Half-integer fast resonant extraction with quasi rectangular spill

Neutrino experiments at the SPS require short bursts of protons which are extracted by a fast resonant mechanism once or twice per cycle. The extraction process is triggered by a thyristor controlled pulse generator, discharging a capacitor bank into an extraction quadrupole. The beam being pushed onto resonance at nearly constant speed during the 'linear' part of the rising ramp, the time signal of the spill (i.e. the number of particles extracted per time unit) is almost Gaussian. A relatively simple and inexpensive modification of the pulse generator allowed to improve this Gaussian spill time structure such as to become more rectangular. (author) 2 refs.; 3 figs.; 1 tab