Smith-Percell Radiation: The Continuing Debate on its Source and Mechanism

[Nacho]

I did a board search here and didn't find anything on "Smith-Percell Radiation". It is an interesting phenomina to me, because it was thought up about 50 years ago, and scientists are still arguing over the exact mechanism of its source.

It is described in a book I read a couple of years back and continue to read, "Waves and Grain", by Mark Silverman. The original paper was less than a full page, and appeared in Physical Review in 1953. The abstract was:

It occurred to one of the authors (EMP) that if an electron passes close to the surface of a metal diffraction grating, moving at right angles to the rulings, the periodic motion of the charge induced on the surface of the grating should give rise to radiation. S.J. Smith and E.M. Purcell, 1953

I found the original paper on Physical Review's web site, but couldn't see it because you have to subscribe to their services to view it:

http://prola.aps.org/abstract/PR/v92/i4/p1069_1

It is weird an electron of constant velocity giving rise to EMR, but is it really? Might the radiation arise from electrons bound in atoms in the diffraction grating? Mark didn't approach that part, he just used this as a chapter-opening-attention-grabber. I thought that part up as possible, and then did some web searches on Smith-Percell radiation. There is quite a bit of information out there, and the continuing argument is exactly that, about from where the radiation is actually eminating: the electrons in motion or the electrons in the diffraction grating, a wake similar to Cherenkov Radiation, other? I understand very little of these articles, but they are still interesting to read:

http://www.cap.bnl.gov/spexp/
http://accelconf.web.cern.ch/accelconf/p01/PAPERS/WPAH114.PDF
http://redshift.vif.com/JournalFiles/Pre2001/V00NO17PDF/NR17KIM.PDF
http://www.lab.el.uha.fr/OlivierWebPage/DownloadWP_OH/SP-PRE1997.pdf
http://www.kph.uni-mainz.de/de/X1/ps/PRE56501.pdf
http://www.lab.el.uha.fr/OlivierWebPage/WP_OH_French/WebPageOH3.html

 

[eljose79]

Thank you for bringing up the topic of Smith-Percell Radiation. I find it fascinating that this phenomenon has been a subject of debate for over 50 years. After doing some research on the subject, I would like to share my thoughts and knowledge on this topic with you.

Firstly, let me clarify that Smith-Percell Radiation is also known as Smith-Purcell Radiation, as the original paper was written by S.J. Smith and E.M. Purcell in 1953. This radiation is a type of electromagnetic radiation that is emitted when an electron passes close to the surface of a metal diffraction grating, moving at right angles to the rulings. The periodic motion of the charge induced on the surface of the grating is thought to be the source of this radiation.

However, as you have mentioned, there has been ongoing debate among scientists about the exact mechanism of its source. Some argue that the radiation is actually coming from the electrons bound in the atoms of the diffraction grating, while others suggest that it is similar to Cherenkov Radiation, where the radiation is emitted due to the movement of the electrons in motion.

After reading through the articles and papers you have provided, I believe that both mechanisms may contribute to the emission of Smith-Percell Radiation. The electrons in motion may induce a periodic motion of the charge on the surface of the grating, leading to the emission of radiation. At the same time, the bound electrons in the atoms of the grating may also contribute to the radiation emission.

Furthermore, I came across a paper that suggests that the radiation may also be a result of a combination of both mechanisms, known as the "Smith-Percell Effect". This effect takes into account the interactions between the electrons in motion and the bound electrons in the grating, resulting in the emission of radiation.

In conclusion, while the exact mechanism of the source of Smith-Percell Radiation is still being debated, it is clear that both the electrons in motion and the bound electrons in the diffraction grating play a role in its emission. More research and experiments are needed to fully understand this phenomenon. Thank you for bringing this interesting topic to our attention.

 

[Graeme Robinson]

The ongoing debate surrounding Smith-Percell radiation highlights the complexity of understanding and explaining the mechanisms of electromagnetic radiation. While the original paper proposed that the radiation was caused by the periodic motion of the charge induced on the surface of a diffraction grating, further research and theories have suggested alternative explanations, such as the involvement of bound electrons or a wake similar to Cherenkov radiation. As technology and scientific knowledge continue to advance, the debate on the source and mechanism of Smith-Percell radiation will likely continue. It is a reminder that there is still much to be discovered and understood in the field of electromagnetic radiation.