Heavy Inertial Confinement Energy: Interactions Involoving Low charge State Heavy Ion Injection Beams

During the contract period, absolute cross sections for projectile ionization, and in some cases for target ionization, were measured for energetic (MeV/u) low-charge-state heavy ions interacting with gases typically found in high and ultra-high vacuum environments. This information is of interest to high-energy-density research projects as inelastic interactions with background gases can lead to serious detrimental effects when intense ion beams are accelerated to high energies, transported and possibly confined in storage rings. Thus this research impacts research and design parameters associated with projects such as the Heavy Ion Fusion Project, the High Current and Integrated Beam Experiments in the USA and the accelerator upgrade at GSI-Darmstadt, Germany. Via collaborative studies performed at GSI-Darmstadt, at the University of East Carolina, and Texas A&M University, absolute cross sections were measured for a series of collision systems using MeV/u heavy ions possessing most, or nearly all, of their bound electrons, e.g., 1.4 MeV/u Ar{sup +}, Xe{sup 3+}, and U{sup 4,6,10+}. Interactions involving such low-charge-state heavy ions at such high energies had never been previously explored. Using these, and data taken from the literature, an empirical model was developed for extrapolation to much higher energies. In order to extend our measurements to muchmore » higher energies, the gas target at the Experimental Storage Ring in GSI-Darmstadt was used. Cross sections were measured between 20 and 50 MeV/u for U{sup 28+}- H{sub 2} and - N{sub 2}, the primary components found in high and ultra-high vacuum systems. Storage lifetime measurements, information inversely proportional to the cross section, were performed up to 180 MeV/u. The lifetime and cross section data test various theoretical approaches used to calculate cross sections for many-electron systems. Various high energy density research projects directly benefit by this information. As a result, the general public benefits indirectly. The original intent of this project was to measure absolute cross sections for electron loss from fast, low-charge-state, heavy ions for a wide range of charge states, impact energies, and projectiles in order to provide sufficient information for extrapolation to other energies or collision systems. Ideally, data for singly charged ions in the several to tens of MeV/u energy range was sought. Because of the limited number of facilities available that are capable of accelerating heavy ions to high velocities, several collaborations were established. Accelerator access for measurements plus specific accelerator limitations with respect to energies and charge states that could be accessed were the primary limiting factors in achieving these goals. However, as outlined below, we were able to obtain data for a broad range of parameters. These data, coupled with data taken from the literature, enabled us to provide guidance with respect to design parameters needed for various high energy density projects.« less