffraction peak widths are as low as 10 minutes (d/d = 8 × 10^-4) with ideal Gaussian line shapes. The instrument can be used with furnaces, refrigerators, and cryostats so that data may be collected at temperatures from 0.3 K to 1200 K, and magnetic fields to 12 T. For room-temperature data collection, a six-position sample changer is available.
BT-5 Perfect Crystal Diffractometer for Ultra-High Resolution Neutron Scattering (USANS). The newest instrument for small-angle scattering at the NCNR is a Bonse-Hart type, perfect crystal diffractometer. This instrument extends the measurement range of the pinhole collimation SANS instruments (at NG-1, NG-3, and NG-7) to larger sizes by over an order of magnitude, i.e., to over 5000 nm. The instrument utilizes two large triple-bounce channel-cut Si (220) perfect crystals to achieve angular resolution of a fraction of an arcsec. This instrument is used to characterize micrometer-scale (100 nm to > 5000 nm) structure in, for example, gels, composites, engineering alloys, structural ceramics and porous media. This instrument is part of the NSF/NIST Center for High Resolution Scattering.
BT-8 diffractometer. This is a state-of-the-art diffractometer for residual stress, texture, and single-crystal studies. A basic monochromator drum has been modified to safely allow take-off-angles up to 120 degrees for high-resolution diffraction measurement of residual stresses. Unique primary and secondary beam-aperture systems, which allow a choice of potential sampling volumes from 5 × 5 × 5 mm³ down to 1 × 1 × 1 mm³, are incorporated. Each system translates toward or away from the sample to facilitate the study of large material structures or components without requiring realignment of apertures or repositioning of samples. The sample table has 170-millimeter translational motion in the x, y, and z directions and can accommodate samples up to 100 kg. Among the other features are a new 1-millimeter resolution position-sensitive detector system and a three-crystal monochromator system with remote selectability. One of the three is a double-focusing Si monochromator, with variable horizontal curvature.
NG-3 30-meter small angle neutron scattering instrument. Sponsored by the National Science Foundation as part of the Center for High Resolution Neutron Scattering, this instrument is installed on a dedicated neutron guide, NG-3. Designed to cover a wide Q-range, from 0.015 nm^-1 to nearly 6 nm-¹, it is suitable for examining structural features in materials ranging from roughly 1 nm to 500 nm.
NG-7 30-meter small-angle neutron scattering instrument. The 30-meter small-angle neutron scattering (SANS) instrument on neutron guide NG-7 is virtually identical to the NG-3 SANS. It is sponsored by NIST, the ExxonMobil Research and Engineering Co., the University of Minnesota, and the NSF-funded consortium Cold Neutrons for Biology and Technology comprised of researchers from the University of California at Irvine, the University of Pennsylvania, Rice University, Duke University, and Carnegie-Mellon University.
Together, the 30-meter SANS instruments combine long flight paths and variable collimation to provide flexibility, angular resolution, and beam intensities that compare favorably with any SANS instruments in the world. Large-area position-sensitive detectors provide exceptional sensitivity to materials structures ranging from roughly 1 nm to 500 nm. Computer automated equipment is available for maintaining samples at temperatures from 4 K to 700 K and in magnetic fields up to 2 T (20 kG). To extract structural information from the data, the researchers analyze SANS patterns with an interactive color graphics system and related programs. Polarized neutron capabilities are available on the NG-3 30-meter instrument.
NG-1 8-meter small-angle neutron scattering instrument. The 8-meter SANS instrument is located at the end of neutron guide NG-1 where the guide cross section is 50 mm × 50 mm. This is a moderate resolution instrument suitable for examining structural features in materials from roughly 1 nm to 100 nm. This SANS instrument is used primarily for the study of polymers.
NG-7 NIST/IBM/University of Minnesota neutron reflectometer. Neutron reflectometry probes the neutron scattering density at depths up to several thousand angstroms, with an effective depth resolution of a few angstroms. What is measured is the profile of reflectivity as a function of angle beyond the critical angle for total external reflection for samples that present a smooth, flat surface, preferably several square centimeters in area. The method is extensively used for studies of polymer and biological surfaces, Langmuir-Blodgett films, and thin films and multilayers of metals and semiconductors, both magnetic and non-magnetic. This cold neutron reflectometer permits routine measurement of reflectivities as low as 10^-7 in typical run times of a few hours. Independent movement of both sample and detector allows measurement of off-specular scattering. A position-sensitive detector permits simultaneous measurement of specular and off-specular scattering.
NG-1 cold neutron reflectometer with polarized beam option. This reflectometer is used in investigations of magnetic multilayers, artificial biological membranes, semiconductor surfaces, and other materials and phenomena in surface and interfacial science. In contrast to the reflectometer on guide NG-7, the sample surface geometry is vertical rather than horizontal. Reflectivities below 10^-8 can be measured. It has full polarized beam capability, provided by transmission supermirror polarizers. The incident beam can be polarized, and polarization analysis of the reflected beam can be performed in a routine fashion. Polarization efficiencies as high as 98 percent are possible.

Materials Dynamics—Medium Resolution, Incident Neutrons: E>5 meV

BT-2 triple-axis/polarized-beam spectrometer. This instrument is used extensively for magnetic scattering studies. It can be operated either as a standard triple-axis spectrometer or as a polarized-beam spectrometer, depending on the monochromator crystal choice, and has an incident neutron energy range from 5 meV to 54 meV. The monochromator can be selected to be a pyrolytic graphite (002) crystal for standard 3-axis operation or a ferromagnetic Heusler alloy crystal for polarized beam experiments. Remotely positionable filters, either 15.2 cm (6 inches) of cooled (77 K) polycrystalline Be, or 5.1 cm (2 inches) of pyrolytic graphite, may be inserted in the beam before the monochromator. The collimator housings before and after the sample position have been designed to provide guide fields for polarized beam operation, and the Soller collimators and blades are made from non-magnetic materials for the same reason. Spin-rotator devices can be mounted before and after the sample position to flip the neutron spins. There is also a guide field that can be selected by computer control to be either vertical to the scattering plane or in it. An extensive variety of ancillary equipment to control the sample environment is available.
BT-4 triple-axis/filter-analyzer spectrometer (FANS). This inelastic scattering instrument offers choices for analyzer and monochromator that make it the most versatile of the thermal-neutron scattering instruments at NIST. One may use either the standard triple-axis analyzer or a cooled (77 K) filter analyzer, which covers a solid angle of about 4 percent of 4 pi steradians. The filter analyzer option employs a combination of polycrystalline Be, followed by a block of polycrystalline graphite. The latter determines the effective analyzer energy resolution, which in this case is 1.1 meV. The monochromator choices are Cu (220) for higher resolution studies or for measurements with higher incident neutron energies, and pyrolytic graphite (002) for lower incident energies, with moderate resolution and higher beam intensities. The incident neutron energy range is from 3.5 meV to 250 meV. Monochromator changes can be made within a few minutes from the instrument console. Both monochromators are vertically focusing with a radius of curvature, which changes to optimize intensity during the course of data acquisition.The instrument is particularly well-suited to measurements of the vibrational spectra of materials.
BT-9 triple-axis spectrometer. This instrument is a conventional triple-axis spectrometer, usually employing a vertically focusing pyrolytic graphite monochromator. A new monochromator assembly is in construction, which will permit remote selection of a focusing Cu (220) monochromator, Ge (311) or PG (002), providing an incident energy range from 10 meV to 100 meV.
BT-7 thermal triple-axis spectrometer. This instrument currently employs a double monochromator system of pyrolytic graphite to produce a fixed incident energy of 13.5 meV. However, a new state-of-the-art thermal triple axis instrument is under construction and will be installed in 2003. This new instrument takes full advantage of the large diameter beam tubes at the NCNR and will employ horizontal focusing for both monochromator and analyzer systems. Combined, these improvements will boost the observed signal by two orders of magnitude for problems where the relaxed Q resolution can be employed. Full polarized beam capability also is under development and will be implemented as soon as available.

Materials Dynamics—High Resolution, Incident Neutrons E=1-15 meV

Spin-polarized triple-axis spectrometer (SPINS). This instrument is part of the Center for High Resolution Neutron Scattering supported by the National Science Foundation. Two-thirds of its beam time is reserved for guest researcher experiments through the NCNR proposal system. Located on guide NG-5, it is currently operated in four different modes: a conventional triple-axis mode, a horizontally focusing analyzer mode, a flat-analyzer mode employing a position-sensitive detector, and a polarized beam mode. A vertically focusing pyrolytic graphite (PG) monochromator produces a high intensity beam with a wavelength from 2.2 Å to 6.1 Å (17 meV down to 2 meV). Energy resolution is in the range of 30 meV to 1 meV, depending on incident wavelength and collimation. In the horizontally focusing analyzer mode, a multicrystal analyzer with 11 independently rotating 2 cm × 15 cm (width × height) PG blades can be used to focus scattered neutrons of a particular energy onto a single detector (diameter of 2.54 cm and length of 15 cm) and yield a signal increase of a factor of approximately four by relaxing the Q (wave vector) resolution. Alternatively, the analyzer can be used in flat mode with a position-sensitive detector to simultaneously collect data over a region of wave vector and energy. In the polarized beam mode of operation, supermirror transmission polarizers, consisting of a stack of single-crystal Si plates with Fe/Si supermirror coatings, are inserted in the incident and scattered beams.
NG-6 Fermi-chopper time-of-flight spectrometer. This spectrometer directs a monochromatic pulse of neutrons at a sample and measures the energies of scattered neutrons by using the time a neutron takes to travel from the sample to the detectors. The pulsed monoenergetic neutron beam is produced by a combination of monochromator crystals and a Fermi chopper. The double monochromator consists of two PG crystals, one of which can be curved vertically to focus neutrons onto the sample position. The curvature can be varied automatically to adjust for changes in monochomator-sample distances as the incident energy is varied. Two Fermi choppers with different blade curvatures are available. An oscillating radial collimator between the sample and detectors eliminates scattering from cryostat and furnace shields around the sample position. The range of incident energies available on this instrument, the first of two time-of-flight spectrometers operating in the NCNR, is from 2.2 meV to 15 meV. With the energy resolution ranging from 60 µeV to 1000 µeV, the spectrometer allows a broad range of quasielastic scattering experiments on diffusive motions in solids and liquids, and inelastic scattering experiments on magnetic and vibrational excitations.
Disk chopper time-of-flight spectrometer (DCS). The DCS measures the energies of scattered neutrons using the time a neutron takes to travel from the sample to the detectors. The pulsed monoenergetic neutron beam is produced by a set of disk choppers which rotate at speeds up to 20,000 rpm. There are three slots in the disks.