We describe commonly used strategies for the control of charged particle beams and the manipulation of their properties. Emphasis is placed on relativistic beams in linear accelerators and storage rings. After a brief review of linear optics, we discuss basic and advanced beam control techniques, such as transverse and longitudinal lattice diagnostics, matching, orbit correction and steering, beam-based alignment, and linac emittance preservation. A variety of methods for the manipulation of particle beam properties are also presented, for instance, bunch length and energy compression, bunch rotation, changes to the damping partition number, and beam collimation. The dierent procedures are illustrated by examples from various accelerators. Special topics include injection and extraction methods, beam cooling, spin transport and polarization.

/pdf/beam-techniques-beam-control-and-manipulation-5ga5j9mrx0.pdf

Beam Techniques - Beam Control and Manipulation

The Stanford Linear Collider (SLC) is the first and only high-energy e/sup +/e/sup -/ linear collider in the world. Its most remarkable features are high intensity, submicron sized, polarized (e/sup -/) beams at a single interaction point. The main challenges posed by these unique characteristics include machine-wide emittance preservation, consistent high intensity operation, polarized electron production and transport, and the achievement of a high degree of beam stability on all time scales. In addition to serving as an important machine for the study of Z/sup 0/ boson production and decay using polarized beams, the SLC is also an indispensable source of hands-on experience for future linear colliders. Each new year of operation has been highlighted with a marked improvement in performance. The most significant improvements for the 1994-95 run include new low impedance vacuum chambers for the damping rings, an upgrade to the optics and diagnostics of the final focus systems, and a higher degree of polarization from the electron source. As a result, the average luminosity has nearly doubled over the previous year with peaks approaching 10/sup 30/ cm/sup -2/ s/sup -1/ and an 80% electron polarization at the interaction point. These developments as well as the remaining identifiable performance limitations will be discussed.

/pdf/the-stanford-linear-collider-equvnbqxsi.pdf

The Stanford Linear Collider

The Stanford Linear Collider (SLC) was the first prototype of a new type of accelerator, the electron-positron linear collider. Many years of dedicated effort were required to understand the physics of this new technology and to develop the techniques for maximizing performance. Key issues were emittance dilution, stability, final beam optimization and background control. Precision, non-invasive diagnostics were required to measure and monitor the beams throughout the machine. Beam-based feedback systems were needed to stabilize energy, trajectory, intensity and the final beam size at the interaction point. A variety of new tuning techniques were developed to correct for residual optical or alignment errors. The final focus system underwent a series of refinements in order to deliver sub-micron size beams. It also took many iterations to understand the sources of backgrounds and develop the methods to control them. The benefit from this accumulated experience was seen in the performance of the SLC during its final run in 1997-98. The luminosity increased by a factor of three to 3*10**30 and the 350,000 Z data sample delivered was nearly double that from all previous runs combined.

SLC Final Performance and Lessons

The Next Linear Collider (NLC) uses a damping ring for the electron beam, a pre-damping ring and a main damping ring for the positron beam to reduce the beam emittances. The requirements of the main damping ring kickers are to bend a 2 GeV beam by an angle of 2 mrad over a length of 1.2 m. This results in a required field of 139 G. The magnet aperture is 30/spl times/30 mm. The pre-damping ring kicker requirements are based on a 2 GeV beam with a bend angle of 8 mrad in 1.2 m, or a field of 308 G. The magnet aperture is 62/spl times/45 mm (H/spl times/V). A pulse width is 130 ns with rise and fall times of less than 60 ns is the same for both the pre-damping ring and main damping ring kickers. The three rings operate at a 180 Hz repetition rate. The kicker magnets being developed to meet these requirements consist of two strip line conductors in the vacuum chamber, for the pre-damping ring kickers they may be loaded with ferrite, to give a matching impedance of 25 /spl Omega/. The buses are separated from magnetic flux linkage by a grounded flux excluder, which also serves as a low impedance return for the beam current. Both busses of the magnet are driven in parallel from the same modulator and are grounded at the end opposite the feed. The modulator uses two IGBT stacks which both act as opening switches in order to meet the rise time requirements.

/pdf/damping-ring-kickers-for-the-next-linear-collider-2a7e0jjcm6.pdf

Damping ring kickers for the Next Linear Collider

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 /spl gamma//spl epsi//sub x/=3 mm-mrad and /spl gamma//spl epsi//sub y/=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.

/pdf/the-next-linear-collider-damping-ring-lattices-47sy68z96p.pdf

The Next Linear Collider damping ring lattices

New low-impedance vacuum chambers were installed in the SLC damping rings for the 1994 run after finding a single bunch instability with the old chamber. Although the threshold is lower with the new vacuum chamber, the instability is less severe, and we are now routinely operating at intensities of 4.5/spl times/10/sup 10/ particles per bunch (ppb) compared to 3/spl times/10/sup 10/ ppb in 1993. The vacuum chamber upgrade is described, and measurements of the bunch length, energy spread, and frequency and time domain signatures of the instability are presented.

/pdf/high-intensity-single-bunch-instability-behavior-in-the-new-2ki9nj0w2p.pdf

High-intensity single bunch instability behavior in the new SLC damping ring vacuum chamber

We report progress on the design of the Next Linear Collider (NLC) damping rings complex (DRC). The purpose of the DRC is to provide 120 Hz, low emittance electron and positron bunch trains to the NLC linacs. It consists of two 1.98 GeV main damping rings, one positron pre-damping ring, two pairs of bunch length and energy compressor systems and interconnecting transport lines. The 2 main damping rings store up to 0.8 amp in 3 trains of 95 bunches each and have normalized extracted beam emittances /spl gamma//spl isin//sub x/=3 /spl mu/m-rad and /spl gamma//spl isin//sub y/=0.03 /spl mu/m-rad. The preliminary optical design, performance specifications and tolerances are given. Key subsystems include: 1) the 714 MHz RF system, 2) the 60 ns risetime injection/extraction pulsed kicker magnets, 3) the 44 m wiggler magnet system, 4) the arc and wiggler vacuum system, 5) the radiation management system, 6) the beam diagnostic instrumentation, 7) special systems used for downstream machine protection and 8) feedback-based stabilization systems.

/pdf/the-next-linear-collider-damping-ring-complex-2dtrrw63o0.pdf

The Next Linear Collider damping ring complex

The Next Linear Collider (NLC) injector system is designed to produce low emittance, 10 GeV electron and positron beams at 120 hertz for injection into the NLC main linacs. Each beam consists of a train of 95 bunches spaced by 2.8 ns; each bunch has a population of 1.15/spl times/10/sup 10/ particles. At injection into the main linacs, the horizontal and vertical emittances are specified to be /spl gamma//spl isin//sub x/=3/spl times/10/sup 16/ m-rad and /spl gamma//spl isin//sub y/=3/spl times/10/sup -8/ m-rad and the bunch length is 100 /spl mu/m. Electron polarization of greater than 80% is required. Electron and positron beams are generated in separate accelerator complexes each of which contain the source, damping ring systems, L-band, S-band, and X-band linacs, bunch length compressors, and collimation regions. The need for low technical risk, reliable injector subsystems is a major consideration in the design effort. This paper presents an overview of the NLC injector systems.

/pdf/the-nlc-injector-system-18my0cfyn2.pdf

The NLC injector system

THE NEXT LINEAR COLLIDER DAMPING RING COMPLEX * J. Corlett † , D. Atkinson, S. De Santis, N. Hartman, K. Kennedy, D. Li, S. Marks, Y. Minamihara, H. Nishimura, M. Pivi, D. Reavill, R. Rimmer, R. Schlueter, A. Wolski, LBNL, Berkeley, CA, USA S. Anderson, B. McKee, T. Raubenheimer, M. Ross, J. C. Sheppard, SLAC, Stanford, CA, USA Abstract We report progress on the design of the Next Linear Collider (NLC) Damping Rings complexes. The purpose of the damping rings is to provide low emittance electron and positron bunch trains to the NLC linacs, at a rate of 120 Hz. As an option to operate at the higher rate of 180 Hz, two 1.98 GeV main damping rings per beam are proposed, and one positron pre-damping ring. The main damping rings store up to 0.8 amp in 3 trains of 190 bunches each and have normalized extracted beam emittances γe x = 3 mm-mrad and γe y = 0.02 mm-mrad. The optical designs, based on a theoretical minimum emittance lattice (TME), are described, with an analysis of dynamic aperture and non-linear effects. Key subsystems and components are described, including the wiggler, the vacuum systems and photon stop design, and the higher- order-mode damped RF cavities. Impedance and instabilities are discussed. Table 1: Parameters for the Main Damping Ring and Positron Pre-Damping Ring. Circumference (m) Max. Current (A) Bunch trains x Bunches per train x Bunch separation (ns) ν x , ν y , ν s γe x equilib. (mm-mrad) γe x extract. , γe y extract. (mm-mrad) σ e (%), σ z (mm) ξ x uncorr. , ξ y uncorr τ x , τ y , τ e (ms) MDR 3 x 190 x 1.4 PPDR 2 x 190 x 1.4 2.95 x 10 -4 7.05 x 10 -3 INTRODUCTION The NLC damping ring complexes provide damping of the e + /e - beams from the sources, producing stable, low- emittance beams which pass on to bunch length compressors and pre-acceleration before entering the main linacs [1]. The main damping rings of both e + /e - systems are identical. Due to the large emittance of positrons produced from the target, a pre-damping ring is required to reduce the e + beam emittance to be accommodated by the main damping ring acceptance. Each ring will store multiple trains of bunches at once, and a single fully damped bunch train is extracted while a new train from the source is injected. The repetition rate is 120 Hz, although options to operate at 180 Hz have been explored. U sr (kV/turn) α p V RF (MV), Frequency (MHz) Lattice 36 TME cells 16 TME cells sources and the B-Factories in that they must store high current beams (~ 1A) while attaining small emittances, low vacuum pressure, and large synchrotron radiation power loading. Many design and technology issues for Electron complex DESIGN The damping ring designs use Theoretical Minimum Emittance (TME) arc cells, with a racetrack layout in which damping wigglers, RF systems, feedback systems, a circumference adjustment chicane, and injection/ extraction hardware are located in the long straights. Damping wigglers are required to provide the necessary damping at 1.98 GeV, given a 120 Hz injection/extraction rate and the extracted beam emittance requirement. General discussion of design criteria are given in [2], and details of the current lattice designs in [3]. Principal parameters of the rings are listed in Table 1. The rings resemble third-generation synchrotron light Positron complex Figure 1. Damping rings layouts, showing e + and e - complexes at the ends of the main linacs. Work supported by the US DOE under contract DE-AC03- 76SF00098 (LBNL), and DE-AC0376SF00098 (SLAC) jncorlett@lbl.gov

The next linear collider damping ring complex

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High-intensity single bunch instability behavior in the new SLC damping ring vacuum chamber

The Next Linear Collider damping ring complex

The NLC injector system

The next linear collider damping ring complex