Reference

NBS

PUBLICATIONS

A111DE b7TE37

NATL INST OF STANDARDS & TECH R.I.C.

A1 11 02679237

IBS research reports C100 .U57 SP 680-1 ;1984 C.1 NBS-PUB-R 1

-QC

100

.U57

No ,630-1

1934

NBS Research

Reporter

US. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NBS SPECIAL PUBLICATION 680-1
Cover photo: This Automatic

Inspection Workstation will be the final stop for parts

made in the AMRF.

Metrologists Bruce Borchardt

(foreground) and Ralph Veale

are "teaching" working

positions to the robot that

tends the coordinate

measuring machine (CMM) in this workstation. When the

AMRF is fully operational, this

"teaching" step will not be

necessary. See page 6.
WmONAl BUREAU Of STANDARDS

LIBRARY CONTENTS

NBS

Research

Reports

Focus on Cooperation and Communication: An Introduction 2 Research Update 3

Standard Interfaces Key to Factory Automation 6 Standard Data Formats: Transferring Part Designs Between Systems 10 How to Secure Your Computer Systems 1

1

Cold Circuits Next Step in Electronics Revolution? 14

New Particles for Measuring Pigments, Flour, Blood Cells 16

Measurement Methods for a New Industry: Industrial Radiation 20

Compositional Mapping:

NBS Researchers Take a Glimpse Into the Atomic World 23

Tools of the NBS Compositional Mapping Program 25

New Publications 26

Conference Calendar 28

U.S. DEPARTMENT OF COMMERCE

Malcolm Baldnge, Secretary

National Bureau of Standards

Ernest Ambler, Director

National Bureau of Standards

Gaithersburg, MD 20899

301/921-1000

National Bureau of Standards

Boulder, CO 80303

303/497-3000

October 1984 NBS Special Publication 680-1 Prepared by the Public Information Division A903 Administration Building National Bureau of Standards

Gaithersburg, MD 20899

301/921-3181

Library of Congress

Catalog Card Number: 84-601124

CODEN: XNBSAV

1
Focus on Cooperation and

Communication: An Introduction

eliable measurements are funda- mental to growth and development in industry, to the advancement of science, and to equity in commerce. Consequently, the measurement science and tech- nology work of the National Bureau of Standards relates di- rectly to every segment of this society. NBS is, in fact, unique

among national laboratories in serving such a broad clientele. Today's National Science Policy is based on the premise that the public investment in federal science and technology should

yield maximum public benefit. The

President's Science Advisor, the Panel of the White House Sci- ence Council on Federal Laboratories, and the Congress all emphasize the importance of cooperation between the national laboratories and the potential users of federal science and technology in government, the universities, and

industry. In particular, the 1980

Stevenson-Wydler Technology In- novation Act calls for improved

communications by the national laboratories to stimulate such

cooperation.

NBS works today, as it has for more than 80 years, to achieve

these goals of involvement and

outreach. For instance, each year more than 500 researchers from

outside the Bureau—from universities, private companies, and

other areas of government—work

in NBS laboratories alongside Bureau staff members. Before this year is out, 15,000 individuals from around the country and

abroad will journey to Gai- thersburg, Md., or Boulder, Colo.,

to attend one of our technical conferences or workshops. Another 6,500 people will tour our

laboratories. We send our staff members to technical meetings and confer- ences. We produce about 200

publications each year—available from the Government Printing Office or the National Technical In- formation Service. Our researchers contribute well over 1 ,000 papers to the scientific literature. And some 470 of our staff participate in domestic or international standards-making bodies.

NBS Research Reports is our newest mode of communication.

It looks at a number of Bureau programs in some detail—to give

to managers and policymakers, as well as researchers and inter- ested observers, a broader per- spective on how NBS functions to benefit American science and

industry.

We hope this publication will stimulate interest in NBS activities overall, a first step in strengthening the partnerships that in turn strengthen the nation's scientific base, its public services, and its industrial economy.

Ernest Ambler

Director

2
RESEARCH UPDATE

ESEARCHERS PATENT IM- PROVED ACOUSTIC FLOWMETER

Two NBS physicists have re- ceived a patent on a device that uses long-wavelength sound waves to measure the rate of flow of a fluid in a

pipe or duct. According to inventors James Potzick and Dr. Baldwin

Robertson, the long-wavelength acoustic

flowmeter represents an important im- provement on earlier acoustic flowmeters

that used ultrasonic sound waves be- cause it can be used to measure the

flowrate of gases—a fact confirmed by

extensive experiments at NBS—and be- cause it makes accurate measurements

even when the temperature and velocity

profiles of the gas fluctuate. Potzick and Robertson's flowmeter design was received with considerable in- terest by private industry when the inventors applied for a patent in 1981. Two

firms already have expressed interest in manufacturing a commercial version of the flowmeter. The Potzick-Robertson

long-wavelength acoustic flowmeter was

awarded patent number 4,445,389. Patent licensing is handled by the National Technical Information Service. For fur- ther information on the patent, contact George Kudravetz, Office of Govern- ment Inventions and Patents, NTIS, P.O. Box 1423, Springfield, VA 22151,

703/487-4732.

IDS FOR MEASURING TOXIC

METALS IN HUMAN URINE

NBS has developed a Standard

Reference Material (SRM) that should improve measurements

made when human exposure to a variety

of toxic substances is monitored. Urine

tests have been shown to be good indi- cators of exposure to toxic elements

such as arsenic, mercury, and lead. For

indications of long-term exposure to toxins, medical professionals normally rely on blood tests, but for an accurate gauge

of short-term exposure, urine analysis

usually is the method of choice. The urine reference material (SRM

2670) is in powdered, freeze-dried form. Four bottles are included in the SRM:

two each at low and elevated toxin levels. Included at both low and elevated

levels are arsenic, cadmium, calcium,

chloride, chromium, copper, lead, magnesium, manganese, mercury, nickel, po- tassium, selenium, sodium, and sulfate. For more information, contact: Office of Standard Reference Materials, B311

Chemistry Building, National Bureau of Standards, Gaithersburg, MD 20899,

301/921-2045.

BM STAFFER JOINS NBS TO

STUDY EMI PROBLEMS

The IBM Corporation, as a member of the Computer and Busi- ness Equipment Manufacturer's

Association, has joined with NBS to study electromagnetic interference (EMI)

with data processing and electronic of- fice equipment. Robert F. German of IBM

will spend a year or more as a research

associate at the NBS Boulder, Colo., lab- oratories working with NBS scientists to develop test procedures for small computers and electronic office equipment.

In order to comply with a Federal Communications Commission regulation is- sued in 1982, the office equipment industry needs improved procedures and

techniques that will minimize the amount

of unwanted electromagnetic (EM) radi- ation given off by this equipment while preventing the equipment from being af- fected by environmental EM radiation.

ETROLEUM CRUDE OIL REFERENCE MATERIAL AVAILABLE

NBS researchers have devel- oped a Standard Reference Material (SRM) for evaluating analytical methods used to measure trace or- ganic constituents in petroleum oil samples. Known as SRM 1582, Petroleum

Crude Oil, the new material will allow lab- oratories to check their measurements

and determine how well they are per- forming the steps—sample preparation

and handling, for example—required to analyze complex oil samples.

The material is certified to contain

specified concentrations of six compounds on the Environmental Protection Agency's list of "priority pollutants"

benz[a]anthracene, benzo[a]pyrene, di- benzothiophene, fluoranthene, perylene,

and phenanthrene. The SRM also is useful in evaluating analysis methods for similar compounds in alternate fuels such

as coal-derived liquids. It complements

an earlier-developed shale oil SRM and

consists of five vials, each containing 2

milliliters of petroleum crude oil sample.

SRM 1582 is available for $178 from the

Office of Standard Reference Materials,

B311 Chemistry Building, National Bu- reau of Standards, Gaithersburg, MD

20899, 301/921-2045.

ERAMIC POWDER CHARACTERIZATION LABORATORY ES- TABLISHED

Advanced ceramics are being

used in high-temperature engines

and turbines, electrical capacitors, semiconductors, and other aerospace and

electronic technologies. To help manufacturers, NBS has established a fine- powder laboratory that will enable sci- entists to conduct basic research on key

"powder signatures" that will permit

them to quantitatively correlate powder

characteristics with the physical and

chemical properties in finished ceramics.

The new NBS ceramic powder characterization laboratory contains several clean room stations for use in deter- mining the physical properties of ceramic

powders as small as .003 micrometer. It is equipped to permit researchers to make small-particle materials; determine

particle size and measure distribution of powders in unfired materials or measure

3
RESEARCH UPDATE

particle grains in sintered (fired) materials; classify or size fractionation of powders; and measure physical properties of powders, green-state (unfired), and fin- ished ceramic products. Cooperative pro- grams with university and industry sci- entists will be undertaken in the new

facility. For more information on this facility, write or call Samuel J. Schneider,

A257 Materials Building, National Bureau

of Standards, Gaithersburg, MD 20899,

301/921-2845.

NDUSTRY TO WORK AT NBS

ON POLYMER MATERIALS

Bethlehem Steel Corporation's

Homer Research Laboratories is sponsoring a research associate

at NBS to study the piezoelectric and pyroelectric properties in polyvinylidene flu- oride polymers. Dr. John R. Kastelic,

from Homer's Deformation Processes Di- vision, will use NBS technology as a basis for developing a commercial trans- ducer material. He will characterize films produced by Bethlehem for potential use

in pressure sensors and thermal and

acoustic detectors. NBS offers a wide variety of research

tools within a single laboratory, as well as a staff of scientific experts with more

than 10 years experience in polymer pi- ezoelectrics. Kastelic will work with NBS

scientists to perform thermal pulse ex- periments to measure the distribution of

electrical charges in the interior of poly- mers. He also will use the NBS dielectric spectrometer, various x-ray instruments

for crystallographic studies, a differential scanning calorimeter, and other devices

to measure molecular properties of poly- mers under stress at both static conditions (for several minutes or longer) and

dynamic conditions (as little as 10 milli- seconds).

The NBS Research Associate Program

provides an opportunity for people from

industry, professional societies, and other organizations to conduct cooperative re- search at NBS on projects of mutual in- terest, with their salaries paid by the sponsor.

NTERNATIONAL MEASUREMENTS FOR ORGANOTINS UNDER STUDY

At the request of the Office of Naval Research, NBS is conducting the first international laboratory comparison of organotin measurement methods. The results will be used to develop

a reliable reference material and recom- mended measurement methods for use

by those trying to detect organotin in the environment and to determine the ele- ment's effect on biological processes. Over the past 25 years, worldwide

production of tin has expanded to a point

where toxic exposure from organotin

compounds used as stabilizers in plastics

and as biocides in antifouling agents ex- ceeds the amount of tin that is released by the natural weathering of the Earth's

crust. To carry out the comparison, NBS

has developed a special organic compound solution of tributyltin that has been

sent to more than 45 industrial, aca- demic, and government laboratories worldwide. The research samples may

be analyzed for either total tin or organotin species. The results are to be

returned to NBS for statistical analyses

and evaluation of the measurement

method that was used by each laboratory.

LATING PROCESS TO IM- PROVE USE OF CHROMIUM

DEVELOPED

At the request of the American

Electroplater's Society, NBS has

developed a process, and applied for a

patent, to electrodeposit binary nickel- chromium and cobalt-chromium alloys on

plain low-carbon steel or aluminum sur- faces.

It is estimated that up to 30 percent of imported chromium can be saved if low- carbon steels are substituted for bulk

stainless steels which contain a large

percentage of chromium and nickel. Many of the desired performance properties of stainless steels are required only

at the surface of the material. Alloy coat- ings of nickel with chromium show superior wear performance and corrosion re- sistance when compared with commonly

used bulk 316 L stainless steel. For information on the plating process,

contact: Dr. David S. Lashmore, B162

Polymers Building, National Bureau of Standards, Gaithersburg, MD 20899,

301/921-2958. For information on licens- ing agreements, contact: Office of Gov- ernment Inventions and Patents, NTIS,

P.O. Box 1423, Springfield, VA 22151,

703/487-4732.

ATERIAL TO HELP EVALUATE PERFORMANCE OF

KEY MEASURING DEVICES

NBS has issued a new Stan- dard Reference Material (SRM)

for evaluating the performance of coordi- nate measuring machines (CMM's). CMM's

report the three-dimensional coordinates

of the tip of a probe which is moved over

the surface of the object that is being

measured. Physical limitations introduce

small errors in the reported position of the probe tip, and CMM users must be

careful to purchase machines accurate enough to meet their requirements. To

date, however, no single agreed-upon

method for assessing the accuracy and

precision of such machines exists. Recently, the American Society of Mechanical Engineers released a trial standard to provide such a method. The new NBS

reference material, Socketed Ball Bar (SRM 208), is designed for use with this proposed standard. Ordering information

is available from the Office of Standard

Reference Materials, B311 Chemistry

Building, National Bureau of Standards,

Gaithersburg, MD 20899, 301/921-2045.

4
EUTRON SCATTERING USED

I TO STUDY STRUCTURES IN mm EP0XIES

NBS scientists are looking at the microscopic structures in cured

epoxy resins with a small angle neutron

scattering (SANS) technique. SANS, a

nondestructive tool that uses low-energy

neutrons to characterize three-dimensional properties in materials, permits re- searchers for the first time to study the

uniformity of crosslinking networks that grow out of polymer chains. Crosslink density distribution is a major

factor in determining the structural properties of cured polymers. This information

will help scientists to predict product per- formance and assist manufacturers in controlling curing processes. This type of information is especially useful in the production of graphite fiber composites

for high-performance aerospace components and sports equipment and fiber- glasses for molded items, housewares,

and automobile bodies. For information on the characterization analysis, contact:

Drs. Donald L. Hunston, Wen-Li Wu, or Barry J. Bauer, A209 Polymers Building, National Bureau of Standards, Gaithersburg, MD 20899, 301/921-3318.

ORROSION ENGINEERS' RE- SEARCH ASSOCIATE TO DE- VELOP DATA

The National Association of Corrosion Engineers has selected David E. Clausen, a materials scientist experienced in the use of computers, as

a research associate for the NBS Corrosion Data Center. Clausen will work with NBS researchers in providing industry

with critically needed data for the design

of industrial plants, structures, equipment, and other products that are susceptible to corrosion.

In the Corrosion Data Center, re- searchers will use computers to store and evaluate data collected from the liter- ature, companies, and trade associations. Clausen will help develop computer graphics that will provide basic in- formation for designers and help others

in diagnosing corrosion failures. Corrosion data can be divided into two

classes of information: thermodynamic

data that deals with the long-term stability of metals and kinetic data that shows the rate of the corrosion process.

ATT REPORT ON TECHNICAL

BARRIERS TO TRADE PUBLISHED

Manufacturers, exporters, and

others concerned with inter- national trade will be interested in the annual report on GATT Standards Code Activities of the National Bureau of Stan- dards (SP 678). NBS is the official U.S. GATT (General Agreement on Tariffs and

Trade) inquiry point for standards-related

notifications from the GATT Secretariat

in Geneva, Switzerland. The GATT report lists, by country and

product, proposed foreign mandatory

standards and certification systems that may create technical barriers to trade. Other activities reported include assist- ance to industry to solve standardsrelated trade problems, coordination of comments from industry on proposed for- eign regulations, translations of texts, and the NBS GATT "hotline" that pro- vides the latest information on foreign

notifications. For copies of the report or for information on the GATT inquiry point, contact: JoAnne R. Overman, Standards Code

and Information. A629 Administration

Building, National Bureau of Standards,

Gaithersburg, MD 20899, 301/921-2092.

SING A SYSTEMATIC AP- PROACH TO SOLVE EMI PROBLEMS

The proliferation of sources of electromagnetic (EM) radiation in recent years has created some extremely

hostile environments within which electronic equipment must operate, especially where there are dense concentrations of both high-powered EM

radiating sources and sensitive receiving

equipment. The result has been increasing numbers of complex electromagnetic

interference (EMI) and electromagnetic

susceptibility problems. NBS engineers

have been successful in reducing EMI

levels in several practical applications by

utilizing a systematic approach they de- veloped to attack this type of problem. A

paper describing a particular situation and outlining the problem-solving ap- proach used is now available by contacting Fred McGehan, Division 360.2, National Bureau of Standards, Boulder,

CO 80303, 303/497-3246.

EADLINE SET FOR FIRST ASSESSMENTS OF FILM TESTING

LABS

The application deadline for onsite assessments of laboratories

that test film for microforms—microfilm,

microfiche, aperture cards—and other photographic film is December 1, 1984. The new laboratory accreditation pro- gram (LAP), which will serve a $5 billion market, was established by NBS as a

part of its National Voluntary Accreditation Program at the request of the Association for Information and Image

Management (AIIM). The "film LAP" will provide regulated

industries, utilities, financial groups, and

governments with a list of testing laboratories that are able to ensure that photographic film used for record maintenance

and for copying important historical documents is manufactured and processed to the standards and test methods included

in this program. For additional information or an application package, contact: Manager, Laboratory Accreditation, A531

Administration Building, National Bureau

of Standards, Gaithersburg, MD 20899,

301/921-3431.

5
Standard Interfaces

Key to Factory Automation

bout 1970 we decided that the two most important areas of NBS

concern in the manufacturing

industries—measurement science

and standardization—were going

to be revolutionized by the intro- duction of the computer," recalls

Dr. John Simpson, director of the NBS Center for Manufacturing

Engineering.

That revolution led NBS to a new way of thinking about the machine shop and how it functions. "We now believe," says Simpson, "that the factory of the

future will look like the computer

installation of today, except that the 'peripherals' will have muscles. Instead of printers and plot- ters you will have lathes, milling

machines, and robots." The factory may be in the fu- ture, but much of the technology

that will make it work is here to- day at NBS, where engineers,

machinists, and computer specialists from industry, government,

and academia are at work on the Bureau's unique Automated Manufacturing Research Facility

(AMRF).

The AMRF, which, as Simpson

promised, looks like a cross be- tween a computer installation and

a machine shop, is a research

testbed—the equivalent of an

electronics technician's "breadboard." NBS is building the facility to study fundamental questions affecting factory automation,

questions that affect the modernization and competitiveness of American industry. What is the best way to develop standardized

"interfaces" between different types of equipment? What are the most useful "architectures" for manufacturing systems? How do

you provide for accurate measurements—consistent with national standards—and quality control in an automated shop?

Cooperative research programs

that draw on the expertise of both

NBS scientists and researchers

from private organizations and

other government agencies are an important factor in the Bureau's program. The Navy Manufacturing Technology Office is a major partner in the AMRF, because the Navy

looks forward to significant cost savings when advanced automation research is applied to the manufacturing and warehousing

of spare parts. Thirty-four re- searchers from industry have

worked at the AMRF over the past 3 years, and a number of pri- vate firms and universities have

contributed to the project by

loaning guest workers and equip- ment. The Air Force Intelligent

Task Automation Project and

other government agencies have

also sponsored specific parts of the AMRF effort. When the facility is fully operational in 1986, it will include

several types of automated machine tools, such as milling machines and lathes, automated

materials-handling equipment (to move parts, tools, and raw materials from one "station" to another), and a variety of industrial robots to tend the equipment.

The entire facility runs under

computer control using an ad- vanced control system pioneered

at NBS. The AMRF "factory" in- corporates the most advanced

automated manufacturing control techniques in the world.

In November 1983, NBS ran the

first stage of the AMRF, a demonstration that included two

computer-controlled machine

tools, two industrial robots, a ro- bot cart to move materials around, and a complex computer

network that coordinated the entire facility under a high-level control system. No two components came from the same manufacturer. The system used 34 "stan- dard" interfaces between differ- ent pieces of equipment.

Interface Standards

The AMRF researchers have a

favorite metaphor for their view of the future—machine tools, robots,

and computers should plug to- gether with the ease of a component stereo system. And the user should not be required to have a degree in computer

science. Why? Economics. Specialized,

flexible manufacturing systems al- ready exist, and they are within reach of our large industrial firms.

All that is required is sufficient resources—tens of millions of dollars—to buy a completely inte- grated automated factory or to

hire the experts necessary to work out complex interfaces be- tween otherwise incompatible

equipment.

But close to 90 percent of the

firms in the discrete parts

industry—about 100,000—are

small firms with fewer than 50

employees.

The only feasible way for such

companies to adapt to a world of automated manufacturing is incrementally—buy one sophisticated machine tool this year, operate for a year or two until the

profits make it possible to buy,

say, a computer-aided process

planning system, eventually buy a second machine tool, and so

forth. Such companies need the flexibility to buy from different manufacturers at different times with the assurance that the machines

they buy can be made to work to- gether in the same control sys- tem without expensive, customdesigned interfaces. When the typical "production

run" is comparatively small—say, less than 1 ,000 of any one part at a time—the manufacturer needs

a system flexible enough to switch from the production of one
part to another quickly and with- out expensive reprogramming. It is worth noting that even the most advanced flexible manufacturing systems of today are

limited in their repertoires to a few families of generally similar

parts. How can all this be accomplished? According to the AMRF

researchers, by the clever use of software (computer programs)

and an intelligently designed control system.

"If you write your control soft- ware in a proper, highly structured, highly disciplined fashion, you can have plug-to-plug compatibility for your machines and

computers," says Simpson.

"We believe we know how to set up such a control system, and

last November we proved that such a system can work."

The Software Solution

"One effect of the arrival on the shop floor of the computer and

the microprocessor is that they

are teaching production engineers

to think more formally and more

rigorously," according to Simpson.

Nowhere is this more evident

than in the control structure devised by NBS engineers to manage the Automated Manufacturing

Research Facility. The modular, highly structured programs that run the AMRF

have several features of interest

to the builders and users of modern machine tools. The various subprograms are

not only modular, they also follow

strict rules of format. Various

parts of the system can be re- moved or replaced, as needs dictate, without major changes to the rest of the program. And

since all the modules look somewhat alike—strict formats—they

are easy for humans to under- stand and "debug."

NBS engineer Kang Lee (seated) and technician Michael Huff run tests on a robot

at the AMRF Turning Workstation. This robot uses a precision gripper mechanism

invented at NBS for the delicate task of loading part blanks into the collet of an automated lathe.

Control functions and data are kept strictly separate. The entire

facility is—in the words of project

engineers—"data-driven," that is, the motions that any machine in the facility goes through to pro- duce a part are based on the description of that part in a data- base of the sort produced by

computer-aided design (CAD)

systems. This is in contrast to present-day manufacturing sys- tems that require a separate pro- gram for each part or family of

parts. Changing the part manufactured by the AMRF requires

only a change to the part- description database, not a completely new program. The sensor systems required to monitor the AMRF also use this

database. For example, a unique

feature of the robot vision system

used in the AMRF is that it does

not need to be "taught" to recognize a new part—it knows what

the part should look like from its description in the database.

The interface between any two machines in the AMRF is a com- mon area of memory, where the necessary information is stored in a standard format. "The idea," says Simpson, "is that you never

let any machine call up another on the phone, because they

might interrupt something important. You require them to
leave messages for one another

in memory 'mailboxes'." The "mailbox" system has

several advantages. For machinetool manufacturers, it means that no outside parties need know

anything about their proprietary

control systems and programming

languages. No machine in the system needs to know anything

about any other machine except

the address of its "mailbox."

It also means that the NBS

control system does not tie the AMRF to any one programming

language. "We feel that there is no one language for everything

you might wish to do in a factory," notes Simpson, "and therefore an attempt to standardize a language probably will not work. One of the powers of our scheme

is that it is comparatively easy to agree on the data to exchange

and the format of that data, and

you do not have to specify a lan- guage. Right now we are using

Praxis, RATFOR, Lisp, PROLOG,

C, and Forth." The control system behaves

like an "expert system." The control programs at each level of the AMRF are structured as a series

of directives in the form of "IF (some condition occurs) THEN

(do the following things)." The

last item in the list is always "IF (anything else) THEN (ask for help)." (These are called "state tables" by computer specialists.)

Whenever an unforeseen condition occurs, the system stops and

asks for directions, at which point an engineer must figure out the

Robol Cart Path Computer Racks a Oi J hi D

a Do : 10 D

a Do

On D D

a no i .3 Terminate

Sensory

Processing

Control

Support

This floor diagram shows the arrangement of workstations in the AMRF. Most of the machinery, with the exception of the

automated storage equipment in the upper left corner, is now

in place.

problem and the appropriate solution, which is then added to the

"state table." As a result, the sys- tem gradually absorbs manufacturing knowledge from its users, and the older the system is, the "smarter" it gets. Artificial in- telligence researchers call this a

sort of "expert system."

The Bureau's researchers are

optimistic that they can convince

industry of the merits of their sys- tem. "We believe that you pay a

very small price to have a properly configured control system," says Simpson, "and we do not

believe that adding the ability to interface to this system will in- crease the cost of the product

that much. We will see."

Quality Control

There is another side to the NBS

automation program, the result of the Bureau's traditional goal to supply industry with an accurate system of measurements for quality control. For much of the manufacturing industry, this means supplying gage blocks and

screw-thread gages calibrated against national standards. But this too is changing, say NBS researchers, with the arrival of the microprocessor. Historically, manufacturing and measuring have always been two separate processes. For instance, a

machinist will shape a part on a

lathe and stop periodically to check dimensions with calipers

and gages, or an automated machine will be set to produce a

particular part, and the resulting

products will be measured to as- sure that they are "in tolerance."

If the two processes could be

done at the same time, so that machining a part would be the same as measuring it, the system

would be many times more effi- cient. It would take less time and

there would be fewer parts

scrapped because they are out of tolerance.
The thing to do, according to NBS researchers, is to take ad- vantage of the fact that with modern, computer-controlled machine

tools, the position of the cutting

edge of the tool is known and

controlled at all times, at least in theory, by the computer. So why

not make the tool a measurement

probe?

"The key," says Simpson, "is to realize that if there are no people involved in the actual manufacturing process, then the sys- tem is completely deterministic. In other words, if the system ever once produces a good part, then

something has to change before

it can produce a bad part. With

the appropriate sensors and feed- back mechanisms, you can detect

that change and take corrective measures before a bad part is actually produced."

Looked at another way, continues Simpson, the NBS ap- proach to quality control is to push the theories of Dr. Arthur Deming, a folk-hero in quality- control circles, one step further. "Deming, you may recall, said

that you can get useful information on the performance of your manufacturing processes by making appropriate measurements on

the products and applying statisti- cal analyses. You then can use

that information to improve your

quality control," explains Simpson.

"What we are saying is that in- stead of using the product to monitor the process, it is now possible

to monitor the process itself, and

so control the quality of the

product."

In practice this means that each machine must first be analyzed to determine how it errs. Most such machines can position the tip of a drill, for example, any- where within a three-dimensional

"work space," but there will be a

difference between the actual lo- cation of the drill tip and its "nominal" position according to

the machine's control system.

This is a "static" error, caused by

minor inaccuracies in the machine's parts, and it is very predictable. AMRF engineers use la- ser interferometry and similar techniques to "map" these static errors, and then program compensating "offsets" into the control system.

Machine tools are also subject

to "dynamic errors," errors that

For machine-tool manufacturers, it means that

no outside parties need

know anything about

their proprietary control

systems and programming languages.

change with operating conditions. As a machine heats up or cools down, for example, its parts ex- pand or contract, and this affects

its ability to position a tool accurately. The treatment is to measure the degree of error intro- duced as the machine's

temperature changes and to mount temperature sensors on

the critical parts. The control sys- tem then can monitor the temperature itself and make appropri- ate corrections. NBS researchers have applied

these ideas to a standard vertical machining center and improved

its performance in terms of accuracy and control by five to ten

times. Other sensors can check for more unpredictable problems.

Faced with a common manufacturing problem—drill breakage—NBS engineers built a

small microprocessor-controlled

device which "listens" to the sound made by a bit as it drills holes. As it turns out, the sound

made by a drill in the fraction of a

second before the bit breaks is very distinctive and, through the monitor (dubbed "Drill-Up" by its inventors), the control system can

detect this sound and pull the drill up before it breaks.

Will American companies adopt

the ideas and techniques of the AMRF? That is already happening.

One company has adapted NBSdeveloped error-correction tech- niques to the control system of its machining centers, and another is developing a commercial version

of "Drill-Up." The list of large and

influential companies that work

with NBS on the AMRF project

guarantees that the results of this research at least will receive seri- ous consideration in private

industry.

Where is all this technology

leading? One thing is sure, ac- cording to Simpson, it will change

the jobs of plant engineers and

machinists. "They will need to think more in terms of systems,

the way computer scientists do. Our own staff runs about 2-to-1, computer scientists to mechanical

engineers," says Simpson.

As for larger social effects, he

says, "it will be another several years before we find out if this new technology is a force for in- dustrial aggregation or disaggregation. It could simply lead to more and more vertical integration in the industry, with fewer

and fewer small companies.

"But it might lead to small, dis- aggregated firms. The Norwegian

government, for example, is pushing this route as a way to avoid

the social problems of large

cities. You can do it. With world databases, satellite communications, small flexible manufacturing systems, it is technologically possible."

by Michael Baum

NBS Public Affairs Specialist
Standard Data Formats: Transferring

Part Designs Between Systems

One of the most important con- cepts used in the NBS Automated

Manufacturing Research Facility

is the standardization of data for- mats and the use of commonmemory "mailboxes" as inter- faces between separate modules

of the integrated system.

The AMRF is not the first appli- cation of that idea, however. It has already achieved commercial success among computer-aided

design (CAD) system users as the

Initial Graphics Exchange Specifi- cation (IGES).

Five years ago CAD system us- ers were in about the same situ- ation as automated machine tool users today. There was a broad

selection of commercial CAD sys- tems available, each with its own

software and method of repre- senting data, no two of which were alike. If you needed to transfer a part design from one

system to another, you would

have to have the first system pro- duce the appropriate drawings of the part, carry them over to the second system, and re-enter all of the data. The users were not happy about this. IGES began in a meeting at the

National Academy of Sciences on

October 11, 1979. There, repre- sentatives of the three branches

of the military, the National Aeronautics and Space Administration,

NBS, and suppliers and users of CAD systems discussed existing

efforts to write interface stan- dards for CAD systems and cre- ated the IGES Technical Committee, under the sponsorship of the

Air Force Integrated ComputerAided Manufacturing Program.

NBS agreed to direct and coor- dinate the effort, and a joint industry-government group, with technical assistance from Boeing

and General Electric, produced

the first draft of the graphics ex- change specification in 3 months.

IGES Version 1 was adopted by

the American National Standards

Institute (ANSI) as a major portion

of its standard Y14.26M ("Digital

Representation for Communication of Product Definition Data") in September 1981, and

has been advanced for recognition as an international standard. IGES provides a format for the drawings and the three-dimensional part models typical of CAD

systems. Designers and engi- neers can transfer data between

otherwise incompatible CAD sys- tems by using the IGES format as an intermediate step.

In practice, each CAD system

manufacturer that wants to sell a machine compatible with IGES

simply writes an extra program

that translates data from the in- ternal system used by the machine to the IGES format (and

back again). There is no need to reveal any of the (usually secret)

details of the internal system.

A formal committee structure,

still coordinated by NBS, has

been set up to continue work on

IGES. Last year IGES Version 2 was released to extend the range

of the specification to the types

of data found in electronic "printed" circuit board design and

finite element models.

In July, six companies and federal agencies agreed to cooperate on a 1 -year test of an extension that would expand IGES to encompass modeling systems

that use solid geometry to repre- sent objects. NBS, Bendix Corporation (Kansas City), the Ford Motor Company, the General

Electric Automation Systems Laboratory, the National Aeronautics

and Space Administration, and

Structural Dynamics Research

Corporation will build translators

to test the effectiveness of the experimental solids proposal.

Solid models are important in design and engineering when it is necessary to compute the weight

or volume of a part, model the

structural or thermal performance

of a part, or find out whether a

particular design calls for two

parts to occupy the same space. IGES has been publicly demonstrated several times, most recently in November 1983, at AUTOFACT 5, when 12 major vendors

of computer-aided design/computer-aided manufacturing sys- tems joined together to demonstrate that they could transfer a

typical mechanical part data file accurately from one system to another. Industry figures indicate

that IGES-translation capability is now offered by over 80 percent of the CAD industry. For additional information on

IGES, write or call Bradford

Smith, IGES Coordinator, A353

Metrology Building, National Bu- reau of Standards, Gaithersburg,

MD 20899, 301/921-3691.
How To Secure

Your Computer Systems

Computer researchers Dennis Branstad (standing) and Stuart Katzke investigate techniques for protecting data in computer

systems.

ntil a few years ago, "hacker"

meant someone who drove a cab

or coughed a lot. Recently, it has come to mean someone who

trespasses in another's computer

files. But, while hackers can cause

problems, most experts agree

that the computer security problem is much larger. Computer in- formation, they say, must be

guarded from loss by operator

error, natural disasters, and so- phisticated high-technology attacks on classified systems.

Security experts also agree that there are many straightforward

and relatively inexpensive countermeasures. Dr. Stuart Katzke, an NBS computer security expert, asserts that "between 80 and 90

percent of the problems have

been addressed by the computer

security community and could

easily be avoided by using avail- able management and technical

solutions." Katzke says these in- clude ways to protect against

cross-country break-ins made by

dialing into an organization's

computer system via a telephone

link-up, by getting unauthorized access to computer rooms be- cause of lax physical security, or by other relatively simple routes. NBS is not a regulatory agency,

but through its Institute for Computer Sciences and Technology

(ICST) the Bureau has a special

responsibility to help organizations manage and use computers

effectively. For more than 10

years, NBS specialists have been

developing cost-effective methods to protect data. These methods include sound management

practices as well as automated

techniques that are integrated

into computers and terminals. In

developing these practices and

techniques, NBS works with users and industry to find out what their needs are and to stimulate devel- opment of off-the-shelf commercial products.

According to Katzke, manager

of ICST's computer security man- agement and evaluation group, the first step toward protecting data is to form a comprehensive

computer security program. Al- though this may seem obvious,

Katzke says, it is a step that often

is overlooked. Such a program

should help make computer security an integral part of management and keep everyone in the

organization more aware of problems and solutions. One safeguard that users can

apply is a password system to

11
identify authorized computer users. "Passwords are among the

least expensive ways to protect

data," says Dr. Dennis Branstad,

who heads ICST's computer in- tegrity and security technology

This standard specifies a cryptographic algorithm

for protecting unclassified but sensitive data

that is transmitted between terminals and

computers or between

computers.

group. "If properly used, they pro- vide a reasonable level of control over who has access to a computer system."

NBS soon will issue a standard

with basic guidelines for designing and putting into place a pass- word system. For example, a password should not be used

longer than 1 year and should be

changed as often as is practical.

Also, passwords should be se- lected at random and should not be tied to a user's identity. In other words, says Branstad, it is not a good idea to use the name

of your spouse or child or even

the family pet. And you should

not choose a word related to your

profession. So, a poor choice for a banker's password would be

"money" or "check."

But passwords may not be

enough to protect some systems.

Branstad and his staff have been

investigating other techniques

and devices designed to keep un- authorized people out of computer systems. Some of the devices they have looked at include automated signature verifiers and

machines designed to match fin- gerprints or hand contours

against those already on file. "In our laboratory experiments, we have found that while many

high-technology identification sys- tems work quite well, they are of- ten too expensive for applications

that involve identifying a computer user at a remote terminal,"

Branstad says. Probably the best way to en- sure that data cannot be read,

according to Branstad, is to encrypt it —or scramble the infor- mation—so only those with a "key" can unscramble it. In I977, NBS published the Data Encryption Standard. This standard

specifies a cryptographic algorithm for protecting unclassified but sensitive data that is transmit- ted between terminals and computers or between computers.

NBS has been working with the

financial community to develop

standards needed to protect fi- nancial networks. Its encryption

standard has been adopted by

the American National Standards

Institute and the American Bankers Association for protecting

transfers of funds and securities over communications lines, a pro- cess known as electronic funds

transfer (EFT). And, the Department of the Treasury has drafted a policy calling for all such federal EFT systems to use equipment

which relies on the NBS standard. Several manufacturers have

begun producing devices based

on the NBS standard, and such

systems are available for as little as $295.

In 1983, NBS computer sci- entists Miles Smid and Branstad

received a U.S. patent for devel- oping a way to further protect

data. Used in conjunction with the encryption standard, the Key Notarization System notarizes or "seals" the key used to scramble

and unscramble data with the names of the transmitter and in- tended receiver. With NBS assistance, the De- partment of Energy has used the key system at several of its national laboratories. The financial community is considering making

it part of its voluntary industry

standard on cryptographic key

management.

No matter how secure a sys- tem seems to be there is still the chance that an accident may

damage or destroy valuable data. The NBS experts recommend

that organizations be prepared to recover from major disasters such

as floods as well as disruptions

from hardware and software fail- ures and operator errors. While

the latter may seem minor, they are more of a problem because

they can occur more frequently.

With the proliferation of small desktop computers and networks,

NBS experts recommend

that organizations be prepared to recover from

major disasters. . .as well as disruptions from hardware and software fail- ures and operator errors.

both Katzke and Branstad agree

the potential for problems is increasing. But, Katzke says computer owners are starting to real- ize that their systems are vulner- able and they are beginning to "lock their electronic doors." He adds, "It is going to take a

while for everyone to get the word." In the meantime, the computer security experts at NBS will continue to investigate new locks and develop ways to protect the

keys.

by Jan Kosko

NBS Public Affairs Specialist
For More

on Computet

Security . .

.

In the process of developing

methods for protecting data in computer systems, NBS re- searchers have produced a number of publications. The following

list is a sample of the computer

security publications that are

available. For further information on the NBS computer security

program or to get a complete list of NBS computer security publications, write or call the Institute for Computer Sciences and Technology, B253 Technology Building, National Bureau of Standards, Gaithersburg, MD 20899,

301/921-3414.

Send orders for the publications below to National Technical

Information Service, 5285 Port Royal Road, Springfield, VA

22161.

Data Encryption Standard,

FIPS-PUB-46 (January 1977), $7

prepaid. Specifies an algorithm to be implemented in electronic hardware devices and used for the cryptographic protection of

sensitive, but unclassified, computer data. The algorithm uniquely

defines the mathematical steps

required to transform computer

data into a cryptographic cipher

and the steps required to trans- form the cipher back to its origi- nal form. Guidelines for Security of

Computer Applications, FIPS- PUB-73 (June 1980), $10 prepaid.

Describes the different security

objectives for a computer application, explains the control measures that can be used, and identifies the decisions that should be

made at each stage in the life cycle of computer systems which

require protection.

Guidelines for Implementing

and Using the NBS Data Encryption Standard, FIPS-PUB-74

(April 1981), $8.50 prepaid. Pro- vides guidance for the use of cryptographic techniques when

such techniques are required to protect sensitive or valuable computer data. For use in conjunction

with FIPS-PUB-46 and FIPS-PUB81.DES Modes of Operation,

FIPS-PUB-81 (December 1980), $8.50 prepaid. Defines four modes of operation for the Data

Encryption Standard which may

be used in a wide variety of appli- cations. The modes specify how

data will be encrypted and decrypted. Included in this standard

are the electronic codebook

(ECB) mode, the cipher block

chaining (CBC) mode, the cipher

feedback (CFB) mode, and the output feedback (OFB) mode.

Guideline on User Authentication Techniques for Computer Network Access Control,

FIPS-PUB-83 (September 1980),

$8.50 prepaid. Provides guidance

in the selection and implementation of techniques for authenti- cating the users of remote termi- nals in order to safeguard against

unauthorized access to computers and computer networks. Describes use of passwords, identi- fication tokens, verification by means of personal attributes, identification of remote devices,

role of encryption in network ac- cess control, and computerized

authorization techniques.

Guidelines for ADP Contingency Planning, FIPS-PUB-87

(March 1981), $8.50 prepaid. Describes what should be considered when developing a contingency plan for an ADP facility.

Provides a suggested structure and format which may be used to design a plan to fit each specific

operation.

Guideline for Computer Security Certification and Accreditation, FlPS-PUB- 102 (September 1983), $11.50 prepaid.

Describes how to establish and

how to carry out a certification and accreditation program for computer security. Certification consists of a technical evaluation

of a sensitive system to see how

well it meets its security require- ments. Accreditation is the official management authorization for the operation of the system and is based on the certification process. Maintenance Testing for the

Data Encryption Standard,

Jason Gait, NBS SP 500-61 (August 1980). Order from NTIS as PB 8022121 1, $8.50 prepaid. Describes four tests that can be

used by manufacturers and users

to check the operation of data

encryption devices. These tests are simple, efficient, and independent of the implementation of the Data Encryption Standard (FIPSPUB-46).

Executive Guide to ADP Contingency Planning, James K. Shaw and Stuart W. Katzke, NBS

SP 500-85 (July 1981). Order

from NTIS as PB 82165226, $7

prepaid. Provides, in the form of questions and answers, the back- ground and basic essential infor- mation required to understand the developmental process for auto- matic data processing (ADP) contingency plans. The primary in- tended audience is executives

and managers who depend on ADP resources and services, yet

may not be directly responsible

for the daily management or su- pervision of data processing activities or facilities.
Cold Circuits Next

Step in Electronics Revolution?

he electronics revolution has

been spurred on by rapid ad- vances in the development of large-scale integrated circuits, the

driving force behind today's electronic products. But another kind

of circuit technology being in- vestigated at NBS and other laboratories holds the promise of making today's integrated chips

look laggard by comparison. Ex- tremely cold electronic circuits, based on superconductors in- stead of semiconductors, are at the heart of new devices already being

put to use by NBS. The Bureau

is using such "cryoelectronic"

To provide a more precise

voltage reference for

maintaining the U.S. legal

volt, NBS is exploring the use of superconducting

microelectronic circuits. Here, electronics engineer

Richard Kautz lowers a prototype into a liquid

1 4 helium dewar for testing.

circuits to analyze and count

electrical signals more quickly

and to detect magnetic fields and

electrical currents more sensitively than any other known in- struments. Superconductors are metals and alloys that conduct

electricity with no resistance

whatever when cooled to temperatures near absolute zero

( — 460 T). Besides having zero

resistance, they exhibit several other related phenomena:

An electrical current established in a superconducting loop

will flow forever without additional power.Only an extremely strong

magnetic field will penetrate the surface of a superconductor;

most fields are simply repelled by

the surface.

If a superconductor is inter- rupted by a very thin insulating

barrier, a Josephson junction is formed. Such junctions can be

connected into circuits that detect magnetic fields more sensitively

than any other known devices

and can be made to produce pre- cise voltage increments proportional to the frequency of an exciting current. Superconducting circuits have

been produced that perform certain functions, such as logic, counting, sampling, and analogto-digital conversion, faster than

any other technology.

NBS is one of several research

organizations blazing new trails into this relatively unexplored

field. The Bureau's goal is to im- prove our ability to measure

faster and more sensitively a wide range of phenomena important to U.S. industry, science, and

defense.

Dr. Richard Harris, leader of the

cryoelectronic metrology group at the Bureau's Boulder, Colo., laboratories, explains that the NBS

program concentrates on the the- ory and experimental construction

of superconducting circuits, rather than on development of new

cryoelectronic materials. "We are especially interested in devices useful for measurements,

rather than for digital computation," he says. One of the intriguing uses of cryoelectronics ("cryo" derives

from the Greek, meaning "icycold") is the SQUID, or Superconducting Quantum Interference Device. A SQUID is essentially a superconducting loop interrupted

by one or two Josephson junctions. SQUID'S are exquisitely sensitive to changes in magnetic

fields—for example, those associ- ated with currents in the brain or

heart. Information gained about

brain or heart functions through

SQUID'S complements that of electroencephalograms and elec- trocardiograms and gives doctors a diagnostic tool that localizes the source of a signal more accurately than conventional

techniques.

Sandro Barbanera, an NBS

guest worker from the Italian National Research Council, points out that the SQUID magnetic

measuring device uses a noninvasive technique that avoids the

risks of catheterization and the

errors inherent to skin-contact

electrodes. Barbanera works with Dr. James Zimmerman, an NBS re- searcher who was one of the in- ventors of SQUID'S in the middle

1960's and who has been devel- oping SQUID's for biomedical and

other purposes for more than 15

years. Zimmerman comments:

"While biomedical applications,

particularly non-invasive brain re- search, are the most widespread

and exciting uses of SQUID'S to- day, there are numerous other

applications. They include detecting unusual magnetic patterns

in the ocean (to discover submarines, mines, or sunken vessels) and on land (to prospect for ore bodies or other subsurface

features). In space, SQUID's are
used to measure weak inter- planetary magnetic fields as well as geomagnetic fields close to Earth." Future applications may

include very-low-frequency communications receivers (a leading

prospect for shore-to-submarine

communications). Another appli- cation of SQUID'S is in several

astrophysical experiments to try to detect gravity waves from

outer space. NBS' efforts in superconducting

microcircuit technology extend

beyond SQUID'S to more complex kinds of circuits. Harris explains, "The objective is to establish cryoelectronic microcircuits as practical tools for meeting the demands on NBS for measure- ment support of U.S. industry and

defense. Our program has three main facets: to demonstrate practical instruments of superior per- formance; to explore the funda- mental limits of speed, accuracy, and precision in electromagnetic

instrumentation; and to solve peripheral problems of practical in- strumentation, such as devel- oping a compact, self-contained

refrigeration system to achieve

the extremely low temperatures

needed for superconducting in- struments." Zimmerman and oth- ers have been working in this

third area for several years. "Using NBS-developed super- conducting microcircuits, in only 6

years we have set 'world speed

records' in high-speed sampling,

counting, and analog-to-digital

conversion, and other records in the sensitivity of magnetic field detection and millimeter wave detection," says Harris. Samplers and converters are used to analyze electrical signals. For many of today's applications,

they must operate extremely fast

to detect and record the details of fast-changing signals. One potential use for a superconducting

analog-to-digital converter is in military radar applications. For instance, it would be advantageous

not to let an enemy know that its planes were being tracked by ra- dar. To do this, the emitted radar

signal would need to be "dis- guised" in a sea of simulated

electromagnetic noise. A converter would be needed to pro- cess the returning echo so that a computer could subtract the noise

and recognize the target. The

converter is needed because a computer cannot process raw ra- dar signals—first the signals must

be converted into digital form. Samplers are used to analyze

repetitive signals, such as those

used in computers or other electronic instruments, with extra-high

resolution. They work by picking out a very narrow segment of the

signal, measuring its value, and

then on the next repetition, picking out an adjacent narrow seg- ment, and so on. After thousands

of segments have been examined, an accurate picture of the whole signal is built up in a computer's memory, from where it can be recovered and analyzed.

Dr. Clark Hamilton, who leads

the subgroup working on samplers and converters, points out, "The speed of the super- conducting circuit is its advantage: we have built converters

that operate at 4 billion samples

per second, and our samplers

have achieved a resolution of better than 9 trillionths of a second.

Both are roughly three times

faster than semiconductor devices built to date, and we hope

to achieve at least another factor

of three in samplers and perhaps

10 in converters before we are through."

Ultra-high-speed counters also have been designed in the NBS

labs, operating at up to 100 billion counts per second. These de- vices have possibilities in several

applications, including accurate

voltage measurement and signal

averaging and integration.

Since one of NBS' missions is

to provide measurement stan- dards for science and industry, it is appropriate that the NBS labs are also using superconducting

circuits to improve the nation's voltage standard. A standard

(chemical) cell generates about 1 volt, but its value drifts with time,

temperature variations, and other environmental influences. Using

Josephson junctions, NBS can

generate precise voltage incre- ments that depend only on the frequency of an exciting current. That is noteworthy because fre- quency can be controlled and

measured more accurately than

anything else. So NBS uses the

junctions to monitor the cells, and

thus greatly improves their usefulness as standards. Research is underway at NBS

to try to build a circuit that could make the monitoring process easier and maybe replace the cells

entirely. In January 1984, Dr. Jurgen Niemeyer, a guest worker

from West Germany working with

Dr. Richard Kautz of NBS, demonstrated an array of 1 ,474 Jo- sephson junctions that produced

a constant voltage of 1 .2 volts when exposed to 90-GHz micro- waves. Kautz says, "This demonstrates the feasibility of a much

more accurate, convenient, and

less expensive way to calibrate the standard cells. It may offer a replacement of standard cells for some applications, as well." Cryoelectronic circuits are not

likely to find their way into the av- erage home as components of computers or televisions because

of their need for refrigeration to near absolute zero and because

those applications do not need

the added speed and sensitivity. But for areas of communications

and measurement that require

those advantages, superconducting circuits offer a valuable

alternative.

by Collier Smith

NBS Public Affairs Specialist
New Particles for Measuring

Pigments, Flour, Blood Cells

redictions abound about the super-pure pharmaceuticals and

flaw-free alloys that will someday

be made aboard factories in space. But the very first commercial product to be manufactured

in space has already been pro- duced aboard the space shuttle, and it may seem humble in comparison. As part of a larger pro- gram to explore the basic science

affecting space-based manufacturing, researchers from the National Aeronautics and Space

Administration (NASA) and Lehigh University have developed a process for making plastic beads

in space. Of course, these are not ordi- nary plastic beads. They are tiny polystyrene spheres, only 10 mi- crometers (about 1/2500 of an

inch) in diameter, and they are more perfectly spherical than anything that can be made of comparable size on Earth. NBS will have the honor of measuring and selling them. The

spheres produced in space are the star attraction of a new line of small-particle Standard Reference

Materials (SRM's) that will be

used to calibrate instruments that

They are tiny polystyrene

spheres. . .and they are more perfectly spherical

than anything that can be

made of comparable size

on Earth.

measure the size of everything

from human blood cells to paint

pigments to gunpowder to flour. Manufacturers of such products, says Stanley Rasberry, chief

of the Bureau's Office of Stan- dard Reference Materials, are "all very interested in the size of the

particles in their products and in

trying to keep them within specifi- cations." A photocopier toner

with particles too large or too

small may produce unreadable

copies; pigments in cosmetics or paints may not blend as well as

they should. Even ordinary flour must be ground to the right particle size if it is to produce bread

with the right consistency.

The particle SRM program was

begun, according to Rasberry, at the urging of ASTM, a voluntary

industry standards group, following requests by manufacturers for better standards. "We had a real measurement gap in the range of

0.1 micrometer to 100 micrometers," says the SRM chief. In addition, notes NBS physicist Dr. Thomas Lettieri who heads the

particle SRM certification pro- cess, "each company [manufacturing particle-measuring instru- ments] had its own standards and none of them agreed."

Particle SRM's, explains

Rasberry, make it possible for manufacturers to evaluate their products with confidence. Each of the more than 900 different SRM's sold by the Bureau is carefully analyzed, and then one

or more of its chemical or physical properties are certified by Bureau scientists. In the case of the

small-particle standards, polystyrene spheres in several sizes,

0.1, 0.3, 1, 3, 10, 30, and possibly

100 micrometers, will be certified to have a certain diameter with a

small measurement uncertainty.

The certified spheres can then be

used to calibrate or reset particlemeasuring instruments to give correct readings.

It is more difficult, however, to make the perfectly spherical polystyrene particles needed for measurement standards 10 micrometers and larger than the smaller

sizes, such as 0.3 and 1 micrometer, which have been made successfully on Earth.

The NASA project to make the spheres in space, which is headed by Dr. John W. Vanderhoff

of Lehigh University, will allow the Bureau to extend the range of the

particle SRM series to larger sizes than would be possible oth- erwise. Dale Kornfeld, a NASA

chemist at the Marshall Space

Flight Center in Huntsville, Ala., and coinvestigator for the space

shuttle particle project, explains

why.

The process of producing the spheres, says Kornfeld, is anal- ogous to swelling millions of tiny sponges with water. Microscopic

"seed" spheres made of polystyrene and suspended in water

are mixed with a carefully measured amount of styrene monomer, individual styrene molecules. The monomer, which has a consistency similar to a light oil, penetrates the seed spheres and

swells them from the inside out. When the process is conducted on Earth, the new, larger spheres

rise to the surface because the

oily monomer is lighter than water. Once at the surface, they

tend to pack and clump together,

distorting their shape.

After the spheres are swollen,

they are injected into a chemical

reactor and "baked" to retain

their new, larger size. Chemicals

in the reactor cause the monomer

molecules in the spheres to link together, or polymerize, turning the liquid droplets into solid beads. As the spheres solidify, they become heavier and sink to the bottom of the reactor. This once again causes clumping and

distortion. Stirring can alleviate some of the problem, Kornfeld

says, but when the spheres reach

sizes as large as 10 micrometers,

the liquid must be stirred so vigorously that the stirring itself causes clumping. As a result, a suspension that should look like
skim milk ends up looking like cottage cheese instead. The microgravity environment

of the space shuttle in low Earth

orbit eliminates these problems.

The low gravity prevents the spheres from rising and falling and so they remain uniformly dis- persed in the liquid throughout

the swelling and polymerization

process. Consequently, the particles can be made in batches

that are much more uniform than

similar-sized spheres made on

Earth. Uniformity is critical in the pro- duction of SRM's. The more uni- form each SRM sample is, the more confident users of SRM's

can be that their instruments will be calibrated correctly. For example, SRM 1690, one

of the smali-particle reference

materials, consists of a small vial containing millions of polystyrene

spheres, each approximately 1 micrometer in diameter, in a water solution. Based on measurements performed by Bureau

scientists, the SRM is certified to contain spheres with an average

diameter of 0.895 micrometer and

a standard deviation of about

0.008 micrometer. In other words,

each sample drop of the SRM

contains spheres that vary in size by only about 1 percent.

Accuracy is important because

measurement error is introduced

in each step of a manufacturing

process. A company that sells

particle standards in bulk to manufacturers may buy an SRM and

use it to calibrate particlemeasuring instruments used in their own quality control. Or the instrument manufacturers may

buy the SRM to ensure the accuracy of their particle counters. For

example, even when the particle

standards or measurement instru- ments are used in a bread factory

to regulate the grinding of flour, Physicist Gary Hembree uses a scanning electron microscope to make

electron profiles of the spheres which can be measured with a resolution of about

15 nanometers.

17
COUNTER

AMP/

DISC

HeNe LASER

SCATTERING ANGLE

Top: Schematic diagram of apparatus used in laser light scattering technique. Bottom: Light

scattering pattern for 1 -micrometer-diameter

polystyrene spheres. The dashed line represents

the experimental data; the solid line shows the

theoretical calculations.

additional error can be intro- duced. "We make the best measurements we can," says Lettieri, "so that the measurement uncertainty will still be acceptable by

the time it gets down to the guy

grabbing the flour out of the vat." Bureau scientists achieve this high degree of confidence in their measurements by using at least two different measurement tech- niques to evaluate the same

batch of SRM material. For example, the diameters of the smallparticle SRM's will be certified using at least two of the following

techniques: light scattering, opti- cal microscopy, or scanning electron microscopy.

The first of these techniques,

light scattering, utilizes a laser and a photoelectric detector. Just as the size of a large object can

be gauged by the size of the shadow it casts on a wall, the

size of small particles can be de- termined by noting the behavior

of the laser beam passing

through a solution in which the

particles are suspended in water. The detector is mounted on a movable platform so that the in- tensity of light scattered by the

particles can be measured from

many different angles. The

pattern of light scattering is then

compared with the patterns

predicted by equations for various sizes of spheres. The

particle size is determined from

the theoretical curve that most

closely matches the actual pat- tern of light scattering.

Light scattering can also be

used to measure individual spheres rather than many

spheres in solution. One tech- nique uses electrostatic levitation and involves trapping individual particles with an electric field. A

sample of the spheres in solution

is first sprayed into a closed

chamber. Using a microscope to view the particles, researchers

adjust the voltage in the chamber

until a single sphere is caught

within the electric field and the la- ser beam. The light scattering

pattern from the trapped sphere

is scanned in much the same way

as in the technique described

above.

A similar light scattering

method uses optical levitation of the particles. In this relatively new

technique, a single particle is trapped in the laser beam using

its radiation pressure; the intense

light from the laser beam actually

supports the particle in mid-air. Once the sphere is stabilized in place, the frequency of the laser radiation is changed until the particle resonates or vibrates. A

large particle will resonate at a

lower laser frequency than a

smaller one, the same way that a

large bell vibrates at a lower fre- quency than a small bell. The fre- quencies at which the spheres

Particle SRM's, explains

Rasberry, make it possible for manufacturers to

evaluate their products

with confidence.

resonate make it possible to cal- culate their sizes very precisely.

Lettieri calls this method "the ulti- mate" in particle sizing and says, "We would like to see how far we

can push this technique."

Lettieri and his coworkers re- cently built an optical levitation

light scattering instrument and

plan to use it to measure the 10- and 30-micrometer spheres manufactured on the space shuttle.

Lettieri wants to be able to make

measurements 100 times more

precise than is possible with other

light scattering techniques. The

resolution of the new instrument,

he says, should be about 1 nano- meter or about the width of a few

atoms. The other two methods used by Bureau scientists to measure the spheres involve more direct ap- proaches, but are no less sophisticated in their execution. NBS

physicist Arie Hartman uses an

optical microscope to measure

the spheres directly against an- other SRM, a finely calibrated

linewidth standard. Hartman

18
smears a drop of the spheres in solution on a glass microscope

slide and allows the water to evaporate. He then scans the

slide for a region where the spheres are closely packed into an easily measured array. Comparing the total width of about 20 spheres against the

linewidth standard, and dividing

by the number of spheres in the

array, he arrives at an average di- ameter. This process is repeated

several times with different arrays. To ensure that each set of spheres is measured in exactly

the same way, Hartman devised a method for pinpointing the center

of each particle. A beam of parallel light is directed at the slide and the transparent particles act

like tiny lenses, focusing the light to a small spot just above each

sphere. These tiny spots act as markers for the location of each

sphere and are used to note the beginning and ending points of the measurement with a precision

about ten times better than can

be obtained from microsphere

images.

The other method used, scanning electron microscopy, also can involve viewing the particles

directly, but once again a special

1 v"' ,

procedure is used by Bureau sci- entists to ensure an exact measurement. Most scanning electron microscopes move a beam of electrons across the object being

examined. The electrons "bounce" off the surface of the

object, they are counted by a detector, and an electron intensity

picture of the object is constructed on a television monitor. In this project, however, NBS physicist

Dr. Gary Hembree is using an in- strument that reverses the pro- cess: the electron beam is sta- tionary and a single sphere is moved across it. The spheres are mounted on a platform attached

to a piezoelectric "pusher." As

voltage is applied to the pusher, it expands in tiny increments

thereby moving the sample under

the beam. The exact distance the sample has been moved is deter- mined with a laser interferometer, an extremely precise instrument

that measures distance using in- tersecting beams of laser light. The result is a scattered electron

profile of the particle which can be measured with a resolution of about 15 nanometers. The 0.3- and 1 -micrometer particle SRM's, manufactured on

Earth, have been certified and are

available now for sale. If all goes according to plan, the 10-micrometer space spheres

should be ready for sale by early 1985. Proceeds from the sale of the space spheres will be shared

by the Bureau and NASA to re- cover some of the costs of pro- ducing and certifying the stan- dard. Meanwhile, through the NBS Research Associate Pro-

"We make the best measurements we can," says

Lettieri, "so that the measurement uncertainty will

still be acceptable by the

time it gets down to the

guy grabbing the flour

out of the vat."

gram, the ASTM will provide the services of Russell C. Obbink to help with the NBS certification process. Once in the Office of Standard

Reference Materials' inventory, the particle standards will join a growing list of other unusual products. So far, the Bureau has pro- duced standard metals and al- loys; standard glasses; standard

thermometers; standard urban

dust, river sediment, and oyster

tissue; standard oil; standard

computer tapes; and even stan- dard water. Among such a menagerie of wares, spheres from

space seem pretty ordinary after

all.(For further information about

these or any other SRM's, write or call the Office of Standard Ref- erence Materials, B311 Chemistry

Building, National Bureau of Standards, Gaithersburg, MD 20899,

301/921-2045.)

by Gail Porter Photomicrograph Washington, DC, Science Writer at left shows 5-micrometer polystyrene

spheres made on Earth; 5-micrometer spheres made on the

space shuttle are shown in right photomicrograph.
Measurement Methods for a

New Industry: Industrial Radiation

n the not-very-distant future, Americans may see startling new

products on the grocery shelves: radiation-processed foods.

It may take a while—there are some questions concerning the

regulations and economics of this technology—but irradiated fruits, grains, and meats will almost

surely turn up in our markets sooner or later. More than 20 for- eign countries have already ap- proved the use of at least some

"cosmic-processed" or "radappertized" foods. Depending on the dose, radi- ation such as gamma rays or

x rays can retard the spoilage of fresh fruits, vegetables, and fish.

It can be used in place of danger- ous chemicals such as ethylene

dibromide (EDB) to control insect pests in grains and fruits—it is al- ready used in processing spices—

or to kill disease organisms such

as salmonellae, Campylobacter,

and trichinae in meats. At higher

doses, radiation treatment will sterilize foods, leading to those

long-predicted space-age meats

that can sit on a pantry shelf for years without spoiling.

Most of these treatments, however, require a fairly narrow range

of irradiation. Too little will not achieve the desired effect, too much may damage the food. Food preservation is only one

of the growing number of uses for "industrial radiation." Gamma

rays, x rays, and high-energy

electron beams are also being

used to sterilize disposable medical devices in hospitals and clin- ics and to induce useful changes

in plastics. Tires, for example, are sometimes irradiated to make the elastomer easier to handle in production, and radiation is used

to make dry lubricants out of waste plastic. These industrial uses of radiation are also quite sensitive to dosage, and dosimetry is the most convenient and

accurate means of quality control. As the commercial uses of radi- ation multiply, researchers at NBS

and other federal agencies are developing a number of literally "colorful" techniques to bring ac- curate measurement to radiation processing. In a way, it all goes

back to 1881 and Thomas

Griffiths' gatepost. Griffiths' gatepost was as different from other

gateposts as night and day. In fact, it was different night and

day. It was white during the night

and black during the day.

Griffiths' gatepost, which cre- ated something of a stir in the chemical literature of the time,

had been painted with a zinc- based pigment called lithopone.

Lithopone went through a chemical reaction when light fell on it and changed from white to black. What was curious was that the

reaction was reversible—when

the light source was removed, the compound changed back to white

again. Chemists of the day called the phenomenon "phototropy."

The gatepost was a good indi- cator for telling whether it was

night or day, but since better methods were available, nothing

much came of it at the time. About 40 years later, the gatepost and related phenomena came to the attention of Dr. Lyman Chalkley, Jr., a private

chemist who was working on a

detailed investigation of phototropic substances. Chalkley be- came a world authority on photochemistry and, in particular, on

light-sensitive dyes. In 1964, he went to meet with William McLaughlin, an NBS physicist.

Chalkley had a collection of chemical compounds that would

change from clear to colored when they were exposed to ultra- violet radiation, and he wondered

if the same thing would happen if they were exposed to x rays. Radiation physics was McLaughlin's

speciality.

The first experiments were not promising. "We tried out comparatively low doses of x rays

with no discernible effect," McLaughlin recalls, "so I continued exposing the colorless samples to higher doses. It turned out that they not only

changed color, but they did it lin- early, and the effect was the same at both low and high dose

rates." That is, the color changed at a

rate that was constant with the

radiation dose, and it did not make any difference whether you exposed the compounds to a high

dose rate for a short time or a low dose rate for a long time. Now when you want to measure something like light or radi- ation exposure, those are very handy characteristics for your measurement tool. McLaughlin was immediately interested in Chalkley's dyes. Up to that time, there were no visually discernible chemical detectors that changed

linearly with high radiation doses. Over the next several years, McLaughlin and a handful of col- leagues, from groups such as the Food and Drug Administration (FDA), the U.S. Army, and the Federal Emergency Management

Agency (FEMA), studied the color-changing dyes, which they

called "radiochromic leucodyes."

(Leukos in Greek means "white," so these are literally "radiation- colored colorless dyes.")

The dyes proved amazingly

versatile: they could be used in liquid solutions or mixed into gelatins or plastics. In a chemically

20
neutral medium, the dyes would

become colorless again as soon

as the radiation source was removed—just like Griffiths' gatepost. In a slightly polar-acid medium, they would stay colored once changed, and the color would deepen with successive ex- posures to radiation. McLaughlin and his colleagues

developed a number of applications for the radiochromic dyes

that are now commonplace. Thin

plastic films impregnated with such a dye became industrial dosimeters, used in radiation pro- cesses to sterilize hospital equipment or to create plastics with

special, radiation-enhanced properties. Specially-designed radio- chromic dosimeters were used in defense research to monitor the performance of nuclear weapons.

A particularly elegant application was found in medicine. Physi- cians trying to calculate the dose

of x radiation received by a patient at a particular site in the body have to contend with the

fact that when x rays are deliv- ered to an area where two differ- ent types of tissue, such as bone

and muscle, come together, the

radiation scatters in a complex,

difficult-to-determine pattern of

intensities. McLaughlin and Harry Levine

and Marvin Rosenstein of the Bureau of Radiological Health (part

of the FDA) showed that radio- chromic plastics could be made

with the same x-ray absorbence

properties as different types of body tissue. These could be used

to construct three-dimensional

shapes that mimic the body's re- sponse to x rays at complicated

tissue interfaces and display the

result in color. Dye dosimeters also could be

designed to mimic the radiation

response of other things, such as

foodstuffs, avoiding a critical limitation of previous methods of dosimetry.

An annoying problem remained.

The depth of the color change was proportional to the radiation dose received, so at low doses,

Physicist William McLaughlin

studies the use of speciallytailored, radiation-sensitive

dyes and fiber optics to make

cheap, convenient industrial

radiation dosimeters that can be read with a beam of light.

only a small percentage of the molecules in the dosimeter

changed color. In order to notice any change, either large doses of radiation or very thick dosimeters were needed.

The film and plastic dosimeters

developed up to this point were good for doses of 1,000 rads or more, but they were not very useful for measuring smaller doses.

This ruled out a very important range of dosimetry, from the known threshold for biological ef- fects in humans to the average

21
1 1 1 1

.j 5 frequency = 600 nm

I I I I frequency = 656 nm y/_

i i i i frequency = 680 nm

-1.0

-0.5 / I I I i / i i i i i i i i 0 0.05 0.10 0.15 0.20 0 0.5 1.0 1.5 2.0 0 5 10 15 20 Absorbed dose in kilograys

Three different radiation response curves for a radiochromic dye dosimeter show how the

effective range of the dosimeter changes depending on the wavelength of light used to read the

dosimeter. Lowest range, 0.01 to 0.25 kilograys, is useful for the elimination of insects in fruits. A good range for increasing the shelf life of meats and vegetables and for killing certain

pathogenic organisms such as salmonellae and trichinae is 0.25 to 2 kilograys. Highest range, 2

to 25 kilograys, might be used for the pasteurization and sterilization of fish and meats. The

prototype dosimeter used for these measurements showed some tendency to decay over time

at higher radiation levels (note curves on chart). Later versions reduced this problem.

lethal dose (roughly, from 10 to 500 rads). McLaughlin, Levine,

and two additional colleagues,

Carl Siebentritt of FEMA and

Stanley Kronenberg of the U.S. Army Communication Electronics Command, considered this new

problem.

They calculated that a dye do- simeter of the necessary sensitivity for this range would be

about 1 meter thick—not very convenient—and started thinking

about other approaches.

The answer, they decided, was

to use fiber optics—light pipes. "After all," says Kronenberg, "it

is the light path that must be that

long, not the dosimeter itself." A thin plastic tube filled with the proper radiochromic compound made an excellent optical

pipe or "waveguide." You could make it as long as you would

need and still fit it in a compact

space by simply coiling it up. The first experiments with the waveguide dosimeter brought some surprising results. For in- stance, the particular dye

McLaughlin and the others were

using turned blue when irradiated. When they irradiated one of their

new optical fiber dosimeters and

looked through it, however, the

color was red. That required some thought.

The explanation was discov- ered in the physical theory of light and optics, and in a phenomenon

called "anomalous dispersion."

This phenomenon carried with it a

The dyes proved

amazingly versatile: they

could be used in liquid

solutions or mixed into

gelatins or plastics.

surprise bonus. Because of its ef- fect on the transmission effi- ciency of the waveguide at differ- ent wavelengths of light, it is possible to control the sensitivity range of the dosimeter simply by

selecting the appropriate fre- quency of light to use in reading

it. The same dosimeter can be

used to measure radiation doses

in ranges from about 1 to 1,000,000 rads, depending on the

light source used. Various permutations of this

long-established, if informal, re- search group continue working on

these amazingly versatile dyes.

Very thin fiber-optic dosimeters,

they say, could offer a new ad- vance in medical dosimetry—

catheter-sized dosimeters that could be slipped into very re- stricted parts of the body, such as

the brain, to measure radiation doses at the actual site of tu- mors. The U.S. Army is considering the fiber-optic dosimeters

for use in "wrist-watch radiacs," a combination digital wrist-watch and radiation monitor for military

personnel.

The researchers continue to look for improvements in their dyes as well as the dosimeter

materials and techniques. At a

recent speaking engagement,

Kronenberg stopped before a cup

of hollow plastic coffee-stirrers to consider their resemblance to the

plastic tubes they were using for waveguides. Before he left, he

collected a few samples. After all, you never know where the next good idea will come from.

by Michael Baum

NBS Public Affairs Specialist
Compositional Mapping:

NBS Researchers Take a

Glimpse Into the Atomic World

t first glance, aluminum wiring, dental bridges, and semiconductors for computers may not seem to have much in common.

At least not on a scale visible to the naked eye. But to a group of NBS analytical chemists, these

commodities and many others are

playing key roles in a program to advance the science of measure- ment within atomic dimensions.

To observe this minute region,

NBS scientists are probing and

analyzing materials with an array

of state-of-the-art equipment and

determining why, for instance,

aluminum wiring connections in electrical outlets can get hot enough to start fires. By creating

"compositional maps" with one or

Metallurgist Dale Newbury

makes an adjustment on the

secondary ion mass

spectrometry (SIMS)

instrument. This instrument

allows researchers to map

the distribution of elements

both on and below a sample's

surface.

several of these analytical instru- ments, researchers can learn much about aluminum wire and

many other materials. They can

tell at a glance what processes

are occurring chemically in an

area of 1 micrometer—about

1/1 00th the width of a human

hair—or less.

In existence about 3 years, the Bureau's compositional mapping

program is refining measurement

techniques that ultimately will be

of value to analytical laboratories,

manufacturers, universities, and

federal agencies, says Dr. Dale E. Newbury, head of the program. He explains that since a vast number of physical and biological

processes are controlled by events that take place within atomic dimensions, these maps

of elemental distribution can give

researchers clues about how to analyze or even to modify these

processes. Compositional maps

can be valuable, for example, to makers of alloys attempting to create dental bridges that will not corrode or to manufacturers of semiconductor devices trying to figure out why such products

sometimes fail. Much like a road map tells trav- elers which cities are located in a

given geographic area, a compositional map tells scientists which

elements or compounds are present at any point in a given

sample. Some compositional

maps are actually photographs

that look like aerial maps, while others more closely resemble

graphs, with the concentration of elements plotted along one axis and their depth distribution along

another. With a compositional map in hand, researchers can examine

not only those elements present on the surface of a sample, but

also those in the atom-thin layers

under the surface. This can be

especially important when evaluating semiconductor samples, be- cause impurities in active regions

beneath surface layers may "poi- son" a device, rendering it inef- fective. Knowing the nature of the subsurface elements can give

manufacturers the key to modifying device processing for max- imum reliability. Newbury attributes much of the success of the NBS program to the variety of instruments his lab- oratory is stocked with, some of which are bought, some modified,

and one built from scratch. A few

of these instruments do their work by using electron beams, one uses ions, and still others operate with photons (light energy). Individually, these instru- ments are powerful analytical

tools, but they are not without shortcomings. Used together,

however, the strengths of one

machine can compensate for the weaknesses of another. "No one instrument we have

here at NBS is so unusual that we are the only ones who have

it," says Newbury. "What makes

us unique is that we have such a

variety of instruments that complement each other for compositional mapping. This allows us

to tackle just about any situation." The "central workhorse," as Newbury calls it, of the compositional mapping program is the

electron probe microanalyzer.

This instrument is a scanning

electron microscope combined

with an x-ray microanalyzer. It al- lows a highly magnified picture to be made—up to a magnification

of 100,000 times—as researchers

perform a compositional analysis on the sample. Newbury speaks

highly of these instruments: "They are the ones we have the most faith in. We understand

them the best, and in a way they

are the most powerful —because

you can see something and analyze it too, especially on a scale

23
70 keV Boron-10 in Silicon

Dose = 1016 10 B/cm2 30 Min Anneal at 1000° C

102

1020 E

on

©

CD 101

101

o Secondary Ion Mass Spectra

• Neutron Depth

Profile

0 200 400 600 800

Depth in Nanometers

Above: An example of a

lateral compositional map

showing the distribution of

oxygen on the surface of a copper alloy. This image was

produced by the secondary

ion mass spectrometry

(SIMS) instrument.

Left: Two independent

compositional mapping

techniques, neutron depth

profiling (NDP) and secondary

ion mass spectrometry

(SIMS), were used to produce

this map showing the depth

distribution of boron in silicon.

that is of great interest to many

practical problems."

It was by using the electron probe microanalyzer that NBS re- searchers discovered why alumi- num wiring fastened loosely at electrical outlets in houses could

arc, causing a "glow phenomenon." Temperatures in excess of 1500 °C—enough to melt iron components or to start a fire

were shown to be feasible. By ex- amining compositional maps, re- searchers found that highresistance "intermetallic" compounds were being formed

through reactions between the aluminum wire and the iron screw

holding it in place. The wire in ex- perimental NBS setups was essentially being turned into a

heating coil similar to those in toasters. The glow phenomenon,

however, was shown to be pres- ent only where the aluminum

wire was connected loosely. Tight

connections generated very little heat. While the electron probe micro- analyzer is considered an excellent tool for analyzing samples

about 1 micrometer in size, NBS

scientists sometimes need a machine that will image and analyze a much smaller realm for compositional maps. In these instances,

researchers turn to the analytical electron microscope, or AEM.

With this instrument, it is possible

to view and analyze an area 10

billionths of a meter—or about 30

atom diameters—in size. And

while it uses the same tech- nology, electron beams, as the

electron probe microanalyzer, the

AEM gives an image with much

higher resolution and thus is more

suited for analyzing tiny airborne

particles. (The electron probe in- strument, on the other hand,

works best with solid specimens

like aluminum wire.) The shortcomings of the AEM—it cannot, for example,

easily analyze light elements such

as boron, oxygen, and carbonare overcome at NBS by using a

laser microprobe mass analyzer

(LAMMA). With this instrument,

researchers can identify any ele- ment in a sample.

NBS is putting the AEM/

LAMMA combination to use in a

cooperative program with the University of Maryland to study the

"Arctic Haze," a dark cloud that hangs over the North Pole. At NBS, researchers are trying to determine where the haze comes

from by analyzing single particles

and drawing compositional maps.

Some scientists in the past have

guessed that the haze comes

from coal power plants in Europe

and Asia, but the NBS/Maryland

research is expected to give some of the best information

available on the haze's origin. While the Bureau's compositional mapping program has

made some important measurement advances, Newbury

says there is room for improvement. For example, while re- searchers can identify a molecule

in a sample, they hope to develop

techniques to quantify them.

But for now, whether NBS re- searchers are working on im- proving compositional mapping in- struments or interpreting the

results from those already in use, the program continues to forge new ground in understanding

what goes on at the atomic level of processes.

by John Henkel

NBS Public Affairs Specialist

24
Tools of the NBS

Compositional Mapping Program

In the area of compositional mapping, NBS is unique in that it has

a full range of analytical equipment at one geographic location. While some of these instruments

have shortcomings, NBS re- searchers often use them in tan- dem to compensate for weaknesses and increase measure- ment accuracy. Instruments are

either electron, photon, ion, or neutron beam analyzers. Brief descriptions follow: Electron probe microanalyzer

An electron beam technique that combines a scanning electron mi- croscope and an x-ray microanalyzer, this instrument is nor- mally used for preliminary, nondestructive analyses of solid specimens such as aluminum

wire. It allows a photograph up to 100,000 times in magnification to be made and a compositional

analysis to be performed within an area of 1 micrometer—about

1 /100th the width of a human

hair—or more. The technology for these instruments dates back to the late 1940's.

Analytical electron microscope

(AEM)—Much more elaborate in

its analyzing capabilities, this electron beam device allows an

image up to 500,000 times in magnification to be viewed and

an analysis within 10 billionths of a meter—about 30 atom diameters in size—to be made. A nondestructive technique, the AEM is normally the instrument chosen

for particle analysis because of its higher resolution capabilities.

Though it gives an illuminating im- age of the sample, the AEM cannot give good quantitative anal- yses of light elements such as

lithium, boron, oxygen, or carbon. And the AEM is useless when try- ing to measure the different types

of atoms of a particular element

(isotopes), which among other

things can give scientists clues about the age of a specimen.

Laser microprobe mass analyzer (LAMMA)—When NBS re- searchers want a complete analysis of elements, especially within

particles, but do not mind if the sample is destroyed, they use the LAMMA. This photon-energy in- strument works by concentrating

a beam of light at a 1 -micrometer

target in a sample, destroying the specimen by evaporation. In the process, charged ions are cre- ated from some of the sample's

atoms. These ions are aimed into a tube-like device, and since all the ions are created at the same

instant, they are accelerated si- multaneously. But because ions

of different elements have varying masses, they are accelerated at different velocities, so the lightest ion will get to the end of the tube

first. By examining a readout from

the LAMMA, researchers can tell which elements are in the sample, and how much is there. Secondary ion mass spectrometry (SIMS) instrumentKnown commonly as an ion mi- croscope, the SIMS instrument

allows NBS researchers to map

the distribution of elements both on and below a sample's surface. While literally sputtering away the atom layers, much like peeling an

onion, the SIMS instrument takes a series of stop-action pictures of each layer being analyzed. Researchers can record the data ei- ther photographically or by storing

it in a computer where this data can be enhanced for better inter- pretation. SIMS, by nature of its sputtering action, destroys the sample. Neutron depth profiling

(NDP)—This technique is often used when researchers want the same kind of depth distribution in- formation the SIMS instrument

provides, but do not want to destroy the sample. Using NBS'

20-megawatt reactor to produce a neutron beam, Bureau researchers have to date most often applied NDP in the analysis of semiconductor samples. NDP, however, works only on a few ele- ments such as helium, lithium, boron, and nitrogen. But NDP is valuable because it provides a reference method which can be

used to calibrate other techniques

such as SIMS.

Laser Raman microprobe

Built from scratch at NBS several years ago, this device allows re- searchers to analyze the compounds present in samples. Other

instruments used in the program

are best suited for detecting ele- ments. Before this invention,

Raman instruments could be

used only on fairly large samples—1 millimeter or larger. What

NBS scientists did was to create an instrument that could profile areas down to 1 micrometer in size. And while the Bureau's Raman instrument can show the presence of some compounds, it cannot at present show how

much of a compound is in a

sample.
NEW PUBLICATIONS

MEASUREMENT SYSTEMS AND

METHODS FOR OPTICAL FIBERS

Chamberlain, G.E., Day, C.W., Franzen,

D.L., eta/., Optica/ Fiber Characterization— Volume 2, Natl. Bur. Stand. (U.S.), NBS Spec. Pub. 637-2, 234 pages (October 1983). Order by stock no. SP 637-2

from the National Bureau of Standards,

Division 360.2, Boulder, CO 80303, $15

prepaid.

NBS fiber optics measurement systems

and methods are described in detail in this hardbound book. It covers measurements of attenuation, bandwidth

(frequency-domain), and far-field/nearfield radiation patterns, plus a glossary of

fiber optics terms and definitions. It sup- plements an earlier publication (SP

637-1) on the measurement of optical fi- ber backscatter, time-domain bandwidth,

and index profile, which is also available from the same address for $15 prepaid.

CENTER FOR FIRE RESEARCH

GRANTS AND IN-HOUSE PROGRAMS

Cherry, S.M., editor, Summaries of Center for Fire Research Grants and In- House Programs— 1983, Natl. Bur. Stand. (U.S.), NBSIR 83-2800, 156 pages

(December 1983). Order by stock no. PB

84-155340 from NT/S, $16 prepaid.

This publication contains one- and two- page abstracts of grants and contracts

for fire research sponsored by the NBS

Center for Fire Research. In addition, the Center's internal research programs are

described.

NEW NBS STANDARD REFERENCE

MATERIALS CATALOG

Hudson, C.H., editor, NBS Standard

Reference Materials Catalog

1984-1985, Natl. Bur. Stand. (U.S.), NBS

Spec. Pub. 260, 174 pages (February

1984). Order by stock no. SP 260 from

the Office of Standard Reference Materials, B311 Chemistry Building, National

Bureau of Standards, Gaithersburg, MD

20899, telephone 301/921-2045.

This new catalog lists more than 900

Standard Reference Materials (SRM's)

available from NBS. For more than 75

years, NBS has provided SRM's to scientific, industrial, and commercial users throughout the world. They are used to help improve measurement accuracy by

providing a way to calibrate instruments. SRM's, which are well-characterized materials with specific chemical or physical

properties certified by NBS, include such

items as cements, ores, metals, glasses,

plastics, foods, and environmental and

clinical reference materials. The catalog's format provides quick access to material description, certified characterization, unit size, and type.

LIQUEFIED NATURAL GAS DENSITIES

Haynes, W.M., McCarty R.D., and Hiza,

M.J., Liquefied Natural Gas Densities:

Summary of Research Programs at

the National Bureau of Standards,

Natl. Bur. Stand. (U.S.), NBS Monograph

172, 240 pages (October 1983). Order by

stock no. 003-003-02528-3 from GPO,

$6.50 prepaid.

Knowing the densities of liquefied natural gas (LNG) and its components is crucial

for those involved in the production,

transport, use, and, especially, the sale

of this important commodity. Domestic

and international trade in LNG amounts

to billions of dollars per year, and accurate knowledge of its properties, especially density, is essential to equity in trade and efficient processing and utiliza- tion. This publication provides results of a 1 0-year program to develop mathematical models, instrumentation, and an

accurate database for LNG density. It also reprints 14 original papers on LNG

density published by NBS researchers

since 1 972 in a variety of media.

CRITERIA FOR STORING PAPER

RECORDS

Mathey, R.G., Faison, T.K., and

SiIberstein, S , Air Quality Criteria for Storage of Paper-Based Archival

Records, Natl. Bur. Stand. (U.S.), NBSIR

83-2795, 51 pages (November 1983). Or- der by stock no. PB 84- 135607 from

NT/S, $13 prepaid.

To save time and money, many organi- zations now preserve records on microfilm and discard the original paper materials. But some records, such as his- torical documents or valuable books,

need to be preserved permanently in ideal storage conditions. When storing

these archival documents, factors such

as temperature, humidity, and air pollut- ants need to be controlled. A study by

the NBS Center for Building Technology

on the air quality in the National Archives

Building in Washington, D.C., describes

damage that may otherwise occur, and

proposes criteria for setting environmental conditions. Examples of air quality cri- teria now used by various libraries and museums also are given. Although this study was conducted to improve the air quality in a particular building, it should

be useful in the design or modification

of other facilities used to store archival materials.

AN OVERVIEW OF ARTIFICIAL INTEL- LIGENCE

Gevarter, W.B., An Overview of Artificial Intelligence and Robotics: Vol- ume 1—Artificial Intelligence, Part A—

the Core Ingredients, Natl. Bur. Stand.

(U.S.), NBSIR 83-2799, 66 pages (Jan- uary 1984). Order by stock no. PB

84- 178037 -A04 (paper) or -A01 (fiche) from NT/S, $10 (paper) or $4.50 (fiche). NBS, in cooperation with the National Aeronautics and Space Administration (NASA), has published a new overview to the field of artificial intelligence (Al). The

overview, by Dr. William B. Gevarter of NASA, discusses the nature of Al and its history, techniques, and applications. It also lists the principal organizations, both

26
foreign and domestic, now pursuing Al research. The two other parts of this study were published by NASA and are

available from NTIS: Part B—Fundamental Application Areas (NTIS

#N84-10834, $13 paper/$4.50 fiche) and Part C—Basic Al Topics (NTIS

#N84-14805, $10 paper/$4.50 fiche).

TEXT ON EXPERIMENTATION AND

MEASUREMENT

Youden, W.J., Experimentation and

Measurement, Natl. Bur. Stand. (U.S.), NBS Spec. Pub. 672, 127 pages (March

1984). Order by stock no. 003-003-

02575-5 from GPO, $3.75 prepaid.

NBS has republished a popular text to in- troduce science students to the role of elementary statistics in the design and in- terpretation of experiments. It was first published in 1962 as part of a series of books developed and produced by the

National Science Teacher's Association,

and has been out of print for several

years. In short, essay-like chapters,

Youden takes the student from a general

discussion of the importance of measurements in science, through the harsh

fact of the existence of experimental error, to the use of statistics to bring some

order to chaos. Along the way he in- vokes examples from everyday life and

practical situations in science and engineering. Youden, who died in 1971, was a recognized master in the field of the statistical design of experiments.

ECONOMIC MODEL ASSESSES BENEFITS OF IMPROVED TEST ACCURACY

Weber, S.F., and Hillstrom, A.P., Economic Model of Calibration Improvements for Automatic Test Equipment,

Natl. Bur. Stand. (U.S.), NBS Spec. Pub.

673, 84 pages (April 1984). Order by

stock no. 003-003-02580- 1 from GPO,

$3.25 prepaid.

NBS has developed an economic model

to calibrate the benefits of improving the

quality of measurements made in mainte- nance or production testing programs. The model will assist managers in as- sessing the value of improving the accuracy of electronic test equipment, especially "automatic test equipment"

(ATE). NBS researchers say it also can

be applied easily to many other types of testing situations. Quality assurance managers must take into account the

fact that ATE, like all test equipment, occasionally will make a mistake and either

reject a good unit or accept a faulty unit. Rejecting or retesting good products is obviously expensive, but accepting bad

products can be even more costly, particularly if lives depend on the proper

functioning of the product. The model

can be used to optimize policies for pro- curement of new test equipment, for maintenance and calibration of existing

test equipment, and for setting test specifications to achieve the proper balance

between "consumer's loss" and "pro- ducer's loss."

COMPUTER SECURITY GUIDELINE

Guideline for Computer Security Certi- fication and Accreditation, Natl. Bur. Stand. (U.S.), NBS FIPS - PUB- 1 02, 95

pages (September 1983). Order by title and stock no. FIPS-PUB-102 from NTIS,

$11.50 prepaid.

Probably as important as having a general computer security program is being

assured it meets an organization's specific security requirements. The Institute for Computer Sciences and Technology

at NBS has developed a guide designed

to give managers a structured way of de- termining whether their computer security

safeguards are adequate for their individ- ual needs. This report is designed especially to help protect highly sensitive computer systems and data, but it can be used for less sensitive systems as

well. This Federal Information Processing

Standards publication details steps on how to establish and carry out a certifica- tion and accreditation program. It also discusses evaluation techniques which can be used, including risk analysis; vali- dation, verification, and testing; EDP audit; and security safeguard evaluation. A

companion document, Overview of

Computer Security Certification and

Accreditation , is available through GPO

for $1.50 prepaid. Order by stock no. 003-003-02567-4.

SUPERCRITICAL FLUID EXTRACTION

Fly, J.F., and Baker, J.K., A Review of

Supercritical Fluid Extraction, Natl. Bur. Stand. (U.S.), NBS Tech. Note 1070. 77 pages (December 1983). Order by

stock no. 003-003-02537-2 from GPO,

$4.50 prepaid.

The use of dense gases in a supercritical state as solvents in chemical extractions and separations has grown rapidly in the

last 10 years as an alternative to liquid solvents and distillation methods. Supercritical fluid extraction (SFE) offers im- proved thermal efficiency in some cases, avoids thermal degradation of extracted components in other systems, and substitutes non-toxic solvents for toxic ones

in certain food and drug processes. SFE

also has applications as an analytical

tool and for thermophysical properties measurements. This review summarizes

the physical phenomena and describes

several applications of SFE in the energy and chemical industries (coal conversion,

de-ashing, de-caffeination) and in analysis and measurements.

ORDERING INFORMATION

To order publications from NTIS, send

request with payment to: National Technical Information Service, Springfield, VA

22161. Publications can be ordered from

GPO by mailing order with payment to: Superintendent of Documents, U.S. Gov- ernment Printina Office, Washington, DC

20402.

27
CONFERENCE CALENDAR

Winter Simulation Conference, Sher- aton Dallas Hotel, Dallas, TX

November 28-30, 1984

The 1984 Winter Simulation Conference

will feature papers, tutorials, state-of-theart review sessions, and panel discus- sions on discrete and combined (discrete

continuous) simulation. The following topics will be discussed: distributed simulation, offshore technology, manufacturing, environmental systems, mini and

micro applications, graphic applications, health care systems, transportation, en- ergy and petroleum systems, communications, military systems, aerospace

applications, and planning scheduling.

Sponsored by the Association for Computing Machinery, the Institute of Electrical and Electronics Engineers, the In- stitute of Industrial Engineers, NBS, the Operations Research Society of America,

the Society for Computer Simulation, and

the Institute of Management Sciences.

Contact: Patsy Saunders, A1013 Administration Building, NBS, Gaithersburg, MD

20899, 301/921-3132.

Computer Networking Symposium,

NBS, Gaithersburg, MD

December 12, 1984

This symposium will highlight discussions

of the design, selection, performance,

and implementation of current and soonto-be-available networking systems. Pa- pers are being solicited on such topics as long-haul networks, PBX systems, satellite systems, video systems, electronic

mail, teleconferencing, network testing,

network procurement, and videotext. Sponsored by the Institute of Electrical and Electronics Engineers Computer Society and NBS. Contact: Robert

Rosenthal, B226 Technology Building,

NBS, Gaithersburg, MD 20899,

301/921-3516.

Eighth Conference on Materials for Coal Conversion Utilization, NBS,

Gaithersburg, MD

February 27-March 1, 1985

The latest materials research and devel- opment information pertinent to fossil en- ergy systems will be presented at the

Eighth Conference on Materials for Coal

Conversion and Utilization. The systems

to be discussed include conventional and

advanced coal-fired power plants, coal

gasification and liquefaction, heat en- gines and heat recovery, and fuel cells. The conference will broadly cover both metal and ceramic applications. Sponsored by NBS, the Electric Power Research Institute, the Department of Energy, and the Gas Research Institute. Contact: Samuel J. Schneider, A257

Materials Building, NBS, Gaithersburg, MD

20899, 301/921-2845.

The Mechanical Failures Prevention

Group (MFPG) Symposium, NBS,

Gaithersburg, MD

April 16- 18, 1985

This MFPG symposium will attempt to improve communications among the people who are responsible for reducing mechanical failures in weapons systems and

supporting defense equipment. Participants will be given an opportunity to

identify new and advanced techniques

for mechanical failure detection. These

technologies will help Department of Defense (DoD) design and test engineers,

their industrial suppliers, and DoD consultants to improve the readiness and reliability of military weapons, support

equipment, and structures. Sponsored by

NBS, the Office of Naval Research, and

the Army Materials Mechanics Research

Center. Contact: Dr. James Early, A153

Materials Building, NBS, Gaithersburg,

MD 20899, 301/921-2976.

OM 85 Topical Conference on Basic

Properties of Optical Materials, NBS,

Gaithersburg, MD

May 7-9, 1985

The use of optical materials in advanced

applications such as optical signal pro- cessing, optical computing, integrated

optics, optical coatings, optical domes,

and laser windows is placing increasingly

stringent requirements on material per- formance. The purpose of this NBS con- ference is to bring together researchers

from industry, academia, and government

to discuss the physical and structural properties of optical materials as they af- fect performance. The scope of the con- ference will include the measurement

and theory of basic properties of optical materials in bulk and in thin film form and

the dependence of these properties on

atomic structure, morphological structure, impurity content, and inhomogeneity.

Sponsored by NBS, the Air Force Office

of Scientific Research, and the Office of Naval Research. Contact: Dr. Albert Feldman, B328 Materials Building, NBS,

Gaithersburg, MD 20899, 301/921-2817.

International Conference on Biologically Induced Corrosion, NBS,

Gaithersburg, MD

June 10-12, 1985

This conference will focus on mechanisms, case histories, and experimental

methods of and remedial measures for biologically induced corrosion in both

natural and artificial environments. Special emphasis will be placed on corrosion

mechanisms and on establishing the causative links between the simultaneous

observations of corrosion and the pres- ence of microorganisms. The conference

will also define topics for further re- search. Sponsored by the National Association of Corrosion Engineers and NBS.

Contact: Dr. Warren Iverson, A331 Materials Building, NBS, Gaithersburg, MD

20899, 301/921-2953.

28
he National Bureau of Standards' was established by an act of Congress on March 3, 1901. The

Bureau's overall goal is to strengthen and advance the nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a

basis for the nation's physical measurement system, (2) scientific and technological services for industry and

government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety.

The Bureau's technical work is performed by the National Measurement Laboratory, the National

Engineering Laboratory, the Institute for Computer Sciences and Technology, and the Center for Materials

Science.

The National Measurement Laboratory

Provides the national system of physical and chemical measurement;

coordinates the system with measurement systems of other nations and

furnishes essential services leading to accurate and uniform physical and

chemical measurement throughout the Nation's scientific community, in- dustry, and commerce; provides advisory and research services to other Government agencies; conducts physical and chemical research; develops,

produces, and distributes Standard Reference 'Materials; and provides

calibration services. The Laboratory consists of the following centers:

• Basic Standards2 • Radiation Research

• Chemical Physics

• Analytical Chemistry

The National Engineering Laboratory

Provides technology and technical services to the public and private sectors to address national needs and to solve national problems; conducts research in engineering and applied science in support of these efforts; builds and maintains competence in the necessary disciplines required to carry out this research and technical service; develops engineering data and measurement

capabilities; provides engineering measurement traceability services; develops

test methods and proposes engineering standards and code changes; develops

and proposes new engineering practices; and develops and improves

mechanisms to transfer results of its research to the ultimate user. The

Laboratory consists of the following centers:

Applied Mathematics

Electronics and Electrical Engineering2 Manufacturing Engineering

Building Technology

Fire Research

Chemical Engineering2

The Institute for Computer Sciences and Technology

Conducts research and provides scientific and technical services to aid Federal agencies in the selection, acquisition, application, and use of computer technology to improve effectiveness and economy in Government

operations in accordance with Public Law 89-306 (40 U.S.C. 759), relevant Executive Orders, and other directives; carries out this mission by managing

the Federal Information Processing Standards Program, developing Federal ADP standards guidelines, and managing Federal participation in ADP

voluntary standardization activities; provides scientific and technological advisory services and assistance to Federal agencies; and provides the technical foundation for computer-related policies of the Federal Government. The Institute consists of the following centers:

Programming Science and

Technology

Computer Systems

Engineering

The Center for Materials Science

Conducts research and provides measurements, data, standards, reference

materials, quantitative understanding and other technical information fundamental to the processing, structure, properties and performance of materials; addresses the scientific basis for new advanced materials technologies; plans

research around cross-country scientific themes such as nondestructive

evaluation and phase diagram development; oversees Bureau-wide technical programs in nuclear reactor radiation research and nondestructive evaluation; and broadly disseminates generic technical information resulting from

its programs. The Center consists of the following Divisions:

Inorganic Materials Fracture and Deformation3 Polymers

Metallurgy Reactor Radiation

'Headquarters and Laboratories at Gaithersburg, MD, unless otherwise noted; mailing address

Gaithersburg, MD 20899.

2 Some divisions within the center are located at Boulder, CO 80303.

3 Located at Boulder, CO, with some elements at Gaithersburg, MD.
U.S. UtHAH 1 MbN 1 OF CUMMERCfc

National Bureau of Standards

BULK RATE

POSTAGE & FEES PAID INDo

"" Gaithersburg, MD 20899

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