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Anisotropic free-energy limit of halos in high-intensity accelerators
G Franchetti1, I Hofmann, D Jeon
1GSI Darmstadt, Planckstrasse 1, 64291 Darmstadt, Germany.
Physical Review Letters
|July 5, 2002
Abstract:
We study halo emittance growth in anisotropic beams and show that the rms emittance growth resulting from mismatch is highly anisotropic, depending on the tune ratio. We find that the free-energy limit calculated by Reiser [J. Appl. Phys. 70, 1919 (1991)] for an axisymmetric 1D halo can be extended to 2D if understood as an upper bound to the rms emittance growth averaged per degree of freedom. The thus-obtained "free-energy limit" of an ideal transport system is compared with the halo rms emittance growth in simulations of the Spallation Neutron Source linac.