pleted on about 60 well-characterized inorganic compounds. Information on the d-spacings, relative intensities, cell size, structure type, and density are being published.

Inorganic Materials Studied by Infrared Spectroscopy. Infrared studies of B10 and B11 substituted-anhydrous borates were carried out in the 2,000 to 300 cm-1 range. Spectral bands for all ortho-, pyro- and some meta-borates could be assigned satisfactorily. From correlations between spectra and structure it appears that boron in threefold or in fourfold coordination can be identified on the basis of the infrared spectrum alone. Triangularly coordinated boron is characterized by the presence of strong, broad absorption in the 1,100 to 1,300 cm-1 region. In addition, there is absorption in the 700 to 780 cm-1 region. Both of these characteristic bands are strongly dependent on isotope mass and thus isotopic substitution can be used to differentiate these bands from others occurring in these regions.

The most characteristic feature of tetrahedrally coordinated boron is the presence of strong, broad absorption in the 800 to 1,100 cm-1 region. Also, absorption bands, which are not sensitive to isotope mass and therefore can be distinguished from triangular boron, occur in the 700 to 800 cm-1 region.

These studies were used to predict that tetrahedral coordination of boron occurs in SrB,O,. This was confirmed by single-crystal x-ray diffraction studies.

2.2.5. REACTOR RADIATIONS

During the past year the Reactor Radiations Division was created from the former Reactor Group. The new division continues with its responsibility for the procurement, operation, and maintenance of the National Bureau of Standards Reactor facility, the NBSR, a high-flux, tank-type, heavy water moderated reactor using enriched fuel. The reactor has an eventual power capacity of 20 megawatts, but will operate initially at 10 megawatts, with an in-pile flux of 1014 neutrons per square centimeter per second. It will have 15 beam ports, and will be housed in a building providing 50,000 square feet of usable laboratory space. The reactor is designed to meet the needs of a number of Federal agencies and scientific institutions in the Washington area, and thus has many unique features as a radiation source. Ground was broken and construction started in the past year, with completion scheduled for spring of 1965.

The division has been supervising construction of the reactor with a staff in offices established at the site. Preparations are under way for training operators and generating technical specifications and further hazards analyses in pursuit of an AEC operating license.

The aim of the Reactor Radiations Division is to promote reactor-oriented work of general significance to NBS and of particular significance to the Institute for Materials Research. Staff competencies are being created in three scientific sections in the formative stage. By title, these are the Neutron

Nuclear Physics, Neutron Solid-State Physics, and Radiation Effects Sections. They will not only generate work of their own, but will also embark with other divisions on cooperative projects of mutual interest.

Flux Standardization. The reactor facilities of the Argonne National Laboratory, the Brookhaven National Laboratory, and the Naval Research Laboratory were utilized to begin several research and development programs. An investigation is being made into the absolute measurement of neutron flux relative to thermal flux standardization. Glass beads containing boron and an element that can be activated, for example, dysprosium, have been made by NBS. These beads are to be activated in a neutron beam at the Graphite Reactor of the Brookhaven National Laboratory. If the neutron current density of the beam is measured by absolute neutron counting, the glass beads can be calibrated for measuring an unknown flux. Boron added to the glass makes a bead that is essentially black to thermal neutrons.

Research and development effort began on a fast neutron spectrometer for reactor spectrum fast neutron flux standardization. The graphite reactor at the Brookhaven National Laboratory is being used as the neutron source. A semiconductor He3 spectrometer is used for neutron measurements. The system will ultimately assist radiation effects studies at NBS by characterizing the fast flux spectra of the NBSR.

Molecular Motion. The research reactor, CP-5, at Argonne National Laboratory was used by members of the NBS staff to study the molecular motions in solids and liquids. Neutrons with energies of the order of or lower than the energies of the molecular motions to be studied were scattered from the sample, and their energy change was measured by a time-of-flight spectrometer. The measurements provided direct information on the molecular binding in ammonium salts and on the motion of methyl groups in various compounds.

Lattice Vibrations. The lattice vibrations of gray tin (diamond structure) and white tin (tetrahedral structure) were studied using the slow neutron facility at Brookhaven National Laboratory. The energies of the peaks in the phonon spectrum of gray tin are in good agreement with the corresponding peaks in silicon and germanium if the energies are scaled using the square root of the atomic mass. This implies that the interatomic forces are of the same order of magnitude in the diamond structures— silicon, germanium, and gray tin.

Neutron Moderation Study. Preliminary results were obtained in a second experiment at Argonne to measure the ability of various materials to moderate neutrons to subthermal energies. A large volume of heavy water ice (D2O) about 18 inches in diameter held at 22 °K was shown to be quite effective.

Neutron Optics. A study of the properties of several neutron optical devices was undertaken at the Brookhaven National Laboratory Graphite Research Reactor. These experiments centered mainly on the investigation of the properties of curved totally reflecting pipes and curved totally reflecting soller collimators.

A neutron reflecting pipe in connection with reactor neutrons can be used as a neutron conductor, a background suppressor, and a neutron filter. These properties were studied for both metal and glass pipes coated (electroless) with nickel and installed in a beam hole at the Brookhaven Graphite Reactor.

In addition to their uses as neutron filters and background suppressors, curved totally reflecting soller collimators can be employed as order-removing devices when used in conjunction with a crystal monochromator. An investigation is being conducted on the further use of these soller slits as magnetized cobalt-iron shims to obtain 100 percent polarized cold neutrons. Establishing Vacua. The establishment of high vacua in the intense radiation field of a reactor core is limited by poor conducting geometry (i.e., systems with a large length-to-diameter ratio), suitable reactor materials (i.e., materials having low neutron absorption), and radiation-induced outgassing. An investigation was made of the magnitude of the radiationinduced outgassing rate of a well-cleaned and baked 6061 aluminum system. Measurements performed in both the NBS 31 kCi cobalt-60 gamma facility and the Naval Research Laboratory's 1 megawatt reactor facility disclosed that the phenomenon of radiation-induced outgassing was principally due to the gamma and its associated electron field, rather than to the fast neutron field. The magnitude of the effect observed was 6X 10-11 torr liters/sec cm2 per watt/gram, which can be compared with the field free value for the system of 5× 10-14 torr liters/sec cm2.

2.2.6. CRYOGENICS

The Bureau's Cryogenic activities, centered at the Boulder Laboratories, provide data on the bulk properties of materials in the environmental extreme of very low temperatures. Research is conducted at cryogenic temperatures to determine the physical properties of materials, the engineering properties of systems, and to develop methods for measuring these properties. In addition, a national cryogenic data center is maintained where information is collected and organized for use by other Government agencies, industry, and the public.

An addition to the Cryogenics Laboratory Building has just been completed, increasing the space available by nearly 30,000 square feet. Research on properties of cryogenic fluids and measurement methodology, now conducted in two temporary buildings, are being moved to the new addition.

Viscosity of Parahydrogen Determined. The most advanced chemical and nuclear rockets use hydrogen as fuel or as monopropellant. Because of these important applications, the thermodynamic and transport properties of hydrogen need to be known with higher accuracy and over wider ranges of temperature and pressure. The Bureau is engaged in an extensive experimental program to determine these data, a major part of which is supported by the National Aeronautics and Space Administration (NASA). Previously pressure-volume-temperature and thermal properties were deter

mined, and extensive provisional tables of thermodynamic functions were published.

In the past year, measurements of viscosity were concluded covering the same pressure and temperature ranges as the previous work, up to about 3.4 × 10 newtons per square meter (N/m2) (340 atm) and from 15 to 100 °K, thus including the liquid and gaseous phases and the critical region. The viscosity was determined via the damping of a torsionally oscillating piezoelectric quartz cylinder.

It is conventional to separate the viscosity into a low-pressure component and a remainder, termed the “residual" viscosity. Some published correlations and extrapolations were based on the assumption that the low-pressure component contains the entire effect of temperature on the viscosity, so that the residual viscosity is a pure function of density. The present data show clearly that this is a gross oversimplification. Also, there is no evidence for an anomalous peak at the critical point, as was obtained for some other fluids by other experimental methods.

Solid-Vapor Equilibrium in the Hydrogen-Methane System. Phase equilibrium studies of mixtures are of great practical value in designing fluid purification systems. In addition, provided the components have widely different critical constants, condensed phase-gas equilibria lead to sensitive determination of the parameters for interaction of the unlike molecules.

The hydrogen-methane system was investigated by measuring compositions of gaseous mixtures of hydrogen and methane in equilibrium with solid methane at temperatures from 35 to 87 °K and pressures up to about 1.5×10 N/m2 (150 atm). Enhancement factors and cross virial coefficients were derived. The data will be useful in designing hydrogen gas purifiers. In addition they can be used to evaluate various physical models for the interaction forces between hydrogen and methane molecules.

Mixtures of Solid and Liquid Hydrogen. Space vehicles fueled with hydrogen in liquid form have required the development of new technology. Although relatively high density at low pressures is accomplished by gas liquefaction, problems exist with fluid behavior before, during, and after launch. Some of these problems are (a) short holding or storage time caused by low heat of vaporization and temperature combined with minimal insulation, (b) fluid temperature stratification resulting in pump cavitation problems, (c) sloshing of the liquid in such a manner to effect flight stability, and (d) safety problems associated with the high vent rates before and after launch. Further refrigeration of the liquid to form a "slush" or mixture of solid and liquid should eliminate or greatly reduce a number of these problems.

Under sponsorship of NASA, the Bureau is conducting a program on "slush" hydrogen aimed towards an optimization of the concepts to be incorporated in a space vehicle launch facility. The effort will be carried out on a laboratory scale with emphasis on the applicability to the ultimate largescale requirement. Specific objectives are to evaluate, correlate and combine

all known applicable properties of slush hydrogen, to investigate production methods, and to study flow characteristics. Instrumentation of the threephase (single-component) system is a crucial portion of the program. A study of the behavior of solid hydrogen crystals in the solid-liquid mixture is also of great importance. The attainment of these objectives will assist in the establishment of standard specifications for instrumentation and production of flowable mixtures of solid and liquid hydrogen.

Superconductivity. The Atomic Energy Commission (AEC) is sup porting Bureau work on thin film and high field superconductors. In thin film experiments, careful sample alinement resulted in much better agreement with the Ginsburg-Landau theory than previous workers reported. This supports the use of the theory, which rests on not too firm ground, in high field superconducting problems. A parallel experiment to test another prediction of the theory on bulk superconducting niobium is well under way. Finally, experiments are under way to deduce the topology of the Fermi surface of niobium from magnetoresistance measurements, and to relate this as far as possible to the Class II superconducting behavior of this element.

Metallurgy. Investigation showed that small changes in the elastic moduli observed in certain 300-series stainless steels are related to antiferromagnetic transitions in these metals at about 40 °K. Based on this research, consultation was given to interested groups in NASA and the Air Force who are concerned about possible structural failures due to martensitic phase transformations in stainless steels subject to high stresses at liquid hydrogen temperatures.

Electronic Properties of Copper Investigated. Magnetoresistance measurements indicate that the simple concept of a (scaler) electron mean free path in copper, and presumably in other metals, must be abandoned in favor of more sophisticated analyses involving details of the electronic

structure.

The theoretical implications of this advance are being investigated, and related experimental work is beginning.

Aluminum Cryogenic Magnet Tested. The AEC is supporting an investigation into the feasibility of generating strong magnetic fields at low cost by using liquid hydrogen cooling of aluminum electromagnet windings. Such a magnet was tested to burnout at 9.4 tesla (94,000 gauss). It was found that the cryogenic part of the system (heat transfer ratio, fluid flows, pressures, temperatures, and pumps) performed in accordance with engineering expectations. Additional measurements are necessary in order to be able to predict accurately the resistivity of the aluminum under stress at high fields and at the operating temperature.

Thermophysical Properties of Cryogenic Materials. With support from NASA and the National Standard Reference Data System, the Cryogenic Data Center is critically evaluating and compiling data on the thermophysical properties of materials from the scientific literature. The objective is to publish authoritative and comprehensive tables and graphs of data in a form convenient to scientists and engineers studying cryogenic phenomena and