Muon g-2: The anatomy of the ring

While the large ring that was transported contained mostly the superconducting coils and their cryostat, there's a lot more to the final ring than that. We have to add quite a bit of material: vacuum chambers, yokes and poles, and so on. And in the end, of course, we also need to put our detectors into place. To complicate matters, the electrostatic quadrupoles take up their own fair share of space, and the inflector and kicker are necessary to allow muons into the ring in the first place. All this gets rather complicated fairly quickly, so before I get any further into the details of the experiment, I wanted to present a simplified picture of what's involved in the ring.

 

This is a somewhat simplified and very much not-to-scale sketch of where various components go in the ring. It's a view from above, and from here, we'll see the muons whiz around clockwise. Once any muon decays, some of its momentum is carried off by neutrinos, and the resulting positron ends up with lower total momentum. Since it's in the same magnetic field as before, this causes it to curl inwards, where the experiment detects it using calorimeters (energy-measurers) and trackers (which, as their name suggests, help to track particles and figure out their trajectories). In the case of the detectors (possibly including the not-yet-shown fiber harp) and inflector, I will hopefully write a bit about each component at another point in time, but here's a brief overview:

• Inflector: The issue with having an enormous ring with a strong magnetic field is that it's hard to get muons (or any particle, for that matter) into it in the first place. They are affected by the field too early, and end up on all sorts of funky trajectories. That's where the inflector comes in. It's another magnet, and it generates a magnetic field opposite to that in the ring, so that the muons can really just drift inside, blissfully unaware of the extreme bending forces within.
• Kicker: Well, now we have another issue: the inflector injects particles at a bit of an angle compared to the ideal trajectory. This can be viewed as the particles moving along a circular trajectory (since they're in a uniform magnetic field) with its center offset somewhat from the actual center of the ring. What the kicker does is produce a time-dependent burst of magnetic field that jolts the muons into the orbit we want them in. Of course, time dependent fields bring in their own sorts of problems, so the kick is an interesting area of study.
• Quads: I've previously mentioned the importance of quadrupole magnets (also known as strong-focusing magnets) for vertical focusing of a beam. Since a magnetic quadrupole would disrupt our beautiful, uniform-to-within-a-few-parts-per-million magnetic field, Muon g-2 actually uses electrostatic quadrupoles, which operate on the same principle but do so using electric fields. These extend for long sections of the ring, and (fun fact alert!) one of the quad plates on the first quadrupole (the one right after the inflector) is actually in the way of muons being injected! 
• Calorimeters: In any particle physics experiment, calorimeters, which measure the energy of incident particles, play a central role in identifying and describing particles. This is especially true in Muon g-2, since the critical measurement is the energy of decay positrons over time, which gives us a clue to the wiggle (precession) of the muons that produce them. We have 24 calorimeter stations, positioned in order to catch as many of the decay positrons as possible. They're outside the vacuum chamber (shown in thin black lines above), but only barely.
• Trackers! New in this iteration of the measurement, the Muon g-2 experiment has two tracker stations in front of calorimeters. These are useful in identifying pileup events, when two low-energy positrons hit the calorimeter at nearly the same time, and thus masquerade as a single higher-energy one. They also allow us to trace the trajectory back to the decayed muon, and that gives us a pretty good look at how the beam is behaving, a valuable asset in an experiment in which beam dynamics crucially affect the measurement.

Well, that's the whirlwind summary of the structures in the ring. I haven't mentioned things like the fiber harps, which monitor the beam, and collimators, which filter out muons that get too far away from the ideal parameters, and all of the magnetic field measurements. They're essential to the experiment, but I'm not even nearly an expert on them, so I'll leave their explanation to people more experienced than I.