Innovation and reliability in hyperfine frequency standards and clock systems are discussed. Hyperfine standards are defined as those precision frequency sources and clocks which use a hyperfine atomic transition for frequency control and which have realized significant commercial production and acceptance (cesium, hydrogen, and rubidium atoms). References to other systems such as thallium and ammonia are excluded since these atomic standards have not been commercially exploited in this country

Kern, R.

English

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INNOVATION AND RELIABILITY' OF ATOMIC STANDARDS FOR
PTTI APPLICATIONS
Robert Kern
KERNCO, Inc.
Danvers, Mass.
ABSTRACT
Over the past 20 years, the U.S. Government has been the
largest single customer for hyperfine frequency standards
and clocks. In this same period the government directly
and indirectly has provided financial support of extensive
research, development and manufacturing methodology efforts
in industrial and government laboratories.
The GPS/NAVSTAR Program requirements for a spaceborne clock
has provided new impetus and development monies to generate
multiple sources of reliable frequency standards and clocks
with life expectancies of 5 to 7 years. These multiple
sources will produce significant economies and performance
improvements to PTTI users in the U.S.
The GPS/NAVSTAR designs should result in units with improved
stability and environmental tolerance that will provide U.S.
systems planners with strategic advantages .in the PTTI field.
I would like to address the subject of innovation and reliability in
hyperfine frequency standards and clock systems. Hyperfine standards
are defined as those precision frequency sources and clocks which use
a hyperfine atomic transition for frequency control and which have
realized significant commercial production and acceptance. I refer to
the cesium, hydrogen, and rubidium atoms and exclude references to
other systems such as thallium and ammonia since these atomic standards
have not been commercially exploited in this country.
275
https://ntrs.nasa.gov/search.jsp?R=19810018941 2020-03-21T13:00:21+00:00Z
In the\1ate 50's and early 60's several companies pioneered in the
development and production of atomic standards. In the mid 60's
statistically significant quantities of cesium and rubidium standards
were produced, sold, and put into service by PTTI user agencies. The
reliable performance established by the Hewlett Packard hyperfine
standards in the 1960's stimulated government interest in additional
system applications and further development of the hyperfine family
of standards.
In the early 70's the Department of Defense issued military speci-
fications (MIL F 28734 & Elex F 105) which defined four types of
cesium standards. Our industry saw the issuance of these MIL
specifications as a clear signal by the government that there was
a growing opportunity in cesium and hyperfine clocks for system
applications.
Until the 1970's government support of hyperfine standards was
focused on research and technology development. In the 70's the
emphasis shifted and intensified toward the development of specific
hardware with direct application to major systems concerned with
navigation, communications, Very Long Baseline Interferometry (VLBI)
and space experiments. The GPS/NAVSTAR need for development of a
spaceborne clock provided great impetus for innovative activities in
all three hyperfine clocks. New companies and new concepts advanced
rapidly in this period producing new miniature rubidium standards,
small long lived cesium standards, and prototype passive H masers.
The stong levels of government funding matured these new designs
and spawned a broad series of commercially available products.
In the late 70's and now into the early 80's, our industry con-
tinues to benefit and mature from both continuing government support
and an active commercial marketplace for quality hyperfine standards.
Contractual funding from the Department of Defense is directed
toward higher system performance and multiple sources of cesium,
rubidium, and hydrogen clocks.
To summarize this development activity the following table describes
the companies who have been recipients of government funding and a
parenthetical estimate of this funding (to date) in millions of
dollars.
276
CESIUM RUBIDIUM HYDROGEN MASER
Atomichron, Inc.*
Freq. Control Corp.*
FEI
FTS
Hewlett Packard
Kernco, Inc.
NBS
National Radio*
Pickard & Burns*
Varian Associates*
Autonetics - (Rockwell)
Collins - (Rockwell)
Efratom
E G & 6
General Radio*
General Technology*
Hewlett Packard
Tracer*
Varian Associates*
(20 - 25) (15 - 20)
*No longer active in this business
Applied Physics Lab./JHU
Hewlett Packard*
Hughes Research Lab.
Jet Propulsion Lab.
NASA Goddard
NBS
Sigma Tau Corporation
Smithsonian Astro ,
U. S. Naval Res. Lab.
Varian Associates*
Universities: Harvard
Laval
Williams
(25 - 30)
The figures support public statements made that there is more support
and more work available than the hyperfine companies can ingest. Many
companies in this field have doubled over the past two years. Perhaps
this preoccupation with growth in this period of prosperity has caused
a diversion of industry attention from the issues of performance and
reliability.
The U.S. Government, as a customer, has had a vested interest to de-
velop both improved clocks and competitive sources for them. The
hyperfine technologies have enjoyed strong levels of direct and in-
direct customer support these past ten years and must now address
the question of customer payback. Current programs to qualify
several suppliers for GPS/NAVSTAR clocks should favorably impact
both the economics and the stability of the source(s) of supply.
277
The payoff to the government customer is rooted in the fact that for
the first time in our business qualified competition exists in all the
hyperfine standards. It is no longer adequate for the manufacturer to
certify his design, build, and verify by test that the equipment
initially meets all applicable acceptance specifications. In the
future it should be necessary for the manufacturers both to guarantee
and to demonstrate that the customer will actually realize the called
for lifetime expectations. Demonstration of the lifetime cost para-
meter must be an integral condition for a manufacturer to receive
future business.
Let me suggest a valid signal that development is truly complete when
a manufacturer releases a quantity of commercial products directly
spawned from the government sponsored development effort and assumes
a significant commercial warranty obligations for these commercial
units. It is then that the government customer, after paying for the
development, has a right to expect a stable price structure, con-
tinuing product improvement and a purchase price that is less than ten
times the price of the commercial unit.
The specific point I wish to make today concerns innovation and re-
liability in hyperfine physics packages. The intensive developments
now underway would not be necessary if our industry had achieved the
equipment which the government customer(s), some 90% of the market,
funded to bring into being.
The technology base for hyperfine physics packages had been estab-
lished and remained locked away under a "proprietary information"
label by a few companies. Government scientists and engineers did
not have the opportunity to participate in and evaluate the under-
lying design and processing philosophy of the physics packages. Nor
have the manufacturers revealed the details of factory and field
failure history of the design. Only by customer-supplier discussion
and analysis of such data can specific problems be quantified and
user insights applied to yield simple environment compatible solutions
to engineering or processing weaknesses.
This lack of physics package 'know-how' and the lack in the visibility
of data make it difficult for a user to evaluate whether a given
supplier can consistently meet his lifetime and performance require-
ments. Usually the customer can provide verification that the
electronic components are procured, screened and assembled to a speci-
fied practice. When it comes to the physics package used in the
equipment, the PTTI user must accept company assurance that the
'proprietary unit1 was built according to strict process specifi-
278
cations and in facilities unique to the system requirements. Then,
screening and in-house unit testing will do the rest of the reliability
and performance job.
Until recently the development sponsoring agency could not purchase
cesium or rubidium physics packages without buying the whole standard
or clock. In my opinion what remains to be done is for the Department
of Defense customer to conduct specific in-house testing and make
design appraisals of the hyperfine physics package. By establishing
end user data concerning the reliability and lifetime performance of
a given design, in a government laboratory, the customer could compare
results with data provided by the manufacturer.
The tests to be performed by the government laboratory can include
several tests usually conducted by the manufacturers and can be ex-
panded to include tests which reveal the design limits of the device.
A
 PHYSICS PACKAGE TESTS
FOR DESIGN CHARACTERIZATION
o Accelerated Life Testing
o High/llow Ambient Temperature Runs
o Irradiation
o Over Voltage Testing
o Temperature Gradient Induction
o R.F. Power Shift Stimulation
o Spectral Sensitivity
The appearance of multiple manufacturers in the GPS/NAVSTAR hyperfine
marketplace will provide economic and performance benefits to the
whole of the PTTI community. It now remains for the U.S. Government
to establish an in-service capability for the assessment, evaluation
and lifetime testing of the physics units utilized by these manu-
facturers. With data and the institution of manufacturing controls
and safeguards the government's support can finally produce an
economic and performance return on investment.
279
QUESTIONS AND ANSWERS
DR. HELLWIG:
Maybe just a comment on the availability of physics packages for
testing. If I remember right, Varian was willing and able to sell
tubes in the '60's. I think Hewlett-Packard did so in the early
days -- 1970's -- and FTS has sold tubes over the past years to the
U.S. government. That is not a question of lack of availability.
It is a Tack of focus on this problem which I totally agree
with you, Bob. I think this is one of the major problems.
CHAIRMAN STOVER:
Well, there seems to be a common thread through the papers we have
heard so far of need for more cooperation between industry and
government. We will see if that continues with our other two papers.
280


Innovation and reliability of atomic standards for PTTI applications

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