Subcategory: Physics (not Nanoscience)
Luis Jauregui - California State University, San Bernardino
Co-Author(s): Yves Roblin
The electron accelerator at Jefferson Lab is used for electrons and nuclei collisions in order to examine the structure of matter. To produce consistent data, it is critical to have a well-focused beam of constant size. To keep the beam focused, quadrupoles (quads) are used. Quads are magnets which focus the beam in one direction (x or y) and defocus in the other. When two or more quads are used in series, a net focusing effect is achieved in both vertical and horizontal directions. The focal length of the quad depends on both the momentum of the particles passing through and the magnetic fields inside the quads. Ideally, the radio frequency (RF) cavities at Jefferson lab would have constant electric fields for all runs, causing the momentum to be the same at each quad in every run. In actuality, at start up there is a 5% calibration error. This means that the momentum of particles passing through the quads isn’t always what is expected. The objective is to find exactly how sensitive the focusing in the linac is to this 5% error. To analyze the electron beam through the linac, the software ELEGANT (ELEctron Generation ANd Tracking) was used.
First a simple arrangement of quads was simulated to see how the beam behaved when there was no increase in momentum. Following that, a full linac was simulated, which contained 208 RF Cavities with constant electric fields, a total momentum kick of 1090 MeV, and quads with the appropriate magnetic fields. Next, the electric fields in the RF cavities were randomly decreased in some, while being randomly increased in others, while maintaining a total momentum kick constant. Here we show that when the fields in the RF cavities randomly vary by up to 5%, the beta functions only change by a couple of percent as compared to the ideal case. The linac’s focusing is sensitive to this 5% calibration error, but the response is not very large. If this calibration error is to ever be reduced to near 1%, or lower, we can expect the effect on the focusing to be nearly negligible.
Funder Acknowledgement(s): Old Dominion University
Faculty Advisor: Yves Roblin,