15,719 research outputs found
A tracking algorithm for the stable spin polarization field in storage rings using stroboscopic averaging
Polarized protons have never been accelerated to more than about GeV. To
achieve polarized proton beams in RHIC (250GeV), HERA (820GeV), and the
TEVATRON (900GeV), ideas and techniques new to accelerator physics are needed.
In this publication we will stress an important aspect of very high energy
polarized proton beams, namely the fact that the equilibrium polarization
direction can vary substantially across the beam in the interaction region of a
high energy experiment when no countermeasure is taken. Such a divergence of
the polarization direction would not only diminish the average polarization
available to the particle physics experiment, but it would also make the
polarization involved in each collision analyzed in a detector strongly
dependent on the phase space position of the interacting particle. In order to
analyze and compensate this effect, methods for computing the equilibrium
polarization direction are needed. In this paper we introduce the method of
stroboscopic averaging, which computes this direction in a very efficient way.
Since only tracking data is needed, our method can be implemented easily in
existing spin tracking programs. Several examples demonstrate the importance of
the spin divergence and the applicability of stroboscopic averaging.Comment: 39 page
Achieving diffraction-limited performance on the Berkeley MET5
The Berkeley MET5, funded by EUREKA, is a 0.5-NA EUV projection lithography tool located at the Advanced Light Source at Berkeley National Lab. Wavefront measurements of the MET5 optic have been performed using a custom in-situ lateral shearing interferometer suitable for high-NA interferometry. In this paper, we report on the most recent characterization of the MET5 optic demonstrating an RMS wavefront 0.31 nm, and discuss the specialized mask patterns, gratings, and illumination geometries that were employed to accommodate the many challenges associated with high-NA EUV interferometry
Three-Dimensional Analysis of Wakefields Generated by Flat Electron Beams in Planar Dielectric-Loaded Structures
An electron bunch passing through dielectric-lined waveguide generates
erenkov radiation that can result in high-peak axial electric field
suitable for acceleration of a subsequent bunch. Axial field beyond
Gigavolt-per-meter are attainable in structures with sub-mm sizes depending on
the achievement of suitable electron bunch parameters. A promising
configuration consists of using planar dielectric structure driven by flat
electron bunches. In this paper we present a three-dimensional analysis of
wakefields produced by flat beams in planar dielectric structures thereby
extending the work of Reference [A. Tremaine, J. Rosenzweig, and P. Schoessow,
Phys. Rev. E 56, No. 6, 7204 (1997)] on the topic. We especially provide
closed-form expressions for the normal frequencies and field amplitudes of the
excited modes and benchmark these analytical results with finite-difference
time-domain particle-in-cell numerical simulations. Finally, we implement a
semi-analytical algorithm into a popular particle tracking program thereby
enabling start-to-end high-fidelity modeling of linear accelerators based on
dielectric-lined planar waveguides.Comment: 12 pages, 2 tables, 10 figure
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