NSLS-II Seminar

ALS has been upgraded recently by adding a new mode of operation, the Top-Off Mode, which is in addition to the existing modes of Fill and Stored Beam. The Top-Off Mode permits injection of 1.9GeV electron beam into the Storage Ring, with the safety shutters open, once certain strict conditions are met and maintained. Top-Off Mode enables User operation without an interruption caused by mode switching between the Stored Beam Mode when safety shutters are open, to the Fill Mode with the safety shutters closed and back. The conditions necessary to permit Top-Off Mode are; stored beam is present, the energies are matched between the injector and storage ring, a select set of storage ring lattice magnets are operating at the correct current levels, and radiation losses are minimized. If certain combinations of these conditions are not met, a potentially dangerous condition of injecting electrons down a users beam line can exist. Therefore in addition to the configuration controlled beamline apparatus, a system of mode control, energy match, lattice match and stored beam interlocks are needed to actively control the injected beam prohibiting potentially dangerous conditions. In this talk I will present the Top-Off Mode Beam Interlock system requirements, specification, design, implementation and the operational experience from the first two years of operation.