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@ Kasuha: I think jmc is referring to beam size, that is diameter, not beam intensity. But you are quite right about the injections. @ jmc2000: I see the ramp that I think you're referring to. In fact, the linear increase in beam size comes before the ramp, when there is no beam. In any case beam si...

As far as I know, lower emittance is quite hard to achieve but it doesn't really cause any problems. It does make the 'space charge' effect worse (this is the defocusing effect of having so many positive charges close to each other) but this is more a problem in the injectors than the LHC (space cha...

Out of interest, which instrument is the beam size which you see spiking measured with? I believe he means the Dashboard , there's a Beam Size graph on the left. I think that the beam size shown there is the one measured by the BSRT (synchrotron light measurements) although I'm not sure why there a...

jmc2000 wrote:I've noticed that there is now a single very large beam size spike when rampling up the energy,

Is this causing any problems?

Out of interest, which instrument is the beam size which you see spiking measured with?

Now. Protestation movement no beam, no access Ummm, what ? Page 1 says access ongoing. That was this morning on CPS page!! There was a 4 hour work stoppage by CERN staff this morning in protest at proposed changes to their pension scheme. I don't know how many people took part or what effect it had...

Oh and a barn is technically a unit of area, equal to 10^-24 square cm. So the luminosity can also be given as cm-2. For example, right now the ATLAS instantaneous luminosity is 600 * 10^30 cm-2 s-1, which is the same as 600 *10^6 inverse barns per second or 600 inverse microbarns per second. Theref...

The coefficient is called the cross-section. Cross-sections can be defined for each type of collision but I guess what you're interested in is the 'total inelastic cross-section' which will give you the total number of collisions (the 'total cross-section' also includes elastic colisions, where two ...

Photino is correct. I'll just add that the Lorentz contraction affects only the length in the direction of movement. So the photons get shorter (in the direction of travel) but keep the same diamater (in the perpendicular directions). Thus they do indeed end up looking like pancakes. But since their...

As pcatom said, redundancy is not quite as simple as 'let's buy two of everything'. There is also the question of finding space for 2 systems, having suitable alarms to know when the primary system is failing, whether the backup can kick in fast enough to prevent a dump...

I haven't had the time to check your figures, but I think there's a false assumption in the way you're using the cosmic ray data anyway. If you assume that cosmic rays are evenly distributed, then it's true that the flux and thereforer the rate of collisions in a given volume) is much smaller than i...

No, Reuters got it right on this occasion - there is a possibility that the energy will be increased to 4TeV in 2012, energy increase has only been ruled out for 2011.

Hah, I guess I should have read the basics before I answered that last part:
http://en.wikipedia.org/wiki/Speed_of_sound
The speed of sound is given by square root (coefficient of stiffness / density), known as the Newton-Laplace formula.

To clarify my general point that heat and sound can both be vibrations within the lattice but behave diferently, perhaps this page will help: http://en.wikipedia.org/wiki/Phonon To clarify point 2: There's a difference in what it means to transfer 5W of heat energy and 5W of sound energy. Let's say ...

1. The difference is between an oscillation and a one-way movement. If you shift the metal rod by one micron, then after an extremely short time the other end will also move by one micron. But if you oscillate one end of the rod with an amplitude of one micron, the other end will oscillate with a sm...

The rate of heat propagations is slow because the amplitude of the vibration is small. This means that the perturbation to neighbouring atoms is also small. the energy in a vibrating atom is a function of the amplitude and the frequency of vibration. Increasing the heat energy increases the frequenc...