What would happen to me if I was in the LHC while it was running? This is possibly a stupid question, but one I have been always wondering. What would happen to me if I was in the center of the Large hadron Collider while it was running? Would the energy of the beam cause any short-term or long-term damage?
 A: The LHC luminosity is $4.6\cdot 10^{32} /cm^2/s$ (reference) - that is an incredibly intense beam, but there is a finite number of protons going around.
The thing that really matters though is the number of protons in the beam at one time: there are 2808 bunches in the beam (http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/collisions.htm) with a total energy of 362 MJ.  All that energy is going to end up inside you in a hurry. You will be cooked, vaporized, and the bits outside of the main beam will be destroyed by radiation. Let's assume you are a 100 kg person; if you were made purely of water, your heat capacity would be approximately 4.2E5 J/K, so you entire body could be heated to boiling, evaporate, and continue to around 800 C - glowing red hot.
For comparison, proton therapy (of the kind used to treat brain tumors) uses a 10-100 nA, 70 MeV beam (typically). That's 0.7 - 7 W - and that's enough to take out a (cancerous) piece of your brain. Here, we are talking about far more energetic protons - they will typically lose much less power per unit length, but as they go around and around (assuming they remain focused) they would lose energy and do more harm. The power deposited per unit time would be many orders of magnitude greater than that of proton therapy as the beam current is so much greater.
Oh - and you may have trouble breathing in the ultra high vacuum.
If you stay away from the beam itself, the place where the most radiation damage occurs is in the collider section - see for example http://www.lhc-closer.es/1/4/13/0 . The average dose rate there is on the order of 7500 Gy/year - so just hanging around there would for sure kill you in a couple of days (lethal dose is about 75 Gy).
A: When they need to empty the beam of particles they are directed into a "beam dump" target

Absorption
Each beam dump absorber consists of a 7m long segmented carbon
  cylinder of 700mm diameter, contained in a steel cylinder, comprising
  the dump core (TDE). This is water cooled, and surrounded by about 750
  tonnes of concrete and iron shielding. The dump is housed in a
  dedicated cavern (UD) at the end of the transfer tunnels 

If that is what is needed to safely absorb a beam - you can imagine what that would do to you.
edit: Interestingly they use graphite to slow the beam more slowly than say lead/tungsten so that the energy is absorbed through the whole mass of the target and cooling it is easier.
A: Nobody ever tried with LHC, but here is Anatoli Bugorski:
http://en.wikipedia.org/wiki/Anatoli_Bugorski
Given the damage he received with a beam of 70 GeV protons (intensity ~10^13) you can probably imagine the damage you would receive from 6500 GeV protons (intensity ~10^32).
For more info about the "danger" of the LHC beams, I suggest you read about the LHC beam dumping system:
http://www.symmetrymagazine.org/article/december-2007/protecting-the-lhc-from-itself
You definitely don't want to replace this piece of graphite :)
