## LHC 2015 Run II upgrades

When people refer to particle colliders, it’s often in reference to the beam energies as these numbers are both indicative of what kinds of new particles can be created and because it’s cool. Another less-cited but very important number is the luminosity which is proportional to the number of particles passing through some area in some time. You run your particle collider for some amount of time and the multiplication of time and luminosity gives you integrated luminosity, these days often cited in units of inverse femtobarns ($\displaystyle \text{fb}^{-1}$). The previous great collider, the Tevatron, produced about 10 $\displaystyle \text{fb}^{-1}$ during its last run, which we can take (as CERN does) to be essentially the total amount produced by all colliders prior to the LHC. In its first run, the LHC produced about 25 $\displaystyle \text{fb}^{-1}$, mostly from 2012.

Upgrades and repairs are currently being performed at CERN to bring the LHC up from its present energy of 8 TeV to the originally specified 14 TeV. If all goes according to plan, it should be back up and running for Run II in 2015. One big change is the addition of 27,000 “shunts” to the superconducting connections between the supercooled magnets called splices, which will provide a low-resistance path for current to traverse. Hopefully, this will prevent the kind of electrical problems that caused a large amount of helium to be dumped back in 2008 that necessitated six months of repairs.

Once this is complete, Run II should last for a few years, producing about 40 $\displaystyle \text{fb}^{-1}$ per year. I’m not actually sure for exactly how long, but I think it’s either 2017 or 2018. This means that Run II could produce from around, say, 100 $\displaystyle \text{fb}^{-1}$ to 200 $\displaystyle \text{fb}^{-1}$.

By the end of Run II, the marginal gain of running the LHC for another year will not be great as the error bars will not be constricted much more (it would take 10 years of running to halve the statistical error after 2019). Therefore, after Run II comes a major upgrade of the LHC, the High Luminosity LHC (HL-LHC [formerly called the Super LHC]) which will boost the peak luminosity tenfold from $\displaystyle 10^{34} \, \text{cm}^{-2} \text{s}^{-1}$ to $\displaystyle 10^{35} \, \text{cm}^{-2} \text{s}^{-1}$ and will then be producing around 300 $\displaystyle \text{fb}^{-1}$ per year. The goal is for Run III to last a decade, meaning a total of 3000 $\displaystyle \text{fb}^{-1}$ which utterly obliterates everything that has come before.

Between the Dawn mission arriving at Ceres, New Horizons arriving at Pluto, Run II of the LHC commencing, and the release of Intel’s Skylake architecture, 2015 is seriously looking like a great year for science and technology.