INSTITUTE FOR BASIC In support of the general mission of the National Bureau of Standards, the Institute for Basic Standards (IBS) provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. This central base consists of a complete, consistent set of units and national standards for physical measurement having precision and accuracy matched to national needs. It is accompanied by a chain of measurement extending to such multiples and submultiples as are needed for continued technological advancement. PHYSICAL QUANTITIES, NATURAL CONSTANTS, MEASUREMENT SERVICES The International System of Units (SI), defined by the 11th and 12th General Conferences on Weights and Measures, is the base for the international system of measurement and for most national systems. Six of these SI units-the kilogram, meter, second, degree Kelvin, ampere, and candela—are the arbitrarily chosen values of six quantities of the physical world-mass, length, time, temperature, electric current and luminous intensity. Consistent units for other quantities may be derived from these, with appropriate values fixed by the units selected for the basic six. The English system-pound, inch, second, degree Fahrenheit, etc.—and other systems of units are related to the SI units by definite conversion factors. At present, the range of items in NBS measurement services. covers those quantities known to be of major importance to science and technology. As new developments appear, there will be shifts of emphasis in the Bureau's R&D program aimed at providing measurement, calibration and test services for new quantities, at extending ranges, and at improving accuracies. The following specific program accomplishments and improved calibration services relating to basic physical quantities and constants were realized in fiscal year 1966: INTERNATIONAL BASE UNITS Length Line Standard Interferometer. The automatic length-scale interferometer mentioned in the 1965 Technical Highlights has been applied to routine calibration activity with a decrease in calibration fees by a factor of ten. Ultimate accuracy of the instrument has still to be determined, but is at least as great as the method previously used. Phase Correction Equations.-Decrease in the uncertainty of phase corrections as applied to length measurement has been achieved by the development of equations more adequately relating polarization measurements of surface effects to interferometric measurements of length. Laser Research.-Previous research and development work has contributed to widespread applications of continuous-wave gas lasers in length metrology. To provide the required knowledge of the laser wavelength in terms of the fundamental standard of length, the wavelength of the 3s-2p4 transition of neon was measured by comparing a helium-neon laser with a standard krypton-86 lamp. However, the gas pressure in the laser discharge tube appears to be an important factor, and this will be studied. further. Additional work is under way to measure laser wavelengths in cooperation with the national laboratories in other countries. Mass A new mass standardization program at NBS will enable scientists to provide selected scientific, commercial and industrial users with a complete evaluation of their mass-measuring procedures at a tremendous saving of time and money. NBS provides the user with two, one-kilogram (about 2.2 pounds) weights rather than a complete set of test weights that previously took from three to six months to calibrate. Using these two weights as a reference, the user makes his mass measurements and records necessary data (scale readings, relative humidity in the measurement room, etc.), and teletypes this data to NBS. With the aid of a computer the data is analyzed and the results of the measurement are teletyped back to the user. This entire procedure can take place in one hour. There are advantages of this system to the laboratories, to NBS, and to the Nation. The analysis provides laboratories with control data to establish and check the precision of their measurement process. Statistical procedures for doing this have been developed and verified at NBS, using many years of mass measurement data. By knowing the capabilities of their system and monitoring its performance on a day-to-day basis, laboratories are in the position of knowing at once when something goes wrong as well as having irrefutable evidence to substantiate the values they arrive at. Time and Frequency NBS work in the area of time and frequency includes all aspects of the subject (except for astronomical observations) ranging from basic research on atomic frequency standards to the operation of radio stations for disseminating time and frequency. The four main categories are (1) Atomic Time and Frequency Standards, (2) Atomic Standards Research, (3) Radio Broadcast Services, and (4) Time and Frequency Dissemination Research. Atomic Frequency Standard. The present NBS Frequency Standard is the cesium atomic beam standard NBS III, located at the Boulder, Colo., Laboratories. Located close to this standard are some oscillators of high stability whose frequency is compared to the NBS III on a routine basis. The counting of cycles of these oscillators forms the basis of NBS Atomic Time Scale (NBS-A). These standards are disseminated by radio stations WWVB (60 kHz) and WWVL (20 kHz) at Fort Collins, Colo., the high frequency station WWVH at Maui, Hawaii, and the new station at Fort Collins replacing WWV. Frequencies of the Fort Collins transmitters are automatically controlled so that the accuracy of the transmitted signals is essentially that of the NBS III-about one part in 10. Signals received from WWVB and WWVL at WWV and WWVH are used to correct the frequencies of the latter two stations. Further comparison between these stations and others is accomplished by monitoring, and by carrying portable clocks to other laboratories. Improved Frequency Standard Studies.-The needs imposed by the tracking of deep space satellites require the development of frequency standards with accuracies at least two orders of magnitude better than the present NBS III. As part of this effort, one hydrogen maser has been constructed and another is being assembled. At present an atomic beam machine is operating with thallium for evaluation as a possible standard. Also, a move is being made to establish a cooperative effort with a commercial firm for the development of an atomic beam machine of improved characteristics. Time Signals at 20 kHz.-Until recently the 20 kHz signals have been basically standard frequency signals only, and there has been uncertainty whether time information could be conveyed effectively by them because of the narrow antenna bandwidth. However, in the past year a study has shown that signals of this type hold great hope of carrying time information. Temperature Copper-Constantan Thermocouple Calibration.-A substantial improvement was made in reporting calibration results for copperconstantan thermocouples (in the range -190 to 300 °C) by using a computer program to reduce data and to print tables with entries at 1 degree intervals. Manometer Pressure Standard for High-Temperature Gas Thermometry.-A precision manometer constructed for the hightemperature gas thermometry project is unique as a pressure standard. Uncertainties of height, mercury density and gravitational acceleration yield a root-mean-square error of 1 ppm for pressures above 3.5 kN/m2. The instrument exhibits rapid thermal recovery, thereby allowing the operator to take measurements five times faster than was previously possible. A second important unit developed is a very high quality pressure-transducer which features high vacuum, small volume (33 mm3), high sensitivity (0.13 mN/m2), and high stability of the null point. Equality of pressure on opposite sides of the diaphragm is ascertainable to +10-6 cm Hg (±1.3 mN/m2). Stability Test for Liquid-in-Glass Thermometers.-Largely based upon work done in the NBS Temperature Section, a stability test for liquid-in-glass thermometers has been written up and adopted for use by the American Society for Testing and Materials. Its use is now under consideration by the International Standards Organization. Freezing Point of Zinc.-In a cooperative effort with the NBS Office of Standard Reference Materials, thermal analysis was used to establish that high purity (>99.9999 percent) zinc had freezing point ranges of not more than 0.0002 °C at a temperature not more than 0.001 °C from the assigned temperature on the International Practical Temperature Scale (IPTS). While the zinc cell has long been a useful device in realizing IPTS, material of this exceptional purity has never been available. More precise calibration at the zinc point will now be possible. MECHANICAL QUANTITIES 12-million-pound Force Testing Machine.-A universal testing machine of 12 million pounds capacity has been erected at the Bureau's Gaithersburg site. This machine provides a unique facility which will be used in calibration of force-measuring devices with capacities up to 12 million lbf (53 million newtons) and in the investigation of the behavior of full-scale structural components such as compression or tension specimens up to 55 feet in length, and beam specimens up to 85 feet in length. It is anticipated that cooperative tests will be undertaken with universities This twelve-million-lbf capacity hydraulic testing machine, believed to be the world's largest, is being installed in the new NBS Engineering Mechanics Building. A unique facility, the machine will provide the force to calibrate multi-million-lbf capacity force-measuring devices for space and industrial applications and to test full-scale structural components. The machine has a total height of 101 ft, including 21 ft in a pit. |