PAC07 - List of Authors (Corbett, W. J.)

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Corbett, W. J.

Paper	Title	Page
TUPMS051	Low Alpha Mode for SPEAR3	1308
	X. Huang, W. J. Corbett, Y. Nosochkov, J. A. Safranek, J. J. Sebek, A. Terebilo SLAC, Menlo Park, California
	In the interest of obtaining shorter bunch length for shorter X-ray pulses, we have developed a low-alpha operational mode for SPEAR3. In this mode the momentum compaction factor is reduced by a factor of 21 or more from the usual achromat mode by introducing negative dispersion at the straight sections. We successfully stored 100~mA with the normal fill pattern at a lifetime of 30hrs. The bunch length was measured to be 6.9ps, compared to 17ps in the normal mode. In this paper we report our studies on the lattice design and calibration, orbit stability, higher order alpha measurement, lifetime measurement and its dependence on the sextupoles, injection efficiency and bunch lengths.
TUPMS055	SPEAR3 Accelerator Physics Update	1311
	J. A. Safranek, W. J. Corbett, S. M. Gierman, R. O. Hettel, X. Huang, J. J. Sebek, A. Terebilo SLAC, Menlo Park, California
	The SPEAR3 storage ring at Stanford Synchrotron Radiation Laboratory has been delivering photon beams for three years. We will give an overview of recent and ongoing accelerator physics activities, including 500 mA fills, work toward top-off injection, long-term orbit stability characterization & improvement, fast orbit feedback, new chicane optics, low alpha optics & short bunches, low emittance optics, and new insertion devices. The accelerator physics group has a strong program to characterize and improve SPEAR3 performance.
FRPMS002	Parametric Modeling of Electron Beam Loss in Synchrotron Light Sources	3853
	B. Sayyar-Rodsari, E. Hartman, C. A. Schweiger Pavilion Technologies, Inc, Austin, Texas W. J. Corbett, M. J. Lee, P. Lui, J. M. Paterson SLAC, Menlo Park, California
	Funding: DOE Phase II STTR: DE-FG02-04ER86225 Synchrotron light is used for a wide variety of scientific disciplines ranging from physical chemistry to molecular biology and industrial applications. As the electron beam circulates, random single-particle collisional processes lead to decay of the beam current in time. We report a simulation study in which a combined neural network (NN) and first-principles (FP) model is used to capture the decay in beam current due to Touschek, Bremsstralung, and Coulomb effects. The FP block in the combined model is a parametric description of the beam current decay where model parameters vary as a function of beam operating conditions (e.g. vertical scraper position, RF voltage, number of the bunches, and total beam current). The NN block provides the parameters of the FP model and is trained (through constrained nonlinear optimization) to capture the variation in model parameters as operating condition of the beam changes. Simulation results will be presented to demonstrate that the proposed combined framework accurately models beam decay as well as variation to model parameters without direct access to parameter values in the model.
FRPMS064	Electron Beam Lifeime in SPEAR3: Measurement and Simulation	4153
	W. J. Corbett, X. Huang, M. J. Lee, P. Lui SLAC, Menlo Park, California B. Sayyar-Rodsari Pavilion Technologies, Inc, Austin, Texas
	Funding: Work supported by US Department of Energy Contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences. The primary contributing factors to electron beam lifetime in a storage ring are elastic and inelastic gas scattering, and intrabeam scattering. In order to further quantify the relative contributions of each mechanism, a series of measurements using vertical scraper position and rf-voltage sweeps were performed in SPEAR3 with fill patterns featuring different single-bunch and total beam currents. In parallel, an analytic beam-lifetime simulator was developed taking scattering cross-sections, rf-bucket height and bunch lengthening effects into account. In this paper, we compare measured results with the simulated results in an effort to develop a comprehensive model for electron beam lifetime under a variety of operating conditions.
FRPMS065	Bunch Length Measurements in SPEAR3	4159
	W. J. Corbett, A. S. Fisher, X. Huang, J. A. Safranek, J. J. Sebek SLAC, Menlo Park, California A. H. Lumpkin ANL, Argonne, Illinois W. Y. Mok Life Imaging Technology, Palo Alto, California
	Funding: Work supported by US Department of Energy Contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences. In the nominal SPEAR3 storage ring optics, the natural radiation pulse length is 40ps fwhm per bunch. Due to the double-bend achromat lattice configuration, it is relatively straightforward to reduce the momentum compaction factor (α) and hence reduce the bunch length by modest values. In this paper we present streak camera measurements of the bunch length in the nominal optics, and with ~α/20 and α/50 optics as a function of single-bunch current. The results demonstrate <10ps fwhm radiation pulses with up 5x10⁸ particles/bunch (~100μ amp). Radiation pulse power, bunch length scaling and broadband impedance estimates are discussed.