A new 14 GHz electron-cyclotron-resonance ion source for the heavy ion accelerator facility ATLAS

A 14 GHz electron-cyclotron-resonance (ECR) ion source has been designed and built at Argonne National Laboratory. The source is a modification of the AECR [D. J. Clark, C. M. Lyneis, and Z. Q. Xie, 14th Particle Accelerator Conference (PAC), IEEE Conference 91 CH3038-7, 1991 (unpublished), p. 2796 and C. M. Lyneis, Z. Q. Zie, D. J. Clark, R. S. Lam, and S. A. Lundgren, 10th International Workshop on ECR Ion Sources, Oak Ridge, ORNL CONF-9011136, 1990 (unpublished), p. 47.] at Berkeley and incorporates the latest results from electron-cyclotron-resonance (ECR) developments to produce intense beams of highly charged ions, including an improved magnetic confinement of the plasma electrons with an axial mirror ratio of 3.5. The aluminum plasma chamber and extraction electrode as well as a biased disk on axis at the microwave injection side donate additional electrons to the plasma, making use of the large secondary electron yield from aluminum oxide. The source is capable of ECR plasma heating using two different frequencies simultaneously to increase the electron energy gain for the production of high charge states. The main design goal is to produce several e mu A of at least U-238(35+) in order to accelerate the beam to coulomb-barrier energies without further stripping. First charge state distributions for gaseous elements have been measured and 210 e mu A(16)O(7+) has been achieved. A normalized, 90% emittance from 0.1 to 0.2 pi mm mrad for krypton and oxygen beam has been found.