The best accelerator operators in the past have been undergraduate physics majors, because in undergraduate E & M they have been exposed to the equations of motion of charged particles in magnetic fields, and the concept of e/m and the Lorentz force. Basic accelerator concepts such as the cyclotron accelerator and betatron acccelerator also are sometimes taught to undergraduate physics majors. In any case, undergraduate physics majors have been exposed to all the basic tools for understanding charged particle accelerators.
Humphries' book covers most types of charged particle accelerators, and requires no new physics concepts beyond undergraduate E & M. For me, it would have been a much easier read than Dirac's book on Quantum Mechanics. No textbook on accelerators is perfect, and Humphries' book is no exception. But it does expose the reader to most types of accelerators. One glaring overlook is the total exclusion of the BNL contribution to alternating gradient focusing in the 1950's, including any reference to the Courant, Livingston and Schneider paper.
All accelerator operators must get training in radioactivation, radiation shielding, radioactivity, ionizing radiation, rads, rems, half lives, etc. None of this is included in any accelerator physics book. Having an undergraduate nuclear physics course that covers nuclear activation cross sections and beta decay is certainly helpful.
Any applicant for an accelerator operator position who does not aspire to a higher position than just operating accelerators (including finding vacuum leaks, disconnected cables, and radioactivity hot spots) is not as good a hire as someone who wants to learn more about how accelerators really work. Certainly having someone in the control room who understands how magnets bend (and focus) particle beams, and how resonant RF cavities can accelerate beams is an asset to the accelerator team. Certainly more than someone whose main interest is string theory.
Go for it, Az.
Bob S