Properties of the disrupted NLC beam at the Interaction Point (IP) and particle loss in the extraction line are analyzed as a function of beam-to-beam position and angular offset at IP. The simulations show that disruption and beam loss maximize when the vertical beam separation at IP is about 20 times the rms vertical beam size. The horizontal offset does not increase the disruption and the beam loss. The angular offsets cause particle loss in the extraction line mainly because of the beam orbit oscillations.
The NLC extraction line provides a secondary focal point with a low beta function and 2 cm dispersion which can be used for measurement of the beam energy spectrum. In this study, tracking simulations were performed to transport the 0.5 TeV electron beam from the Interaction Point (IP) to the secondary focus (SF), ``measure the resultant transverse beam profile and reconstruct the disrupted IP energy spread. In the simulation, the obtained energy spectrum reproduced the initial IP spread reasonably well, especially with the vertical dispersion at SF which provides larger ratio of dispersion to the betatron beam size.
In this note, we briefly review the current lattice of the NLC extraction line which was designed for the nominal NLC beam parameters. Then we describe the beam parameters for the high luminosity option with larger beam disruption parameter and discuss its effect on beam loss in the extraction line. Finally, we present a summary of the optics study aimed at minimizing the beam loss with high disruption beams.
Realistic calculation of NLC luminosity has been performed using particle tracking in DIMAD and beam-beam simulations in GUINEA-PIG code for various values of beam emittance, energy and beta functions at the Interaction Point (IP). Results of the simulations are compared with analytic luminosity calculations. The optimum range of IP beta functions for high luminosity was identified.
Extensive beam-based feedback systems are planned as an integral part of the Next Linear Collider (NLC) control system. Wakefield effects are a significant influence on the feedback design, imposing both architectural and algorithmic constraints. Studies are in progress to assure the optimal selection of devices and to refine and confirm the algorithms for the system design. We show the results of initial simulations, along with evaluations of system response for various conditions of ground motion and other operational disturbances.
New crystal technique - array of bent strips and a fan-type reflector, based on thin straight plates - have been used for research of extraction and collimation a circulating beam in the U-70 accelerator at the energy 50 GeV and 1.3 GeV. It is shown, that new devices can effectively steer a beam in a wide energy range. For protons with energy 50 GeV efficiency of extraction and collimation about 90 % has been achieved which is record for this method. Reduction of particle losses in 2-3 times was observed also in accelerator at application of different crystals in comparison with the usual one-stage collimation scheme of beam with a steel absorber.
Y. Nosochkov
,T.O. Raubenheimer
,K.A. Thompson
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(2001)
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"NLC Beam Properties and Extraction Line Performance with Beam Offset at IP"
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Yuri Nosochkov
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