Use of a large bulb, long-multipole magnet, automatic tuner and aluminum cavity provides an improved hydrogen maser which is accurate over long periods of time and suitable for tracking station environments

Mc Gunigal, T. E.

Peters, H. E.

English

NASA Technical Reports Server

September 1969	 Brief 69-10341 
NASA TECH BRIEF 
_____.= •- ________ 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
An Improved Atomic Hydrogen Frequency and Time Standard 
.
The problem: 
To develop a hydrogen maser frequency and time 
standard which is highly stable and accurate over 
long periods of time and suitable for tracking-station 
environments. 
The solution: 
Use of a large bulb, long-rn ultipole magnet, auto-
matic tuner and aluminum cavity provides an im-
proved hydrogen maser. 
How it's done: 
Cost, size, weight, and the need for special train-
ing to operate the maser have been restraining fac-
tors in its widespread use in laboratories. When this 
problem was recognized work was started to improve 
the maser and develop auxiliary systems for its use 
by nonspecialists. An experimental model, which has 
beet Operating continuously since September 1967, 
is providing stable signals and further experimental 
data. Based on the experimental work, four complete 
prototype field operable standards have been de-
signed and constructed and are, as of June 1969, all 
in operation and undergoing tests. 
The new model, which utilizes an aluminum cavity, 
provides several advantages: (1) electrically opaque, 
(2) reproducible high Q, (3) mechanically stable, (4) 
readily available and, (5) inexpensive. The large ther-
mal expansion, fifty times that of fused silica, can be 
used advantageously to tune the cavity. This elimi-
nates the need for problematic mechanical tuners, 
or varactor diode tuning methods. Long-term cavity 
drifts, although small, are corrected completely by
a unique automatic cavity tuner which is part of the 
system. 
One improvement incorporated by this maser is the 
use of a bulb much larger than usual. Use of the 
large bulb is based upon operation of the cavity very 
near waveguide cutoff diameter, where the frequency 
depends primarily upon diameter and loading, while 
the length may be increased as desired. 
Modifications have been made to the state selector, 
for example, a long, small bore, high-flux multipole 
magnet is used to "capture" the maximum possible 
flux of upper state atoms from the source, and to re-
move the lower state atoms from the beam. The long 
magnet was found to be desirable because it assures 
that a larger number of atoms actually enter the bulb. 
Notes: 
1. The information described in this innovation may 
be of interest to personnel working with masers 
and atomic frequency standards. 
2. Documentation is available from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Price $3.00 
Reference: TSP69- 10341 
Patent status: 
No patent action is contemplated by NASA. 
Source: H. E. Peters, T. E. McGunigal, 
and E. H. Johnson 
Goddard Space Flight Center 
(GSC- 10706) 
Category 02 
S
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
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An improved atomic hydrogen frequency and time standard

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