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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

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

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 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

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

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

Distortion of Crabbed Bunch Due to Electron Cloud and Global Crabbing

Description: Crab cavities may be used improve the luminosity in colliding beam colliders with crab crossing. In a global crab crossing correction, only one crab cavity is installed in each ring and the crab cavities generate a horizontally titled bunch oscillating around the ring. The electron cloud in positively charged rings may distort the crabbed bunch and cause the luminosity drop. This paper briefly estimates the distortion of positron bunch due to the electron cloud with global crab and estimates the effect in the KEKB and possible LHC upgrades.
Date: August 1, 2008
Creator: Wang, L.; Raubenheimer, T.O.; Cai, Y. & /SLAC
Partner: UNT Libraries Government Documents Department

Suppression of Beam-Ion Instability in Electron Rings with Multi-Bunch Train Beam Fillings

Description: The ion-caused beam instability in the future light sources and electron damping rings can be serious due to the high beam current and ultra-small emittance of picometer level. One simple and effective mitigation of the instability is a multi-bunch train beam filling pattern which can significantly reduce the ion density near the beam, and therefore reduce the instability growth rate up to two orders of magnitude. The suppression is more effective for high intensity beams with low emittance. The distribution and the field of trapped ions are benchmarked to validate the model used in the paper. The wake field of ion-cloud and the beam-ion instability is investigated both analytically and numerically. We derived a simple formula for the build-up of ion-cloud and instability growth rate with the multi-bunch-train filling pattern. The ion instabilities in ILC damping ring, SuperKEKB and SPEAR3 are used to compare with our analyses. The analyses in this paper agree well with simulations.
Date: August 18, 2011
Creator: Wang, L.; Cai, Y.; Raubenheimer, T.O.; /SLAC; Fukuma, H. & /KEK, Tsukuba
Partner: UNT Libraries Government Documents Department

Suppression of Secondary Emission in a Magnetic Field Using a Sawtooth and Isosceles Triangle Surface

Description: The effect of surface roughness on the secondary electron emission from a sawtooth and isosceles triangle surface in a magnetic field under electron bombardment is investigated using a Monte-Carlo method. Some of the secondary electrons emitted from the surface return to the surface within their first few gyrations, resulting in a low effective secondary electron yield. Both sawtooth and isosceles triangle surface in magnetic field can significantly reduce the secondary emission yield below the multipacting threshold with weak dependence on the size of surface and magnetic field.
Date: September 26, 2006
Creator: Wang, L.; Raubenheimer, T.O.; Stupakov, G. & /SLAC
Partner: UNT Libraries Government Documents Department

Simulation of Wakefield Effect in ILC IR Chamber

Description: To achieve super high luminosity, high current beams with very short bunch length are needed, which carry high intensity EM fields. For ILC, two bunch trains with bunch length of 300 {micro}m and bunch charge of 3.2nC are needed to collide at the IR to achieve the ILC luminosity goals. When the 300 {micro}m bunches pass through the IR chamber, wakefields will be excited, which will cause HOM power flowing through the IR chamber beam pipe to the final doublets due to the high frequency characteristic of the induced wakefields. Since superconducting technology is adopted for the final doublets of ILC BDS, whose operation stability might be affected by the HOM power produced at the IR chamber, quench might happen. In this paper, we did some analytical estimation and numerical simulation on the wakefield effects in ILC IR chamber.
Date: June 26, 2008
Creator: Pei, S; Seryi, A.; Raubenheimer, T.O. & /SLAC
Partner: UNT Libraries Government Documents Department

Electron-Cloud Effects in Transport Lines of a Normal Conducting Linear Collider

Description: In the transport lines of a normal conducting linear collider, the long positron bunch train can generate an electron cloud which can then amplify intra-train offsets. This is a transient effect which is similar to the electron-cloud driven coupled bunch instabilities in a positron storage ring. In this paper, we study this phenomenon analytically. Some criteria on the critical cloud density with respect to given collider parameters are discussed.
Date: June 15, 2005
Creator: Wu, Juhao; Raubenheimer, T.O.; Pivi, M.T.F.; Seryi, A. & /SLAC
Partner: UNT Libraries Government Documents Department

Multi-Stage Bunch Compressors for the International Linear Collider

Description: We present bunch compressor designs for the International Linear Collider (ILC) which achieve a reduction in RMS bunch length from 6 mm to 0.3 mm via multiple stages of compression, with stages of acceleration inserted between the stages of compression. The key advantage of multi-stage compression is that the maximum RMS energy spread is reduced to approximately 1%, compared to over 3% for a single-stage design. Analytic and simulation studies of the multi-stage bunch compressors are presented, along with performance comparisons to a single-stage system. Parameters for extending the systems to a larger total compression factor are discussed.
Date: May 27, 2005
Creator: Tenenbaum, P.; Raubenheimer, T.O.; /SLAC; Wolski, A. & /LBL, Berkeley
Partner: UNT Libraries Government Documents Department

Resistive-wall Wake Effect in the Beam Delivery System

Description: General formulae for resistive-wall induced beam dilution are presented and then applied to the final beam delivery system of linear colliders. Criteria for the design of final beam delivery systems are discussed.
Date: June 2, 2005
Creator: Delayen, J. R.; Wu, Juhao; Raubenheimer, T. O. & Wang, Jiunn-Ming
Partner: UNT Libraries Government Documents Department