Observations of effects of ion accumulation in the Maxwell model 1.2-400 synchrotron light source

The commissioning phase of the Maxwell model 1.2-400 synchrotron light source was successfully completed at the end of August, 1992, with more than 200 mA accelerated to 1.3 GeV. This is the first synchrotron light source built by a commercial firm in the U.S. The injector is a 200 MeV linac. Ions trapped in the beam have played a major role in beam accumulation during injection, despite ion clearing electrodes which cover 70% of the circumference. The dependence of the maximum stacked current on the location of ion clearing electrodes and on the applied voltages is discussed. Other observed effects due to ions include the vertical blow-up of the beam at injection as seen on an optical monitor, and beam stability at negative chromaticity. These effects are discussed in relation to some prevailing theories