Beam studies in the LBL MBE-4 device

The multiple-beam accelerator MBE-4 is a device for research toward a heavy ion driver for inertial confinement fusion based on the induction linac concept. Its main goal is proof of the principle of current amplification by acceleration and controlled self-similar beam pulse compression. Into the 16-m long electrostatic alternate-gradient focusing lattice four beams are injected. Each carries an initial current of 10 mA of Cs/sup +/ ions from a Marx-driven diode at 200 keV. The current amplification is up to ninefold, with a final beam energy in excess of 800 keV in the middle of the current pulse. Available diagnostics include transverse double-slit emittance and position measuring devices; current-sensing Faraday cups; and electrostatic energy analysis. Diagnostic access is possible along the entire device at a number of stations and is fully computer controlled. The longitudinal and transverse properties of the 10-mA beams with and without acceleration are being studied. The diagnosis of the transport of a 100- mu A pencil beam, 1.5 mm in diameter, through an accelerating channel of a 5.7-cm diameter has begun. This beam has been used to determine the zero-current phase advance for various beam and machine parameters and to address some mechanical alignment issues as well.<>