Talk:Particle accelerator/Archive 1

Possible vandalism
There have been a lot of major deletions in the particle accelerator article since 18 November 2007, with no discussion on the talk page. I expanded the article by about 35% on 25-26 October 2007, and the current version seems to have lost all that work. There was no comment or criticism that I know of since that period, only some minor corrections.

I am a newbie to Wikipedia editing, so I may have missed something important, but the deletions since 18 Nov by anonymous editors (especially 169.204.228.210, who has been the main offender, as far as a quick look tells me), with no discussion or justification, seem like vandalism to me.

Without careful study, it seems to me that the versions of the 3 Nov to 19 Nov interval, up to the one by Cloudguitar, are probably the last best ones to go back to.

I had been thinking about working on the organization of the article some more, and described my ideas on the talk page under the "Organization" and "Safety concerns?" sections. I guess I will hold off on this project until the current flurry is resolved. It may be that my additions were massively inappropriate, as they were somewhat unreferenced and based on my experience and general knowledge as a particle physicist grad student and professional physicist and (gamma-ray) astronomer. I do think I know a lot of stuff that is correct, interesting, and useful, and hoped the needed references could be filled in later, maybe partly by others.

Most of this has been reported to ClueBot, w/r its 21:42 Nov 21 revert, which seems about the same length as before the attack, but the current article looks pretty much like it did before 25 October.

I do have the qualification of 40+ years experience, a PhD in physics, and I am a staff astronomer at Caltech. (None of this necessarily means anything, of course!!) But let me know if I am off base in my approach, and thanks. Wwheaton (talk) 20:16, 21 November 2007 (UTC)

Frequently Ask Questions About Accelerators
1. Q : What do different particle accelerators sound like when in operation?


 * A : Basically, you cannot hear the motion of the particles nor the sound produced by the collision with the target. The walls of the vacuum chambers are about one inch thick of solid metal, so they are great accoustic isolators. However, to operate an accelerator facility, a lot of electronics is needed. Just imagine a room full of computers and you will be close...


 * Umm... All of our particle accelerators at work are composed mainly of 1mm thick stainless tubing, nowhere near one inch thick. Many smaller and midsized electrostatic accelerators have moving charging belts or chains and actually are quite loud when in operation. Martyman 10:43, 16 Mar 2005 (UTC)


 * speaking as a former SLAC employee, i can tell you that most (all?) RF accelerators are either cooled by water (for room-temperature cavities) or by cryogenics (for superconducting cavities). the various pumps that run these cooling systems, along with the pulsed switch tubes in the klystrons usually generate one hell of a racket while the accelerator is operational.
 * Natelipkowitz 00:46, 6 December 2005 (UTC)


 * A tandem Van de Graaf makes a bang when there is a ten million volt spark, but they had to have a sound system for us to be able to hear it in the control room.


 * A Synchrotrons repeatedly cycle their bending magnetic field B up to keep the radius of the particle orbits closely constant as the beam momentum increases during acceleration. At the end of each cycle (typically a few seconds), the B field has to be turned down in preparation for the next cycle.  Because the energy density in the B field is proportional to B2, the total energy stored in the field for a large synchrotron can be very large; for the Large Hadron Collider at CERN, with 7 TeV beams in a 27 km long tunnel, the stored magnetic energy at the peak of each cycle is about 10 GJ, roughly the equivalent of the energy in 2.5 tons of TNT.  It is not economic to simply draw this much energy out of the power grid and dump it at the end of each cycle.  Hence historically a system was provided for large synchrotrons to store this energy, after the accelerating cycle.  I am not sure about the machinery to do this energy storage nowadays, but for the first large synchrotrons --the Cosmotron, Bevatron, and AGS, a large set of flywheels was provided, along with a powerful motor-generator system, so that energy stored in the rotating flywheels was converted into electrical power during the B field ramp up, and then during the latent part of the cycle the stored magnetic induction energy was converted back into electrical energy, and used to spin up the flywheel for the next cycle.  As a result, those synchrotrons had a characteristic whine that could be heard all over the site, with the pitch dropping as the MG set slowed down on acceleration, and rising again as the magnets were turned down.  I suspect this must still be the case for the Tevatron and LHC, though probably the cyclic undulating whine is not audible everywhere.   —Preceding unsigned comment added by Wwheaton (talk • contribs) 00:52, 25 October 2007 (UTC)

2. Q : Do particle accelerators have any characteristic oder or visual effect?


 * A : Yes in Ion implantation toxic odor when opened to atmosphere. Visual effects?

3. Q : Why do physicists create particle accelerators?


 * A : Particle accelerators are developed by physicists who want to get a better understanding of the fundamental laws of nature. When particles collide in a particle accelerator, physicists can see attributes of subatomic particles by using a bubble chamber (modern) or a cloud chamber (less modern, less expensive).  The chamber will allow scientists to collect the path of particles after the collision.  These paths tell physicists a lot.


 * Particle accelerators are used for much more than high end nuclear physics research. They are used in the fabrication of semiconductors, the treatment and diagnosis of cancer and production of medical radioisotopes to name a few uses. These more mundane everyday accelerators greatly outnumber the giant super colliders of sub atomic physics. Even a cathode ray tube in a television or computer screen is a very low energy particle accelerator. Martyman 10:43, 16 Mar 2005 (UTC)


 * Particle accelerators are also used by nuclear physicists, interested in the structure of the atomic nucleus and nuclear reaction rates. Nuclear structure is fundamental information about the matter making up Earth and most of the visible universe (although only comprising some 4% of the energy density in the universe).  Nuclear reaction rates may be applied to stellar nucleosynthesis to understand the energy production in stars (which are giant nuclear fusion reactors) and abundance of the chemical elements.  All elements heavier than lithium are produced in stars, including the carbon and oxygen on which life on Earth depends upon.DAID (talk) 09:06, 3 July 2008 (UTC)

4. Q : Can you cook food with a particle accelerator, like a microwave?


 * A : surely this is a joke. i'm sure physicists don't spend millions of dollars, and even more valuable technology, in building a particle accelerator, just to heat up their hot pockets...


 * Actually, I recall that one physicist stuck a glass of beer in the beamline of the bevatron to test the theory that cosmic rays where what caused bubbles to nucleate in it. It got him a brief write-up in "Discover" magazine (and the answer was "no, something else causes nucleation"). --Christopher Thomas 01:37, 22 June 2006 (UTC)

5. Q: What is the purpose of building extreamly large circular accelerators - like the one in Texas? Is the information that could be learned really worth the billions these devices cost? Themepark


 * Circular accelerators are built because particles pass through any given set of RF cavities many times, being boosted each time, unlike a linear accelerator, where they make only one pass through. This allows higher energy for a given size of accelerator. However, forcing particles to follow a curved path causes losses due to synchrotron radiation, which places an upper limit to the energy that can be attained by any given circular accelerator. Linear accelerators are used for lighter particles like electrons and positrons (which have more severe synchrotron losses in curved accelerators), and ring-shaped accelerators are used for proton/antiproton experiments and experiments that collide heavy atomic nuclei.


 * Whether or not these devices are worth the money depends on what goals are considered important when judging "worth". They are unlikely to produce data that has practical application, but they are the only way to test many aspects of our theories of how the universe works. In other words, they are "pure research" devices. --Christopher Thomas 17:48, 12 March 2007 (UTC)


 * "Someday you'll tax it", as I believe Faraday responded to a similar question posed to him by an MP. The period of development before uses are found and applications developed is likely to be very long and unpredictable, in my opinion, so in the short term the value may really be cultural:  helping us to learn about the universe that is the context of all our human stage, wherein we move and do and have our being.  I personally believe these vast machines are our equivalent of medieval cathedrals, monuments to our deep curiosity and our striving to understand where and who we are. Wwheaton (talk) 22:21, 18 November 2007 (UTC)


 * A particle accelerator formerly known as RIA (the Rare Isotope Accelerator) has been in the funding proposal stage for perhaps 10 years now. I believe a reduced cost facility named FRIB has now received funding approval.  Physicists at Argonne National Laboratory and the National Superconducting Cyclotron Laboratory have spent countless hours planning this facility and promoting its applications, and yet the total cost was a mere US $2 billion.  Given the cost of the Iraq war of US $341 million per day (http://www.nationalpriorities.org/costofwar_home), one RIA facility could be built every week for the last 5 years, totaling more than 250 of these particle accelerators starting in the spring of 2003.  Certainly the brain power spent per dollar of funding requested for a facility like RIA is very large.  The Big Dig, which is just to alleviate traffic congestion in the greater Boston area, has now exceeded US $15 billion, or 7 facilities like RIA.  Yet, for environmental concerns and commuter time, effective public transit in the US metropolitan areas based on the Japanese train system model would be much more advantageous to those outside the oil and automotive industries.  About half of all medical treatments conducted at hospitals now are based on results from nuclear technology, so clearly these facilities give back to the community in the long run.  Any large-scale project will seem like a huge cost compared to the average citizen's bank account or stock investments.  But considering the US National Debt now exceeded $4 trillion, asking for half of .01% that cost for primary research is not so much on the grand scale.DAID (talk) 09:26, 3 July 2008 (UTC)

6. Q: Is the amount of energy created when the collision occurs equal to the amount of energy put in to the process of acceleration? 83.146.14.113 17:04, 12 March 2007 (UTC)B Briggs


 * No. There are inefficiencies in the acceleration mechanisms (energy put into the RF cavities doesn't all end up in the accelerated particles, by a long shot; most of it probably ends up as heat). There are also losses due to synchrotron radiation in ring-shaped accelerators that cause energy to be drained from the accelerated particles (lost as x-rays). When particles collide, not all of the energy goes into producing new particles, and the vast majority of particles produced aren't the ones any given experiment is interested in (high-energy accelerators are built to produce heavy, exotic particles, but it's much easier for lighter particles to be produced, so many more are). --Christopher Thomas 17:48, 12 March 2007 (UTC)


 * The process of acceleration also includes things like the vacuum system pumps, bending magnets, and cooling systems. So on one hand much energy from the system is radiated as heat, and on the other more energy is spent to remove that heat.  The small size of particles also results in statistical factors where many of the beam particles do not even collide with anything useful.  But total energy is still conserved, it's just not all going into the collision reactions! DAID (talk) 09:33, 3 July 2008 (UTC)

7 Q: Will the failure of the project cause a black hole to appear in the core of Earth and in four years from its production reach a size big enough to absore the hole Earth and cause its destruction? Will the End came in 2012? I hope no, but I cannot hide from what was written.



8. Q: What do you call those photographs of the subparticle paths? Have any of the subparticle paths been determined to be logarithmic (or golden or Fibonacci) spirals? Thanks! -- TimeDog (talk) 03:43, 14 September 2008 (UTC)

Is this really still a stub?
This seems to me like a pretty complete layman's treatment of the subject. Shall we remove the stub template? It could perhaps use some additional wikifying, but it sure doesn't seem stubby to me. --Kgf0 18:03, 11 October 2005 (UTC)

Feel free to add....Scott 18:30, 11 October 2005 (UTC)

honestly, in my opinion this article is rather incomplete, very poorly organized (separate sections on synchrotron light and synchrotron radiation, for instance) and in need of attention. i will do it when i can find the time! Natelipkowitz 00:48, 6 December 2005 (UTC)

Removed from article
I have just removed teh following text from the article. I couldn't find anything online that backed it up. If anyone knows anything about it feel free to re-add it. --Martyman- (talk) 05:49, 26 November 2005 (UTC)

There is also a new larger accelerator being built in Sweden crossing over the border into Switzerland. It will span in an underground tunnel under the border over 3 km and has two different acceleration magnets at each end to help in extensive study of different things done with the accelerator.


 * Well, Swededen and Switzerland don't border each other, so a 3km linac wouldn't help much. Looks like somebody was confused and/or writing a silly hoax. -- SCZenz 16:40, 26 November 2005 (UTC)


 * You know the thought that Sweden and Switzerland wheren't anywhere close to each other did cross my mind, but strangely it didn't click as evidence that this was a hoax. ;-) The big CERN accelerator is in a ring that crosses the Switzerland-France border, but this is not what they are talking about (not a linear accelerator 3km long). --Martyman- (talk) 21:06, 26 November 2005 (UTC)

Typos
The last sentence of the first paragraph of Astrophysics is broken, too broken for me to figure out what it is meant to say.

Removed "Black Hole production". Not relevant to discussion of particle accelerators, per se. This should instead go into an article on exotic physics at colliders.--131.225.233.132 16:21, 11 September 2006 (UTC)

Spam? == ==

A recent reversion of the external link to a pdf for free download of a textbook [Stanley Humphries (1999) Principles of Charged Particle Acceleration ] seems like a needless loss to me. The web page is indeed by the author, a professor emeritus at the University of New Mexico, but the work seems to be scholarly, fairly recent, and useful, with a lot of material covered. It seems to me that the purpose of the link is to make the text widely available for personal use, not to promote it commercially, although the latter motive cannot be excluded. The web site does have links to other services and tools provided by the author's company, so it seems a borderline case.

Also, the contributor of the Wiki reference, (User:Comparat, no information on user or talk pages; the edit in question was on 4 March 2007), has made only a few edits to Wikipedia, which seem to be technical improvements, and I see no evidence of systematic spamming. It would be useful for someone to download the .pdf and study the book carefully, but based on the table of contents it appears to be valuable.

All things considered, I suggest reconsideration of the deletion of this link, as the book appears to be a useful source for deeper study of material on particle accelerators that would be beyond the reasonable for direct inclusion in an encyclopedia. Wwheaton (talk) 19:52, 4 January 2008 (UTC)

I've reinserted the link.--Hu12 (talk) 20:41, 4 January 2008 (UTC)

Detectors?
The "targets and detectors" section says nothing about detectors! --Slashme (talk) 07:54, 10 September 2008 (UTC)
 * I see there are lots of articles on different kinds of detectors. I'll try to link to some of them if I get the time, and nobody beats me to it. Start with Particle physics article to find the detector articles.  I think we could also use more material on particle beams and beam optics, BTW, which might go in an expansion of this section. Wwheaton (talk) 19:33, 20 December 2008 (UTC)

Link problem
The second external link is wrong there should only be one cpa in the link. —Preceding unsigned comment added by 134.39.11.2 (talk) 18:10, 2 October 2008 (UTC)     totalllyy


 * Fixed - thanks Richerman (talk) 18:02, 4 October 2008 (UTC)

AC/DC
when we use ac partical accelarator when weuse dc? —Preceding unsigned comment added by 41.178.249.24 (talk) 17:35, 21 November 2008 (UTC)

DC accelerators are only used for low energy, I think some tandem Van de Graaff ones now go up to above 100 MeV, but not much higher. In general to go higher you need radio-frequency accelerating sections, and usually a circular arrangement. This probably needs to be clarified near the beginning. Wwheaton (talk) 20:45, 21 November 2008 (UTC)

Protection?
I see we have been protected by a bot, but there has been little editing and no vandalism I know of for several weeks. Any idea why, and is protection really needed? LHC has certainly had problems with vandals, but I don't see much spillover here. Wwheaton (talk) 18:04, 20 December 2008 (UTC)
 * I see the BOT in question only tags with the little lock, it does not actually protect. So it must have been protected a while back.  Can someone who knows how get us unprotected?  Or comment if you think we need protection?  Thanks. Wwheaton (talk) 19:28, 20 December 2008 (UTC)


 * Unprotection can be requested at WP:RFPP just like protection. Whether protection is necessary is always a judgement call. Chris Cunningham (not at work) - talk 00:27, 21 December 2008 (UTC)

I updated the information on the LHC in the History section. :) Ti-30X (talk) 02:16, 17 May 2009 (UTC)

"Atom smasher"
A particle accelerator is not the same thing as an atom smasher. An atom smasher is a machine that collides particles, while an accelerator is a machine that accelerates them, and, while this may seem like petty semantics, the majority of accelerators (from big machines like LCLS, XFEL, and ESRF, to the hundreds of thousands of medical accelerators in the world) don't actually collide particles. Also, as a professional physicist, the term "atom smasher" makes me cringe :D. Perhaps the statement equating these two terms could be removed or altered? —Preceding unsigned comment added by 134.79.81.36 (talk) 04:38, 26 January 2009 (UTC)

Revert unexplained mass deletion of external links
Some of the links reverted by IP editor User:86.160.242.13 may need removal, but mass deletion w/o comment seems unwarranted. Please justify before removing again. Thanks. Wwheaton (talk) 02:19, 29 October 2009 (UTC)

Particle accelerators in popular culture
I was surprised to see the article doesn't have such a section. Was there any earlier consensus not to include one? patsw (talk) 19:15, 8 November 2009 (UTC)


 * They tend to be discouraged, unless the popular culture references are extremely notable. In practice, the section tends to fill up with every reference ever made, no matter how minor. In this case, I think the main popular culture references are already covered in the Large Hadron Collider article and the articles of the specific accelerators in question. If there are specific references you think are noteworthy enough to justify a section in this article, by all means propose them on the talk page. Just make sure you hear back from many other editors before adding such a section. --Christopher Thomas (talk) 01:44, 9 November 2009 (UTC)


 * I disagree on several points:
 * "In popular culture" sections are not discouraged when they are well written. WP:IPC.
 * Notability in the Wikipedia sense refers to the inclusion of a topic as a standalone article. The article content itself is subject to other guidelines.
 * I don't have an editing crystal ball to know beforehand what editors are going to contribute what. In other articles I have not seen such sections "fill up".
 * There's no prior restraint on me or other editors on adding "in popular culture" content, just the usual collaboration. patsw (talk) 02:43, 10 November 2009 (UTC)


 * To address your points:


 * One of the criteria for being well-written is to not have trivial content in lists like this. I think you'll find that this is supported by WP:IPC (in particular, "Detailing the impact in popular culture can be a quality part of a topic when this kind of content is properly sourced and consistent with policies and guidelines. However these lists can attract non-notable entries and should be carefully maintained." (emphasis added).


 * Examples of IPC and IPC-equivalent sections that keep filling up with non-notable cruft are Wormhole, and Space elevator's fiction section before it was spun off to space elevators in fiction, off the top of my head. These sections are rarely, if ever, pruned, only added to. I have no problem with listing the handul of most noteworthy fictional references, but they should not overwhelm the article. This article is about particle accelerators, not particle accelerators in fiction (feel free to create an "...in fiction" or "...in popular culture" article if you want a comprehensive list rather than a list of the most noteworthy examples).


 * I agree that this is a collaborative project. I have not forbidden you from adding any popular culture references - I have suggested that you discuss such additions, and make sure that they have consensus on the talk page, before adding them. Surely you'd agree that unilaterally adding something contentious is not collaborative? Surely you'd expect that the rest of us would agree with the addition of suitably relevant popular culture information? I'm having trouble seeing why you take offense at the suggestion that this be discussed. --Christopher Thomas (talk) 03:23, 10 November 2009 (UTC)

What say you to Gregory Benford's Cosm and Timescape as entries in this proposed section? patsw (talk) 05:09, 11 November 2009 (UTC)


 * I have read "Cosm" and I liked it. However, fictional particle accelerators are not actually particle accelerators, so I think mentioning them in this article is inappropriate. By all means create a separate article on "Cosm". JRSpriggs (talk) 11:15, 12 November 2009 (UTC)


 * What is your basis for calling this content inappropriate beyond your personal preference? What content guideline makes it inappropriate? patsw (talk) 14:59, 12 November 2009 (UTC)


 * I read the LHC Popular culture section and this echos a concern of mine by adding a section on fictional works. "...descriptions of what it is [the LHC], how it works, and projected outcomes of the experiments are often only vaguely accurate." I am sure fictional works mentioned in the proposed section for this article would have the same degree of inaccuracy.


 * Also, I agree with Christopher Thomas. A section like the one proposed, once started, would most likely list trivial and non-noteable works after a short time. In fact, as I project into a possible scenario, each of these additions might have to be vetted to determine notability - if the editors at Wikiprojects Physics are to be vigilant. Hence, this may be an opening for having to focus attention on disagreements about additions to this section. Conversly, the science is something which is more easily agreed upon, except for marginal or non-mainstream views. This is because the agreement is derived from relailble sources.


 * I also agree with JR Spriggs. This is an article about real particle accelerators and I think that fictional stories which have fictional particle accelerators are not appropriate here. In other words, it may be somewhat off topic here. I think creating an article entitled "Particle accelerators in fiction" or "...popular culture" (or some other similar title) is the better option. Also, editors are free to create articles about the books, which is another option. Steve Quinn (formerly Ti-30X) (talk) 15:11, 12 November 2009 (UTC)


 * I just placed this article, Particle accelerators in popular culture on Wikipedia. I am sure the proposed content that we are discussing has a place in this article.Steve Quinn (formerly Ti-30X) (talk) 16:49, 12 November 2009 (UTC)


 * I also oppose an IPC section in this article, except possibly as a lead-in to a separate article on cultural issues. I think the focus here should be on the physics and technology of these machines, which is a big subject, but the core on which many related or specialized articles can build.  Wwheaton (talk) 01:51, 13 November 2009 (UTC)

Photoelectron clouds
Have filled an important hole in the area of photoelectron clouds, the fundamental limiting and efficiency factor to colliders, with a short note and reference. This will get even more interesting with the higher energies planned at the LHC.Docjudith (talk) 14:23, 18 March 2010 (UTC)


 * First, please don't flag substantial changes like this as "minor". "Minor" edits are things like spelling fixes. Secondly, I have enough concerns about your addition that I'm moving it here for other editors to discuss. Some or all of it may be re-added by them, depending on how the discussion goes.


 * Lastly, contacting you is going to be difficult, because you seem to have moved/redirected your user-space page to a main-space article (this isn't supposed to be done, and you only get automatic notifications of messages from your user-space talk-page).


 * Regarding this addition:

A key part of development has been in understanding the synchrotron radiation and persuant photoelectron density and frequency, which increases with acceleration. Minimising this is considered crucial to performance. Propagation rates of oscillating particles is lower than with electrons, but for each proton up to 6.7keV can be lost at each turn at high energies due to increasing activity and oscillation frequency. The primary 'cloud' activity circulates with the bunches, but collisions with the pipe walls exacerbate secondary 'standing' clouds in the tube and an overall particle density in excess of 7x1010 per bunch. Screening and damping has been developed but it remains a major concern with the planned increased energies at the LHC. The radiation generates wave particle activity which allows compliance with the Law of Conservation of Energy, and relates to maximum bunch velocity with respect to the vacuum but it is not yet fully understood.


 * (Reference tag converted to an ordinary external link to avoid adding a reference to the talk page.)


 * First, the limit to energy that synchrotron radiation imposes is already discussed in the Wikipedia article. Second, this paper doesn't talk about limits to beam energy - it's talking about the evolution over time of the shape of the group ("bunch") of protons being accelerated. Synchrotron radiation causes the bunches to shorten (faster particles slow down and slower ones speed up), and noise in the RF driving signals in the accelerator cavities causes the bunches to smear out. Two other, smaller effects are also considered (Landau damping focuses the bunch, and random scattering of particles against each other de-focuses the bunch). None of this has impact on the maximum energy attainable by the accelerator.


 * Long story short, this paper doesn't say what you seem to think it says. --Christopher Thomas (talk) 17:46, 18 March 2010 (UTC)

Electric fields
"particle accelerator...is a device that uses electric fields..." Just being pedantic but this seems to imply that accelerating a particle by means other than electric fields would produce something other than a particle accelerator - this seems wrong. Does anyone disagree? Mtpaley (talk) 22:53, 29 March 2010 (UTC)


 * All past and present types of particle accelerator that I'm aware of do use electric fields to perform the acceleration. While in principle it might be possible to use a changing magnetic field to accelerate particles, what that ends up doing is creating an electromotive force across part of the accelerator, which you could argue amounts to the same thing as creating an electric field (I'm sure that statement just caused several lurkers to spit-take; whether it's correct or not depends on the precise definitions used, so I'm probably oversimplifying). --Christopher Thomas (talk) 00:27, 30 March 2010 (UTC)


 * And of course it is actually a well-known principle of electromagnetic theory that a magnetic field cannot do work on a charged particle, since the magnetic part of the E-M (Lorentz) force is perpendicular to the velocity. The other three fundamental forces (strong, weak, gravitational) can and do "accelerate" elementary particles, strictly speaking, but never as instrumentalities intended for that purpose, so far as I can think.  Some devices do produce beams of high energy neutrons or neutral mesons (eg, K0), but the ultimate energy source is charged particles, first energized by electric fields (except for fission reactors used to produce beams of moderately energetic neutrons; but these are never termed "particle accelerators"). So, logically, yes; but it is really a matter of the standard usage of the term.  Anyhow, I can't think of any way to say it better in the introduction, that is not so pedantic as to be confusing. Wwheaton (talk) 22:10, 2 April 2010 (UTC)


 * ObNitpick: The Lorentz force applies to unchanging magnetic fields. I've seen certain types of accelerator described as acting like transformers (coupling a strong driving current to a lower-current, higher-voltage beam current). While this implies use of changing magnetic fields for acceleration (per Faraday's law of induction), I'm pretty sure it's an oversimplied description of a device that used more conventional acceleration techniques. --Christopher Thomas (talk) 22:15, 2 April 2010 (UTC)
 * This is a confusing point I admit, but I still think my statement is true. I believe the Lorentz formula for the force vector, F:


 * $$\mathbf{F} = q (\mathbf{E} + \mathbf{v} \times \mathbf{B}),$$


 * is valid for any point in space and time, and for any Lorentz frame. However the vector fields, E & B, are changed by a Lorentz transformation, along with the velocity, v.  If so, then the magnetic term can do no work (and therefore cannot accelerate the particle), as it is always perpendicular to v because of the properties of the vector cross product.  The particle accelerators (betatrons, in particular) you refer to do indeed work much as you describe, but the magnetic field at the particle does not cause the force.  I think this can be seen from the following gedanken experiment:


 * If we made (case a) a machine with a static uniform field in the beam region, bending the orbit into a circle, the beam would of course not be accelerated. But if then (case b) we added a separate, additional, magnetic field B linking the orbit, but confined in such a way as to be zero in the beam region, uniform (up, say) in a small circle of area A near the center of the orbit, with the field lines returning (down) entirely outside the beam region, the flux Φ would be A|B|, and the beam would still not be accelerated.  But if then (case c) we increase B without changing the geometry of the linking field, we would find a finite rate of change in the linking flux, and the particles would be accelerated (or decelerated, depending on the sign of their charge) by the induced EMF (which is really an induced E field parallel to and around the orbit), which is proportional to the time rate of change of the total magnetic flux linking the orbit.  Since the B field at the orbit is static, they would spiral out or in, correspondingly.  But one can see that the B field at the orbit plays no role in accelerating them (that is, changing their speed or kinetic energy; it does of course accelerate them perpendicular to the beam direction).  But if further at the same time we turned up the uniform field at the orbit, we could keep the curvature constant, and if (case d) we simultaneously adjust the linking flux field (which does not touch the orbit!) to maintain the flux rate of change we had in case c, then the acceleration would remain the same also.  This is in fact just what a betatron does.  The transformer analogy you mention is perfectly correct, only another way of expressing it, but with the understanding that the EMF is an electric field unconnected with the B field at the particle.
 * Anyhow, I think it all has to do with the way the fields transform under a Lorentz transformation. It is slightly amazing to me that the induced E field at the beam, caused by the changing flux, can be spatially entirely separated from the B field responsible for it.  (How does it know?!)  Of course in the rest frame of a charged particle, there is never any magnetic force at all because v = 0, so it's all the transformed E.  One good question I have never completely worked through is, "How the hell does an electric motor work??" -- if magnetic fields cannot do work on charged particles (or currents).  Nothing daunted, I look at the Lorentz force equation and think "all the particles are moving in the vacuum between them, so all the transformed fields and resulting forces must add up properly."  Sometimes you just gotta have faith in this business....
 * Sorry for going so far astray from the original question, or the article. I suppose we should take any further discussion of this murky area to our personal talk.  Cheers, Bill Wwheaton (talk) 07:46, 4 April 2010 (UTC)

Organization
It seems to me, on first looking back on this article to need help. High and low energy are related to how the energy is applied to the particles, but that is not the way to start the article. We should say something about the scale and use of high and low energy accelerators, describe some technology and then say what techniques have proven most useful for what types of accelerators.


 * I agree the article does need a good going over. There is also the problems of a confused terms in the article. I am under the understanding that a linear accelerator is any accelerator that does not follow a curved path, this would include large linacs, smaller electrostatic accelerators and could even be stretched to cathode ray tubes, etc. The term "linac" obviously a shortening of linear accelerator seems to be solely applied to large superconducting RF type accelerators, though is used interchangably in this article. --Martyman- (talk) 05:07, 20 January 2006 (UTC)


 * I think "linac" includes all straight-line accelerators that use radio frequency fields to accelerate the particles, at leas if they have high enough energy to induce nuclear reactions. I can't remember for sure, but I think the professors I worked with when I did my thesis used the temp to apply to the Luis Alvarez proton linear accelerator.  I also believe the term was used to describe the second injector stage of the CERN PS.  David R. Ingham 19:54, 22 January 2006 (UTC)


 * Linacs and electrostatic accelerators are not the same thing due to linacs using varying electric fields controlled by an rf-source, as stated here. DAID (talk) 09:45, 3 July 2008 (UTC)


 * I agree that talking about the energy scale is not a good place to start the article. The high and low energy differentiation is also mostly wrong and unhelpful.  Those of the electrostatic type listed on this wiki are grouped under high energy machines with RHIC and the LHC!  In fact, electrostatic acceleration technology has an upper limit of around 25 million volts (note, 25 MV is not 25 MeV) due to discharge by sparking, and so it is highly inappropriate to group this method with the likes of the Tevatron.  If we like to continue to distinguish accelerators both by output (energy) and type (presently geometric linear/circular, suggested errata to acceleration technique), then there should be 1) High energy machines 2) Low energy machines 3) Everyday use machines (for TVs and medical X-rays).  In fact, we could even make a third grouping for application, such as 1) Medical 2) Nuclear 3) Particle 4) Other.  'Other' could include things like radiodating artifacts.  Probably it is best to have the latter suggested category as applications. DAID (talk) 09:43, 3 July 2008 (UTC)

At present, the accelerators are grouped by geometry (linear or circular) rather than by physical accelerating method. Importantly, the tandem accelerator is mis-categorized as a linear accelerator. In the first place, tandems may be U shaped, but physically, tandems do not use linac technology. A tandem is a special type of electrostatic accelerator, which includes those of type Van de Graaff (mis-spelled in its own picture at present), Cockcroft-Walton, and Dynamitron. This technology uses a single high-voltage terminal (acting as a giant capacitor) to accelerate the particles in a single step, producing a time-independent beam. Linear accelerators use oscillating radiofrequency electric field cavities to energize the beam, thus bunching the beam into packets of particles, much like a cyclotron; yes, I am saying a linac has more in common with a cyclotron than a tandem. So no, just going in a line does not make a linac.DAID (talk) 09:43, 3 July 2008 (UTC)
 * As there has been no opposition to this change in two years, I have now made the change. I appreciate if you discuss this change before reverting the change, as I have been very patient waiting for feedback. DAID (talk) 14:13, 7 April 2010 (UTC)
 * Wonder about making an independent article on electrostatic accelerators since apparently I had a lot to say, and most of the other accelerators here have their own articles and so don't pollute the whole page with all the details! Then I need to make a concise discussion here. May hold off on this, since a discussion of these early accelerators also gives some important historical points. DAID (talk) 07:15, 8 April 2010 (UTC)


 * For the record, lack of response doesn't mean endorsement. I feel that the change in structure is not the best way to go, as the geometry is the main difference between large accelerators being built in recent decades, is the most noticeable feature of accelerators for non-experts reading the article, and has a very large impact on what you can do with the accelerator (circular accelerators have a very hard time with electron/positron collisions, for reasons which you're aware of). That said, I plan to look at your changes over the weekend before providing detailed commentary on them.


 * Also, I respectfully suggest that in the future, if an old thread about changes to the article goes stale, you start a new thread and poll again for comments about the topic. Stale threads indicate a lack of consensus, rather than a decision, and also don't necessarily reflect present feelings of editors (half of the people presently active in WP:PHYS won't have been around at the time of the old thread, for instance). --Christopher Thomas (talk) 08:03, 8 April 2010 (UTC)


 * I've created the new page for electrostatic nuclear accelerators and made the discussion shorter here to keep in line with the rest of the article. I've retained the geometric distinction for oscillating accelerators.  The problem is that electrostatic accelerators are not linear accelerators.  It will get really confusing.  To be correct, what we then have is a category, say "Accelerators that go in a line" and then we write "linear accelerators are a special class of accelerators that go in a line" and "some of the electrostatic accelerators go in a U shape and not a line."  I've had to answer the question on various comments page and edit the linear accelerator page for correctness on this point as well.  So I have evidence of actual confusion.  I agree silence is not consent, but it's wikipedia, and if I have a change I want to make and no one will talk with me about it, then I'm going to proceed.  People can change it back or alter what I've done as they like, but otherwise my ideas are lost.  DAID (talk) 11:16, 8 April 2010 (UTC)


 * Sorry, that would be electrostatic nuclear accelerator page. Also, I totally think what you're saying about not using an old thread, but now where should I talk to you?   —Preceding unsigned comment added by DAID (talk • contribs) 11:18, 8 April 2010 (UTC)


 * I think you make a good point about the geometry and the way a general readership may see things. My main concern is to avoid the confusion of, say, a tandem, with a linac.  Electrostatic accelerators were in use before the linac was even invented, so it's clear just on this ground that they aren't the same.  However, here is my suggestion if you like a geometric organization.  Make three categories: Terminal accelerators, Linear accelerators, and Circular accelerators.  See, an electrostatic accelerator is like a "box" accelerator (that geometry is a little too crude for me in the classification, though): there's just one acceleration phase.  The linac is accelerating particle in a line, that is, it sequentially increases the beam energy step by step along a line.  With a terminal accelerator, you've got one, or in the case of a tandem, two steps of acceleration through a single unit.  A single box is not a line, and there are U shaped tandems.  If you like that way, we should go for it!   On a slightly different note, cyclotrons don't accelerate particles in a circle, but in a spiral.  Not sure what to do about that one, but it's bothering me a little on the accuracy side.  I've written a section on why electrostatic accelerators aren't linacs on the electrostatic nuclear accelerator page, and I'm going to expand it a little more.  DAID (talk) 11:31, 8 April 2010 (UTC)


 * What exactly is the problem with electron-positron collisions and circular accelerators? This did not seem to be a significant problem at LEP. Just curious. TimothyRias (talk) 09:34, 8 April 2010 (UTC)

I reorganized and expanded the section on circular & cyclic accelerators a bit last month. I also added the lead-in section on the "Uses..." of accelerators. Now I am thinking of moving most of the present subsections on high and low energy machines to the linear accelerator section, as appropriate, and incorporating most of the rest of those subsections into the present section on "Uses...". I think I would organize the "Linear..." section roughly by energy, which would also pretty much follow the historical sequence. Does this sound sensible? I am also thinking of retitling the sub-section on "Black hole..." to a section on "Safety issues" or maybe "Hazards", and expanding it with some of the material in my comments here in the discussion yesterday, even though I cannot reference most of that very thoroughly or very quickly, most of it being based on my experience as a particle grad student in the late 1960s, and as an interested bystander since. I hope others might step in to rescue the useful and winnow out the rest. Anyhow, comments are solicited. Wwheaton (talk) 21:56, 18 November 2007 (UTC)

The cyclotron section needs to link to the cycltron wiki. Furthermore, the mention of how particles in a cyclotron may get out of sync with the rf due to relativistic effects was solved with employment of an azimuthally varying field, which is briefly mentioned in the main cyclotron article. DAID (talk) 09:43, 3 July 2008 (UTC)
 * Good points. This brings up the whole subject of beam stability, which probably deserves some explicit discussion in a paragraph or even a section.  Wwheaton (talk) 19:39, 20 December 2008 (UTC)

The references also need a lot of work. DAID (talk) 09:43, 3 July 2008 (UTC)

Micro black hole hazard
The wording User:84.56.237.95 deleted in the article was indeed so poor as to be incorrect. I have attempted to fix it. The subject has been discussed extensively (and mostly ignorantly, I think) on the LHC talk page and elsewhere. I personally think the risk is negligible (note that it cannot possibly be zero, since we do not know everything ), but deserved careful scrutiny by experts, which I hope (& trust) it has already received. Wwheaton (talk) 13:55, 21 May 2008 (UTC)


 * Part of the problem here is, if I can say it like this, a detachment from reality that appears arrogant. For instance the LHC is seldom even given its full title.  It is generally considered simply impolite to not, in the first instance, use the full name rather than expect the reader to be already familiar with it.  I have added the full title to this article.  I neither have the confidence in my peers nor the experience of their behaviour that would justify a  belief that it is at all wise to simply "hope" that safety concerns have been addressed!!  There are many conflicting egos and a lot of money being made on the project.  If there are some decent citations then let's have them here on this page.  If there are not then ipso facto the point is proven LookingGlass (talk) 07:01, 21 July 2008 (UTC)
 * I agree that an acronym or initials should always be defined, once, when first used in a Wiki article, but I think it is unrealistic to impose a longer name repeatedly everywhere in an article. Since my previous post in this section, the Safety of particle collisions at the Large Hadron Collider article has come to some maturity.  It appears inefficient and unwise to repeat this material again and again (and keep its quality up when it gets mangled) in every related article, so I beg that we refer to this one article wherever the issue is mentioned, and leave it at that.  The more difficult issues you raise about expert opinion, trust & "hoping to goodness" (in an ancient Peanuts cartoon, Linus pointed out that this is "not theologically sound") have been discussed at considerable length on the  Talk:Safety of particle collisions at the Large Hadron Collider.  The matter will never be settled in general and probably deserves a separate article (if one does not exist already) on epistemology, but again I think it is futile to try to debate it everywhere it comes up.  Best, Wwheaton (talk) 19:53, 22 October 2008 (UTC)


 * Please see the new voting under the Safety section above this one on if we should limit the discussion on black holes on a page describing all particle accelerators, including household Televisions. —Preceding unsigned comment added by DAID (talk • contribs) 13:14, 8 April 2010 (UTC)

Discussion of Large Hadron Collider risks
This subject has been knocking around several talk pages: here, LHC itself, Hawking radiation, and Black holes, in particular. I have just proposed to separate the subject into a separate article; see the Talk:Large Hadron Collider page if you are interested. I think it could help to keep some of these other articles on-topic. Cheers, Wwheaton (talk) 19:47, 4 June 2008 (UTC)

I totally agree. I also question the inclusion of so much information about black holes, which is more of a media feeding frenzy than a terrible lot of real physics at this point. While perhaps worth inclusion, saying that black hole production concerns are acute at LHC is nonsense, particularly on the general accelerator page (at least keep it limited to LHC). While some physicists look forward to possible confirmation of Bekenstein-Hawking radiation, this is interesting physics and not a concern. I'll keep my opinions to the discussion page, but black hole production is primarily a "concern" to laymen without much physics background, and anything further should be left to a more appropriate wiki and not particle accelerators.DAID (talk) 16:29, 2 July 2008 (UTC)

The article Safety of particle collisions at the Large Hadron Collider now contains a fairly complete discussion of the public safety issues, and has lately been promoted to good article status. I have just fussed over the old Black hole production subsection, re-titled and generalized it slightly to include other possible hazards (eg, strangelets and monopoles), tried to clarify the chain of "if then..., but then if...." etc, and added the white dwarf and neutron star point. However, I really think the argument is too long and complex to treat properly in this article, an should perhaps be shortened and referred to the one article regarding the LHC. Wwheaton (talk) 12:39, 19 October 2008 (UTC)

The section on risks in the Large Hadron Collider article has been revised in the light of the Safety of particle collisions at the Large Hadron Collider article, and seems more appropriate to me than the longer paragraph we have. I think it could be the basis for a shorter section here. Wwheaton (talk) 19:34, 22 October 2008 (UTC)


 * This has been a long going discussion, but the material is still here. I have proposed a vote on downsizing the discussion on this page.  It is under Saftey.  Please vote. DAID (talk) 13:15, 8 April 2010 (UTC)

Very poor article
Wikipedia should really have a better article on such an important topic. Clearly, a phycisist did not not write this article.--190.190.87.136 (talk) 02:53, 14 July 2009 (UTC)


 * Then suggest improvements, or make (properly sourced) improvements. --Christopher Thomas (talk) 04:09, 14 July 2009 (UTC)


 * I suggest a "Livingston plot" like this one: or this one:  Cambion (talk) 13:56, 30 July 2009 (UTC)


 * I can't say who has written the article. Personally I don't see much problems other than organization and some irrelevant points.  I'm a physicist and I'm reviewing the article this week, so in any case.  It's not clear to me how you could know a physicist did not write the article if you are not one.  And if you are, then help is always appreciated.  Plenty of articles need work, but it's not exactly paid work we're doing.  DAID (talk) 13:18, 8 April 2010 (UTC)

Safety Concerns?
Should there be a section on some of the possible safety concerns? The article on the Large Hadron Collider contains a section that might be a good starting point.GreenGourd 18:10, 3 November 2007 (UTC)
 * I'd agree. I've always wondered what would happen if one stuck his or her head in one. My best guess is that it would break, but how can I be sure? I'm interested in any theories Lancensis 13:18, 5 November 2007 (UTC)


 * With modern large synchrotrons like the LHC, with high intensity beams, you would receive a fatal radiation dose in a few seconds or less (ignoring the problem of the vacuum, of course). The simple beam electrical power, current times voltage (voltage being the particle energy, 1 volt per eV, so typically many billions of volts), was 30 GeV X 20 microampere (average) at SLAC in its earliest operation, ie, 600 kilowatts in a beam about mm in diameter.  A real Death Ray, in other words.  On a more modest scale, I remember at the old Bevatron, one of the first (1950s) accelerators to extract particle beams from the main ring for experimental use, there were places where one could walk through the beam-lines (which sometimes passed through air for short distances), and these reportedly featured signs saying "Walk Fast Through Here", or advising one to time ones' passage to avoid the pulse of particles, coming every five seconds or so, marked by a bell and the audible cyclic  whine of the motor-generator units.Wwheaton (talk) 02:47, 18 November 2007 (UTC)

Whether you agree with them or not, there are scientists and others who warn about dangers. This is an encyclopedia, not a pro- or con-pamphlet, and we should provide balanced coverage. GreenGourd 03:03, 10 November 2007 (UTC)


 * The primary safety protection is of course that very large, very high energy machines have been invariably buried in deep tunnels since about the mid-1960s, so that shielding of the order of 10 m of earth is automatically provided. The tunnels themselves are generally accessible by unprotected workers when the machine is off, but regions downstream of targets may receive very high doses of scattered high-energy particles, and can become significantly radioactive.  Managing these hazards is rather like safety in laboratory or medical contexts where radio-isotopes are handled, or around nuclear reactors, except that there is no danger of runaway fission or meltdown as with nuclear fission situations.  Since beams are now routinely stored for times of hours in storage rings, the technology of confinement for millions of cycles with very low particle loss has necessarily come quite far.   Also, considerable care is taken nowadays, when beam intensities are much higher than formerly, to avoid allowing the beam to leak stray particles and to avoid accidental "beam dumps" (loss of particle bunches from the nominal orbit) because of the danger of cumulative radiation damage to nearby structures (like superconducting magnets), and also the desire to avoid producing secondary induced radioactive materials, which would contaminate the tunnel and complicate access for normal maintenance. I can add some words about these issues to the article, but references and documentation would require more time than I have available now. Wwheaton (talk) 02:47, 18 November 2007 (UTC)

IMHO this issue is being treated disdainfully. To me it seems serious and relevant. The "safety" concerns re LHC are actually "existence" concerns! (See above) LookingGlass (talk) 06:46, 21 July 2008 (UTC)

After long discussion and a lot of work by many other editors, concerns about public safety have been discussed at length in Safety of particle collisions at the Large Hadron Collider, which has lately been promoted to Wiki good article status. For so long as the LHC remains the most powerful machine in the world (probably several years to come), that seems to me to be the best place to treat this subject. Wwheaton (talk) 11:42, 19 October 2008 (UTC)


 * My problem is not about how valid the argument about black hole creation at the LHC is. My problem is that firstly it's theoretical, and secondly, it only applies to one accelerator, so it should go on that accelerator's page.  Maybe one sentence and a link to that discussion elsewhere is okay.  So it's an encyclopedia and we do need fair and balanced coverage. So it's not balanced to have a paragraph on the theoretical danger of a single machine.  This is even more clearly a media feeding frenzy and a hype because those creating the content have not made a general "accelerator safety" section.  There ARE real KNOWN dangers of working with accelerators.  I work at one, and I'm not suggesting the work is unsafe, but if one was careless it could be dangerous or hazardous.  Getting irradiated by the beam is no joke, not to mention compressed and liquified gases, high electric fields, high magnetic fields (ie: pacemaker hazard), and the list goes on and on.  Clearly those in charge of inserting and advocating this black hole material, which is an extremely recent development and has a very targeted and narrow scope, did not take a balance perspective towards accelerator safety. As the origin of the material is biased, I am slating this for removal in favor of the insertion of a general discussion of safety, of which this can be a small part if its contents are reduced.  —Preceding unsigned comment added by DAID (talk • contribs) 07:24, 8 April 2010 (UTC)


 * Per above, it doesn't just happen for one accelerator - it happens for every new one that comes online. "Looking for evidence of large extra dimensions" is one of the standard lines used when pitching a new accelerator (the other two being "Higgs boson" and "Supersymmetric particles", with "top quark" being a previous favourite until it was unambiguously discovered, along with "fourth generation of quarks" until that was ruled out). The media hears "large extra dimensions would mean we could be making tiny black holes", and throws a fit. You'd think they'd learn after the first couple of times, but they don't. --Christopher Thomas (talk) 07:52, 8 April 2010 (UTC)


 * But to me if it's going to keep happening for every accelerator, that's not verifiable. I take the stance that it's an N=1 case.  Right now that 1 is the LHC.  It can apply to other machines, but onces that's true, it won't apply to the LHC anymore.  I think it's fringe science anyway.  The 'public safety' concern indicates that the LHC creates a black hole, that black hole does not evaporate, and the earth is destroyed.  So, if this concern turns out to be correct, then all the other machines and the earth are destroyed.  If it is not correct, then the prediction has been falsified, and at best we will wait for a new theory, which presently does not exist to my knowledge, which predicts them at higher energies.  If the idea is "well, theorists will keep making new predictions at higher energies for non-evaporating black holes that are a public safety concern" then I am concerned if this can be verified.  It's a prediction of how people will make predictions!  So, it's either N=1 or not verifiable, and you can take either of those that you like, but they both indicate that the material needs to be downsized or removed from this page. DAID (talk) 10:52, 9 April 2010 (UTC)


 * I want to be even more explicit. I have taken safety lectures at no less than 4 accelerators in 3 countries.  I have done work at twice that many instituions, and visited yet again as many accelerators for fun.  You know how many times in all my safety lectures black holes came up?  Never.  Why?  Because I've never been to CERN, not to say anything of the practical dangers of this matter.  You want to talk about public safety hazards?  If the LHC and blackholes deserves one paragraph of 'fair coverage' on the particle accelerator page, how about 20 paragraphs on RIBF at RIKEN?  Not because it's unsafe; there have been no incidents of outside contamination at the Nishina Center or RIBF of RIKEN.  But there's that much paperwork and safety procedures.  And these aren't safety concerns about theoretical dangers.  They are safety concerns as serious as taking a long walk of a tall building.  A few hundred meters from RIBF is a children's school.  Are you more worried about the dangers of the top quark or drinking polonium that's gotten into a water supply?  (We aren't running a fission reactor here, so polonium production is not significant, but you get the idea.)  Particle accelerators have about a 100 year history, and besides perhaps very early on, safety has been a top concern of all directors of accelerator laboratories.  At the NSCL, there is a large sign in the hallway: days without accidents.  The last time I was there the number of days was in the thousands.  I'm in the data room right now on an experiment, and if I want a drink of water or to use the washroom, it's going to take me 5 minutes to take the elevator past all the cement shielding, scan myself for a minimum of 20 seconds, wash my hands, change my shoes, and scan myself out.  So let's talk about real safety problems in accelerator science, and not some theoretical hypotheses at applying to one lab.  After world war II, all the cyclotrons in Japan were either blown up or dumped into Tokyo bay by helicopter.  All that remains is some pictures of Nishina sitting on one of them in the hallway.  Why was this?  Because of nuclear weapons and the US army decided it didn't want Japan to have accelerators.  Look at the IAEA and inspections.  Is a black hole any more dangerous than thermonuclear weapon detonation?  I'm digressing a lot here, but this is outrageous. We have a small minority.  If you want to talk about black hole production, go to either the astrophysics pages or the LHC page please, or tell me how one of the 7 cyclotrons or the Pelletron at my institute can make them.  DAID (talk) 07:47, 8 April 2010 (UTC)
 * I agree with DAID here. The LHC "safety concerns" are not characteristic for particle accelerators and should not have focus on this page other than a passing mention. Those concerns are typical for any "new physics" machine, as the risks are inherit at exploring new physics. Similar issues were raised at Los Alamos when first testing the A-bomb. No nuclear explosion had ever happend in the Earth's atmosphere so nobody new for certain that this would not have a catastrophic consequences. I'm also surprised that no concerns were raised when phycistists first tried to create BECs in the 1990 (talking about unprecedented physics conditions!).
 * Particle accelerators, however, are typically not "new physics" machines only the very big ones are. And as such they do not bear the associated risks. TimothyRias (talk) 09:07, 8 April 2010 (UTC)


 * I think we need to have a voting, since obviously there is considerable disagreement, and if we are not able to reach a consensus, then a majority will have to do. I am not saying we cease discussion, but it would be nice to get some voting in.  I will agree to refrain from moving this section to, say, the LHC discussion page, until we either wait awhile or have at least more than a small number of votes. DAID (talk) 13:06, 8 April 2010 (UTC)


 * Please vote on if you Oppose or Support limiting the text on black holes on the particle accelerator page. DAID (talk) 13:06, 8 April 2010 (UTC)


 * SUPPORT, Strong Support 1) This discussion is biased. People working with particle accelerators have a lot of history of safety procedures, and this gives a false impression.  If the authors cared about accelerator safety, they would have made that a section and put all the good work that's been done to that end.  2) The scope is limited.  It only applies to one particular machine, and if theories predicting black hole production that is actually dangerous (rather than evaporating as predicted by Hawking, which, for example, follows a fundamental conservation in physics: entropy) are refuted by the LHC, then this no longer applies to other accelerators, which I do not think will be complete before these energies are reach and the theory is falsified.  Thus, it is an N=1 case.  3) The discussion is too long, hence we should cut it back.  The discussion of this matter in terms of page content is longer than any single discussion on a type of particle accelerator!  4) This is a media hype, not proper science.  I am not convinced a single scientist actually believes these ideas.  Since I don't personally care about the LHC, they can keep it on their page or not.  But that still makes me oppose it being on this one.  5) This is a technical article, not a results article.  We only refer briefly to other results, so excessive emphasis on this subject is not appropriate for the article.  6) Thank you. DAID (talk) 13:06, 8 April 2010 (UTC)
 * Sorry, point 3) uses false information. It is not longer than all sections.  But it is longer than some, and of comparable length to most. DAID (talk) 13:11, 8 April 2010 (UTC)
 * 0 When Theodore Roosevelt was running New York City, crimes were printed in large font and discussion of them took up a lot of space. This was instigated namely by two specific reporters, and other newspapers started to follow suit.  Naturally, Teddy started getting a lot of complaints to reduce the crime.  Know what he did?  He asked the newspaper companies to stop putting so much emphasis on the crime compared to other things that might be more relevant news.  Sound a little familiar, anyone? DAID (talk) 13:45, 8 April 2010 (UTC)


 * Support: Concerns about BH & strangelet production are relevant to typically one (ie, the newest, highest energy) machine, of about 26,000 accelerators worldwide (arbitrarily excluding ordinary medical X-ray machines and CRTs). The concerns about these exotic issues should be in a separate article (which will likely shift from one machine to the next every few years or decade, as the limiting edge moves).  The issues are extremely technical, and cannot be treated properly in this general article without grossly distorting it.  Right now the LHC safety article seems to be the place. The other issues may belong in a more general radiation safety or health physics article, as they overlap with reactors, medical isotope users, industrial applications, etc, etc.  (DIAD, I've taken the liberty of bold-facing your line to make it more visible in a long section.)  Wwheaton (talk) 20:11, 8 April 2010 (UTC)


 * Neutral - Just my tuppence worth, there is only an LHC safety article because it received considerable media attention prior to the LHC's start up which made it notable. To start a section on safety of particle accelerators in general, they needs to be reliably sourced and verifiable concerns or safety issues, not original research, and not meet umpteen other criteria like WP:FRINGE, WP:REDFLAG etc. I know I'm throwing guidelines at alot of established editors here, but it became very obvious in the early days of the LHC media furor and the subsequent safety article, that a lot of editors were coming in and trying to use Wikipedia as an outlet for their latest fears, and once the snowball started it became very hard to stop. Regards Khu  kri  14:08, 9 April 2010 (UTC)

Terminology
It's not accurate to say that the latter term was only used in the "early 20th century". It was used quite commonly throughout the late 20th century and continues to be used today.

This is probably due to the fact that, as pointed out in a previous post, particle accelerators and atom smashers are not the same thing. Kafziel Complaint Department 21:24, 31 March 2010 (UTC)


 * Editor Kafziel Complaint Department has reverted my late correction of the lead paragraph re. "atom smashers", which I think was accurate and reasonable. He is correct above that particle accelerators and atom smashers are not the same thing; the latter are a subset of the former.  But calling a collider an "atom smasher" is not just an anachronism, it is really incorrect, as colliders mostly collide elementary particles (and sometimes heavy nuclei, but never atoms), and singling colliders out as synonymous with atom smashers in an article on particle accelerators, as the previous lead seems to me to have done, is especially misleading, and we should not encourage it.  In modern usage, particle accelerators mostly have little or nothing to do with atoms or "atomic physics" anyway; rather they are mainly used in the sub-atomic domain.  (Note that this article is not even about colliders, except as one important type of accelerator.  I believe that the references mostly just reflect the need of journalists and editors for shorter headlines.)  So, I have changed it back.  I request that it not be reverted without discussion and consensus here and on the physics project talk page.  I think that the redirect to this article from "Atom smasher" is entirely adequate.  Thanks, Wwheaton (talk) 03:58, 3 April 2010 (UTC)
 * It is not our job to "discourage" usage, as you suggested here. Take that up with the people who write newspapers. Multiple modern, reliable sources are cited to demonstrate its use in current publication. The lead doesn't say they are atom smashers; it says they are often called atom smashers. And I don't need to wait for consensus here; the term has been used in the lead for years - if you want to remove it, you can wait for consensus. It was listed as an alternate term right in the first sentence. All I did was move it further down the paragraph and add sources to support its use in the modern era. That's how it's done. If you have sources to support your claim that nobody has called them that since the 60s, please present them. Kafziel Complaint Department 04:40, 3 April 2010 (UTC)

Hopefully my latest version is a good compromise. I hadn't intended to spend so much time pointing out how the term has changed over the years, but if you think that's important then I'm okay with it. I'm not entirely satisfied with the lack of a cite for how it's easier to split atoms now without an accelerator, though. In other words, you point out that colliders collide elementary particles or nuclei... but where do they get those particles in the first place? How do we "smash" atoms if not in an accelerator? It would be nice if we could cite a good, scholarly (but concise) source to explain that. Kafziel Complaint Department 06:38, 3 April 2010 (UTC)
 * OK, let's wait for comments from others. I think your revision makes the lead section unbalanced, but of course I can live with it if other editors want it to stay.
 * The lead reference (to the foundational standard text, Livingston, M. Stanley & Blewett, John (1962), Particle Accelerators, New York: McGraw-Hill) explains the details you ask about. The protons and electrons at the start, which are mostly used as beam particles, are produced by very low energy (tens of eV) ion sources that simply remove electrons from hydrogen, deuterium, or helium, producing the fragments that are then accelerated to energies millions to trillions of times higher.  The term "atom smasher" originated I think when atoms (after long being conceptually indivisible by definition), were first disintegrated by Rutherford and co-workers in 1919 who, using energetic α-particles from radioactive sources like radium, converted nitrogen into oxygen through the nuclear reaction:


 * 14N + α → 17O + p.


 * This first example of the transmutation of one element to another was a sensation, and popularly described as "atom smashing", though it was more properly an example of what we now call nuclear fusion. But the research was limited by the lack of powerful and intense sources of "hammer" particles that could truly smash nuclei.  In the late 1920s and early 1930s this need was met with low-energy DC accelerators (eg, Cockroft-Walton's, Van de Graaf's), and then E. O. Lawrence's cyclotrons, which could produce beams of particles adequate to truly smash atoms by routinely knocking major fragments out of nuclei.  That was the heyday of the term atom smasher, and they played a big part in establishing the US as the equal of Europe in fundamental physics, which US media rightly celebrated.  I believe these machines are still useful for studying the details of nuclear structure.
 * But after WWII fundamental physics moved on to study the elementary constituents of nuclei themselves, and nuclear physics spawned elementary particle physics which (in search of maximal simplicity) generally uses the simplest particles (protons, electrons, and deuterons) as both beam and target, creating hundreds of unexpected new (& unstable) particles at the Bevatron in the 1950s. By 1970 the study of "elementary" neutrons and protons had advanced to a state analogous to the study of atoms in 1910, as it became clear that n's and p's are composed of yet more elementary quarks.  This branch of the tree of accelerator technology has produced the sensational and gigantic machines built since 1950, but it really does not smash atoms; atoms are only directly involved in the compact ion sources at the beginning of it all, where they are at most chipped a bit (electrons being 1/1860 times less massive than the lightest nuclei).
 * With a few more references, I suppose much of the above could be split off into a stub article on the "History of particle accelerators", or put into the subsection here. Anyway, I hope it helps make my problem more comprehensible.  Thanks.  Wwheaton (talk) 05:18, 4 April 2010 (UTC)

Dear all, please accept my apologies I've been away for a week or so so haven't had time to respond. I've left replies on both mine and Bill's talk pages. As I put on his talk page, the more I think about it and inline with what you have both written above, I think there is a lot of scope for expanding this article around the history area where this information would be ideal and can see the beginnings of a very interesting read. Khu kri  07:32, 9 April 2010 (UTC)

I think not explaining the term "atom smasher" in the lead actually gives it more credibility. The hatnote at the top states that "atom smasher" redirects to the article, so we need to say why. Otherwise, the only conclusion that readers can possibly draw is that the two terms are synonymous. Why else would one redirect to the other? Maybe the best thing to do is to not redirect atom smasher to the particle accelerator article, and give it its own page instead. Then we wouldn't need a hatnote here, and the hatnote at "atom smasher" could say something like "For the modern device commonly mislabeled as an atom smasher, see particle accelerator." Something tells me the existence of an article about atom smashers would irk physicists, too, and that would eventually lead to it being merged and redirected back into the particle accelerator one, but it might be worth a try. Kafziel Complaint Department 02:56, 12 April 2010 (UTC)


 * Not sure I understand how it would give it more credibility? From what you've written above it suggests to me that the redirect would be better served going to the dab page, with a link to this article from there and not create a content fork to another article. I think the term itself of atom smasher within this article would then be more suited to history, and expand on as I've said previously how the terminology and technology has advanced. Though I also think we may not be seeing the forest for the trees, as I think this could all be bundled into the other ongoing discussions on articles regarding accelerators, colliders, targets and experiments. There is hints of what could be an all encompassing article which looks at the development of what started out as nuclear research to particle physics and now HEP etc, but that would need the input of the guys at WP:PHYSICS as you say there would be alot of irking going on if we mixed the wrong topics and subject matters. Khu  kri  13:13, 12 April 2010 (UTC)
 * A few points. First, by redirecting atom smasher here we are saying atom smasher is a synonym; that's what redirects are for. We don't redirect "milk" to "cattle"; we redirect cow to cattle. Second, a separate article is not a content fork. If an atom smasher is really a different thing, it should have its own article. A square is a kind of rectangle, which in turn is a type of quadrilateral, which in turn is a type of polygon, but it doesn't constitute a content fork to give each of them their own pages. Finally (and this is just a minor quibble, a pet peeve of mine): We don't "need" the input of anyone. Wikiprojects don't own the articles in their respective topics, and the best contributors are often not members of projects.
 * Now, as it applies to this article, the term "atom smasher" is not historical; it is currently&mdash;not just historically&mdash;used to refer to particle accelerators in general, as multiple reliable sources demonstrate. This goes back to the original point: It is not our job to try to dictate usage. If the scientific community is unhappy with it, that's not really our concern, as we are not a scientific journal. Its common usage is clearly demonstrable, and that's all that matters here. Many articles put common names right at the top of the article (see crotalus horridus, for instance); at least when we use it in the lead, we can take the time to explain how it isn't technically accurate in this context. Kafziel Complaint Department 16:41, 21 April 2010 (UTC)

Should collider be merged here?
All particle colliders are particle accelerators, and I don't think there are many particle accelerators that do not perform collision experiments. Collider is a stub article so whatever useful content it has (if any) should be merged her and the article should just redirect here. At least IMHO. TimothyRias (talk) 09:19, 8 April 2010 (UTC)


 * It could be that particle colliders are a class of accelerator that collide two beams. I have to check, but I think that's the case.  In this sense, I'm suggesting that collider is in error.  However, I still agree that they are types of accelerators.  It's basically a question of length and if the term collider is used explicitly to mean impinging two or more beams together.  Consider the LHC: it's got collider in the name, and it's colliding two beams together.  As it stands, the article is not too long for inclusion here, but in principle someone might expand on the subject (if indeed it is the specific case of merging two beams), and then it's better to make a short summary here and keep that page.  I'm not a high energy guy, so I'm not much use besides commenting, sorry! DAID (talk) 13:23, 8 April 2010 (UTC)


 * I'm not sure that collider is used exclusively for setups that collide beams together. Of course that is the setup for any modern collider doing collision experiments, simply because fixed target setups have such a low center of mass energy compared to the energy you put in. A quick google search, seems that at least some people make the explicit distinction between "collider" and "fixed target" setups. TimothyRias (talk) 15:21, 8 April 2010 (UTC)


 * Colliders (and the term does always mean colliding beam accelerators) are sufficiently important and specialized that they probably do deserve an article of their own, but the present collider article is wrong-headed. The main issue with colliders is not relativity, but conservation of both momentum and energy.  The old Bevatron wanted to make anti-protons, which would seem to require only twice 0.938 GeV, but it needed over 6 GeV because you have to conserve momentum in a collision between a beam and stationary target proton, so you have to look at the energy available in the C.M. frame.  If I recall the available energy in the CM for a fixed target (of the same mass) scales as the square root of the beam particle energy, so colliding beams are a big win.  The big loss is intensity, since beams have much lower density than targets.  There, focusing the beams down to the smallest possible size at the collision point is critical.  For the LHC, this is ~16 microns, if I recall.  Explaining all this is why a separate article seems warranted, but I can't do it now; maybe someone else can. For now I think we might just redirect collider here, and build the more specialized article later.  Wwheaton (talk) 21:27, 8 April 2010 (UTC)

Automatic archiving?
This page has some really old threads. Would anybody mind if I setup automated archiving for threads older than say 6 months? TimothyRias (talk) 15:29, 8 April 2010 (UTC)
 * Six months sounds good to me. Bill Wwheaton (talk) 20:58, 8 April 2010 (UTC)
 * This seems good. We have many discussions of the same matter, and I have become confused as to where to discuss topics with multiple threads.  Thank you. DAID (talk) 10:36, 9 April 2010 (UTC)

Electrostatic accelerators are the most common claim
I wrote this today, and I'm pretty sure it's true, but someone may ask how I can verify this. I have a 250 page book on 'Research Facilities in Nuclear Physics.' Although published in 2003, I can count how many of each kind of accelerator there are. It was a study by the International Union of Pure and Applied Physics, so I think it should be a fine source. If you are extremely skeptical of my claim before I've counted in the book, you can delete the material from the page until I confirm. However, the number of tandems is extremely high. A number of years ago, practically every major university in the United States had one, for example, although now some of them have been shipped elsewhere. Some universities have or have had 2 of them! I've talked to friends who are attending school at various places, and they don't even know there's a tandem at their school. In fact, my father has been working at the same university for about 15 years now (Education department), and when I was visiting their tandem over winter break he said to me, "I didn't even know we had one." This is literally how common they are! Yes, I know maybe this first hand accounts are not verifiable, and I will count in this book very soon to confirm and cite! DAID (talk) 11:48, 8 April 2010 (UTC)


 * By pure chance today I happened across the statistics I put in just now on accelerator types & uses, which I have added. Despite the obvious fact that almost all of this article deals with the 1% that are high-energy research machines, I think the term "particle accelerator" does generally refer to just that 1%, but maybe lowering the energy threshold to ? ~30 MeV ? to catch some cyclotrons and linacs.
 * I don't have a serious problem that we spend a lot of time discussing the smaller percentage of machines. Despite that I work in low energy, I wouldn't say all machines are equal.
 * A holdover from this article two years ago is a bunch of photos of DC accelerators that the article now goes out of its way to declare are not linear accelerators at all. I think the article should probably begin the lead with a classic in-tunnel photo of the LHC as most representative, and also have nice photos of a Van de Graaf, a linac, a cyclotron, and a classic weak-focusing synchrotron (? Cosmotron or Bevatron?) appropriately placed. Wwheaton (talk) 22:00, 8 April 2010 (UTC)
 * I'm not sure the LHC is 'most representative' but I don't oppose whatever images people like to show. I don't really worry about pictures much myself.  However, I may consider to move the DC photos to the electrostatic nuclear accelerator page.  Thoughts? DAID (talk) 10:40, 9 April 2010 (UTC)
 * I think putting those low-energy DC accelerator pix in the electrostatic nuclear accelerator page would be good. How about renaming "electrostatic nuclear accelerator" to "electrostatic particle accelerator"?  The vast majority of those are apparently not used for nuclear physics or research any more, and the others seem to be mostly for industrial or medical, therapeutic use.  At least one image, probably the Van de Graaf, should be kept here I think.  I envisage an LHC picture in the lead here as it seems the current iconic particle accelerator, and the state-of-the-art, though Lawrence's original 10 cm cyclotron might be equally appropriate.  What do you think about the "atom smasher" debate above BTW?  I would put some of the historical info in that I described in that discussion (and maybe move the historical section up after the "Uses" section?) but I need to reference it a bit. Wwheaton (talk) 14:18, 9 April 2010 (UTC)

Relativistic mass
Part of the article says this:


 * To reach still higher energies, with relativistic mass approaching or exceeding the rest mass of the particles

But doesn't relativistic mass always exceed rest mass? Does the article mean additional mass from relativistic effects rather than just relativistic mass? David (talk) 17:11, 6 January 2013 (UTC)

Can someone add why modern colliders are deep underground?
The CW Flash series has a supercolider on the surface in a major city. Granted, a major reason for the depth is avoid buying up large plots of real estate--especicially in a major city. But that doesn't explain why the designers of real coliders avoid cities or put it undergroud even in a rural area. Are they trying to avoid interference? The LHC's designers were probably forced by terrain. But the Fermilab is anoher story. When it was built, the surrounding suburbs were nothing like they are today. Will (Talk - contribs) 11:26, 1 May 2015 (UTC)