Tech-X, Boulder, Colorado
KEK, Ibaraki
BNL, Upton, Long Island, New York
Funding: Supported in part by the DOE Office of Science, Office of Nuclear Physics under grant No. DE-FG02-06ER84508.
Non-scaling FFAGs are sensitive to a slew of resonances during the acceleration ramp. An important consideration - because it affects the amount of rf power required - will be the speed at which resonances must be crossed. We present simulations of possible non-scaling FFAGs, focusing especially on the effects of space charge, using newly developed capabilities in the code PTC*.
* E. Forest, Y. Nogiwa, F. Schmidt, "The FPP and PTC Libraries", ICAP'2006.
Tech-X, Boulder, Colorado
BNL, Upton, Long Island, New York
Funding: Supported by the US DOE Office of Nuclear Physics under grants DE-FC02-07ER41499 and DE-FG02-04ER84094; used NERSC resources under grant DE-AC02-05CH11231.
Magnetic field errors can limit the dynamical friction force on co-propagating ions and, hence, increase the cooling time. We present theoretical and numerical results for reduction of the friction force due to bounded transverse magnetic field errors, as a function of wavelength. VORPAL * simulations using a binary collision algorithm ** show that small-wavelength field errors affect the friction logarithmically, via the Coulomb log, while long-wavelength errors reduce the friction by effectively increasing the transverse electron temperature. A complete understanding of finite-time effects and the role of small impact parameter collisions is required to correctly interpret the simulation results. We show that the distribution of electron-ion impact parameters is similar to a Pareto distribution, for which the central limit theorem does not apply. A new code has been developed to calculate the cumulative distribution function of electron-ion impact parameters and thus correctly estimate the expectation value and uncertainty of the friction force.
* C. Nieter and J. Cary, J. Comp. Phys. 196 (2004), p. 448.
** G. Bell et al., J. Comp. Phys. 227 (2008), p. 8714.
Tech-X, Boulder, Colorado
Fermilab, Batavia
Funding: This work was supported by the US DOE Office of Science, Office of Nuclear Physics, under Grant No. DE-FG02-08ER85183
A new set of tools for BBSIM has recently been developed to analyze the nature of the diffusion in multi-particle simulations. The diffusion subroutines are currently used to accelerate beam lifetime calculations by estimating the diffusion coefficient at various actions and integrating the diffusion equation. However it is possible that there may be regimes where anomalous diffusion dominates and normal diffusion estimates are incorrect. The tools we have developed estimate the deviation from normal diffusion and can fit the coefficients of a jump diffusion model in the event that this type of diffusion dominates.
Tech-X, Boulder, Colorado
Fermilab, Batavia
Funding: This work was supported by the US DOE Office of Science, Office of Nuclear Physics, under Grant No.DE-FG02-08ER85183
Recent improvements to BBSIM permit detailed simulations of collective effects due to resistive wall wake fields. We compare results of beam transfer measurements (BTF) in the Tevatron and RHIC with and without the effects of resistive wall wake fields. These are then compared to actual BTF measurements made in both machines and the impact of intensity on our measurements. We also investigate the impact of resistive wall wake fields on various chromaticity measurement approaches.