Once upon a time, in the "golden days" of nuclear physics research, every large - no, I mean every research active - university had their own small accelerator. Hundreds and thousands of papers were published in the 60's and 70's (even into the 80's) by academics working with small cyclotrons or electrostatic accelerators in their department basements, with reasonably cheap detectors, simple electronics, and data acquisition "systems" that ranged from computers to mere photographic plates. It was easy to become familiar with your own particular setup, which in turn meant you produced better results because you knew the experimental strengths, weaknesses and limits. Sure, we were limited in energy, but at the time it didn't matter: the field was still new, still fresh and full of endless possibilities. You'd measure a reaction, not because it was important in Wolf-Rayet stars or because it populated the highest spin state, but because no one had done so before. Everything was novel.
At some point, however, the possibilities began to be exhausted. There was only so much you could do with light ion beams at low energy on stable targets. The field needed higher energies in order to progress, and that cost money.
As running the little basement accelerators slowly produced fewer and fewer publications, more and more universities and other small facilities shut them down. They became unnecessary expenditures, line items on university budgets that were no longer allocated. Only a portion of the existing facilities made the decision to put in the capital to expand their capabilities. And when this happened, nuclear physicists from the smaller places, whose facilities had been shut down, started traveling to the larger facilities.
The trend propagated with the need for even higher energies and new beam species. The advent of the radioactive ion beam (RIB) meant even fewer facilities would be able to "play the game." Those which did continue to operate (or which came into existence at the time) got their funding from the government - DOE, NSF, and others internationally - as the operational costs were now too high for any one facility to cover. And thus the User Facility was born.
User Facilities, like Oak Ridge National Lab, Argonne, Berkeley, Los Alamos or TRIUMF (or abroad, GANIL, GSI, CERN, and others), get their funding from government grants and thus are able to provide research capabilities to smaller groups who cannot otherwise afford it. Most places have a small permanent staff of administrative and technical support, and many have permanent staff scientists as well. But the idea of a User Facility is to be for "outside users," and so a system had to be put in place: hence what is commonly known as the "Program Advisory Committee," "Experimental Oversight Committee" or any number of other bureaucratic names. It's a committee, made up of both locals (from the facility) and renowned outside users (many from other facilities), to whom all proposals for experiments are submitted. The panel reads the proposals (which come from collaborations all over, including universities and smaller facilities, as well as internally), rates them on some kind of predetermined scale of scientific merit, feasibility and general coolness, and then sets the schedule for the next chunk of time (typically about a year). Sometimes, proposals are unsuccessful. Sometimes they are granted a trial run. Sometimes they're lucky, and are scheduled immediately.
But here's where the system begins to break down.
In theory, it works, and everyone is allocated time and experimental opportunity fairly, based on the same rubric. But in reality, because the facilities have grown so large and complex, it is difficult to know the experimental setups so intimately as was once the case. The limit of what is and is not feasible at any given facility is something that no one knows for sure, but that the insiders - the local staff and researchers at a facility - know much better than anyone writing a proposal from outside. And this becomes a hindrance.
If you don't know the ins and outs of a system, it is difficult to know what experiments might be simple and what others might be hopelessly complex. Conversely, if you are lucky enough (as I once was) to be one of the insiders, you are there all the time, you know the system and its quirks, you know what's possible and what isn't, and you're able to tweak any scientific justification with experimental capability such that your proposal is guaranteed to be more successful than one (perhaps even looking to study precisely the same reaction) submitted from outside. It is a fine system for those inside; you are still competing for time with other locals, meaning your science has to be as rigorous as possible. But for those outside, the system is faulty, because they must be scientifically rigorous as well as being absolutely certain of their (as yet nonexistent) experimental setup.
I have been fortunate enough to be on the inside, and to end up with my name on a myriad of papers because of it. But I have seen firsthand the effects of being on the outside as well. Consider the UK, where I now work: because of the dwindling funding of science over the last few decades, essentially no nuclear physics research facilities exist in the UK anymore. As such, one is pushed out of necessity to User Facilities beyond the borders, where one is always an outsider. Even when proposals are accepted - and they still are, for the system does work, if not perfectly - the damage is long term; the students and postdocs who actually do the data analysis suffer from lack of first-hand knowledge of the experiment and the facility (which in turn makes the analysis longer and more difficult), and often don't have the opportunity to participate in more than one experiment in an entire graduate career. Perhaps this is why such a large percentage of PhD graduates in nuclear physics in the UK go on to careers in industry instead of pursuing academia and research. It's difficult to find statistics, but anecdotally, about 50% fail to go on to posts in basic research. Conversely, nearly all of those we hosted as summer students at a national lab went on to join graduate programs.
So there are pros and cons, not all of which are easily quantified. With a new era of even larger User Facilities (like FRIB) dawning, these questions need to be tackled, not ignored. Will having ever more specialized, and ever fewer, facilities lead to an "us versus them" scenario in the end, with everyone fighting tooth and nail to be on the inside, that they might be able to do science? Or will the newer facilities be true to their spirit and actively provide equal opportunities to all researchers, whether locals or not?