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Effects of damping wigglers on beam dynamics in the NLC damping rings

Description: To achieve the required damping time in the main damping rings for the Next Linear Collider (NLC), a wiggler will be required in each ring with integrated squared field strength up to 110 T{sup 2}m. There are concerns that nonlinear components of the wiggler field will damage the dynamic aperture of the ring, leading to poor injection efficiency. Severe effects from an insertion device have been observed and corrected in SPEAR 2. In this paper, we describe a model that we have developed to study the effects of the damping wiggler, compare the predictions of the model with actual experience in the case of the SPEAR 2 wiggler, and consider the predicted effects of current damping wiggler design on the NLC main damping rings.
Date: June 16, 2001
Creator: Wolski, Andrzej & Wu, Ying
Partner: UNT Libraries Government Documents Department

Lattice design for an ILC damping ring with 3 km circumference

Description: We describe a simple lattice that meets the specifications for the damping times and horizontal and longitudinal emittances for the International Linear Collider (ILC) damping rings. The circumference of a little over 3 km leads to a bunch spacing of around 3 ns, which will require advances in kicker technology for injection and extraction. We present the lattice design, and initial results of studies of the acceptance and collective effects. With the high bunch charge and close spacing, the ion and electron cloud effects are expected to be severe; however, the simple structure of the lattice allows for easy variation of the circumference and bunch spacing, which may make it useful for future investigations.
Date: October 11, 2004
Creator: Wolski, Andrzej
Partner: UNT Libraries Government Documents Department

Alternative approach to general coupled linear optics

Description: The Twiss parameters provide a convenient description of beam optics in uncoupled linear beamlines. For coupled beamlines, a variety of approaches are possible for describing the linear optics; here, we propose an approach and notation that naturally generalizes the familiar Twiss parameters to the coupled case in three degrees of freedom. Our approach is based on an eigensystem analysis of the matrix of second-order beam moments, or alternatively (in the case of a storage ring) on an eigensystem analysis of the linear single-turn map. The lattice functions that emerge from this approach have an interpretation that is conceptually very simple: in particular, the lattice functions directly relate the beam distribution in phase space to the invariant emittances. To emphasize the physical significance of the coupled lattice functions, we develop the theory from first principles, using only the assumption of linear symplectic transport. We also give some examples of the application of this approach, demonstrating its advantages of conceptual and notational simplicity.
Date: November 29, 2005
Creator: Wolski, Andrzej
Partner: UNT Libraries Government Documents Department

Intrabeam Scattering in the NLC Main Damping Rings

Description: We use Bane's approximation to the Bjorken-Mtingwa theory of intrabeam scattering to calculate the emittance growth as a function of bunch charge in the KEK ATF. We find that our results are consistent with the experimental data. We then calculate the emittance growth in the NLC Main Damping Rings using the same formulae; we allow for some uncertainty in the ATF data by using two different values for the Coulomb log factor in the formulae for the emittance growth rates. We find that despite the IBS emittance growth, it should still be possible to achieve the specified transverse and longitudinal emittances in the NLC Main Damping Rings at the specified bunch charge.
Date: June 8, 2006
Creator: Wolski, Andrzej
Partner: UNT Libraries Government Documents Department

Resistive Wall Instability in the NLC Main Damping Rings

Description: We study transverse coupled-bunch instabilities driven by the resistive-wall impedance in the NLC Main Damping Rings. We compare the growth rates of the different modes predicted by a simple theory using a simplified lattice model with the results of a detailed simulation that includes variation of the beta functions and the actual fill structure of the machine. We find that the results of the analytical calculations are in reasonable agreement with the simulations. We include a simple model of a bunch-by-bunch feedback system in the simulation to show that the instabilities can be damped by a feedback system having parameters that are realistic, and possibly conservative. The noise level on the feedback system pick-up must be low, to avoid driving random bunch-to-bunch jitter above the specified limit of 10 percent of the vertical beam size.
Date: July 1, 2004
Creator: Wolski, Andrzej
Partner: UNT Libraries Government Documents Department

Multi-Stage Bunch Compressors for the International LinearCollider

Description: We present bunch compressor designs for theInternationalLinear Collider (ILC) which achieve a reduction in RMS bunch length from6 mm to 0.3 mm via multiple stages of compression, with stages ofacceleration inserted between the stages of compression. The keyadvantage of multi-stage compression is that the maximum RMS energyspread is reduced to approximately 1 percent, compared to over 3 percentfor a single-stage design. Analytic and simulation studies of themulti-stage bunch compressors are presented, along with performancecomparisons to a single-stage system. Parameters for extending thesystems to a larger total compression factor are discussed.
Date: May 16, 2005
Creator: Tenenbaum, Peter G.; Raubenheimer, Tor O. & Wolski, Andrzej
Partner: UNT Libraries Government Documents Department

Beam Conditioning for FELs: Consequences and Methods

Description: The consequences of beam conditioning in four example cases (VISA, a Soft X-Ray FEL, LCLS and a ''Greenfield'' FEL) are examined. It is shown that in emittance limited cases, proper conditioning reduces sensitivity to the transverse emittance, and allows stronger focusing in the undulator. Simulations show higher saturation power, with gain lengths reduced up to a factor of two. The beam dynamics in a general conditioning system are studied, with ''matching conditions'' derived for achieving conditioning without growth in effective emittance. Various conditioners are considered, and expressions derived for the amount of conditioning provided in each case when the matching conditions are satisfied. We discuss the prospects for conditioners based on laser and plasma systems.
Date: October 9, 2003
Creator: Wolski, Andrzej; Penn, Gregory; Sessler, Andrew & Wurtele, Jonathan
Partner: UNT Libraries Government Documents Department

Damping ring designs and issues

Description: The luminosity performance of a future linear collider (LC) will depend critically on the performance of the damping rings. The design luminosities of the current LC proposals require rings with very short damping times, large acceptance, low equilibrium emittance and high beam intensity. We discuss the design strategies for lattices achieving the goals of dynamical stability, examine the challenges for alignment and coupling correction, and consider a variety of collective effects that threaten to limit beam quality. We put the design goals in context by referring to the experience of operating facilities, and outline the further research and development that is needed.
Date: May 12, 2003
Creator: Wolski, Andrzej & Decking, Winfried
Partner: UNT Libraries Government Documents Department

Closed orbit response to quadrupole strength variation

Description: We derive two formulae relating the variation in closed orbit in a storage ring to variations in quadrupole strength, neglecting nonlinear and dispersive effects. These formulae correct results previously reported [1,2,3]. We compare the results of the formulae applied to the ATF with simulations using MAD, and consider their application to beam-based alignment.
Date: January 20, 2004
Creator: Wolski, Andrzej & Zimmermann, Frank
Partner: UNT Libraries Government Documents Department

Summary of workshop session F on electron-cloud instabilities

Description: We summarize Session F of the ECLOUD 04 workshop. This session was dedicated to beam instabilities driven by electron cloud. Specifically, we discuss the principal observations of electron-cloud instabilities, analytical models, simulation codes and the next steps that need to be taken to arrive at a predictive theory.
Date: May 27, 2004
Creator: Zimmermann, Frank & Wolski, Andrzej
Partner: UNT Libraries Government Documents Department

A simple way to characterize linear coupling in a storage ring

Description: The techniques of normal form analysis, well known in the literature, can be used to provide a straightforward characterization of linear betatron dynamics in a coupled lattice. Here, we consider both the beam distribution and the betatron oscillations in a storage ring, assuming that the beam emittances and betatron actions respectively are provided as parameters. We find that the beta functions for uncoupled motion generalize in a simple way to the coupled case. Defined in the way that we propose, the beta functions remain well behaved (positive and finite) under all circumstances, and have essentially the same physical significance for the beam size and betatron oscillations as in the uncoupled case. We discuss a technique for making direct measurements of the ratio of the coupled lattice functions at different points in the lattice.
Date: March 24, 2004
Creator: Wolski, Andrzej
Partner: UNT Libraries Government Documents Department

Dynamic aperture study for the NLC main damping rings

Description: A sufficiently large acceptance is critical for the NLC Main Damping Rings (MDR) as the high power carried by the beams demands very high injection efficiency. Chromatic sextupoles and wiggler insertions (needed for rapid damping) are substantial sources of nonlinearities limiting the dynamic aperture. We report on the techniques we are using for analysis of single-particle beam dynamics in the presence of wiggler fields with significant nonlinear components. We demonstrate that our approach gives results in good agreement with experimental data when applied to the BL11 wiggler in SPEAR2, and discuss the present status of studies for the NLC MDR.
Date: July 5, 2004
Creator: Wolski, Andrzej; Venturini, Marco & Marks, Steve
Partner: UNT Libraries Government Documents Department

Normal form analysis of linear beam dynamics in a coupled storagering

Description: The techniques of normal form analysis, well known in the literature, can be used to provide a straightforward characterization of linear betatron dynamics in a coupled lattice. Here, we consider both the beam distribution and the betatron oscillations in a storage ring. We find that the beta functions for uncoupled motion generalize in a simple way to the coupled case. Defined in the way that we propose, the beta functions remain well behaved (positive and finite) under all circumstances, and have essentially the same physical significance for the beam size and betatron oscillation amplitude as in the uncoupled case. Application of this analysis to the online modeling of the PEP-II rings is also discussed.
Date: June 30, 2004
Creator: Wolski, Andrzej & Woodley, Mark D.
Partner: UNT Libraries Government Documents Department

The next linear collider damping ring lattices

Description: We report on the lattice design of the Next Linear Collider (NLC) damping rings. The damping rings are required to provide low emittance electron and positron bunch trains to the NLC linacs, at a rate of 120 Hz. We present an optical design, based on a theoretical minimum emittance (TME) lattice, to produce the required normalized extracted beam emittances gex = 3 mm-mrad and gey = 0.02 mm mrad. An assessment of dynamic aperture and non-linear effects is given. The positron pre-damping ring, required to reduce the emittance of the positron beam such that it may be accepted by a main damping ring, is also described.
Date: June 20, 2001
Creator: Wolski, Andrzej & Corlett, John N.
Partner: UNT Libraries Government Documents Department

A model of ATL ground motion for storage rings

Description: Low emittance electron storage rings, such as those used in third generation light sources or linear collider damping rings, rely for their performance on highly stable alignment of the lattice components. Even if all vibration and environmental noise sources could be suppressed, diffusive ground motion will lead to orbit drift and emittance growth. Understanding such motion is important for predicting the performance of a planned accelerator and designing a correction system. A description (known as the ATL model) of ground motion over relatively long time scales has been developed and has become the standard for studies of the long straight beamlines in linear colliders. Here, we show how the model may be developed to include beamlines of any geometry. We apply the model to the NLC and TESLA damping rings, to compare their relative stability under different conditions.
Date: May 12, 2003
Creator: Wolski, Andrzej & Walker, Nicholas J.
Partner: UNT Libraries Government Documents Department

Wigglers and single-particle dynamics in the NLC damping rings

Description: Wiggler insertions are expected to occupy a significant portion of the lattice of the Next Linear Collider (NLC) Main Damping Rings (MDR) and have a noticeable impact on the single-particle beam dynamics. Starting from a realistic 3D representation of the magnetic fields we calculate the transfer maps for the wigglers, accounting for linear and nonlinear effects, and we study the beam dynamics with particular attention paid to the Dynamic Aperture(DA). A DA reduction is observed but appears to remain within acceptable limits.
Date: May 6, 2003
Creator: Venturini, Marco; Wolski, Andrzej & Dragt, Alex
Partner: UNT Libraries Government Documents Department

Configuration Studies and Recommendations for the ILC DampingRings

Description: We describe the results of studies comparing differentoptions for the baseline configuration of the ILC damping rings. Theprincipal configuration decisions apply to the circumference, beamenergy, lattice type, and technology options for key components,including the injection/extraction kickers and the damping wigglers. Toarrive at our recommended configuration, we performed detailed studies ofa range of lattices representing a variety of different configurationoptions; these lattices are described in Chapter 2. The results of thevarious studies are reported in chapters covering issues of beamdynamics, technical subsystems, costs, and commissioning, reliability andupgradeability. Our detailed recommendations for the baselineconfiguration are given in Chapter 7, where we also outline furtherresearch and development that is needed before a machine using ourrecommended configuration can be built and operated successfully. In thesame chapter, we suggest possible alternatives to the baselineconfiguration.
Date: February 4, 2006
Creator: Wolski, Andrzej; Gao, Jie & Guiducci, Susanna
Partner: UNT Libraries Government Documents Department

Configuration Studies and Recommendations for the ILC DampingRings

Description: We describe the results of studies comparing different options for the baseline configuration of the ILC damping rings. The principal configuration decisions apply to the circumference, beam energy, lattice type, and technology options for key components, including the injection/extraction kickers and the damping wigglers. To arrive at our recommended configuration, we performed detailed studies of a range of lattices representing a variety of different configuration options; these lattices are described in Chapter 2. The results of the various studies are reported in chapters covering issues of beam dynamics, technical subsystems, costs, and commissioning, reliability and upgrade ability. Our detailed recommendations for the baseline configuration are given in Chapter 7, where we also outline further research and development that is needed before a machine using our recommended configuration can be built and operated successfully. In the same chapter, we suggest possible alternatives to the baseline configuration.
Date: February 4, 2006
Creator: Wolski, Andrzej; Gao, Jie & Guiducci, Susanna
Partner: UNT Libraries Government Documents Department

Configuration Studies and Recommendations for the ILC DampingRings

Description: We describe the results of studies comparing differentoptions for the baseline configuration of the ILC damping rings. Theprincipal configuration decisions apply to the circumference, beamenergy, lattice type, and technology options for key components,including the injection/extraction kickers and the damping wigglers. Toarrive at our recommended configuration, we performed detailed studies ofa range of lattices representing a variety of different configurationoptions; these lattices are described in Chapter 2. The results of thevarious studies are reported in chapters covering issues of beamdynamics, technical subsystems, costs, and commissioning, reliability andupgradeability. Our detailed recommendations for the baselineconfiguration are given in Chapter 7, where we also outline furtherresearch and development that is needed before a machine using ourrecommended configuration can be built and operated successfully. In thesame chapter, we suggest possible alternatives to the baselineconfiguration.
Date: February 4, 2006
Creator: Wolski, Andrzej; Gao, Jie & Guiducci, Susanna
Partner: UNT Libraries Government Documents Department

Spin Tracking Studies for Beam Polarization Preservation in theNLC Main Damping Rings

Description: We report results from studies of spin dynamics in the NLC Main Damping. Our studies have been based on spin tracking particles through the lattice under a range of conditions. We find that there are a number of spin resonances close to the nominal operating energy of 1.98 GeV; however, the effects of the resonances are weak, and the widths are narrow. We do not expect that any significant depolarization of the beam will occur during the store time.
Date: July 26, 2004
Creator: Wolski, Andrzej & Bates, Daniel
Partner: UNT Libraries Government Documents Department

A lattice with larger momentum compaction for the NLC main damping rings

Description: Previous lattice designs for the Next Linear Collider Main Damping Rings [1] have met the specifications for equilibrium emittance, damping rate and dynamic aperture. Concerns about the effects of the damping wiggler on the beam dynamics [2] led to the aim of reducing the total length of the wiggler to a minimum consistent with the required damping rate, so high-field dipoles were used to provide a significant energy loss in the arcs. However, recent work has shown that the wiggler effects may not be as bad as previously feared. Furthermore, other studies have suggested the need for an increased momentum compaction (by roughly a factor of four) to raise the thresholds of various collective effects. We have therefore developed a new lattice design in which we increase the momentum compaction by reducing the field strength in the arc dipoles, compensating the loss in damping rate by increasing the length of the wiggler. The new lattice again meets the specifications for emittance, damping rate and dynamic aperture, while having the benefit of significantly higher thresholds for a number of instabilities.
Date: May 12, 2004
Creator: Wolski, Andrzej; Raubenheimer, Tor O.; Woodley, Mark & Wu, Juhao
Partner: UNT Libraries Government Documents Department

Analysis of KEK-ATF Optics and Coupling Using LOCO

Description: LOCO is a code for analysis of the linear optics in astorage ring based on the closed orbit response to steering magnets. Theanalysis provides information on focusing errors, BPM gain and rotationerrors,and local coupling. Here, we report the results of an applicationof LOCO to the KEK-ATF. Although the analysis appears to have provideduseful information on the optics of the machine, it appears that one ofthe main aims of the study to reduce the vertical emittance by correctingthe local coupling was not successful, and we discuss some possiblereasons for this.
Date: January 12, 2004
Creator: Wolski, Andrzej; Ross, Marc; Woodley, Mark; Nelson, Janice & Mishra, Shekhar
Partner: UNT Libraries Government Documents Department

Simulations of the Electron Cloud Builld Up and Instabilities for Various ILC Damping Ring Configurations

Description: In the beam pipe of the positron damping ring of the International Linear Collider (ILC), an electron cloud may be first produced by photoelectrons and ionization of residual gases and then increased by the secondary emission process. This paper reports the assessment of electron cloud effects in a number of configuration options for the ILC baseline configuration. Careful estimates were made of the secondary electron yield (sometimes in the literature also referred as secondary emission yield SEY or {delta}, with a peak value {delta}{sub max}) threshold for electron cloud build-up, and the related single- and coupled-bunch instabilities, as a function of beam current and surface properties for a variety of optics designs. When the configuration for the ILC damping rings was chosen at the end of 2005, the results from these studies were important considerations. On the basis of the joint theoretical and experimental work, the baseline configuration currently specifies a pair of 6 km damping rings for the positron beam, to mitigate the effects of the electron cloud that could present difficulties in a single 6 km ring. However, since mitigation techniques are now estimated to be sufficiently mature, a reduced single 6-km circumference is presently under consideration so as to reduce costs.
Date: March 12, 2007
Creator: Pivi, Mauro; Raubenheimer, Tor O.; Wang, Lanfa; /SLAC; Ohmi, Kazuhito; /KEK, Tsukuba et al.
Partner: UNT Libraries Government Documents Department