MONTE-CARLO SIMULATION OF THE PRODUCTION OF H EXCITED-STATES BY INTERACTION OF H- WITH THIN CARBON FOILS

The conversion of relativistic H- to H+ beams by stripping in a thin c arbon foil plays an important role in the injection of high-energy pro ton accelerators and storage rings. The residual portion of neutral hy drogen in excited states determines the beam loss and the level of rad iation near the first turn of the ring. The understanding of the strip ping is therefore of crucial importance for the optimization of the in jection. We have performed a classical Monte-Carlo simulation of the t ransport of H- and of excited H(n) states through carbon foils at rela tivistic energies. The transport of bound and free electrons in the pr esence of the Coulomb field of the nucleus as well as the multiple sca ttering of the solid is taken into account. We analyzed the relativist ic modification of the collision kernel and found that transverse exci tations are not yet important at moderate gamma (gamma less than or eq ual to 2). The distribution of excited states of H and of survival of H- are presented as a function of the thickness of the foil and compar ed to experimental data from LAMPF.