K.A. Thompson

Parameters of the SLAC Next Linear Collider

In this paper, we 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/spl times/10/sup 33/ cm/sup -2/ sec/sup -1/ at 0.5 TeV and >10/sup 34/ cm/sup -2/ sec/sup -1/ at 1.0 and 1.5 TeV. We will briefly describe the components of the collider and the proposed energy upgrade scenario.

Simulation and compensation of multibunch energy variation in NLC

The SLAC NLC design for a next-generation linear collider utilizes multibunching (acceleration of a train of bunches on each RF fill) to increase the luminosity and energy efficiency. It is necessary to control the energy spread of the beam, in order to minimize chromatic emittance dilution and be within the energy acceptance of the final focus. It is anticipated that the NLC may run with bunch trains having length equal to a substantial fraction of the filling time. Multibunch energy simulation methods and compensation schemes appropriate to this regime are presented.<<ETX>>

Prompt bunch by bunch synchrotron oscillation detection via a fast phase measurement

An electronic system which detects synchrotron oscillations of individual bunches with 4-ns separation is presented. The system design and performance are motivated by the requirements of the proposed B factory facility at SLAC (Stanford Linear Accelerator Center). Laboratory results show that the prototype is capable of measuring individual bunch phases with better than 0.5 degree resolution at the 476-MHz RF frequency.<<ETX>>

Computer modelling of bunch-by-bunch feedback for the SLAC B-factory design

A computer model of the storage ring, including the RF system, wake fields, synchrotron radiation loss, and the bunch-by-bunch feedback system, is presented. The feedback system model represents the performance of a fast phase detector front end (including system noise and imperfections), a digital filter used to generate a correction voltage, and a power amplifier and beam kicker system. The combined ring-feedback system model is used to study the feedback system performance required to suppress instabilities and to quantify the dynamics of the system. Results which show the time development of coupled bunch instabilities and the damping action of the feedback system are presented.<<ETX>>

Manifold damping of the NLC detuned accelerating structure

In order to mitigate the reappearance of the HOM wakefield of a detuned accelerator structure and relax tolerance requirements, we propose to provide low level damping by coupling all cavities to several identical and symmetrically located waveguides (manifolds) which run parallel to each accelerator structure and are terminated at each end by matched loads. The waveguides are designed such that all modes which couple to the acceleration mode are non‐propagating at the acceleration mode frequency. Hence the coupling irises can be designed to provide large coupling to higher frequency modes without damping the acceleration mode. Because the higher order modes are detuned, they are localized and have a broad spectrum of phase velocities of both signs. They are therefore capable of coupling effectively to all propagating modes in the waveguides. Methods of analyzing and results obtained for the very complex system of modes in the accelerating structure and manifolds are presented.

Design parameters for the damped detuned accelerating structure

The advanced accelerating cavities for the NLCTA (and anticipated for NLC) will incorporate damping as well as detuning. The damping is provided by a set of four waveguides (which also serve as pumping manifolds) that run parallel to the structure, with strong iris coupling to each cavity cell and terminated at each end by absorbers. The previously reported equivalent circuit analysis has been refined and the dependence upon design parameters explored. We find that adequate damping can be provided by a single waveguide mode, leading to designs which are more compact than those initially considered. The design parameters and their rationale will be presented.

Energy measurements from betatron oscillations

In the Stanford Linear Collider the electron beam is accelerated from 1 to 50 GeV in a distance of 3 km. The energy is measured and corrected at the end with an energy feedback loop. There are no bends within the linear accelerator, so no intermediate energy measurements are made. Errors in the energy profile due to misphasing of the RF, or to calibration errors in the klystrons RF outputs are difficult to detect. Since the total betatron phase advance down the accelerator is about 30 X 2 pi , an energy error of a few percent can cause a large error in the total phase advance. This will degrade the performance of autosteering programs. A diagnostic program which generates and measures several betatron oscillations in the accelerator has been developed.<<ETX>>

Emittance and trajectory control in the main linacs of the NLC

The main linacs of the next generation of linear colliders need to accelerate the particle beams to energies of up to 750 GeV while maintaining very small emittances. This paper describes the main mechanisms of static emittance growth in the main linacs of the Next Linear Collider (NLC). The authors present detailed simulations of the trajectory and emittance control algorithms that are foreseen for the NLC. They show that the emittance growth in the main linacs can be corrected down to about 110%. That number is significantly better than required for the NLC design luminosity.

Emittance and energy control in the NLC main linacs

We discuss tolerances and correction schemes needed to control single- and multi-bunch emittance in the NLC main linacs. Specifications and design of emittance diagnostic stations will be presented. Trajectory correction schemes appropriate to simultaneously controlling the emittance of a multibunch train and the emittance of individual bunches within the train will be discussed. We discuss control of bunch-to-bunch energy spread using a ramped RF pulse generated by phase-modulating the SLED-II input. Tolerances on ions, wake fields, quadrupole alignment, and accelerating structure alignment will be given.

A damping ring design for the SLAC next linear collider

In this paper, we describe the design of the main damping rings and the positron pre-damping ring for the SLAC Next Linear Collider, a future linear collider with a center-of-mass energy of 0.5 to 1.5 TeV. The rings will operate at an energy of 2 GeV with a maximum repetition rate of 180 Hz. The normalized extracted beam emittances are /spl gamma//spl epsiv//sub x/=3 mm-mrad and /spl gamma//spl epsiv//sub y/=0.03 mm-mrad. To provide the necessary damping, the rings must damp multiple trains of bunches. Thus, the beam current is large, roughly 1 A. We will present the optical layout, magnet designs, and RF systems, along with the dynamic aperture and required alignment tolerances; collective effects will be discussed in another paper.