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A formalism and computer program for coupled lattices

Description: In this paper, a formalism to calculate the lattice functions and emittances of a coupled electron/positron storage ring is presented. The lattice functions are calculated directly from the modal matrix of the betatron transport matrix for the ring. The emittances and damping rates are then calculated from the invariants found in the diagonalized representation. In addition, a computer program is described which uses the formalism to calculate the coupled lattice functions, emittances and damping rates. The program can either reconstruct the closed orbit from BPM data and dipole corrector strengths, or construct an orbit from misalignments entered into the the lattice and then optionally correct the orbit with dipole correctors. The lattice functions, emittances, etc. are then calculated about the resulting closed orbit. 7 refs.
Date: April 1, 1989
Creator: Raubenheimer, T.O.
Partner: UNT Libraries Government Documents Department

Zeroth-order design report for the next linear collider. Volume 2

Description: This Zeroth-Order Design Report (ZDR) for the Next Linear Collider (NLC) has been completed as a feasibility study for a TeV-scale linear collider that incorporates a room-temperature accelerator powered by rf microwaves at 11.424 GHz--similar to that presently used in the SLC, but at four times the rf frequency. The purpose of this study is to examine the complete systems of such a collider, to understand how the parts fit together, and to make certain that every required piece has been included. The ``design`` presented here is not fully engineered in any sense, but to be assured that the NLC can be built, attention has been given to a number of critical components and issues that present special challenges. More engineering and development of a number of mechanical and electrical systems remain to be done, but the conclusion of this study is that indeed the NLC is technically feasible and can be expected to reach the performance levels required to perform research at the TeV energy scale. Volume II covers the following: collimation systems; IP switch and big bend; final focus; the interaction region; multiple bunch issues; control systems; instrumentation; machine protection systems; NLC reliability considerations; NLC conventional facilities. Also included are four appendices on the following topics: An RF power source upgrade to the NLC; a second interaction region for gamma-gamma, gamma-electron; ground motion: theory and measurement; and beam-based feedback: theory and implementation.
Date: May 1, 1996
Creator: Raubenheimer, T.O.
Partner: UNT Libraries Government Documents Department

Zeroth-order design report for the next linear collider. Volume 1

Description: This Zeroth Order Design Report (ZDR) for the Next Linear Collider (NLC) has been completed as a feasibility study for a TeV-scale linear collider that incorporates a room-temperature accelerator powered by rf microwaves at 11.424 GHz--similar to that presently used in the SLC, but at four times the rf frequency. The purpose of this study is to examine the complete systems of such a collider, to understand how the parts fit together, and to make certain that every required piece has been included. The design presented here is not fully engineered in any sense, but to be assured that the NLC can be built, attention has been given to a number of critical components and issues that present special challenges. More engineering and development of a number of mechanical and electrical systems remain to be done, but the conclusion of this study is that indeed the NLC is technically feasible and can be expected to reach the performance levels required to perform research at the TeV energy scale. Volume one covers the following: the introduction; electron source; positron source; NLC damping rings; bunch compressors and prelinac; low-frequency linacs and compressors; main linacs; design and dynamics; and RF systems for main linacs.
Date: May 1, 1996
Creator: Raubenheimer, T.O.
Partner: UNT Libraries Government Documents Department

Ion effects in future circular and linear accelerators

Description: In this paper, the author discusses ion effects relevant to future storage rings and linear colliders. The author first reviews the conventional ion effects observed in present storage rings and then discusses how these effects will differ in the next generation of rings and linacs. These future accelerators operate in a new regime because of the high current long bunch trains and the very small transverse beam emittances. Usually, storage rings are designed with ion clearing gaps to prevent ion trapping between bunch trains or beam revolutions. Regardless, ions generated within a single bunch train can have significant effects. The same is true in transport lines and linacs, where typical vacuum pressures are relatively high. Amongst other effects, the author addresses the tune spreads due to the ions and the resulting filamentation which can severely limit emittance correction techniques in future linear colliders, the bunch-to-bunch coupling due to the ions which can cause a multi-bunch instability with fast growth rates, and the betatron coupling and beam halo creation which limit the vertical emittance and beam lifetimes.
Date: May 1, 1995
Creator: Raubenheimer, T.O.
Partner: UNT Libraries Government Documents Department

Analytic estimates of coupling in damping rings

Description: In this paper we present analytic formulas to estimate the vertical emittance in weakly coupled electron/positron storage rings. We consider contributions from both the vertical dispersion and linear coupling of the betatron motions. In addition to simple expressions for random misalignments and rotations of the magnets, formulas are presented to calculate the vertical emittance blowup due to orbit distortions. The orbit distortions are assumed to be caused by random misalignments, but because the closed orbit is correlated from point to point, the effects must be treated differently. We consider only corrected orbits. Finally, the analytic expressions are compared with computer simulations of storage rings with random misalignments. 6 refs., 3 figs.
Date: March 1, 1989
Creator: Raubenheimer, T.O. & Ruth, R.D.
Partner: UNT Libraries Government Documents Department

The generation and acceleration of low emittance flat beams for future linear colliders

Description: Many future linear collider designs call for electron and positron beams with normalized rms horizontal and vertical emittances of {gamma}{epsilon}{sub x} = 3{times}10{sup {minus}6} m-rad and {gamma}{epsilon}{sub y} = 3{times}10{sup {minus}8} m-rad; these are a factor of 10 to 100 below those observed in the Stanford Linear Collider. In this dissertation, we examine the feasibility of achieving beams with these very small vertical emittances. We examine the limitations encountered during both the generation and the subsequent acceleration of such low emittance beams. We consider collective limitations, such as wakefields, space charge effects, scattering processes, and ion trapping; and also how intensity limitations, such as anomalous dispersion, betatron coupling, and pulse-to-pulse beam jitter. In general, the minimum emittance in both the generation and the acceleration stages is limited by the transverse misalignments of the accelerator components. We describe a few techniques of correcting the effect of these errors, thereby easing the alignment tolerances by over an order of magnitude. Finally, we also calculate fundamental'' limitations on the minimum vertical emittance; these do not constrain the current designs but may prove important in the future.
Date: November 1, 1991
Creator: Raubenheimer, T.O.
Partner: UNT Libraries Government Documents Department

The generation and acceleration of low emittance flat beams for future linear colliders

Description: Many future linear collider designs call for electron and positron beams with normalized rms horizontal and vertical emittances of {gamma}{epsilon}{sub x} = 3{times}10{sup {minus}6} m-rad and {gamma}{epsilon}{sub y} = 3{times}10{sup {minus}8} m-rad; these are a factor of 10 to 100 below those observed in the Stanford Linear Collider. In this dissertation, we examine the feasibility of achieving beams with these very small vertical emittances. We examine the limitations encountered during both the generation and the subsequent acceleration of such low emittance beams. We consider collective limitations, such as wakefields, space charge effects, scattering processes, and ion trapping; and also how intensity limitations, such as anomalous dispersion, betatron coupling, and pulse-to-pulse beam jitter. In general, the minimum emittance in both the generation and the acceleration stages is limited by the transverse misalignments of the accelerator components. We describe a few techniques of correcting the effect of these errors, thereby easing the alignment tolerances by over an order of magnitude. Finally, we also calculate ``fundamental`` limitations on the minimum vertical emittance; these do not constrain the current designs but may prove important in the future.
Date: November 1, 1991
Creator: Raubenheimer, T. O.
Partner: UNT Libraries Government Documents Department

Distortion of Crabbed Bunch Due to the Electron Cloud

Description: In order to improve the luminosity, two crab cavities have been installed in KEKB HER and LER [1]. Since there is only one crab cavity in each ring, the crab cavity generates a horizontally titled bunch along the whole ring. The achieved specific luminosity with crabbed bunch is higher, but it is not as high as that from beam-beam simulation [2]. One of the suspicions is the electron cloud. The electron cloud in LER (positron beam) may distort the crabbed bunch and cause the luminosity drop. This note briefly estimates the bunch shape distortion due to the electron cloud in KEKB LER.
Date: May 28, 2008
Creator: Wang, L & Raubenheimer, T.
Partner: UNT Libraries Government Documents Department

Luminosity Optimization With Offset, Crossing Angle, and Distortion

Description: In a linear collider, sources of beam jitter due to kicker noise, quadrupole vibration and long-range transverse wakefields will lead to beam offsets and tilts at the Intersection Point (IP). In addition, sources of emittance dilution such as short-range transverse wakefields or dispersive errors will lead to internal beam distortions. When the IP disruption parameter is large, these beam imperfections will be amplified by a single bunch kink instability which will lead to luminosity loss. In this paper, we study the luminosity loss and then the optimization required to partially cancel the luminosity loss both analytically and with direct simulation.
Date: June 15, 2005
Creator: Wu, Juhao & Raubenheimer, T. O.
Partner: UNT Libraries Government Documents Department

Parameters of the SLAC Next Linear Collider

Description: In this paper, the authors present the parameters and layout of the Next Linear Collider (NLC). The NLC is the SLAC design of a future linear collider using X-band RF technology in the main linacs. The collider would have an initial center-of-mass energy of 0.5 TeV which would be upgraded to 1 TeV and then 1.5 TeV in two stages. The design luminosity is > 5 {times} 10{sup 33} cm{sup {minus}2} sec {sup {minus}1} at 0.5 TeV and > 10{sup 34} cm{sup {minus}2} sec{sup {minus}1} at 1.0 and 1.5 TeV. They briefly describe the components of the collider and the proposed energy upgrade scenario.
Date: May 1, 1995
Creator: Raubenheimer, T.; Adolphsen, C. & Burke, D.
Partner: UNT Libraries Government Documents Department

Compensation of longitudinal nonlinearities in the NLC bunch compressor

Description: The X-Band linac of the Next Linear Collider (NLC) will accelerate bunches of about 100 {mu}m rms length to energies of 250-750 GeV. The task of the NLC bunch compressor is to reduce the initial bunch length of 4-5 mm, at extraction from the damping ring, by a factor of 40, to the desired value. This task is accomplished in two separate stages. The first stage at 2 GeV consists of an rf section and a wiggler. The second stage at 10 GeV is formed by an arc, an rf section, and a chicane. The system is designed such that the final bunch phase is insensitive to initial phase errors and to beam-loading in the intermediate S-band pre-linac. Additional decelerating rf sections are employed to compensate significant longitudinal aberrations.
Date: October 1, 1995
Creator: Zimmermann, F. & Raubenheimer, T. O.
Partner: UNT Libraries Government Documents Department

A bunch compressor for the Next Linear Collider

Description: A bunch compressor design for the Next Linear Collider (NLC) is described. The compressor reduces the bunch length by a factor of 40 in two stages. The first stage at 2 GeV consists of an rf section and a wiggler. The second stage at 10 GeV is formed by an arc, an rf section, and a chicane. The final bunch phase is insensitive to initial phase errors and to beam loading in the intermediate S-band pre-linac. Residual longitudinal aberrations of the system are partially compensated. The bunch compressor encompasses a solenoid spin-rotator system at 2 GeV that allows complete control over the spin orientation.
Date: June 1, 1995
Creator: Emma, P.; Raubenheimer, T. & Zimmermann, F.
Partner: UNT Libraries Government Documents Department

Superconvergent tracking and invariant surfaces in phase space

Description: The question of long term beam stability in very large storage rings presents an extraordinary challenge in nonlinear dynamics. Since current computational methods seem less than adequate on the long time scales involved, we have undertaken a program of evaluating several methods that either are new or have not been tried in accelerator problems heretofore. The methods we investigate fall into two categories: (1) iteration of maps describing concatenated machine elements, for tracking of single particles, and (2) infinite-time methods for direct computation of invariant surfaces in phase space.
Date: April 1, 1985
Creator: Ruth, R.D.; Raubenheimer, T. & Warnock, R.L.
Partner: UNT Libraries Government Documents Department

A new method of correcting the trajectory in linacs

Description: This paper describes a new method of reducing the transverse emittance dilution in linear colliders due to both transverse wakefields and dispersive errors. The technique is a generalization of the Dispersion-Free correction algorithm; the dilutions are corrected locally by varying the beam trajectory. This technique complements BNS damping which primarily corrects the dilutions resulting from coherent betatron oscillations. Finally, the results of simulations are presented demonstrating the viability of the technique. 6 refs., 1 fig., 1 tab.
Date: May 1, 1991
Creator: Raubenheimer, T.O & Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Betatron phase advance measurement at SPEAR

Description: There are many reasons to determine the betatron phase advance between two azimuthal positions in a circular accelerator or storage ring. We have measured the betatron phase advance between various pairs of azimuthal points in the SPEAR Storage Ring by two different methods. The first method is to excite a steady state coherent betatron oscillation with a network analyzer. The second method is to excite a free coherent betatron oscillation with an impulse kick, and to digitally sample the transverse position of the beam at the pickup stations. The results of these digital samples are Fourier analyzed with a computer to obtain the phase advance. The second method is discussed, and the experimental results compared to theory.
Date: February 1, 1987
Creator: Morton, P.L.; Pellegrin, J.L.; Raubenheimer, T. & Ross, M.
Partner: UNT Libraries Government Documents Department

Damping ring designs for a TeV Linear Collider

Description: In this paper we present a damping ring design for the TLC (TeV Linear Collider). The ring operates at 1.8 GeV. It has normalized emittances of elepsilon/sub x/ = 2.8 mrad and elepsilon/sub y/ = 25.4 nmrad. The damping times are /tau//sub x/ = 2.5 ms and /tau//sub y/ = 4.0 ms. To achieve these extremely low emittances and fast damping times, the ring contains 22 m of wigglers. 30 refs., 7 figs., 7 tabs.
Date: December 1, 1988
Creator: Raubenheimer, T.O.; Rivkin, L.Z. & Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Ions in the linacs of future linear colliders

Description: Ions have been identified as a potential limitation in high current storage rings, but they are not usually thought to be a problem in electron linear accelerators. In this paper, we consider the effects of ions in the linacs of future linear colliders. Future linear collider designs call for long trains of closely spaced bunches and/or very dense bunches. Thus, significant ion densities can be generated through the collisional ionization process and ``trapping`` in a long train of bunches or through the tunneling ionization with very dense bunches. We consider two principal effects of these ions: first, they provide skew fields which cause transverse betatron coupling and increase the vertical emittance of the flat beams, and, second, the ion fields increase the rate of filamentation, making correction of the emittance dilutions more difficult; this could lead to tighter alignment tolerances. Both of these effects are verified with simulations. We will not consider other potential limitations that the ions impose. We will consider these effects in four illustrative linear collider designs: the NLC, the old NLC design, the DESY S-band design, and the Russian design, VLEPP.
Date: July 1, 1992
Creator: Raubenheimer, T. O. & Chen, P.
Partner: UNT Libraries Government Documents Department

Centrifugal space-charge force for bunched beams

Description: In 1990, E. Lee showed for a DC beam that the effect of the centrifugal space-charge force (CSCF) on an electron`s transverse motion in a end is cancelled to lowest order by the effect of the potential depression of the beam. However, this cancellation does not in general occur when the beam is bunched. We solve for the harmonic scalar and vector potentials and explicitly find the energy-independent transverse and longitudinal space-charge forces. We make estimates of the emittance growth as a function of bend angle and path length resulting from these forces.
Date: August 1, 1994
Creator: Carlsten, B. E. & Raubenheimer, T. O.
Partner: UNT Libraries Government Documents Department

Method to evaluate steering and alignment algorithms for controlling emittance growth

Description: Future linear colliders will likely use sophisticated beam-based alignment and/or steering algorithms to control the growth of the beam emittance in the linac. In this paper, a mathematical framework is presented which simplifies the evaluation of the effectiveness of these algorithms. As an application, a quad alignment that uses beam data taken with the nominal linac optics, and with a scaled optics, is evaluated in terms of the dispersive emittance growth remaining after alignment.
Date: April 1, 1993
Creator: Adolphsen, C. & Raubenheimer, T.
Partner: UNT Libraries Government Documents Department

The preservation of low emittance flat beams

Description: Many future linear collider designs require beams with very small transverse emittances and large emittance ratios {epsilon}{sub x} {much_gt} {epsilon}{sub y}. In this paper, we will discuss issues associated with the preservation of these small emittances during the acceleration of the beams. The primary sources of transverse emittance dilution in a high energy linear accelerator are the transverse wakefields, the dispersive errors, RF deflections, and betatron coupling. We will discuss the estimation of these effects and the calculation of tolerances that will limit the emittance dilution with a high degree of confidence. Since the six-dimensional emittance is conserved and only the projected emittances are increased, these dilutions can be corrected if the beam has not filamented (phase mixed). We discuss methods of correcting the dilutions and easing the tolerances with beam-based alignment and steering techniques, and non-local trajectory bumps. Finally, we discuss another important source of luminosity degradation, namely, pulse-to-pulse jitter.
Date: April 1, 1993
Creator: Raubenheimer, T. O.
Partner: UNT Libraries Government Documents Department

A beam-based alignment technique for correction of accelerator structure misalignments

Description: This paper describes a method of reducing the transverse emittance dilution in linear colliders due to transverse wakefields arising-from misaligned accelerator structures. The technique is a generalization of the Wake-Free correction algorithm. The structure alignment errors are measured locally by varying the bunch charge and/or bunch length and measuring the change in the beam trajectory. The misalignments can then be corrected by varying the beam trajectory or moving structures. The results of simulations are presented demonstrating the viability of the technique.
Date: August 1, 1994
Creator: Kubo, K. & Raubenheimer, T. O.
Partner: UNT Libraries Government Documents Department