Talk:Cyclotron

Merger proposal

I would like to merge the article isochronous cyclotron to the article cyclotron, since the first mentioned page has little content and is very closely related the last mentioned article. (Please object within two weeks) BR84 (talk) 20:40, 27 December 2011 (UTC)

BR84 (talk) 18:57, 23 February 2012 (UTC)

Notable Examples

I cleaned up the introductory section by creating a "History" and a "Notable Examples" section. The latter is noticeably underpopulated at the moment, containing only TRIUMF. I don't have time to do it right now, but that section should probably include RIKEN, NSCL, and the one in Germany whose name escapes me at the moment. - PianoDan (talk) 13:09, 1 May 2012 (UTC)

Frequency range of magnetron radiation mis-identified.

As written, the article incorrectly states the magnetron is, "...a device for producing high frequency radio waves..." It then goes on to state the wavelength as "microwaves."

A magnetron does indeed produce microwaves; but microwaves are not considered to be in the high-frequency or "HF" range of the radio spectrum. Instead, they are in the "super-high" or SHF range. This is confirmed by a number of existing Wikipedia articles, including the one titled Super high frequency.

Although this is minor point, it does work against Wikipedia's well-known goal of consistency across related articles. — Preceding unsigned comment added by 107.77.66.16 (talk) 16:55, 10 June 2014 (UTC)

Article showcases lazy editors

This article illustrates the typical shortcomings of technical articles on Wikipedia. The two line introduction tells almost nothing about the subject, and is not an adequate summary in blatant violation of WP:LEAD. The brief explanation of how it works will be pretty much opaque to general readers. The history section discusses obscure Russian cyclotrons but omits the most notable machines of all, Lawrence's 60 and 184 inch cyclotrons.

Most of all, the editors show off their precious math skills with a confused derivation of the relativistic formula for cyclotron frequency, but manage to omit the most important formula of all, what anyone coming to this page wants to know, the formula for the output energy of the particle!!!

All of this is due of course to lazy egocentric editing; when the choice came between writing a comprehensible encyclopedia article and indulging your private interests, the ego won out. Nice going, guys. I made an effort to correct your screwups. --Chetvorno^TALK 15:52, 26 October 2014 (UTC)

1932 or 1931?

The text, Radioactivity: Introduction and History, by Michael F. L'Annunziata on page 2 states that "Ernest Lawrence built the first working cyclotron in 1931..." That's a year prior to the date in the introduction to this article. If anyone can resolve that minor disagreement, please feel free to reply to this question. Thanks! — Preceding unsigned comment added by BobEnyart (talk • contribs) 19:09, 3 August 2016 (UTC)

it shouldn't be the size of the apparatus stated as a reason for notability

the lede ends with this 2 sentence statement: "The largest single-magnet cyclotron was the 4.67 m (184 in) synchrocyclotron built between 1940 and 1946 by Lawrence at the University of California at Berkeley,[4] which could accelerate protons to 730 MeV. The largest cyclotron is the 17.1 m (56 ft) multimagnet TRIUMF accelerator at the University of British Columbia in Vancouver, British Columbia which can produce 500 MeV protons."

now, it seems obvious that size of the machine is of lower importance than the output produced, eg: the maximum energy of the particles. on this ground i suggest deleting the second sentence, and perhaps mention the TRIUMF as a curiousity in the history section.

the current text suggests that TRIUMF is an upgrade of the Berkeley synchrocyclotron (multiple magnets, BIGGER size) which it is not, judged by it's lower energy output. 80.99.38.199 (talk) 20:28, 18 February 2018 (UTC).

or, alternatively, in case TRIUMF is an advancement in some sense (a later section mentions something along the line that it accelerates different particles than protons, or that it is more effective/cheaper to operate due to a difference in the feeding material for the particles to be accelerated) then THIS difference should be stated instead of the size of the apparatus, which in itself is hardly a reason for notability. 80.99.38.199 (talk) 17:06, 19 February 2018 (UTC).

By which metric is TRIUMF's cyclotron largest?

TRIUMF's cyclotron appears to be neither largest in size given that the RIKEN cyclotron appears to be larger in both mass and diameter . Additionally, TRIUMF's cyclotron does not appear to be the most powerful in terms of particle speed or luminosity given that the the Paul Scherrer Institute in has a 590 MeV cyclotron and over 2 mA whereas TRIUMF's seems to be limited to roughly 150 micro amperes when calculating based on claimed power in kW . In one place it mentions that TRIUMF's cyclotron is the the largest "of it's kind," "of it's kind" should be defined. For example, "of it's kind" may refer to "derived from Berkley designs" or "negative ion, isochronous, non-superconducting" - but clarity would be appreciated; I may be misunderstanding. ~~JKumlin~~ 12:06, 27 Jan 2022 (UTC). — Preceding unsigned comment added by 70.36.61.115 (talk)

References

Hi JKumlin! I'm working on revising this article one chunk at a time, and "Current Examples" (including their references elsewhere in the article) is next on the list after revising the section on uses for the things. But feel free to walk down the hall and have a chat about this in person. :) PianoDan (talk) 16:32, 27 January 2022 (UTC)

Leo Szilárd has the prority (1929) in the invention

Just read this article: https://physicstoday.scitation.org/doi/pdf/10.1063/1.1325189 no he doesnt. his alleged patent application doesnt exist in any patent databases. ergo, it was never published, and neither lawrence or anybody else ever saw it. further, max steenbeck claimed an even earlier priority, in 1927. in fact, the first published description of a cyclotron is lawrence's october 1930 paper, which was published after he and his student built the first cyclotron in april of that year. priority goes to lawrence — Preceding unsigned comment added by Ammonitida (talk • contribs) 02:23, 19 August 2023 (UTC)

Minor COI disclosure

Oop. Now that I'm editing the section on medical uses of cyclotrons, I need to disclose that I work for a company that makes targets for medical cyclotrons. I will endeavor to keep my edits in the area of specific isotopes and their uses limited, and hew as closely as possible to cited neutral sources. For example, The isotopes I chose as illustrations for cyclotron produced radioisotopes were the ones listed as most common in the cited IAEA report, plus Technetium-99m, which has been in the news of late. Once this section is fleshed out, I intend to leave it to other editors. Hopefully this is acceptable. PianoDan (talk) 18:53, 27 January 2022 (UTC)

Therapeutic Beams

This sentence in the introduction's last paragraph could be improved by clarifying what therapeutic beams are or adding a link. " Close to 1500 cyclotrons are used in nuclear medicine worldwide for the production of radionuclides and therapeutic beams" ScientistBuilder (talk) 21:04, 8 February 2022 (UTC)

Done - I reworded the sentence slightly to refer to "particle therapy" rather than "theraputic beams", since we already have a Wikipedia article on that topic. The same reference covers both. PianoDan (talk) 21:28, 8 February 2022 (UTC)

Explanation

I think it would be helpful to explain its useful to have more smaller magnets as opposed to one big magnet here: " Later developments included the use of more powerful superconducting magnets and the separation of the magnets into discrete sectors, as opposed to a single large magnet"ScientistBuilder (talk) 17:35, 9 February 2022 (UTC)

Improvements to history

There is a lack of period: "He was assisted by a graduate student, M. Stanley Livingston Their first working cyclotron became operational in January of 1931" I think centimeters should be the main unit and inches the parentheses unit unless it was specified at the time as 4.5 inches. I think it would be helpful to include a qualifier explaining how powerful 80keV is.

I think it would be helpful to explain what RF stands for: As such, modern particle accelerators use alternating (RF) electric fields for acceleration I think it would be helpful to mention some typical values of the Kfactor. Are the elements thorium and plutonium ever used in heavy ion beams? Is there a way to add reference for the 4.5 inch cyclotron in the table? Other than that, I think it is a good article and I do not think these should be reasons to not have it as a good article.

• Period - Already fixed.
• Dimensions - The Lawrence machines were all specified in inches at the time, which is why their sizes are nice round numbers.
• Electron volts - We wikilink to the description of the unit, but I'd be open to other suggestions for how to conextualize what "80 keV" is.
• RF - Expanded to "Radio Frequency".
• K-factor - The range of cyclotron energies is so wide, I'm not sure there's a "typical" value to cite here.
• Thorium and Plutonium - I am unaware of either of these elements ever having been used as the ion in a cyclotron beam, rather than as a target.
• 4.5 inch cyclotron Reference added.

PianoDan (talk) 18:32, 11 February 2022 (UTC)

Awkward mixing of quantities

"... the particles' energy was equal to the accelerating voltage ..." is a convenient shorthand, and this conflation of quantities also occurs elsewhere in the article, and detracts from its quality. In this context, more clarity and correctness may be appropriate. A possible modification might be "... the particles' energy per elementary charge unit was equal to the accelerating voltage ..." Fixing this everywhere may need a little thought, and I'm not promising to do it – only highlighting the need. 172.82.46.53 (talk) 21:28, 20 February 2022 (UTC)

An excellent point. I'm so used to thinking about energies and masses interchangeably in terms of eV that I forget it's not necessarily intuitive. I'll give it some thought. PianoDan (talk) 03:57, 21 February 2022 (UTC)

Type of spiral

Fermat spiral

Archimedean spiral

There are many types of spirals. The following reference says that a Fermat spiral is used; this is a spiral in which successive windings get closer together so that the area of each winding remains constant.

• Vogel, Helmut (June 1979), "A better way to construct the sunflower head", Mathematical Biosciences, 44 (3–4): 179–189, doi:10.1016/0025-5564(79)90080-4

This would match the appearance of Lawrence's patent drawing, but disagrees with the big cutaway diagram at the start of "Principle of operation" which looks more like an Archimedean spiral. However, a paper on biology is not really a good source for a topic about physics. Can this detail be sourced better and clarified in the article? —David Eppstein (talk) 23:53, 16 June 2022 (UTC)

Technically, it's NOT a spiral at all, it's a a connected series of arcs of constant radius. Every time the particle crosses the accelerating gap, and ONLY when it crosses the accelerating gap, it gains energy. Other than at the gap, the particle is "coasting" at a constant(ish) speed, which means it is turning with a constant radius.

The classical cyclotron had a pair of "D" shaped electrodes, so the particle would cross the gap twice per orbit. Modern cyclotrons can have more than two accelerating gaps per orbit, but the principle is the same - the particle is accelerated at the gap, and only there, and that's the only place the orbit radius actually changes. (Amusingly, the accelerating structures are often still referred to as "dees", regardless of their actual shape.)

A stylized approximation of the orbit in a one gap cyclotron (where the particle crosses the gap twice per orbit) would be two sets of concentric half-circles, with each half circle connected to one of slightly larger radius, and the connection points forming a straight line at the gap. (A less approximate model would take into account the fact that the gap has a finite size, so the acceleration doesn't take place instantaneously.)

But since a typical cyclotron particle will orbit hundreds of times before extraction (or collision with an internal target), the orbit is usually described as a "spiral" as a convenient approximation rather than as rigorous technical language.

Additionally, this is all the first approximation where you assume a constant magnetic field. Real cyclotrons also azimuthally vary the field for the purpose of keeping the beam focused in the plane of acceleration (which makes the orbits a bit "lumpy" viewed from above). And isochronous cyclotrons, which represent MOST extant models, also progressively increase the field strength with radius to compensate for the relativistic increase in apparent mass.

I'll see if I can find a reasonable reference for this, and think about how best to incorporate it.

PianoDan (talk) 06:51, 17 June 2022 (UTC)

Here's a diagram I found over on Wikimedia Commons:

Cyclotron

"Afbuigingscondensator" may be my new favorite word for today.

PianoDan (talk) 06:54, 17 June 2022 (UTC)

Merge § Approaches to relativistic cyclotrons and § Cyclotron types

There is a large overlap in the scope of these two sections. We should find a way to merge them. Petr Matas 04:48, 15 July 2022 (UTC)

I see the argument, but I'm not sure the best way to do it. The "Relativistic approaches" section is more focused on the technical details of how to deal with relativity, where "cyclotron types" includes things like superconducting and separated sector machines, which aren't necessarily conceptually a separate type of machine, but ought to be mentioned somewhere. What would be your proposal? PianoDan (talk) 16:29, 15 July 2022 (UTC)

I will have to think about it. Petr Matas 17:50, 15 July 2022 (UTC)

I think I have a solution. The basic types (classical, synchro-, and iso-) are discussed in the relativistic approaches. Remaining are the design considerations regarding focusing and magnet shape (Separated sector cyclotron), and magnet construction (Superconducting cyclotron). These could get their own section. Petr Matas 09:51, 17 July 2022 (UTC)

Table of properties

To editor PianoDan: Can we get rid of the note that synchrotron is not a cyclotron by changing the table caption to "Characteristic properties of circular accelerators"? Petr Matas 16:35, 15 July 2022 (UTC)

Sure, that seems like a good idea. Or to be even MORE generous with information, (and I'd be willing to do this) we could expand it even FURTHER, to add betatrons and any other circular accelerators we can think of, and have a dividing line somewhere between "cyclotrons" and "Other Circular Accelerators."PianoDan (talk) 16:38, 15 July 2022 (UTC)

To editor PianoDan: The "Magnetic field" column is intended to describe the field variation in both time and space. My understanding is that FFA's magnetic field has some non-uniformities, so I would not call it constant (in space). Is it the case that unlike isochronous cyclotron, the FFA's field non-uniformities are smaller or localized? Petr Matas 16:59, 15 July 2022 (UTC)

I agree it's not constant in space, but it IS constant in time, and it's not really clear which the column refers to. PianoDan (talk) 17:07, 15 July 2022 (UTC)

I separated the variation in space and time, hope that helps. Petr Matas 17:49, 15 July 2022 (UTC)

To editor PianoDan: Another issue with FFA: It seems to me that the particle's path radius increase does not match its speed increase, so the frequency cannot be constant and the operation cannot be continuous. Do you agree? Petr Matas 17:49, 15 July 2022 (UTC)

There are different types of FFAs, so this column might need to be something like "variable." Scaling FFAs have frequencies that ramp, non-scaling ones have fixed frequencies in some cases. [1] PianoDan (talk) 19:54, 15 July 2022 (UTC)

I have added a reference to your source and modified the table. Petr Matas 21:00, 16 July 2022 (UTC)

To editor PianoDan: May I ask you for a careful check of the current version of the table including embedded notes, the section Isochronous cyclotron, and the description of the graph there? Petr Matas 09:21, 17 July 2022 (UTC)

Good catch that the AVF concept needs to be separated from the Isochronous Cyclotron one. Probably the best approach is a "Focusing" section between "Particle Trajectory" and "Relativistic considerations." We could talk about both in-plane focusing, which is what AVF is for, and longitudinal focusing, which comes for free with RF acceleration, but is tough to explain simply. PianoDan (talk) 16:56, 18 July 2022 (UTC)

I have written it how I believe it could work, but it needs checking whether it corresponds to reality and sourcing. Petr Matas 22:18, 18 July 2022 (UTC)

The Lorentz factor graph is interesting, but since cyclotrons rarely operate in the ultra relativistic range, it might imply that the situation is worse than it is. Graph of accelerator types looks good. PianoDan (talk) 16:56, 18 July 2022 (UTC)

Ultrarelativistic note removed. Petr Matas 22:18, 18 July 2022 (UTC)

Petr_Matas (talk · contribs) - Thanks for all your effort on this! I've added citations to the section about focusing and rearranged things a little bit.PianoDan (talk) 16:35, 19 July 2022 (UTC)

To editor PianoDan: Thanks for your expert inputs as well. I hope I am not too aggressive with my refinings. By the way, is it necessary to put "horizontal and longitudinal focusing" in the quotation marks, or is it an established term? Petr Matas 20:21, 19 July 2022 (UTC)

That's an excellent question. Typically in linear accelerators, you discuss "transverse" (both x and y) and "longitudinal" (z) focusing, and those are established terms. The weirdness in cyclotrons is that horizontal and vertical focusing are completely different beasts from each other. Also, "vertical focusing" is usually used for keeping particles in the plane, event though MANY cyclotrons (like the GE PETtrace, for example) orient the orbit plane vertically, rather than flat. PianoDan (talk) 20:28, 19 July 2022 (UTC)

Longitudinal focusing

To editor PianoDan: The reference to Edwards, that you have just added, points to page 21, but at page 21 of the 2008 edition I found nothing about longitudinal focusing or phase stability. Section 2.2 Phase stability starts at page 30, but the following two pages are not available for preview. Anyway, I think that it cannot work like I described it previously, because particle's direction of motion in the acceleration plane and thus its phase is unaffected by any tangential force (e.g. from the RF field). Only the bending field changes the direction according to the constant cyclotron frequency. Only if there were locations where the electric field was not parallel to the orbit (which is not the case in narrow radial gaps between the dees), it would be able to alter the phase. Petr Matas 18:31, 28 July 2022 (UTC)

I didn't specify a page for the second Edwards cite, but I can dig it out.

The RF field does not import a tangential force to the particle's direction of motion - it only acts at the accelerating gaps, and only in the direction of motion.

The bending field is a MAGNETIC field, and is completely static in a cyclotron.

The reason alternating electric fields result in phase stability in RF accelerators is exactly what it said in the chunk you deleted. The "reference particle" is travelling at a rate where it crosses the accelerating gap at the same phase every time, and sees the same voltage every time. (And that phase is NOT the maximum of the RF field.) Particles that arrive early arrive when the voltage is lower, and thus get less acceleration. Particles that arrive late arrive when the voltage is higher, and get MORE acceleration.

As such, off-energy particles oscillate between being slightly ahead of, and slightly behind, the reference particle.

The "acceptance" mentioned in the quote you inserted is the range of initial phases that will be kept by this method. Particles that are too far off the reference energy will arrive so late that the RF voltage will have once again started to drop, and will not be focused back to the reference energy.

I hope this is clear. PianoDan (talk) 18:39, 28 July 2022 (UTC)

Can you narrow the location in the source down to a single page, please? I think it should not be necessary to read the entire chapter to verify a claim. A source available online would be great.

I completely agree with your explanation, but only for a linear accelerator or synchrotron: A particle that arrives late receives more acceleration, thus travels longer distance, thus arrives sooner into the next gap. In cyclotron however, the distance travelled by the particle has nothing to do with its phase given by its direction of motion:

1. The direction change rate (caused by the static magnetic field) is independent from the velocity. In other words, a faster particle needs the same time to complete an orbit, because its orbit is longer.
2. The direction is unaffected by any force in the direction of motion (aka tangential force, as I understand the term).

Petr Matas 20:25, 28 July 2022 (UTC)

In a linac, a particle that arrives late receives greater acceleration, but the distances are fixed. It travels FASTER, and therefore reaches the next gap sooner. but it doesn't travel "longer distance."

That said - I'm way off base. You're correct about the longitudinal phase space being frozen in a cyclotron, and I was completely confusing two different concepts. PianoDan (talk) 21:45, 28 July 2022 (UTC)

You are right, a late particle in a linac will travel faster, not further. By the way, it was me who seeded the confusion between linac and cyclotron into your mind. ;-) Petr Matas 10:28, 30 July 2022 (UTC)