Abstract
Recently, the first direct measurement of a full 6D accelerator beam distribution was reported [B. Cathey, S. Cousineau, A. Aleksandrov, and A. Zhukov, Phys. Rev. Lett. 121, 064804 (2018)PRLTAO0031-900710.1103/PhysRevLett.121.064804]. That work observed a correlation between energy and transverse coordinates, for which the energy distribution becomes hollowed near the transverse core. This hollowing is obscured when the 6D phase space is projected onto one- and two-dimensional axes. This article illustrates how a similar structure emerges from simulation of an initially uncorrelated, high density bunched beam as the result of velocity perturbation from initial nonlinear space charge forces. This phenomenon has not been widely recognized in accelerator systems, but parallels can be drawn to observations of laser-ionized nanoclusters and electron sources for diffraction. While this effect provides insight into the origin of the measured core correlation, it does not provide a complete description. A better reproduction of the measured structure can be obtained via self-consistent simulation through the radio-frequency quadrupole.
| Original language | English |
|---|---|
| Article number | 014201 |
| Journal | Physical Review Accelerators and Beams |
| Volume | 24 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 12 2021 |
Funding
The authors are very grateful for assistance with p y orbit and invaluable feedback on drafts provided by Jeff Holmes, Andrei Shishlo, and Sarah Cousineau. Thanks also to George Hine, who first recognized the similarity between the BTF observations and the physics of laser-ionized clusters. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. This manuscript has been authored by UT-Battelle, LLC, under contract No. DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan .