Ion Reaction and Diffusion Problems.-By analytical and computational methods, many factors affecting the interpretation of measurements in an ion reaction tube have been studied: neutral source configuration, ionic model distribution, axial and wall diffusion effects, multi-component reactions, velocity fields, axial pressure and temperature gradients, and the transient diffusion and transport of an ion sheet. Analysis and programming have been carried out to obtain time- and altitude-dependent equilibrium atmosphere ion densities for some models of the ion and neutral reactions.

TECHNICAL ASSISTANCE TO OTHERS

The Institute is a source of technical assistance and consultation to other Government agencies with problems in specialized areas of physical measurement and applied mathematics. Its sponsorship of the National Conference of Standards Laboratories permits joint study of management and operation techniques, and has led to a series of seminars on precision measurement. In cooperation with various technical societies, NBS also conducts conferences and symposia important to wide segments of science and industry.

Studies for Other Agencies

Back-Scatter Visibility Meter.-A prototype back-scatter visibility meter has been designed and constructed for the Bureau of Naval Weapons. The meter will test the feasibility of using instruments of this type aboard aircraft carriers. The instrument consists of a projector with a flashtube as a light source and a receiver that alternately receives flux which (a) is scattered backward from the beam of the projector, and (b) comes directly from the projector. The ratio of the two signals is determined and displayed. Thus the reading is not affected by changes in the output of the projector or sensitivity of the receiver.

Radioactive Contamination of Materials.-An extensive study of radioactive contaminants in chemical reagents and commercial materials is being carried out for the United States Atomic Energy Commission. The extent of this low-level contamination, its variations with time, its nature, and its dependence on manufacturing practices and geographical factors are being considered in order to allow for, or to correct for, the radioactive contaminants in these materials. Special techniques and highly sensitive counting instruments located in appropriate facilities are being used. A study on the transmission of beta particles emitted by "infinitely thick" sources was completed. The purpose of this investigation was to determine the maximum energy of beta particles emitted by low-level sources.

Standard Nuclear Instrument Module System.-The Standard Nuclear Instrument Module System, developed in conjunction with the AEC National Laboratories, is proving to be of increasing utility to nuclear research. Essentially the entire nuclear instrumentation field in this country, and an increasing number of laboratories and industries throughout the world, have adopted the system. It provides for interchangeability of nuclear instruments regardless of the laboratory or commercial concern that designed or produced them. Since the interchangeable modules can be inserted indiscriminately in standard bins, systems can be optimized and component modules reused in different system arrangements with complete flexibility and without the additional expenditures that stocking of incompatible equipment would entail.

International Comparisons.-The Bureau participated in the determination of environmental levels of tritium in water, carbon 14 in starch, and potassium 40 in feldspar. This study was performed for the United Nations International Atomic Energy Agency. NBS also participated in the International Bureau of Weights and Measures international comparison of cobalt 60, and in the second intercomparison of mercury 197 among pharmaceutical laboratories and national laboratories in the United States and Canada.

Strain-Measuring Standards for High-Temperature Use.-A pneumatic extensometer was designed and constructed for the U.S. Air Force Systems Command. This device will determine performance characteristics of strain-measuring devices used under field conditions. The efficient use of materials that will provide the lightest structure that can meet performance requirements with a reasonable factor of safety is especially important in spacecraft, missiles, and high-performance aircraft. These are structures that are exposed to severe environmental conditions, including high and rapidly changing temperatures. Measuring structural strains during prototype development and evaluation under actual or simulated use conditions is one of the best methods of insuring the safety and integrity of the final product.

Wave Studies.-Under sponsorship of the Office of Naval Research, studies are being made on wind-generated waves and tides and on internal waves in a density stratified liquid. A study of wind forces on a water surface is important for understanding the generation of water waves by wind and the formation of wind-generated tides. In these experiments regular trains of smooth waves were mechanically generated by an oscillating paddle at the upwind end of a wind-wave channel in which air is blown at speeds up to 10 meters per second in the direction of travel of the waves. Wind shear force on the wavy

A gas-cooled extensometer is assembled for tests in an oven capable of temperatures up to 1650° C. This apparatus is used to determine performance characteristics of strain measuring devices under field conditions.

surface and wave heights along the channel were determined for each wind speed and initial wave configuration. It was then possible to deduce information on energy transfer from wind to waves and on surface shear-stress coefficients as a function of wave shape.

Highway Culverts.-An investigation of the hydraulics of highway culverts, conducted over a period of several years at NBS under the sponsorship of the Bureau of Public Roads, has now been concluded. Investigation has shown that the water-carrying capacity of highway culverts can be substantially improved over that realized with commonly used types. The problem arises from the fact that the barrel of the culvert (the pipe of duct under the road) does not generally flow full even though the entrance may be fully submerged. Several factors influence these conditions, but the principal one is the shape of the entrance. Laboratory modelling experiments were directed toward a fundamental understanding of these factors, with the principal emphasis being placed on inlet shapes designed to promote fuller flow, and correspondingly greater carrying capacity for a given size and cost under the various conditions met in practice. It was found that by employing tapered inlet structures of simple and practical geometry the flow capacity of culverts having sufficient slope can be increased

from 50 to 75 percent above that obtained with commonly used entrance designs. These figures moreover, apply to flow under unfavorable conditions such as may occur in practice.

Conferences and Seminars

Precision and Accuracy in Measurement and Calibration.-In this 4-day seminar more than 50 participants representing 39 industrial and university laboratories and Government standards laboratories obtained firsthand information on statistical experiment designs especially tailored to the needs of calibration laboratories for making economical intercomparisons among sets of standards. Presentations by NBS statisticians were complemented by reports from Bureau calibration laboratories that are implementing the new computer-aided methods for data analysis, preparation of calibration reports, and surveillance of the measurement process.

Calibration of Thermocouples and Optical Pyrometers.-Scientists and technicians from both Government and industrial standards laboratories attended a 5-day seminar on techniques for the calibration of thermocouples and optical pyrometers led by members of the NBS staff.

Precision Calorimetry.-A four-day seminar was held covering the field of precision calorimetry. Lectures on apparatus design and measurement techniques for use with cryogenic to very high temperatures were supplemented by laboratory demonstrations.

Commission on Illumination.-The International Commission on Illumination (CIE) held its 16th quadrennial Session in Washington, D.C. June 19-28, 1967. The Commission visited NBS laboratories and examined its current program in photometry and radiometry.

RF Voltage Measurement Seminar. This three-day seminar was offered twice in June at the NBS Radio Standards Laboratory in Boulder, Colo. It covered primary voltage standards, calibration equipment and techniques, methods of extending voltage ranges, thermal noise related to voltage measurements, introduction to commercial instruments, and peak pulse standards and calibrations.

Phase Shift Measurement Seminar.-A three-day seminar on phase shift measurement was offered. Subjects included basic concepts and equations, low frequency measurements, a 30 MHz modulated subcarrier system, broadband measurements, UHF and microwave differential phase shifters, and techniques applicable to UHF, microwaves, swept frequencies, and time delay.

THE NATIONAL STANDARD REFERENCE DATA

SYSTEM

The National Standard Reference Data System began in 1963 when the Federal Council for Science and Technology directed NBS to assume responsibility for all Government-wide standard reference data compilation activities. NBS was requested to (1) coordinate existing data compilation and evaluation activities throughout all Government agencies and ensure their compatibility; (2) establish standards. of quality for products to be designated as Standard Reference Data; (3) establish standards of methodology including machine processing; and (4) operate a National Standard Reference Data System.

NSRDS is concerned, under these instructions, with the production and dissemination of compilations of critically evaluated data. A primary emphasis of the system is to maximize the utilization of numerical information already reported in the scientific literature. The program includes collection and evaluation of data from the literature, preparation of critical reviews dealing with the state of quantitative knowledge in a particular technical field, and computation of useful functions derived from Standard Reference Data or used in the interpretation of quantitative experiments.

Within the Federal agencies, broad interest in planning and coordination of scientific information problems is focused in the Committee on Scientific and Technical Information (COSATI), which sponsors a number of Panels and Task Groups on special topics. The newest COSATI Panel, on Information Analysis Centers, has many common interests with NSRDS. Three members of the NBS Office of Standard Reference Data have accepted assignments on this COSATI Panel.

INTERNATIONAL DATA ACTIVITIES

One of the primary functions of the NBS Office of Standard Reference Data (OSRD) is to become affiliated with international groups having special interest in the data process. In addition, since NBS is charged with coordinating all Federal data activities, it is often. called upon to represent the United States in international groups. Fulfilling such responsibility requires that OSRD be familiar with data activities in other countries and with all such work being conducted on an international basis.

International interest in data compilation is increasing markedly. Several years of planning have led to formal recognition of an international structure to channel this interest effectively. Under the stimulus of the Foreign Secretary of the National Academy of Sciences, the