relations between laboratory measured efficiency and energy used by cooks were not significantly different, (2) the cooking practices of the 58 cooks were sufficiently alike that no major modification to the laboratory test method was required, (3) homemakers showed greater variability in energy use than did laboratory tests with the same ranges, (4) energy consumption labels on appliances should include information about that variability, and (5) evaluation of range efficiencies could be done with only three to five energy intensive meals.

NBSIR 78-1558. Development of hydrogen and hydroxyl contamination in thin silicon dioxide thermal films, S. Mayo and W. H. Evans, 39 pages (Mar. 1979). Order from NTIS as PB293556.

Key words: dry oxidation of silicon; hydrogen contamination; hydroxyl contamination; semiconductor device fabrication; silicon; silicon dioxide; thermal oxidation of silicon. Hydrogen and hydroxyl incorporation into thin silicon dioxide films thermally grown on silicon in dry oxygen atmospheres contained in resistance-heated fused silica or polycrystalline silicon tubes is analyzed. The mechanisms leading to incorporation of these impurities in the film are discussed in terms of trace water and hydrocarbon contamination in the oxygen used, room ambient humidity permeation through the fused silica tube, the silicon wafer preparation prior to oxidation, and other environment factors. The most significant reactions occurring the water-silica-silicon system during wafer oxidation at temperatures in the range from 800 °C to 1200 °C are discussed. It is shown that, during the oxidation period required to grow a 100-nm thick silicon dioxide film on a < 100 > silicon wafer in nominally dry oxygen containing water contamination in the ppm range, the introduction of hydrogen and hydroxyl contamination into the oxide film can be explained in terms of the water-silica interaction. The use of polycrystalline silicon oxidation tubes is discussed with reference to the inherent water gettering action of silicon at oxidation temperatures.

NBSIR 78-1564. Tabulation of published data on electron devices of the U.S.S.R. Through December 1976, C. P. Marsden, 137 pages (Dec. 1978). Order from NTIS PB291959.

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Key words: electron devices; electron tubes; semiconductors; U.S.S.R.

This tabulation includes data on U.S.S.R. electron devices as collected from publications, mostly handbooks published by the various ministries and institutes of the U.S.S.R. Information is given on all active devices ranging from receiving to microwave devices, semiconductor devices, and miscellaneous devices such as photographic flash tubes and thermistors.

NBSIR 78-1569. End-of-year-report. Micromechanical properties of beryllium and other instrument materials, B. W. Christ, R. S. Polvani, and R. J. Hocken, 42 pages (Oct. 1978). Order from NTIS as PB299654.

Key words: beryllium; dimensional stability; gyroscope; instrument materials; microcreep; micromechanical properties.

This research program was initiated on October 1, 1977. It is sponsored by the Office of Naval Research. The objective of the program is to evaluate and understand the micromechanical properties of beryllium and other instrument materials for use in gryoscopes, so that dimensional stability can be improved. Improved dimensional stability is expected to lessen the need to periodically align gyroscopes in service.

NBSIR 78-1571. Sprinkler-vent and spray nozzle systems for fire protection of openings in fire resistive walls and

ceilings-The state-of-the-art and a plan for future research work, J. G. O'Neill, 29 pages (Jan. 1979). Order from NTIS as PB291889.

Key words: automatic sprinkler; building code; smoke movement; spray nozzle; stairway protection; ventilated stair.

A review of literature was conducted to determine the stateof-the-art of automatic sprinkler, sprinkler-vent and spray nozzle methods of protecting openings in fire resistive assemblies. A review of nationally used model building codes and standards indicated that they have varying provisions for these types of systems. Generally, the use of these systems is only applied to escalator openings in fully sprinklered buildings. Previous experimental work, however, demonstrated that these systems can also be effective in preventing passage of heat and smoke through other types of openings in structural assemblies.

An outline of a planned research project and a description of the test facility are given. The project will develop design parameters for sprinkler-vent and spray nozzle methods for protecting stairways and other openings through floor ceiling assemblies. Results from this project may suggest improvements to current codes and standards involving these systems and possibly permit their wider use in unsprinklered buildings.

NBSIR 78-1573. Properties and interactions of oral structures and restorative materials, J. M. Cassel, 94 pages (Dec. 1978). Order from NTIS as PB289913.

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Key words: accelerator; alloy; base metal; casting; composite; cyanoacrylate; dental alloy; initiator; resin; wear. To improve the storage stability of dental composite resin systems, alternative catalyst systems to the commonly used benxoyl peroxide-tertiary amine are being developed. Increased storage stability is attainable with organic peresters hydroperoxides but requires more efficient accelerators than the presently used amines. Ascorbic acid or ascorbyl palmitate offer promise as useful accelerators which give good biocompatibility. To develop more reactive amine accelerators with perhaps less toxicity than those currently in use, pdimethylamino-phenylacetic acid (or ester derivatives) and dimethylaminoglutethimide were synthesized and shown to yield composite restorative specimens of good mechanical strength and color stability. A wide range of cyanoacrylates from the simplest, 2-ethyl cyanoacrylate, to the more complex type such as viscous isoamyl product have been examined for their capacity to achieve and retain bonding between acrylic resin and dentin. Very high initial bond strengths were achieved with isobutyl-2-cyanoacrylate on dentin pretreated with dilute acid but a one-month thermal cycling test in water indicated the bonding was not sufficiently stable. Initial pin on disc wear measurements with a synthetic hydroxyapatite pin have shown promise.

A pattern modification to reduce variability in the alloy castability test has been developed. Variations in the number of firing cycles and amount of condensation of green porcelain have been shown to cause significant differences in dimensional characteristics on cooling of fused dental porcelain.

NBSIR 78-1575. Erosion by solid particle impact, A. W. Ruff and S. M. Wiederhorn, 103 pages (Jan. 1979). Order from NTIS as PB291988.

Key words: abrasives; ceramics; erosion; impact; metals; particle erosion; wear.

A review of the methods and findings associated with solid particle impact erosion of metals and ceramics is presented. Modern theories of particle erosion and critically reviewed experimental observations are brought together and compared.

Conclusions regarding the present state of understanding of erosion are given.

NBSIR 78-1576. Final Report—Proximity-vision system for protoflight manipulator arm, J. S. Albus, 22 pages (Aug. 1978). Order from NTIS as PB291335.

Key words: depth image; proximity sensor; robot vision; teleoperator vision; wrist-mounted TV.

The NBS Proximity-Vision System consists of two separate but complementary subsystems: 1) A solid-state TV camera with 128 × 128 resolution elements mounted on the manipulator wrist. Coordinated with this camera is a high intensity strobe flash system with optics which project a thin fan-shaped plane of light into the region viewed by the camera. 2) A pair of close-range infra-red proximity sensors mounted in the fingertips.

The system is built for a manually controlled teleoperator. However, the design is also suitable for computer image analysis in the control of an autonomous robot manipulator.

NBSIR 78-1577. Data bases available at the National Bureau of Standards Library, D. Cunningham, 53 pages (Mar. 1979). Order from NTIS as PB293170.

Key words: bibliographic data bases; computerized data bases; information storage and retrieval systems; librariesautomation; machine-readable-bibliographic data.

An alphabetical listing of data bases available on-line at the National Bureau of Standards (NBS) Library is listed by either acronym or full title of the data base. Other additional information includes description of the data base, period of coverage, producer(s), corresponding hard copy, principal sources and vendors. A general subject and a cross reference index to the data bases is also supplied.

NBSIR 78-1581. Annual Report 1978. Office of nondestructive evaluation, H. Berger and L. Mordfin, Eds., 58 pages (Jan. 1979). Order from NTIS as PB291946.

Key words: acoustic; annual report; eddy currents; inspection; magnetic particles; nondestructive evaluation; penetrants; radiography; statistics; ultrasonics; visual-optical tests.

This report summarizes the activities of the National Bureau of Standards (NBS) Nondestructive Evaluation (NDE) Program. It emphasizes activities over the Fiscal Year, 1978. However, since this is the Program's first Annual Report, some material is included to summarize activities since the Program was formally instituted in June 1975.

NBSIR 78-1584. Submarine compartment fire-Study-fire performance evaluation of hull insulation, B. T. Lee and J. N. Breese, 49 pages (May 1979). Order from NTIS PB298264.

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Key words: combustion products; fire barrier coatings; fire growth; flame spread; foam insulation; heat release; interior finish; laboratory fire tests; material ignitability; submarine compartment.

Certain foam rubber materials which are currently used to insulate the interior of submarines are shown to possess a serious fire risk potential. Flame spread tests often do not adequately reflect the fire hazard potential of these materials. It is shown that compartment fire testing is the only satisfactory method of evaluating these kinds of materials at the present time.

Fire barrier coatings for protecting these hull insulations are also investigated. Two candidate coatings are found to prevent full fire involvement of an insulated compartment following a moderately large flame exposure and at the same time meet the

Navy's elasticity requirement for submarine application. The study includes comparisons of model and prototype compartment fire behavior and demonstrates the practicality of using quarter-scale fire tests for screening compartment finish materi

als.

NBSIR 78-1586. Fire safety guidelines for vehicles in a Downtown People Mover system, R. D. Peacock, 57 pages (Jan. 1979). Order from NTIS as PB292600.

Key words: emergency communications; emergency evacuation; fire detection; fire safety; fire suppression; mass transportation; material flammability; people movers; smoke.

The results of a study to formulate fire safety guidelines to be required for vehicles used in Downtown People Mover (DPM) systems for the movement of people in a congested urban area are presented. Through a review of the design features of existing people mover vehicles and systems, and a review of proposed new systems, fire scenarios are developed and guidelines suggested to minimize the fire risk to passengers. Methods and criteria, based on established test procedures, are proposed for assessing the flammability and smoke generation of interior finish and furnishing materials. Fire and smoke detection and suppression equipment are recommended, along with proposed guidelines for emergency evacuation provisions and emergency communication requirements.

An extensive bibliography of flammability in fixed guideway transit systems is included.

NBSIR 78-1590 (NASA). Loose-particle detection in microelectronic devices, J. S. Hilten, P. S. Lederer, J. F. Mayo-Wells, and C. F. Vezzetti, 73 pages (Jan. 1979). Order from NTIS as PB290679.

Key words: acoustic emission; co-shock; couplant; detection; electronic package; impact noise; microcircuit device; particle detection; particle impact noise detection; PIND; pre-shock; seeded specimens; transducer.

The work described constitutes an evaluation of the test procedures and apparatus specified in MIL-STD-883, Test Method 2020, Particle Impact Noise Detection Test. The major experimental effort described—a comparison of procedures and apparatus—is based on the use of specially prepared specimen device packages known either to have or not to have a particle present. Other experimental efforts reported include characterization of the accelerations imparted to a specimen device by pre- and co-shock apparatus, a brief study of the effectiveness of couplant materials in transmitting mechanical energy to the specimen device, and a comparison of the output signal level from four different ultrasonic detection transducers under otherwise identical test conditions. As part of the plan of work, 252 of the specially prepared devices, representing six package types, were characterized (as containing particles or not) by several test procedures in order to provide a set of specimens for use by the sponsor in a proposed interlaboratory evaluation of PIND testing. Problems associated with this effort are discussed. Results of the work are presented, together with conclusions and recommendations for further work. A result of interest is that the acceleration imparted by the single sample of the pre-test shock apparatus tested is on the order of 1.5 times the maximum specified by the Test Method.

NBSIR 78-1712. Report to AID on an NBS/AID workshop on standardization and measurement services, H. S. Peiser, C. C. Raley, and P. M. Odar, Eds., 156 pages (May 1979). Order from NTIS as PB296326.

Key words: AID; assistance; developing economies; foreign relations; industrializing nations; international relations; LDC's; measurement services; standardization.

From October 1-18, 1977, a Workshop was held at the National Bureau of Standards, Gaithersburg, and at selected universities, research institutes, standards developing organizations, test centers, and industrial companies, under the sponsorship of AID. The object of the Workshop was to give standards officials of industrializing nations insight into the standards and measurement systems of the United States and the role of the National Bureau of Standards, so that these officials might consider what parts of the U.S. system might usefully be adapted to conditions in their home countries. An exchange of standardization experience in each of the participant's countries was presented by delivered papers which are reproduced here. Countries represented included Argentina, Bangladesh, Bolivia, Egypt, Ghana, Indonesia, Iran, Kenya, Korea, Phillipines, and Thailand. In addition, there were representatives from the Arab Organization for Standardization and Metrology and the International Organization for Standardization.

NBSIR 79-1588. Interlaboratory evaluation of the attic floor radiant panel test and smoldering combustion test for cellulose thermal insulation, J. R. Lawson, 38 pages (Feb. 1979). Order from NTIS as PB293159.

Key words: attic floor radiant panel; cellulose thermal insulation; critical radiant flux; flame spread; smoldering combustion; test methods.

An interlaboratory test program was conducted to provide estimates of repeatability and reproducibility of fire tests for cellulose loose fill insulation. The test methods evaluated were for critical radiant flux, using the Attic Floor Radiant Panel, and for smoldering combustion; they were based on Federal Specification HH-I-515D. Seven commercially manufactured cellulose thermal insulations marketed for residential use were evaluated by each procedure. An additional set of four replicate hardboard specimens were tested by each participant using the Attic Floor Radiant Panel. Nine laboratories conducted the Attic Floor Radiant Panel test, and ten conducted tests for smoldering combustion. The testing was conducted during the month of June 1978. The participating laboratories were surveyed prior to testing in order to ensure conformance to the critical details of the test apparatus and procedures.

The between-laboratory coefficient of variation for critical radiant flux ranged from 13 to 30 percent with an average for seven insulation materials of 21 percent. Estimated precision levels of repeatability and reproducibility for the Attic Floor Radiant Panel test when compared to other standard flame spread tests and materials are favorable. Data from the Smoldering Combustion test was evaluated on a pass/fail basis with agreement by nine of ten laboratories for six of the seven materials tested. Seven of ten laboratories also agreed on the seventh material.

Based on work of this study, there is reasonable assurance that results from different laboratories evaluating the same material for compliance with Federal Specification HH-I-515D will be consistent.

NBSIR 79-1591. Semiconductor technology program-Progress briefs, W. M. Bullis, Ed., 12 pages (Jan. 1979). Order from NTIS as PB294846.

Key words: electronics; integrated circuits; measurement technology; microelectronics; semiconductor devices; semiconductor materials; semiconductor process control; silicon.

This report provides information on the current status of NBS work on measurement technology for semiconductor materials, process control, and devices. Results of both inhouse and contract research are covered. Highlighted activities include studies of: laser annealing of low-fluence implants in sil

icon; analysis techniques for spreading resistance profiling measurements; Hall effect measurements in two-layer structures; incorporation of hydrogen and hydroxyl impurities in silicon dioxide films; an integrated gated-diode electrometer test structure; defect-density profiling by constant-capacitance deep-level transient spectroscopy; and a spatial integrity test pattern for electrical measurement of intra- and inter-die line-width variations. In addition, brief descriptions of new and selected ongoing projects are given. The report is not meant to be exhaustive; contacts for obtaining further information are listed. Compilations of recent publications and publications in press are also included.

NBSIR 79-1591-2. Semiconductor technology program-Progress briefs, W. M. Bullis, Ed., 12 pages (Mar. 1979). Order from NTIS as PB298063.

Key words: electronics; integrated circuits; measurement technology; microelectronics; semiconductor devices; semiconductor materials; semiconductor process control; silicon.

This report provides information on the current status of NBS work on measurement technology for semiconductor materials, process control, and devices. Results of both inhouse and contract research are covered. Highlighted activities include studies of: process-induced radiation damage; resistivity-dopant density relationships in silicon; spreading resistance measurements; spreading resistance profiling; cross-bridge sheet resistor test structure; PIND test; and moisture infusion into hermetic packages and conduct of a workshop on power semiconductor devices. In addition, brief descriptions of new and selected on-going projects are given. The report is not meant to be exhaustive; contacts for obtaining further information are listed. Compilations of recent publications and publications in press are also included.

NBSIR 79-1591-3. Semiconductor technology program-Progress briefs, W. M. Bullis, Ed., 12 pages (June 1979). Order from NTIS as PB298064.

Key words: electronics; integrated circuits; measurement technology; microelectronics; semiconductor devices; semiconductor materials; semiconductor process control; silicon.

This report provides information on the current status of NBS work on measurement technology for semiconductor materials, process control, and devices. Results of both inhouse and contract research are covered. Highlighted activities include studies of: reverse-bias second breakdown, an integrated gated-diode electrometer, random fault measurements, pattern generator positional accuracy, intrachip linewidth variation, transient upset in TTL circuits, photoresist sensitometry, optical linewidth measurements, spreading resistance profiling, model spreading resistance data, silicon resistivity SRMs, and sheet resistance measurements. In addition, brief descriptions of new and selected on-going projects are given. The report is not meant to be exhaustive; contacts for obtaining further information are listed. Compilations of recent publications and publications in press are also included.

NBSIR 79-1595. CMOS/SOS test patterns for process evaluation and control: Annual report, March 1 to November 1, 1978, L. W. Linholm, 53 pages (Jan. 1979). Order from NTIS as PB293487.

Key words: CMOS/SOS; process control; process metrology; silicon gate; test patterns; test structures.

The National Bureau of Standards in collaboration with the Jet Propulsion Laboratory, Pasadena, CA, and RCA, Somerville, NJ, has designed a CMOS/SOS test pattern, NBS-16, and

the necessary measurement techniques. RCA is required to process one test pattern wafer with each CMOS/SOS wafer lot being fabricated for the radiation hardened microprocessor chip set. Each test pattern is to be tested at NBS and JPL and recommendations for improvements made to the Air Force Avionics Laboratory (AFAL), the Air Force Materials Laboratory (AFML), and RCA. A second generation test pattern will be designed later based on information and experience obtained from the first. To date, the NBS-16 test pattern has been designed, a pattern generator tape has been delivered to RCA, and the testing hardware and software has been developed. A program schedule and a description and illustration of each test structure are found in the appendices.

NBSIR 79-1596. Studies of flammability test procedures for curtains and drapes, D. E. Hopkins and J. F. Krasny, 25 pages (Mar. 1979). Order from NTIS as PB295039.

Key words: curtains; drapes; fabrics; fire; flammability; international; self-extinguishment; ships; standards.

The Intergovernmental Maritime Consultative Organization (IMCO) is in need of a simple, relevant flammability test method for the curtain and drapery fabrics used aboard ships. Two methods for measuring self-extinguishment of fabrics upon removal of the flame were compared. One was proposed by the United States' representative to IMCO, the other was an adaptation of a recently proposed method of the International Standards Organization (ISO). The effects of variations of the proposed test methods (changes in the ignition flame characteristics, bottom edge or surface ignition, and in the specimen suspension) were also investigated. In general, the relative ranking of the fabrics was not changed, though the individual afterflame time and char length results were affected by some of these variables. The advantages and disadvantages of the two proposed test methods are discussed and an improved method is recommended.

NBSIR 79-1599. Microphone windscreen performance, R. N. Hosier and P. R. Donavan, 85 pages (Jan. 1979). Order from NTIS as PB292967.

Key words: acoustics; flow; insertion loss; microphone; porous sphere; sphere; spheres; wind noise; windscreen; windscreen performance; windscreens.

Measurements were made of the wind-induced noise and acoustic insertion loss of ten microphone windscreens. Eight of these were reticulated polyester spheres of varying porosity. The other two were the metal cage type typically used in long term outdoor noise monitoring. The measurements were made under laboratory conditions for normal and grazing flow incidence at wind speeds up to 14 m/sec. The data show that the windscreens are very different in the amount of wind-induced noise reduction they provide, with some achieving more than 25 dB. In general the foam windscreens provided more windinduced noise reduction than the cage windscreens; however, the cylindrical cage windscreen performed better than any of the foam windscreens for normal flow incidence. The insertion loss measurements proved difficult to make because of the small insertion losses encountered. However, data for grazing flow and normal acoustic incidence show no strong velocity dependence for any of the windscreens tested. Examination of the wind-induced noise spectra provided significant insight into the noise generating mechanisms associated with flow around a porous sphere. Effects of inflow turbulence, self-generated turbulence, mean flow, flow through the sphere, and flow incidence angle were identified. Test results are provided in the form of curves and tables for easy use in evaluating potential wind noise levels in outdoor measurements.

NBSIR 79-1604. A comparison of centrifuge and freezing calorimeter methods for measuring free water in snow, R. N. Jones, 43 pages (May 1979). Order from NTIS as PB296321.

Key words: centrifuge; comparison of measurement methods; free water; freezing calorimeter; hydrology forecasting; microwave remote sensing; snow.

In using microwave measurements in hydrological studies of snowpack or avalanche prediction, the presence of free water in the snow has a strong influence on observed data because it affects the dielectric characteristics. Although several methods are in use for determining the percent of free water in snow, there is very little information in the literature as to how well the various methods agree. This paper reports on a comparison of two popular methods; namely, the centrifuge and the freezing calorimeter. Results from measurements over a two-month period in the Colorado mountains in the winter of 1978 indicate serious disagreement between these two methods. Some reasons for the disagreement are presented and verified. This raises some important questions pertaining not only to what the two methods actually measure, but also which methods may be appropriate for particular applications.

NBSIR 79-1605. A theoretical study of unbalanced ground effects on receiving dipoles, M. T. Ma, 15 pages (May 1979). Order from NTIS as PB296207.

Key words: dipole antenna; ground effect; unbalanced system.

Balanced ground effects on the performance of some antenna systems are relatively well known and can be taken into account by the design engineer. Unbalanced ground effects on a measuring system are, however, more complicated and make a thorough understanding difficult. In this report, specific ground effects on the calibration of a dipole antenna with an arbitrary inclination angle with respect to the ground are analyzed by means of a theoretical model. Numerical results representing this undesired effect are also included.

NBSIR 79-1606. A variational expression for the scattering matrix of a coaxial line step discontinuity and its application to an over moded coaxial TEM cell, I. Sreenivasiah and D. C. Chang, 47 pages (May 1979). Order from NTIS as

PB296324.

Key words: coaxial transmission line; cut-off frequency; equivalent circuit; modal analysis; scattering matrix; step discontinuity; TEM-cell; variational formulation.

A step discontinuity in a coaxial transmission line, where one of the sections is large enough to support both TEM and TM。 modes, may be modeled as a 3-port junction. A variational expression for the (3 × 3) scattering matrix of such a junction is obtained in simple closed form. The scattering matrix, so obtained, is used to analyze the tansmission characteristics of a coaxial TEM cell beyond the cutoff point of the TM。 mode. Finally, an equivalent circuit, along with the expressions for the circuit parameters, is given for the general case where the number of propagating modes in each section is finite but arbitrary.

NBSIR 79-1607. Producing slush oxygen with an auger and measuring the storage characteristics of slush hydrogen, R. O. Voth and P. R. Ludtke, 41 pages (Mar. 1979). Order from NTIS as PB298555.

Key words: cryogenic; hydrogen; oxygen; scraping auger; slush; slush production; slush storage.

Part 1. Producing Slush Oxygen With An Auger: An auger rotating inside a brass tube refrigerated with liquid helium was

used to produce liquid-solid (slush) mixtures of oxygen. The auger produced small particles of solid oxygen so that the resulting mixture could be transferred and sorted. The auger could produce slush continuously in an appropriate system, and it could produce slush at pressures higher than the triple point pressure of the oxygen.

Part 2. Storage Characteristics of Slush Hydrogen: Three long term storage tests were conducted on an Apollo hydrogen vessel. The vessel was filled to 88 percent with normal boiling point liquid hydrogen then the pressure rise rate to 17.6 bar and the venting rate at 17.6 bar were measured. The two other tests were similar except the vessel was filled with slush hydrogen. In one of these tests, the slush was mixed to eliminate thermal stratification. Filling with slush instead of liquid hydrogen increased the storage time before venting by 1.08 to 1.17 times and increased the mass loaded by 1.11 to 1.13 times.

NBSIR 79-1608. Attenuation measurements on optical fiber waveguides: An interlaboratory comparison among manufacturers, G. W. Day and G. E. Chamberlain, 35 pages (May 1979). Order from NTIS as PB296951.

Key words: attenuation; fiber optics; interlaboratory comparison; measurements; optical communications; quality control.

In late 1978, the National Bureau of Standards invited U.S. manufacturers of optical fiber waveguide to participate in an interlaboratory comparison of attenuation measurements. Seven manufacturers performed four different measurements on each of two fibers. The range of results was typically 1 to 1.5 dB/km for fibers with 3 to 7 dB/km nominal attenuation. This report contains the results and an analysis based on additional data taken by NBS.

NBSIR 79-1609. Materials studies for magnetic fusion energy applications at low temperatures-II, F. R. Fickett and R. P. Reed, Eds., 495 pages (June 1979). Order from NTIS as PB299288.

Key words: alloys; fiberglass; mechanical properties; nonmetallics; physical properties; stainless steel.

The reports presented here summarize the work of the low temperature materials research project for the second year of the program. The various projects are outlined and the research results are presented. The major thrust of the measurements has been the evaluation of the low temperature mechanical and physical properties of stainless steel base metal and welds, with particular emphasis on the nitrogen strengthened stainless steels. Aluminum alloys have received some consideration also. Work has been done on the production of nonmetallics, primarily industrial laminates for low temperatue applications and on the measurement of their properties at cryogenic temperatures. The second NBS/DOE Vail workshop was held in October 1978. A brief description is given of that program.

NBSIR 79-1612. Isobutane: Provisional thermodynamic functions from 114 to 700 K at pressures to 700 bar, R. D. Goodwin, 191 pages (July 1979). Order from NTIS as PB299361.

Key words: densities; enthalpies; entropies; equation of state; internal energies; isobars; isobutane; isochores; isotherms; Joule-Thomson inversion; latent heats of vaporization; melting line; orthobaric densities; specific heats; speeds of sound; vapor pressures.

Thermophysical properties of isobutane are tabulated at integral temperatures along isobars over the entire range of fluid states. Results for the compressed liquid, from the triple- to the boiling-point, have been estimated by use of the highly constrained, nonanalytic equation of state, because experimental P-p-T data are lacking in this region.

NBSIR 79-1613. Radar absorber measurement techniques at frequencies above 20 GHz, N. S. Nahman, C. M. Allred, J. R. Andrews, C. A. Hoer, and R. A. Lawton, 70 pages (Aug. 1979). Order from NTIS as PB299576.

Key words: dielectrics; frequency-domain measurements; magnetic materials; microwaves; millimeter waves; permeability measurements; permittivity measurements; radar absorbers; time-domain measurements.

New methods for implementing automatic permittivity/permeability measurements of radar absorber materials for applications primarily above 20 GHz and into the millimeter wave region to about 100 GHz are discussed. A brief review of the state-of-the-art of dielectric and magnetic material measurements is given. Automated time domain and frequency domain methods are considered including time domain automatic network analyzers, correlation measurement systems using noise signal sources, and six-port network analyzers. NBSIR 79-1615. Dispersion and attenuation characteristics of modes in a TEM-cell with a lossy dielectric slab, J. C. Tippet and D. C. Chang, 37 pages (Aug. 1979). Order from NTIS as PB80-105141.

Key words: attenuation; coupled integral equations; dispersion; lossy dielectric slab; modes considerations; TEM-cell. Dispersion and attenuation characteristics of the dominant mode in a TEM cell, loaded with a lossy dielectric slab, are investigated. It is shown that, while the insertion of the lossy material can indeed lower the Q-factor of the higher-order modes, the attenuation of the dominant mode also increases drastically as frequency increases. Correction to that effect must be taken before measurements in the cell are used to correlate those taken in a free-space environment.

NBSIR 79-1618. Helium research in support of superconducting power transmission, D. E. Daney, 61 pages (Oct. 1979). Order from NTIS as PB80-116502.

Key words: cable cool-down; cool-down helium; liquid helium; superconducting power transmission; thermal cycling; thermal stress.

During FY 78, the NBS Thermophysical Properties Division program of supporting research for Superconducting Power Transmission Line (SPTL) development focused on three tasks: 1) Numerical computation of SPTL cool down by both single stream and counter flow methods. 2) Experimental modeling of counterflow SPTL cool down. 3) Thermal cycling of lengths of lead-sheathed model cable destined for testing in the BNL 5th Ave. facility.

The preparation of computer codes and numerical computation of SPTL cool down were completed and the results are given in Section 3. These calculations confirm our original intuitive judgment that cool-down times for the counterflow arrangement can be long-twenty days or more.

Greater than anticipated computer run times and costs required a reduction of effort on experimental modeling of counterflow cool down. Consequently, completion of this task will be delayed until FY 79.

Two sections of cable underwent extensive thermal cycling, and the results of these tests are given in Section 1. The complex structure of the cable leads to unusual (although reproducible) load vs time curves.

Funding limitations required postponement until FY 79 of the experimental evaluation of heat flow sensors as a means of non-intrusive vacuum indication for SPTL vacuum envelopes. This task together with experimental modeling of cool down will form the heart of our program in FY 79.