Charles_Townes_and_first_maser.jpg
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Summary
| Description |
English:
The first
maser
(Microwave Amplification by Stimulated Emission of Radiation), invented by
Charles H. Townes
, James P. Gordon, and H. J. Zeiger at Columbia University in 1953. Townes, Nikolay Basov and Alexander Prokhorov were awarded the 1964
Nobel Prize in Physics
for theoretical research that led to the maser. Townes is shown with the device. This was an ammonia maser. The brass box is the vacuum chamber through which the ammonia ions travel. The ammonia gas nozzle is at left. The four rods at center are the
quadrupole filter
which filters out the lower state ammonia molecules, leaving a
population inversion
. In the
resonant cavity
at right, stimulated emission of microwaves by the molecules excites standing waves in the cavity, which pass out through the vertical output waveguide. The devices at bottom are vacuum pumps which evacuated the box. Masers are used as the timekeeping elements in
atomic clocks
, and as extremely low-noise microwave amplifiers in
radio telescopes
. Alterations to image: cropped out rest of magazine cover
|
| Date | |
| Source | Retrieved February 18, 2015 from Radio-Electronic Engineering magazine, Ziff-Davis Publishing Co., New York, Vol. 26, No. 6, June 1955, cover on http://www.americanradiohistory.com |
| Author | Dan Rubin |
|
Permission
( Reusing this file ) |
This 1955 issue of Radio-Electronic Engineering magazine would have the copyright renewed in 1983. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here . Search of the Renewals for Periodicals for 1978 and later show no renewal entries for Radio-Electronic Engineering . Therefore the copyright was not renewed and it is in the public domain. |
Licensing
|
This work is in the
public domain
because it was published in the United States between 1929 and 1963, and although there may or may not have been a copyright notice, the
copyright was not renewed
. For further explanation, see
Commons:Hirtle chart
and
the copyright renewal logs
. Note that it may still be copyrighted in jurisdictions that do not apply the
rule of the shorter term
for US works (depending on the date of the author's death), such as Canada (70 years
p.m.a.
), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.
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| Annotations | This image is annotated: View the annotations at Commons |
