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| THPMS083 | The EMMA Lattice Design | lattice, acceleration, resonance, quadrupole | 3181 | ||
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Funding: Work Supported by the United States Department of Energy, Contract No. DE-AC02-98CH10886. |
EMMA is a 10 to 20 MeV electron ring designed to test our understanding of beam dynamics in a relativistic linear non-scaling fixed field alternating gradient accelerator (FFAG). This paper describes the design of the EMMA lattice. We begin with a description of the experimental goals that impact the lattice design. We then describe what motivated the choice for the basic lattice parameters, such as the type of cells, the number of cells, and the RF frequency. We next list the different configurations that we wish to operate the machine in so as to accomplish our experimental goals. Finally, we enumerate the detailed lattice parameters, showing how these parameters result from the various lattice configurations. |
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| THPAN063 | Analytic Description of the Phase Slip Effect in Race-Track Microtrons | injection, electron, microtron, synchrotron | 3369 | ||
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Design of modern race-track microtrons (RTMs) requires better understanding of the longitudinal beam dynamics in these machines, in particular of the phase slip effect which is important for low energy beams. We generalize an analytical approach for the description of the synchronous particle motion and synchrotron oscillations, developed in our previous papers, by including the fringe fields of the RTM end magnets. Explicit, though approximate, formulas are derived and an algorithm for improving their accuracy is formulated. The efficiency of the analytic description is checked numerically, in particular by tracking simulations using the RTMTRace code. Explicit examples of low energy injection schemes and applications of this formalism for the injection phase fixing are given.
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| THPAS046 | Transverse-Longitudinal Coupling in an Intense Electron Beam | focusing, electron, coupling, space-charge | 3597 | ||
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Funding: This paper was prepared under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. |
This paper describes the longitudinal expansion of a 10 keV, 100 mA electron beam in the University of Maryland Electron Ring. The expansion of the beam tail was found to be sensitive to the choice of transverse focusing settings due to the presence of an abnormality in the beam current profile. Expansion of the beam head, where no abnormality was observed, is in good agreement with the one-dimensional cold fluid model. |
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| FRPMN099 | Equilibrium Fluctuations in an N-Particle Coasting Beam: Schottky Noise Effects | impedance, collective-effects, plasma, vacuum | 4318 | ||
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Funding: Supported by DOE grant DE-FG02-99ER41104 |
We discuss the longitudinal dynamics of an unbunched beam with a collective effect due to the vacuum chamber and with the discretness of an N-particle beam (Schottky noise) included. We start with the 2N equations of motion (in angle and energy) with random initial conditions. The 2D phase space density for the N-Particles is a sum of delta functions and satisfies the Klimontovich equation. An arbitrary function of the energy also satisfies the Klimontovich equation and we linearize about a convenient equilibrium density taking the initial conditions to be independent, identically distributed random vaiables with the equilibrium distribution. The linearized equations can be solved using a Laplace transform in time and a Fourier series in angle. The resultant stochastic process for the phase space density is analyzed and compared with a known result*. Work is in progress to study the full nonlinear problem. To gain further insight we are studying three alternative approaches: (1) a BBGKY approach, (2) an approach due to Elskens and Escande** and (3) the 'three-level-approach' of Donsker and Varadhan (see "Entropy, Large Deviations and Statistical Mechanics'', by R. S. Ellis).
* V. V. Parkhomchuk and D. V. Pestrikov, Sov. Phys. Tech. Phys. 25(7), July 1980 ** "Microscopic Dynamics of Plasmas and Chaos", Y. Elskens and D. Escande, IoP, Series in Plasma Physics, 2003. |
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| FRPMS092 | Kinetic Description of Nonlinear Wave and Soliton Excitations in Coasting Charged Particle Beams | simulation, plasma | 4291 | ||
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Funding: Research supported by the U. S. Department of Energy. |
This paper makes use of a one-dimensional kinetic model based on the Vlasov-Maxwell equations to describe nonlinear wave and soliton excitations in coasting charged particle beams. The kinetic description makes use of the recently-developed g-factor model [1] that incorporates self-consistently the effects of transverse density profile shape at moderate beam intensities. The nonlinear evolution of wave and soliton excitations is examined for disturbances both moving faster and moving slower than the sound speed, incorporating the important effects of wave dispersion [2]. Analytical solutions are obtained for nonlinear traveling wave pulses with and without trapped particles, and the results of nonlinear perturabtive particle-in-cell simulations are presented that describe the stability properties and long-time evolution.
[1] R. C. Davidson and E. A. Startsev, Phys. Rev. ST Accel. Beams 7, 024401 (2004).[2] R. C. Davidson, Phys. Rev. ST Accel. Beams 7, 054402 (2004). |
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