Accurate intensity measurements for proton beams with a 201 MHz structure

A counting system which measures the absolute beam intensity accurately (<1%) at intermediate energies with a beam microstructure of 201.25 MHz or lower is described in this paper. The number of beam micropulses containing one or more beam particles are counted and time-sequenced coincidences between micropulses correct this number to obtain the actual number of beam particles using formulas based on Poisson statistics. The counting system, both the experimental setup and the correction method, was examined fully with two different beam microstructures, 10 MHz and 201.25 MHz, the two main beam microstructures at LAMPF. Maximum beam intensities, below which the system is accurate within a few tenths of a percent, were determined to be ≅ 0.4 pA and ≅ 0.1 pA average beam currents for the 5 ns and 100 ns beam microstructures, respectively. (orig.)