Experimental study of ion-beam self-pinched-transport for MeV protons

Summary form only given A 100-kA, 1.2-MeV proton beam from a pinch-reflex ion diode on the Gamble II accelerator is used to test the concept of self-pinched ion transport. Self-pinched transport (SPT) uses the self-generated magnetic field from the ion beam to radially confine the ion beam. A proton beam is injected through a 3-cm radius aperture covered with a 2-/spl mu/m thick polycarbonate foil into a 10-cm radius transport region. The transport region is filled with helium at pressures of 30-250 mTorr, vacuum (10/sup -4/ Torr), or 1-Torr air. The beam is diagnosed with witness plates, multiple-pinhole-camera imaging onto radiachromic film, time- and space-resolved proton-scattering, and with prompt-/spl gamma/ and nuclear-activation from LiF targets. Witness-plates and the multiple-pinhole-camera are used to determine the size, location, and uniformity of the beam at different distances from the injection aperture. A beam global divergence of 200 mrad is measured at 15 cm. At 50 cm, the beam fills the transport region. At 110 cm and 100- to 200- mTorr helium, there is evidence of beam filamentation.