LAMPF Hardware Beam Transmission Monitor Systems

The average power in the LANPF primary beam is now approximately 450 kW. At these power levels errant beams can quickly destroy accelerator or experimental area beam line components, while the long-term deposition of even a small fraction (<<1%) of the beam energy in unintended locations can result in activation levels too high for "hands-on" maintenance. This paper describes the present status of the hardware beam transmission monitor, which is one of several evolving redundant protection systems. Beam currents are measured by toroids located at various places along the accelerator and in the experimental areas. Losses are determined by subtracting the signals from appropriate toroids. Long-term (~month) stabilities are sufficient to enable loss tolerances of ±0.5 PA to be maintained with 500-μA average currents, while short-term (~hour) fluctuations are an order of magnitude smaller. The absolute accuracy of the beam measurements is believed to be ±0.5%. These systems have provided reliable protection with little maintenance required for the past few years.