Vol. 46, No. 8, pages 107-110. Scientific Research, June 1966, Vol. 1, No. 6, pages 24-26.

Contact: Dr. C. D. Bowman, Chief of Nuclear Sciences Division, Radiation Physics Building, Room B119, Phone 301-921-2234.

POSITIVE-ION

VAN DE GRAAFF
ACCELERATOR, 3 MeV

The positive-ion 3 MeV Van de Graaff facility at the National Bureau of Standards has been designed primarily for experiments involving keV and MeV energy neutrons. It includes a HVEC model KN-3000 Van de Graaff accelerator and two target rooms. The accelerator is capable of operation in dc mode as well as in a variety of pulsed beam modes. Momentum analyzed beams can be supplied to any of six ports in a low scattering environment or to a single port in a heavily shielded room. Protons and deuterons are the ion species routinely accelerated.

Capability: Values listed are routinely available. Extended capabilities may be developed for special applications.

ENERGY: 0.8 to 3.0 MeV.

BEAM INTENSITY: 1 to 200μA.

-Analyzed Beam:

ENERGY: protons-0.8 to 3.0 MeV; deuterons-
0.8 to 2.8 MeV.

BEAM INTENSITY: 0.3 to 20.9μA.
ENERGY STABILITY: 2.0 keV.

ENERGY REPRODUCIBILITY: 5.0 keV.
Pulsating Capability:

Rf PULSING: 1.0 and 3.3 MHz repetition rates with 15 and 4 ns burst width respectively. "Slow"pulsing: Burst width-variable from 0.1 to 5.0 μs; Rep. rate-variable from 100 kHz to dc.

An on-line data handling capability is being developed based on a D.C. 6024/5 computer. Applications: Standard neutron cross section measurements, neutron flux standards, neutron experiments involving time of flight, neutron capture cross section measurement, fast neutron activation analysis, neutron dosimetry, radiation damage studies, charged particle studies.

Availability: Accelerator time is available to NBS staff and outside users to the extent that the work does not conflict with the neutron standards program. The use of a member of the Van de Graaff staff is recommended for operation of the machine and set-up. Contact: Dr. A. D. Carlson, Neutron Standards Section, Radiation Physics Building, Room B119, Phone 301-921-2677.

SYNCHROTRON
ULTRAVIOLET RADIATION
FACILITY (SURF)

Synchrotron radiation in the far ultraviolet is highly collimated, nearly linearly polarized, and of calculable intensity. It is well-suited for studies in atomic, molecular, biomolecular and solid-state physics, chemistry, engineering and medicine.

Capability: The NBS Synchroton Ultraviolet Radiation Facility (SURF) is now in the process of being converted into a storage ring. Initial injection has been achieved and full operation is expected by the end of 1974. With a microtron injector the storage ring is expected to accelerate a 50 mA beam to a maximum energy of 240 MeV. The expected intensity in the region 600 Å to 1200 Å is 4 X 1011 photons per second per milliradian of orbit for an instrumental resolution of λ/λ = 0.001. Instrumentation planned and existing includes:

a) A source of smooth, calculable intensity distribution, 10,000 Å to 40 Å.

b) 600 Å 40 Å 3-m grazing incidence spectro

A.

aph and monochromator, resolution to 0.05

c) Two 2000 Å 60 Å monochromators (toroidal grating), resolution 0.5 Å to 1.0 Å.

d) 925 Å 40 Å 2.2-m grazing incidence monochromator, resolution to 0.1 Å, with 10-10 torr vacuum chamber, photoelectron analyzer, and manipulators.

e) Medium temperature heat-pipe ovens, 0.3m and 1.0m, to 1100 C. One oven of the rotating type handles materials that wet a wick with difficulty.

f) Calibrated detectors, 2000 Å 200 Å.
g) Two spectrometer calibration lines with a
direct view of the beam.

Applications: The enlarged SURF will be used for atomic and molecular absorption spectroscopy, optical properties of materials, electron density of states. in solids, surface studies (including angular distribution of photoelectrons as a function of angle of incidence and polarization vector), radiation damage studies in substances (including those of biological origin), calibration studies, precision photoabsorption cross-section measurements in solids and vapors, and photoelectron spectroscopy of gases.

Availability: To any qualified research worker from NBS or other Federal agencies.

Contact: Dr. Robert P. Madden, Chief, Far UV Physics Section, Physics Building, Room A251, Phone 301921-2031.

ACOUSTIC FACILITIES

Literature: J. Acoust. Soc. Amer., Vol. 52, No. 4 P

1), Oct. 1972, pp. 1071-1076.

Contact: Walter Koidan, Sound Bldg., Room 84 Phone 301-921-3607.

This facility consists of a sound and vibration-isolated room whose inner surfaces are lined with 1.78-meter long glass-wool wedges and whose free-field dimensions are about 10 X 6.7 X 6.7 meters. Access to the room is by means of a steel wire mesh floor supported by concealed I-beams. Instrument hangers, each capable of supporting about 100 kilograms, are mounted on all six surfaces of the room. The space is lighted, air conditioned and provided with electrical outlets and conduits for communications cables.

Capability: The room provides good free-field sound conditions from about 40 Hz to at least 63 kHz. Upper bounds for wide-band ambient noise are about 30 dB re 20 N/m for C-weighting and 23 dB for Aweighting. (The actual ambient level cannot be measure with a commercial sound level meter since equivalent instrument noise exceeds the ambient acoustic noise.)

Applications: Microphone calibration, loudspeaker measurements, sound level meter calibration, noise measurement, psychoacoustic experiments, radiation and scattering experiments, general use when a quiet environment is needed.

Availability: When not otherwise in use and when staff members are available to ready the facility for

the user.

ACOUSTIC
REVERBERATION
CHAMBER

The chamber is a vibration-isolated, shell-within-shel type structure of massive reinforced concrete con struction with inside dimensions of 9.14 x 7.62 6.10 meters. A steel plate, double-leaf entrance door provides a clear opening to the chamber of approx mately 2 X 3 meters. The chamber is equipped with a unique set of adjustable, variable-speed, rotating vanes to improve the diffusion of the sound field. The interior of the chamber and the surrounding one meter-wide air envelope are lighted, air conditione and humidity-controlled and provided with electrica outlets and conduits for communication lines. No merous pipe-sleeve openings of various sizes als are available for other specialized uses such as con duits for hydraulic, pneumatic, fuel or exhaust line Capability: Although experimental verification not been completed, the chamber is designed to pr vide a highly diffuse sound field in the frequen range 100 to 4000 Hz, and to permit reasonab accurate acoustical measurements to be made at fre quencies as low as 50 Hz and as high as 10,000 H: The wide-band ambient noise level in the chambe with the vanes stationary is about 30 dB re 20 μN for C-weighting and about 36 dB with vanes rotatin at 5 rpm. The reverberation time T (60 decibe decay) is approximately 18 seconds at 100 Hz and

about 5 seconds at 4000 Hz.

60

for rf signal generation and detection under computer control. This provides for the measurement of antenna characteristics such as complex reflection (impedance) and transmission coefficients over the frequency range of 0.1 to 18 GHz. Rigid coaxial cable for frequencies to 18 GHz connect each end of the anechoic chamber back to the automatic network analyzer. Data output is obtained on a high speed electrostatic printer-plotter, or may be viewed as a polar plot or rectangular plot on oscilloscopes.

Availability: To any qualified NBS research worker, after an initial training period with supervisor. In appropriate instances individual research workers from other Federal organizations can gain access to the facility.

Contact: W. E. Little, Program Chief, Automatic Network Analyzer Applications, Radio Building, Room 4633, NBS Boulder, Colo. 80302, Phone 303-499-1000 ext. 3658.

Sur

ard

ANTENNA FIELD STRENGTH FACILITIES. Movable towers used for evaluating horn and dish antennas.

ANTENNA

ANECHOIC CHAMBER

A microwave darkroom which simulates free-space measurement conditions for antenna design and measurement. The outside dimensions are 20' long, 10' wide and 10' high. Nominal inside dimensions are 17' long, 7' wide, and 7' high. Access is through a 3' wide by 62' high door.

Capability: The minimum specified frequency for the Fanechoic material is 500 MHz. The maximum absorber reflectivity is -20 dB at 500 MHz and decreases to 50 dB at 9 GHz. The 16' transmission path between test antennas determines the antenna aperture sizes which can be used. If the commonly used requirement of antenna separation of 2(d, + d)/A is applied and if the antenna dimensions of d, and d., are assumed to be equal then the maximum antenna aperture dimensions are 8 wavelengths for each antenna. Use of the facility can be made with reduced accuracy from 100 MHz to 500 MHz. Applications: The anechoic chamber is located adjacent to an automatic network analyzer which provides

ANTENNA FIELD

STRENGTH FACILITIES

Capabilities: 1) Measuring gain on horn and dish antennas in the frequency range 500MHz to 75GHz, using two 20-foot towers capable of moving 200 feet apart on high-accuracy rails. 2) Scanning near-field radiation. patterns and measuring gain in the frequency range 1 to 75GHz. 3) Measuring field strength and calibrating antennas and field strength intensity meters in the frequency range 10Hz to 1GHz. 4) Evaluation of electromagnetic hazard probes used for checking leakage fields, e.g. from microwave ovens or high power

transmitters.

ROOFTOP

ANTENNA RANGE

The rooftop antenna range is located on the upper flat portion of the roof above Wing 6 of the Radio Building.

Capability: This rooftop antenna range was built to provide a means for antenna design and measurement for antennas too physically large or used at too low a frequency to be measured in the anechoic chamber. Two rigid coaxial rf cables and a multiconductor intercom and power cable connect to the automatic network analyzer in the laboratory below. The automatic network analyzer provides for the rf signal generation and detection requirements.

Applications: Complex reflection (impedance) and transmission coefficients of antennas can be measured by making use of the automatic network analyzer over the frequency range of 0.1 to 18 GHz. Antennas can be measured at frequencies below 100 MHz by connecting the lead-in coaxial cables to other rf sources for signal generators and components for signal detection. Although this later equipment is not presently dedicated for use with the rooftop antenna range it is available for use from other projects.

Availability: To any qualified NBS research worker, after an initial training period with supervisor. In appropriate instances individual research workers from other Federal organizations can gain access to the facility.

Contact: W. E. Little, Program Chief, Automatic Network Analyzer Applications, Radio Building, Room 4633, NBS Boulder, Colo. 80302, Phone 303-499-1000

ext. 3658.

The effects of sunlight, rain, hail, atmospheric con taminants, and salt spray are simulated by accelerated cycling on building materials and systems such awall coverings and sidings, caulking, roofing, flo ing, paints, and plastic coatings. Seven exposure sta tions throughout the United States and Puerto Ric provide a diversity of natural weathering conditions Capability: Radiant-energy sources of the accelerate test machines include single and twin carbon arcs a fluorescent sunlamp/black-light unit, and both wate and air-cooled xenon arcs. Monitoring is by dos. meters, radiometers, or actinometers. Some machines have temperature, humidity, and water spray control or light/dark cycle controls. A high-humidity chambe is used to subject samples to cycles of water conden sation and drying. Flammability of roofing is tested r a small spread-of-flame apparatus. A compressed-agun fires ice spheres up to 21⁄2 inches diameter against roofing and siding specimens at measured speeds up to 145 feet per second.

Applications: Comparative studies of structural mate rials, coatings, claddings, and composites; identifica

tion of relatively detrimental weathering conditions; research on mechanisms of deterioration; development of test procedures.

Availability: On contract agreement with other government agencies, when equipment is not fully utilized by NBS research programs. Members of the Section carry out the various tests.

Literature:

[1] S. H. Greenfeld, Hail resistance of roofing products, Nat. Bur. Stand. (U.S.), Bldg. Sci. Ser. 23 (Aug. 1969)

[2] L. F. Skoda, Performance of residential siding materials, NBS Report 10805 for Naval Facilities Engineering Command (1972)

[3] J. R. Wright and V. E. Gray, Measurement of photochemical degradation in rigid poly (vinyl chloride), Conf. Supp. No. 1, London, 14-16 June 1965, Plastics Institute Trans. Contact: Robert G. Mathey, Assistant Chief of Materials and Composites Section, Building Research Building, Room B340, Phone 301-921-3407.

Capabilities: Tests on systems up to 45 ft. in height and up to 50 ft. in length. Water supply of up to 1000 gpm at constant head in gravity mode; up to 300 gpm in automatically controlled pressure mode up to 70 psi. Hot water at volumes up to 200 gph at 180°F. Continuous measurements and recording of rapidly changing physical parameters such as pressure, discharge rate, water depth, and temperature, according to predetermined criteria, at up to 64 points. Data analysis through NBS central computer if desired. Pre-programmed control of experimentation by computer if desired.

Applications: The development of improved criteria for general hydraulic design of and for prediction of loads on plumbing systems; the development of test methodology for calibration and performance evaluation of innovative plumbing equipment and systems; investigations of performance of piping materials as affected by pressure, flow, and contact with

hot and cold water; methodology for cost effective approaches in needed national programs to update information on plumbing loads and to develop a modern data bank on performance characteristics of innovative equipment and systems.

Availability: To qualified NBS research workers, after an initial training period. In appropriate instances the facilities can be utilized by other governmental research workers, or by university or industry workers. Literature:

[1] UA Journal, August 1972, pp 33-35.

[2] Building Systems Design, May 1972, pp 50-54. [3] Commerce Today, February 21, 1972, pp 30

31.

Contact: Dr. L. S. Galowin, Chief of the Building Service Systems Section, Building Research Building, Room B306, Phone 301-921-3293.

STRUCTURES LABORATORIES

Static and dynamic testing is accomplished by use of a heavily reinforced tie-down floor permitting mounting of complete structural members. Hydraulic actuators provide test loads in static test while closedloop electro-hydraulic actuators provide test loads in dynamic tests. Automatic recording of up to 200 channels of sensor data is accomplished by a minicomputer-controlled data acquisition system.

Capability: The main test floor of heavily reinforced concrete and imbedded I-beams is 53 X 47 feet in size and is supplemented in the long direction by a 25 foot extension, 20 feet wide, for testing long beams. The 53-foot section has a 12,000 ft-kip bending moment capacity, and its 25-foot extension has a bending moment capacity of 8,000 ft-kips. The crosswise section 47 feet in length will withstand a total bending moment of 21,000 ft-kips. The floor will withstand a total horizontal shear force of 1800 kips in either direction and a vertical shear force of 2,000 kips. It is serviced by two 10-ton bridge cranes having a clear hook height of 25 feet. The ninety-nine anchorage tie-down points are designed to withstand 100 kips of either tension force or horizontal shear force. Six additional points have twice this capacity. An associated laboratory, 22 x 75 feet, is serviced by two 2-ton cranes and contains two universal testing machines of 60,000-lbs, one of 200,000-lbs capacity, and two compression machines of 300,000-lbs and 600,000-lbs. capacity. The 600,000-lb capacity machine has adequate clearance for testing an 8-ft. high, 4-ft wide structural member.