Each particle has 5 TeV of kinetic energy.
There will be (roughly) 1e12 particles per bunch, and (roughly) 1e3 bunches per pulse.

This works out as ~800 MJ per pulse.

That is the same energy as a 1e6 kg train moving at ~80 mph, so the comparison is not as daft as it would seem.

(Note: Those numbers are all pretty rough, and I'm sure someone will be along soon to correct me soon, but the point is that the LHC beams store waaay more KE than you would imagine.)

I think he expects to be tried & imprisoned when an IP linked to him is found accessing such sites, and he's saying that online vigilantism will probably appear to be quite a weak defence.

Replying to undo incorrect moderation...

I think the idea is that you need a mechanism whereby two objects close enough together to thermalize, are pushed far enough apart fast enough that they appear to be too far apart to have equalized.

I think.

Never mind. Mod my previous post redundant. If I'd read further in the thread, I would have seen that this had already been pointed out.

http://en.wikipedia.org/wiki/Planck_length#Physical_significance

I don't think you're right. It's just a distance unit formed out of c, h, etc., and is not the granularity of space.

It's only real significance is that, at this length scale, physics will (in some theories) be dominated by quantum effects.

Posting to get rid of unintentional "funny" moderation.

Set up a Facebook group to fight against the continued xmas dominance of Simon Cowell's evolved algorithms.

That's not quite true.

Experimental accelerator physicists (not particle physicists) will come up with a conceptual design for the machine that fits the particle physicists requirements, and they will then work with engineers to design and build it.

Most of the designing and building is done by properly qualified engineers, not scientists.

Hadron collisions were achieved last week in all four detectors.

If anyone else can hear that radio, I hope you've counted the number of "employee units" within earshot, and the number of half hour increments during which you play the radio, and paid the appropriate tariff.

http://www.prsformusic.com/SiteCollectionDocuments/PPS%20Tariffs/I-2009-03%20Tariff.pdf

*shakes head sadly*

I wish I was making this up.

FYI -- I work on this project, and I work with Roger Jones (the guy in the article), so I know a substantial amount about this.

Your definition of damping is quite right, but your definition of detuning is, in this case, not really what he means. What he means is taking a cavity, and changing its shape in order to "detune" some cells.

To explain:

The cavities are traditionally built in such a way that each cell rings (like a bell) at the design frequency of the accelerating rf. Since all of the cells are identical, the beam will excite exactly the same mode frequencies in each one (like a hammer hitting a bell). Since they are resonant with each other, they can and will ring coherently. Thus the amplitude of these modes will be proportional to N^2 (where N is the number of cells).

If they are made to have slight differences (detuned) that cause their resonant frequencies to be slightly different (but still within the bandwidth of each other due to their finite Q -- so they *can* excite one another), they will ring incoherently. This causes the mode amplitude to be proportional to N.

Thus, the amplitude of the incoherent ringing will be lower by a factor of N.

On top of this, they also add absorbing material to take out some of the power (the damping you refer to), and it is this that fits your guitar string analogy, not the detuning that Roger was referring to in the article. Absorbing material cannot change the frequency of the oscillation -- all it can do is remove energy from it, thus damping it's amplitude.

To go further, yes the differing stiffnesses of the springs under my car *does* look like a system of bells ringing at different frequencies. They are each ringing at a different "pitch" in order to detune any destructive vibrations. Your car analogy, including the absorbing rubber, is almost perfect! :)

I think the confusion is coming from the fact that this system can use both the absorbing material that fits your guitar string analogy, and the detuning technique that fit's Roger's bells. His analogy *does* describe the system very well, and I hope you can see that now.

The article's explanation is quite bad -- wakefields aren't really anything to do with twisting and warping "the very fabric of space-time". They're just the electromagnetic energy left behind by the beam as it traverses these cavities.

I think his bell analogy is actually quite good. He goes on to say that damped detuning is much more preferable to strong damping, and it is strong damping that is more like resting a finger on a guitar string. The problem he is trying to solve is that of the entire structure of many cells ringing strongly at a particular frequency. This ringing will add coherently, thus lasting long enough to disrupt the next electron/positron bunch.

His solution is to make each cell ring at a slightly different frequency, thus causing them to add incoherently, and strongly reducing the resultant amplitude.

Just like a collection of bells ringing with different notes.

I think you're wrong.

The object's size subtends an angle from the point of view of an observer. This angle is (roughly) the size of the object divided by its distance from the observer.

It's a very useful way to discuss an object's apparent size in the sky, especially when you compare it to the size of a well known object like the Moon.

So, they're claiming that, if you could see this ring, it would appear to cover an area of sky roughly twice the size of the Moon. Which is surprisingly large.

Both. They vary the frequency over the light pulse so that different parts of the pulse travel with different speeds, thus causing the back of the pulse to catch up with the front.