Beam-chopping system for LNS superconducting cyclotron

Several experiments which foresee the measurement of time of flight require a bunched beam with a FWHM smaller than I ns and a temporal separation from 100 to 200 ns. An H.E. Chopper that achieves this temporal separation between the impulses has been installed along the beam extraction line of the cyclotron. The two electrodes, which deflect the beam and the inductance coil are both under vacuum. The operating frequency range of the LC resonant circuit is 4.5 divided by 9 MHz and the maximum design voltage is 70 kV. The chopper selects only the beam bunches which cross the device at peak voltage, one bunch for cycle. A steerer magnet to recover the selected bunches on the beam axis is used. All the tests, measurements and chopper's performance, will be presented.