• L.R. Prost, A.V. Shemyakin
  Fermilab, Batavia, Illinois

The newly installed high-energy Recycler Electron Cooling system (REC) at Fermilab will work at an electron energy of 4.34 MeV and a DC beam current of 0.5 A in an energy recovery scheme. For reliable operation of the system, the relative beam current loss must be maintained to levels < 3.e-5. Experiments have shown that the loss is determined by the performance of the electron beam collector, which must retain secondary electrons generated by the primary beam hitting its walls. As a part of the Electron cooling project, the efficiency of the collector for the REC was optimized, both with dedicated test bench experiments and on two versions of the cooler prototype. We find that to achieve the required relative current loss, an axially-symmetric collector must be immersed in a transverse magnetic field with certain strength and gradient prescriptions. Collector efficiencies in various magnetic field configurations, including without a transverse field on the collector, are presented and discussed

• C.M. Celata, F.M. Bieniosek, P.A. Seidl
  LBNL, Berkeley, California
• A. Friedman, D.P. Grote
  LLNL, Livermore, California
• L.R. Prost
  Fermilab, Batavia, Illinois

In heavy-ion-driven inertial fusion accelerator concepts, dynamic aperture is important to the cost of the accelerator, most especially for designs which envision multibeam linacs, where extra clearance for each beam greatly enlarges the transverse scale of the machine. In many designs the low-energy end of such an accelerator uses electrostatic quadrupole focusing. The dynamic aperture of such a lattice has been investigated for intense, space-charge-dominated ion beams using the 2-D transverse slice version of the 3-D particle-in-cell simulation code WARP. The representation of the focusing field used is a 3-D solution of the Laplace equation for the biased focusing elements, as opposed to previous calculations which used a less-accurate multipole approximation. 80% radial filling of the aperture is found to be possible. Results from the simulations, as well as corroborating data from the High Current Experiment at LBNL, will be presented.

• S. Nagaitsev, D.R. Broemmelsiek, A.V. Burov, K. Carlson, C. Gattuso, M. Hu, B.J. Kramper, T.K. Kroc, J.R. Leibfritz, L.R. Prost, S.M. Pruss, G.W. Saewert, C.W. Schmidt, A.V. Shemyakin, M. Sutherland, V. Tupikov, A. Warner
  Fermilab, Batavia, Illinois
• W. Gai
  ANL, Argonne, Illinois
• G.M. Kazakevich
  BINP SB RAS, Novosibirsk
• S. Seletsky
  Rochester University, Rochester, New York