Talk:Halbach array

message: Nice pictures that display info, but they need a legend or explanation. Green is polarity A, red B, and strong side emits polarity A.  — Preceding unsigned comment added by 208.80.117.214 (talk) 19:15, 16 June 2023 (UTC)
thread_title:  Please provide legend for green/red images 

message: The field on the strong side of the array should not be twifold as strong because the magnets are discrete, and each has some greattest intensity already.  They would onely be stronger if the magnets are squished to half their volume. -lysdexia 07:26, 31 March 2007 (UTC)
thread_title:  something amiss 

message: This is
NSNSNSNS
or
NSNS
SNSN
NSNS
SNSN
Where a N represents a magnet with it's north pole facing up and a S represents a magnet with it's south pole facing up.
These are often (possibly incorrectly) called hallbach arrays Alan2here 20:24, 24 July 2007 (UTC)
replies: text: They don't cancel the field though, so I don't think they count.- (User) Wolfkeeper (Talk) 18:31, 18 October 2009 (UTC)
thread_title:  The other type of Halbach Array 

message: I'm not sure if there's a formal definition of Halbach array. It seems to me though that the term 'Halbach array' could apply to three dimensional layouts of magnets as well, so it might be a good idea to combine Halbach array and Halbach cylinder together into one article with redirects. Comments?- (User) WolfKeeper (Talk) 16:02, 28 August 2008 (UTC)
replies: text: I see what you mean but I think these should be re-split. The Halbach Cylinder and Halbach Array are related but distinct structures both used for very different engineering applications. (Also, the cylindrical structure is two dimensional, like the array; in three dimensions both suffer from magnetic end effects.) --Hiltonj (talk) 05:41, 10 November 2008 (UTC)
replies: text: Well... I don't see that there's any good reason to split right now, and the article is not big. The section topics meet the definition we use for Halbach array, they're obviously intimately related and even the wiggler is 3D really.- (User) Wolfkeeper (Talk) 18:36, 25 November 2008 (UTC)
thread_title:  Merge with Halbach cylinder? 

message: ... are actually idealised models, aren´t they? If you really want one, you have to build it out of wedges or other kinds of dicrete dipoles. --Maxus96 (talk) 20:37, 8 August 2009 (UTC)
replies: text: So are the cube-style linear ones though. An ideal Halbach array of any description is made of infinitely thin slivers of magnetic material.- (User) Wolfkeeper (Talk) 23:57, 8 August 2009 (UTC)

text: There's no theoretical reason you can't build an ideal one, it's more of a practical issue. They're normally built out of wedges as it's very difficult to impose the correct variation in magnetisation when you fabricate the ferromagnetic material. The practical difference between an eight-wedge design and the ideal one is very small anyway, so there isn't much gain to be had. There are some clever designs, though, that form a perfect magnetic image of a Halbach cylinder in a soft magnetic material. These designs have a continuous magnetisation pattern. If you're interested (and can get access) see "Cylindrical permanent-magnet structures using images in an iron shield",  IEEE Trans. Magn., 39, p1983 (2003).--Hiltonj (talk) 06:16, 27 October 2010 (UTC)
thread_title:  Halbach cylinders 

message: The radiation in a wiggler is emitted in one direction only, and there is no medium to start lasing anyway, so why do you need a mirror? The page on FEL only states that there is no material to mirror x-rays (tough luck ;-), but no explanation why you should want one in the first case. --Maxus96 (talk) 21:10, 8 September 2009 (UTC)
replies: text: Thanks guys. Good spot on the electron path. I spent a very short time copying this diagram out of some book as a Halbach array application for the introduction to my thesis. If I'd known it'd cause so much discussion I'd have checked it more thoroughly, especially the electron path! The figure in the book had mirrors so I left them in, I didn't consider the FEL physics. The mirrors have now been removed and the B field should be in the correct direction for the wiggles. --Hiltonj (talk) 05:40, 27 October 2010 (UTC)
thread_title:  Why mirrors? 

message: The first bullet intem at the end of the "Halbach cylinder" section states that the flux is confined to the centre of the bore (such as k = 3 above, a six pole rotor) but it is obvious from the referred-to picture above to see that k should be 4.
Motivation: it is the number of inward and outward arrows in the picture, that define how many poles the magnetic field has. So K=1 has one that cancels out because it goes in all the directions simultaneously, resulting in no pole, k=2 has two, k=3 has four, and k=4 has six.  —Preceding unsigned comment added by Gwrede (talk • contribs) 08:06, 7 January 2010 (UTC)
replies: text: In literature, k is often defined as γ = (1+k)β, γ being the tilt angle of the direction of magnetization at the azimuthal angle β. That makes an outside field for k<0, no field for k=0, uniform inside field for k=1, inside quadrupole for k=2, and so on. I suspect this got mixed up with the definition metioned in the article. --129.13.72.198 (talk) 23:06, 26 May 2010 (UTC)
thread_title:  Typo in Halbach cylinder section? 

message: Does anybody know what the field of a halbach cylinder looks like, perpendicular to the center of the ring? I guess it´s not just like a long solenoid with the vector tilted by 90°? Uniform in the center, zero outside, but that´d be too easy. --Maxus96 (talk) 22:51, 7 April 2010 (UTC)
replies: text: The ones described in the article have exactly the same field pattern all the way along the axial length if that's what you mean.- Wolfkeeper 23:07, 7 April 2010 (UTC)

text: But there are riffs on the theme where the field lines go axial and oscillate sinusoidally along the length, and you can make sort of spiral staircase field shapes and all kinds of others.- Wolfkeeper 23:07, 7 April 2010 (UTC)
replies: text: OK, being a bit more clear ;-) : In a k=2 halbach cylinder, with uniform field inside, how fast does the field decay if i´m leaving the cylinder in the direction of its axis? Quite fast, of course, but is there an analytical equation for it? --Maxus96 (talk) 12:26, 8 April 2010 (UTC)
replies: text: If it's a continuously varying halbach array, the field is zero. If it's got discrete magnets, then it depends on how many magnets you have. For example this shows you the field outside as well as in:
- Wolfkeeper 15:06, 8 April 2010 (UTC)
replies: text: Sorry, my question really was misunderstandable. If you see the cylinder from above, as a circle, the field along the normal of that circle. Out of the plane of paper of that picture. ;-) In an infinitely long cylinder, its constant, and the value is that of the equation mentioned in the article. I wanted to know if there is an analytical equation for the field alog the axis for a finite cylinder, like there is for a helmholtz coil.  --Maxus96 (talk) 20:43, 8 April 2010 (UTC)
replies: text: Dunno, the article is largely about infinite arrays, it doesn't seem like it really needs to cover finite arrays right now.- Wolfkeeper 17:55, 12 April 2010 (UTC)
thread_title:  field perpendicular to array 

message: Please explain how in the world anyone can believe a "lowly refrigerator" magnet or a Brush-less AC motor is using the Halbach array? I have two of these magnets the "flat" and "Cylinder" comparing these to both the refrigerator magnets and the 6 AC Brush-less motors I have sittig on the bench, it is obvious there is no Halbach array in either. If need be I can provide pictures to prove my point. The "Magnetic field viewer" I received with my Halbach array magnets shows exactly the described magnetic field created by the Halbach array when used with my Halbach magnets, while every refrigerator magnet I could find (25 of them)shows a simple north south magnet is used. AC Brush-less motors (something I work on nearly every day)certainly is not your typical magnet set-up but in no way utilizes a Halbach array as I understand them. Again, I'm looking for someone to explain how either of these items is based on the Halbach array.  —Preceding unsigned comment added by 75.17.201.107 (talk) 00:32, 7 September 2010 (UTC)
replies: text: Those "refridgerator magnets" (at least the ones on my fridge) only have one magnetic side that sticks to the fridge. I guess this must be some sort of halbach. Advantages are clear: Less magnetic material needed for the same "stickyness", plus credit cards in the back pocket of people leaning against the fridge are not in danger. --Maxus96 (talk) 01:32, 17 May 2016 (UTC)
replies: text: Indeed the similarity is from being one-sided multi-pole. The typical Halbach array is made from rectangular pieces, rotating in 90° steps, but this is only for practical reasons as such bar magnets are easy to make and readily available. It is entirely possible to make a Halbach array from shorter pieces rotating in smaller steps, and this can be decreased further until the rotation is continuous. This would require infinite tiny magnets to be assembled, but fortunately this configuration can also be achieved by continuous material such as the ferrite sheet from which refrigerator magnets are made (ideally isotropic = without homogeneous preferred axis, or with rotating preferred axis). Magnetization is then done by a one-sided coil with straight conductors, in order to generate the pole-stripes in the magnet. Such a continuous Halbach "array" is actually superior to a discrete one, since the flux/field concentration on one side (and away from the other) is now perfect to the microscopic level. Actually, I'm about to update the article to include this, which was actually invented even before Mallinson. Langenforth (talk) 07:20, 17 December 2020 (UTC)
thread_title:  no heading 

message: Halbach array Description IS WORD FOR WORD Taken from other sites. I thought this was not allowed? And no the site I'm specifically speaking about did not take the Wiki description, it existed long before this Wiki was made. I'm only talking about the first section.  —Preceding unsigned comment added by 75.17.201.107 (talk) 00:03, 7 September 2010 (UTC)
replies: text: Sounds like a problem that needs to be solved (see WP:COPYVIO)! What specific section are you talking about (I don't see one titled "Description")? Do you mean the introductory paragraph, or all the material before the "Flat Halbach arrays" section begins, or some other paragraph somewhere else? Please let us know the specific source you suspect is the original (the exact URL where you're talking about). DMacks (talk) 05:14, 7 September 2010 (UTC)

text: As long as they attribute the content to us (and a few other details), then it is completely allowed. That's part of making the world's knowledge freely available. See Wikipedia:FAQ/Copyright#Can I reuse Wikipedia's content somewhere else? for details and further links. -- Quiddity (talk) 05:56, 2 October 2010 (UTC)
thread_title:  Copyright concern 

message: Can someone edit the presumably mischievous 'down under with a shrimp on the barbie' comment in the second paragraph and restore to make sense, thanks! Davey5505 (talk) 19:37, 2 October 2016 (UTC)
thread_title:  Intro - second paragraph clean-up  

message: Noticed 1st three .jpg pictures have display problems.  I'm using Ggl Chrome Version 55.0.2883.87 m as of this date, 2017-01-06, 
I'm working on other things today.  I'll try to return to this for the technical fix.
This article may need other improvements such as adding citations.
I'm turning on article alerts so to be notified of changes.
Cheers, johnswolter  — Preceding unsigned comment added by Johnswolter (talk • contribs) 18:13, 6 January 2017 (UTC)
thread_title:  JPEG display problem 

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