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Summary

Description
English: Cloud chamber photograph of the first positron ever observed. The thick horizontal line is a lead plate. The positron entered the cloud chamber in the lower left, was slowed down by the lead plane, and curved to the upper left. The curvature of the path is caused by an applied magnetic field that acts perpendicular to the image plane. The higher energy of the entering positron resulted in lower curvature of its path.
Original caption: A 63 million volt positron (Hρ = 2.1×105 gauss-cm) passing through a 6 mm lead plate and emerging as a 23 million volt positron (Hρ = 7.5×104 gauss-cm). The length of this latter path is at least ten times greater than the possible length of a proton path of this curvature.
Date Photographed 2 August 1932. Published 15 March 1933.
Source Anderson, Carl D. (1933). "The Positive Electron". Physical Review 43 (6): 491–494. DOI:10.1103/PhysRev.43.491.
Author Carl D. Anderson (1905–1991)
Permission
(Reusing this file)		 Obtained from American Physical Society, March 5, 2008. The copyright for the periodical containing this picture, if renewed, would have had to be renewed in 1960 or 1961. I checked the Catalog of copyright entries for Periodicals in 1960 and 1961, http://onlinebooks.library.upenn.edu/cce/, but The Physical Review is not listed there. Therefore, the copyright on the entire issue of The Physical Review, including this picture, has expired.

Licensing

Public domain
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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Captions

The first cloud chamber photograph of a positron's path

Items portrayed in this file

depicts

antimatter

positron

matter

media type

image/jpeg

inception

2 August 1932

File history

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Date/TimeThumbnailDimensionsUserComment
current19:12, 6 May 2013Thumbnail for version as of 19:12, 6 May 20132,408 × 2,374 (1.91 MB)QuibikCombined with a moire- and halftone-free but blurrier version that was also provided in the article. Much more accurate now.
18:10, 6 May 2013Thumbnail for version as of 18:10, 6 May 20132,500 × 2,500 (1.97 MB)QuibikRe-extracted the image from the source article in greater resolution, removed halftone & moiré and adjusted levels.
16:54, 3 May 2008Thumbnail for version as of 16:54, 3 May 2008848 × 755 (71 KB)HPaul{{Information |Description=Cloud chamber photograph of the first positron ever observed |Source=Physical Review, Vol.43, p. 491 |Date=March 15, 1933 |Author=Carl D. Anderson |Permission=obtained from American Physical Society, March 5, 2008 |other_version

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