[Eng-div] Fwd: [Accelerator_staff] Thesis Defense: Michael Spata - 4/27/2012

[Gayle Coleman]

All interested persons are cordially invited to attend -

Michael Spata's Thesis Defense

Friday, April 27, 2012
2:00 p.m. - 3:00 p.m.
ODU Center for Accelerator Science
(Video Feed in ARC, Room 428)

"Application of Chebyshev Formalism to Identify Nonlinear Magnetic Field
Components in Beam Transport Systems"

An experiment was conducted at Jefferson Lab's Continuous Electron Beam
Accelerator Facility to develop a beam-based technique for
characterizing the extent of the nonlinearity of the magnetic fields of
a beam transport system. Horizontally and vertically oriented pairs of
air-core kicker magnets were simultaneously driven at two different
frequencies to provide a time-dependent transverse modulation of the
beam orbit relative to the unperturbed reference orbit. Fourier
decomposition of the position data at eight different points along the
beamline was then used to measure the amplitude of these frequencies.
For a purely linear transport system one expects to find solely the
frequencies that were applied to the kickers with amplitudes that depend
on the phase advance of the lattice. In the presence of nonlinear fields
one expects to also find harmonics of the driving frequencies that
depend on the order of the nonlinearity. Chebyshev polynomials and their
unique properties allow one to directly quantify the magnitude of the
nonlinearity with the minimum error. A calibration standard was
developed using one of the sextupole magnets in a CEBAF beamline. The
technique was then applied to a pair of Arc 1 dipoles and then to the
magnets in the Transport Recombiner beamline to measure their multipole
content as a function of transverse position within the magnets.




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