Let’s say I stood inside the Large Hadron Collider and was hit by a 7 TeV beam of protons. What would happen? Would I fel anything? Would it drill a hole through me? Would I bleed to death?
Maybe something like this.
I don’t know how much he was hit by, but Anatoli Bugorski might be able to shed some (heh) light on the subject.
Bugorski was working on a 70 GeV Synchrotron, so it would be literally 100 times worse in terms of proton energy. The synchrotron had an intensity of 1.7×10[sup]13[/sup] per pulse, with pulses 9 seconds apart, so about 10[sup]12[/sup] per second. I can’t quickly find exactly corresponding numbers for the LHC, but it has an intensity of 10[sup]34[/sup] per cm[sup]2[/sup] per second, so I’m going to guess it’s much much much … much greater.
I’m going to go with drill a hole through you.
The entire beam contains 350MJ of stored energy. Getting rid of that energy in the event of a problem is a significant challenge all of itself.
I think you would be very safe in assuming the beam would hardly notice you as it vaporised whatever part of your anatomy you put in its way. It would probably neatly cauterise minor vessels. I’m suspicious that an explosive blast of plasma (of the ionic not humoric kind) might be the immediate cause of your demise. 350MJ is not far short of 100kg of TNT. You may find yourself painted on the walls of the LHC. Depends how much energy is actually deposited in you versus goes straight through.
I’ll tell you, but you have to promise not to get angry. I wouldn’t like you when you’re angry.
I assume, from the pattern of his injuries, that the beam was off when he leaned over it, then there was a short pulse while his head was in the way, then it was off as he moved out of the way? What’s the duration of a typical pulse in the LHC?
That fits with the parameters of the U-70 synchrotron he was working on, with pulses every 9 seconds (the 0.11 Hz pulse repetition frequency).
From the LHC link in my last post:
So less than 75 ns. Better be quick!
IIRC, radiation is not much different than cooking; basically it destroys molecules by breaking bonds. Destroy enough, the cell dies from gross malfunction. The difference is that particle beams or Xrays can be more focussed and deep-penetrating.
Bugorksi appears to have had a very narrow injury which did not inflict fatal damage. Another risk is that infection sets in with the dead tissue, especially gangrene; however, if the beam is thin enough as in his case, I assume the body’s repair process takes over instead, nothing is isolated enough to become gangrenous while insulated from the body’s protective mechanisms.
In an essentially continuous beam, you would almost cauterise off a chunk of the body, if not bisect it…
Beam me up, Scotty…
One limb at a time!
***On July 13, 1978, Bugorski was checking a malfunctioning piece of equipment when an accident occurred due to failed safety mechanisms. ***
And this was eight years before Chernobyl. Surprise, surprise! 
There was virtually no damage to his intellectual capacity, but the fatigue of mental work increased markedly. Bugorski completely lost hearing in the left ear and only a constant, unpleasant internal noise remained. The left half of his face was paralyzed, due to the destruction of nerves. He was able to function well, except for the fact that he had occasional complex partial seizures and rare tonic-clonic seizures.
In Russia, this is does indeed count as being “able to function well.” 
I think being able to complete your PhD would count as “functioning well” in pretty much any context actually. Frankly I’m not sure why you would just come into this thread about the effects of proton particle beams to take a random off-topic swipe at Russian society, but you must have your reasons. For full points, though, you would have needed to invoke the tired old “In Soviet Russia, proton particle beam malfunctions you!”.
It might do you a world of good and cure your cancer.
I worked for the guy who built the demonstration model that included a moving figure representing a patient undergoing treatment. He was nicknamed Dan “Gurney”, of course.
Don’t those beams run in vacuum? How did he get into the beam?
I guess he was sucked in…
Yeah, I thought the giant colliders were in vaccum; but a small lab unit may have the target in open air.
How do they handle the transition? In synchrotrons only EM waves come out, so they can have a transparent window.
It looks like your experimental proposal has been accepted:
Congratulations! 
Beryllium windows. Beryllium has a low atomic number, so particles can pass through with little loss, and it is metallic so it can be machined (carefully) and will hold vacuum.
Beryllium is very very bad for you if you breathe it though, so machining it is difficult and you live in fear of breaking it.
Oh, I thought that only worked for x-rays. Thanks.
Okay, now that it’s been discussed, it’s okay to post jokes, right?
Here is one cartoonist’s (Tom Tomorrow, to be precise) impression of what getting thus zapped might look like. (Warning! Political Commentary in GQ! I’m posting it just to show what getting zapped looks like!)
(Depending on what news sources you customarily read, you might even recognize who that person is.)