For those who want to know what is happening at the CERN Large Hadron Collider.

The LHC is preparing to restart at almost double the collision energy of its previous run, at 13 TeV. The LHC will start up again end of March 2015.
Video Almost ready for restart

In early 2013, after three years of running, the Large Hadron Collider (LHC) shut down for planned maintenance. Hundreds of engineers and technicians spent two years repairing and strengthening the accelerator in preparation for running at higher energy. Now the world’s largest and most powerful particle collider is ready to start up again. So what’s new?

1) New magnets
Of the LHC’s 1232 superconducting dipole magnets, which steer particle beams around the accelerator, 18 have been replaced owing to wear and tear.

2) Stronger connections
More than 10,000 electrical interconnections between dipole magnets in the LHC have been fitted with shunts – pieces of metal that act as an alternative path for the 11,000 amp current, saving the interconnection if there is a fault.

3) Safer magnets
The LHC’s superconducting magnets have an improved quench protection system. Superconducting magnets conduct electricity without losing energy to resistance, and so can achieve higher magnetic fields. In a quench, a magnet reverts back to a resistive state, releasing a large amount of energy. The quench-protection system in the LHC serves to dissipate this energy in a more controlled manner if it finds any abnormal voltage developing across a magnet.

4) Higher energy beams
The energy of collisions in the LHC in 2015 will be 13 TeV (or 6.5 TeV per beam) compared to 8 TeV (4 TeV per beam) in 2012. Higher energy allows physicists to extend the search for new particles and to check previously untestable theories.

5) Narrower beams
Because transverse beam size – the width of the beam – decreases with increasing energy, beams in the LHC will be more tightly focused, which means more interactions and collisions for the experiments to study.

6) Smaller but closer proton packets
There will be fewer protons per packet – or “bunch”: 1.2 × 10^11 compared to 1.7 × 10^11 in 2012. When dozens of collisions occur at once, it becomes harder for a detector’s computers to disentangle which particle comes from which collision. With fewer protons in each collision, this problem of “pileup” will be less severe. However, the bunches of protons will be separated in time by 25 nanoseconds compared to 50 nanoseconds. The LHC will thus deliver more particles per unit time as well as more collisions to the experiments.

7) Higher voltage
Radiofrequency cavities, which give particles little kicks of energy as they pass, will operate at higher voltages to give the beams higher energies.

8) Superior cryogenics
The dipole magnets on the LHC must be kept at low temperature to be in their superconducting state. The cryogenics system has been fully consolidated, with complete maintenance of the cold compressors, as well as an upgrade of the control systems and renovation of the cooling plant.

9) Radiation-resistant electronics
A full maintenance and upgrade of the electrical systems on the LHC included more than 400,000 electrical tests, and the addition of newer, more radiation-tolerant systems.

10) More secure vacuum
The inside of the beam pipe is kept under vacuum so that the beam does not crash into molecules in its path. But charged beams can rip electrons from the inside surfaces of the pipe, forming an “electron cloud” that interferes with the beam. To dampen this effect the inside of the beam pipe has been coated with non-evaporable getter (NEG), a material that takes up the electrons. In places, solenoids have been wrapped around the beam pipe to keep electrons from deviating from the sides.

Here is a 20 minute video of how photography is used at the LHC

Here is a 20 minute video of how photography is used at the LHC

Big article with lots of pitchers:

LHC restart: ‘We want to break physics’

….In a sense, one of the shiniest new items in the LHC’s armoury for Run Two is the Higgs boson. Now that its existence is confirmed and quantified, it can inform the next round of detection and analysis.

“It’s a new door – a new tool that we can use to probe what is beyond the Standard Model,” says Dr Andre David, one of the research team working on the CMS experiment.

He emphasises that the Higgs is much more than the final item on the Standard Model checklist; there is a great deal still to find out about it. “It’s like a new wrench that we still have to work out exactly where to fit.”

Prof Shears agrees: “We’ve only had about a thousand or two of these new particles, to try and understand their nature.

“And although it looks like the Higgs boson that we expect from our theory, there’s still a chance that it might have partners that would then tell us that we’re not looking at our normal theory at all. We’re looking at something deeper and more exotic.”

That is the central impatience that is itching all the physicists here: they want to find something that falls completely outside what they expect or understand.

“The data so far has confirmed that our theory is really really good, which is frustrating because we know it’s not!” Prof Shears says. “We know it can’t explain a lot of the Universe.

“So instead of trying to test the truth of this theory, what we really want to do now is break it – to show where it stops reflecting reality. That’s the only way we’re going to make progress.”

In the canteen at Cern headquarters I meet Dr Steven Goldfarb, a physicist and software developer on the Atlas team. His sentiments are similar.

“We have a fantastic model – that we hate,” he chuckles.

“It has stood up to precision measurements for 50 years. We get more and more precise, and it stands up and stands up. But we hate it, because it doesn’t explain the universe.”

Full article: http://www.bbc.com/news/science-environment-31162725

If the LHC doesn’t find dark matter, then it’s unlikely that we’ll ever see in out lifetime an accelerator capable of greater energy than this.

Main proposals for extensions after the LHC has run its course are either smaller devices or minor improvements to the LHC. One possibility is for the LHC to be used for electron collisions; that would make it a machine with no more energy but because electrons are pointlike unlike protons (and lead nuclei) it would give a cleaner signal. Even at 13 TeV, the LHC won’t be able to produce anything like a pure quark-gluon plasma; that would require even higher energies.

mollwollfumble said:

If the LHC doesn’t find dark matter, then it’s unlikely that we’ll ever see in out lifetime an accelerator capable of greater energy than this.

Main proposals for extensions after the LHC has run its course are either smaller devices or minor improvements to the LHC. One possibility is for the LHC to be used for electron collisions; that would make it a machine with no more energy but because electrons are pointlike unlike protons (and lead nuclei) it would give a cleaner signal. Even at 13 TeV, the LHC won’t be able to produce anything like a pure quark-gluon plasma; that would require even higher energies.

What sort of energies are you talking about and do we have the technology to produce them, but not the funding and how close do they come to reproducing what’s found in nature.

Cymek said:

mollwollfumble said:

If the LHC doesn’t find dark matter, then it’s unlikely that we’ll ever see in out lifetime an accelerator capable of greater energy than this.

Main proposals for extensions after the LHC has run its course are either smaller devices or minor improvements to the LHC. One possibility is for the LHC to be used for electron collisions; that would make it a machine with no more energy but because electrons are pointlike unlike protons (and lead nuclei) it would give a cleaner signal. Even at 13 TeV, the LHC won’t be able to produce anything like a pure quark-gluon plasma; that would require even higher energies.

What sort of energies are you talking about and do we have the technology to produce them, but not the funding and how close do they come to reproducing what’s found in nature.

How can something that does not have a defined position be said to be point-like?

The Rev Dodgson said:

Cymek said:

mollwollfumble said:

If the LHC doesn’t find dark matter, then it’s unlikely that we’ll ever see in out lifetime an accelerator capable of greater energy than this.

Main proposals for extensions after the LHC has run its course are either smaller devices or minor improvements to the LHC. One possibility is for the LHC to be used for electron collisions; that would make it a machine with no more energy but because electrons are pointlike unlike protons (and lead nuclei) it would give a cleaner signal. Even at 13 TeV, the LHC won’t be able to produce anything like a pure quark-gluon plasma; that would require even higher energies.

What sort of energies are you talking about and do we have the technology to produce them, but not the funding and how close do they come to reproducing what’s found in nature.

How can something that does not have a defined position be said to be point-like?

It interacts as a point like particle- Compton scattering

Cymek said:

mollwollfumble said:

If the LHC doesn’t find dark matter, then it’s unlikely that we’ll ever see in out lifetime an accelerator capable of greater energy than this.

Main proposals for extensions after the LHC has run its course are either smaller devices or minor improvements to the LHC. One possibility is for the LHC to be used for electron collisions; that would make it a machine with no more energy but because electrons are pointlike unlike protons (and lead nuclei) it would give a cleaner signal. Even at 13 TeV, the LHC won’t be able to produce anything like a pure quark-gluon plasma; that would require even higher energies.

What sort of energies are you talking about and do we have the technology to produce them, but not the funding and how close do they come to reproducing what’s found in nature.

For the quark-gluon plasma required energy, all I can say (from attending a high energy physics conference) is that the 8 TeV from the LHC wasn’t anywhere near a large enough energy. At a wild guess I’d say that at least five times that much energy would be needed. The experiment they used to try to produce the quark-gluon plasma was collisions between the nuclei of two lead atoms. All that could be concluded was they we don’t know enough about how large nuclei collide. To learn more a new set of experiments was planned with a proton hitting a lead nucleus. That’s not to learn about the quark-gluon plasma, but to try to get some simpler data to help make sense of the earlier lead-lead collisions.