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Report of the working group for polarization in the SSC main ring

Description: The task of the main ring working group was to study polarized beams in the SSC main ring. Many problems were studied; however, the primary emphasis was in the determination of the acceptable resonance strengths and the number of Siberian Snakes which would be necessary given those resonance strengths. During the workshop all of the members of the working group realized that there was much more work to be done, and consequently there have been some changes in the general conclusions during the following months. The present conclusion really reflects a balance between pessimism and optimism. At present we feel that if the resonance strengths in the SSC main ring are kept below about 5, then about 78 Siberian Snakes would be sufficient to maintain polarization. However, since the calculations here indicate a quadratic dependence on the resonance strength, if resonance strengths could be kept below 3, then only about 26 snakes would be needed. These numbers are estimates, and with further calculation we may find a solution which lowers the number of Siberian Snakes. This paper should be viewed as a brief introduction to the problem and as a 'road map' to the many excellent contributions to these proceedings by the members of the working group.
Date: January 1, 1986
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Report on the international workshop on next generation linear colliders

Description: Many laboratories around the world have begun vigorous research programs on a next generation linear collider (NLC). However, it has been recognized that the research towards NLC is beyond the capabilities of any one laboratory presently. This workshop was organized to begin a series of workshops that address this problem. Specifically, the main goals of the workshop were to discuss research programs of the various laboratories around the world, to identify common areas of interest in the various NLC designs, and finally to advance these programs by collaboration. The particular topics discussed briefly in this paper are: parameters, rf power, structures, final focus, beam dynamics, damping rings, and instrumentation. 2 refs., 3 figs., 6 tabs.
Date: May 1, 1989
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

The status of the SLC

Description: On October 10,1987, the SLC ceased commissioning activities to move the Mark II detector into the beam line for the spring physics run. The planned shutdown is for a period of 13 weeks. In this paper, the various subsystems and their status as of October 10, 1987 are briefly discussed. 3 refs., 4 figs., 1 tab.
Date: November 1, 1987
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Single bunch instabilities in an SSC

Description: In this note coherent instability thresholds are estimated for the SSC and discuss some of the subsequent design restrictions. The various instabilities are set out in a block diagram with the essential features of each. The assumption is made that long wavelength coupled bunch effects can be cured effectively by a feedback system (both longitudinal and transverse) and that the impedance of the feedback system is such as to cancel that of the environment (at low frequency). Alternatively, the long wake field is assumed to be exactly canceled, on the average, by a feedback wake field. This leaves only single bunch effects. Thresholds for fast-blowup are discussed both in the longitudinal and transverse and the transverse mode coupling instability more familiar in electron/positron storage rings is covered. The impedances considered are a broadband impedance and the resistive wall impedance.
Date: January 1, 1984
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Vertical coherent instabilities in bunched particle-beams

Description: The purpose of this paper is to study the vertical coherent instabilities which occur in bunched particle beams. The problem is complicated by the fact that the velocity of a single particle in a bunch is not constant, but rather consists of an equilibrium velocity and an oscillation about that. This synchrotron oscillation occurs at a frequency which is in general much less than the other characteristic frequencies of the system: the revolution frequency and the transverse betatron frequencies. The approach used here to study coherent instabilities illuminates the effect of the synchrotron frequency in setting the time scale for an instability, without making restrictive assumptions on the relative size of the synchrotron frequency and the coherent frequency shift (or growth rate).
Date: July 1, 1981
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Summary of the Linear Collider Working Group

Description: The focus of the Linear Collider Working Group was on a next generation linear collider. Topics discussed are: parameters; damping rings; bunch compression and pre-acceleration; linac; final focus; and multibunch effects. 8 refs., 3 figs., 7 tabs.
Date: January 1, 1989
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Beam dynamics issues for linear colliders

Description: In this paper we discuss various beam dynamics issues for linear colliders. The emphasis is to explore beam dynamics effects which lead to an effective dilution of the emittance of the beam and thus to a loss of luminosity. These considerations lead to various tolerances which are evaluated for a particular parameter set.
Date: September 1, 1987
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Multi-bunch energy compensation

Description: To obtain a luminosity of 10{sup 34} cm{sup {minus}2} sec{sup {minus}1} in a TeV Linear Collider (TLC), it will probably be necessary to accelerate many bunches in one filling of the rf structure. This has the effect of extracting more energy from the structure and thus enhances the overall efficiency of the accelerator. However, this leads to many problems. First, the train bunches is subject to cummulative beam breakup transversely. This can be controlled by damping the transverse modes with slots in the irises coupled to waveguides. In addition, the energy of the bunches must be kept the same to high precision. For the fundamental mode, this entails adjusting the timing of the rf fill and also the bunch spacing. The higher longitudinal modes, although they do not induce instability, also may lead to bunch-to-bunch variations in energy. However, it also seems possible to damp these modes to cure this problem. Of course, there are also problems associated with damping a train of bunches in a damping ring. In this paper we discuss some of the issues of multi-bunch energy compensation. In the first two sections, we review some basics about energy extraction by a single bunch, and then, multi-bunch energy compensation is treated. We discuss various tolerance issues associated with deviations of amplitude and phase of the rf away from the ideal.
Date: February 1, 1988
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Single Particle Dynamics in Circular Accelerators

Description: The purpose of this paper is to introduce the reader to the theory associated with the transverse dynamics of single particle, in circular accelerators. The discussion begins with a review of Hamiltonian dynamics and canonical transformations. The case of a single particle in a circular accelerator is considered with a discussion of non-linear terms and chromaticity. The canonical perturbation theory is presented and nonlinear resonances are considered. Finally, the concept of renormalization and residue criterion are examined. (FI)
Date: October 1986
Creator: Ruth, R. D.
Partner: UNT Libraries Government Documents Department

Single particle dynamics and nonlinear resonances in circular accelerators

Description: The purpose of this paper is to introduce the reader to single particle dynamics in circular accelerators with an emphasis on nonlinear resonances. We begin with the Hamiltonian and the equations of motion in the neighborhood of the design orbit. In the linear theory this yields linear betatron oscillations about a closed orbit. It is useful then to introduce the action-angle variables of the linear problem. Next we discuss the nonlinear terms which are present in an actual accelerator, and in particular, we motivate the inclusion of sextupoles to cure chromatic effects. To study the effects of the nonlinear terms, we next discuss canonical perturbation theory which leads us to nonlinear resonances. After showing a few examples of perturbation theory, we abandon it when very close to a resonance. This leads to the study of an isolated resonance in one degree of freedom with a 'time'-dependent Hamiltonian. We see the familiar resonance structure in phase space which is simply closed islands when the nonlinear amplitude dependence of the frequency or 'tune' is included. To show the limits of the validity of the isolated resonance approximation, we discuss two criteria for the onset of chaotic motion. Finally, we study an isolated coupling resonance in two degrees of freedom with a 'time'-dependent Hamiltonian and calculate the two invariants in this case. This leads to a surface of section which is a 2-torus in 4-dimensional phase space. However, we show that it remains a 2-torus when projected into particular 3-dimensional subspaces, and thus can be viewed in perspective.
Date: November 1, 1985
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Review of polarized proton beam techniques and a report on the workshop on polarized beams

Description: This paper first introduces the basic techniques for polarized proton beams: spin flip, resonance jumps, Siberian Snakes, etc., and then concludes with a report on the Workshop on Acceleration and Storage of Polarized Protons and Electrons in Very Large Machines. 25 references, 5 figures, 2 tables.
Date: October 1, 1984
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Progress on next generation linear colliders

Description: In this paper, I focus on reviewing the issues and progress on a next generation linear collider with the general parameters of energy, luminosity, length, power, technology. The energy range is dictated by physics with a mass reach well beyond LEP, although somewhat short of SSC. The luminosity is that required to obtain 10/sup 3/ /minus/ 10/sup 4/ units of R/sub 0/ per year. The length is consistent with a site on Stanford land with collisions occurring on the SLAC site. The power was determined by economic considerations. Finally, the technology was limited by the desire to have a next generation linear collider before the next century. 25 refs., 3 figs., 6 tabs.
Date: January 1, 1989
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Beam dynamics in linear colliders

Description: In this paper, we discuss some basic beam dynamics issues related to obtaining and preserving the luminosity of a next generation linear collider. The beams are extracted from a damping ring and compressed in length by the first bunch compressor. They are then accelerated in a preaccelerator linac up to an energy appropriate for injection into a high gradient linac. In many designs this pre-acceleration is followed by another bunch compression to reach a short bunch. After acceleration in the linac, the bunches are finally focused transversely to a small spot. 27 refs., 1 fig.
Date: September 1, 1990
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Plasma accelerators

Description: In this paper we discuss plasma accelerators which might provide high gradient accelerating fields suitable for TeV linear colliders. In particular we discuss two types of plasma accelerators which have been proposed, the Plasma Beat Wave Accelerator and the Plasma Wake Field Accelerator. We show that the electric fields in the plasma for both schemes are very similar, and thus the dynamics of the driven beams are very similar. The differences appear in the parameters associated with the driving beams. In particular to obtain a given accelerating gradient, the Plasma Wake Field Accelerator has a higher efficiency and a lower total energy for the driving beam. Finally, we show for the Plasma Wake Field Accelerator that one can accelerate high quality low emittance beams and, in principle, obtain efficiencies and energy spreads comparable to those obtained with conventional techniques.
Date: March 1, 1986
Creator: Ruth, R.D. & Chen, P.
Partner: UNT Libraries Government Documents Department

Comparison of the plasma beat wave accelerator and the plasma wake field accelerator

Description: In this paper we compare the Plasma Beat Wave Accelerator and Plasma Wake Field Accelerator. We show that the electric fields in the plasma for both schemes are very similar, and thus the dynamics of the driven beams are very similar. The differences appear in the parameters associated with the driving beams. In particular to obtain a given accelerating gradient, the Plasma Wake Field Accelerator has a higher efficiency and a lower total energy for the driving beam. 7 refs., 2 tabs.
Date: March 1, 1985
Creator: Chen, P. & Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Research at SLAC towards a 0. 5 TeV linear collider

Description: The purpose of this paper is to review the ongoing research at SLAC toward a next-generation linear collider (NLC). The energy of the collider is taken to be 0.5 TeV in the CM with view towards upgrading to 1.0 TeV. The luminosity is in the range of 10{sup 33} to 10{sup 34} cm{sup {minus}2} sec {sup {minus}1}. The energy is achieved by acceleration with a gradient of about a factor of five higher than SLC, which yields a linear collider approximately twice as long as SLC. The detailed trade-off between length and acceleration will be based on total cost. A very broad optimum occurs when the total linear costs equal the total cost of RF power. 36 refs., 3 figs., 3 tabs.
Date: June 1, 1990
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Progress towards the design of a next linear collider

Description: The purpose of this paper is to review the ongoing research at SLAC toward the design of a next-generation linear collider (NLC). The energy of the collider is taken to be 0.5 TeV in the CM with a view towards upgrading to 1.0 TeV. The luminosity is in the range of 10{sup 33} to 10{sup 34} cm{sup {minus}2} sec{sup {minus}1}. The energy is achieved by acceleration with a gradient of about a factor of five higher than SLC, which yields a linear collider approximately twice as long as SLC. The detailed trade-off length and acceleration will be based on total cost. A very broad optimum occurs when the total linear costs equals the total cost of RF power. The luminosity of the linear collider is obtained basically in two ways. First, the cross-sectional area of the beam is decreased primarily by decreasing the vertical size. This creates a flat beam and is useful for controlling beamstrahlung. Secondly, several bunches ({approximately}10) are accelerated on each RF fill in order to more efficiently extract energy from the RF structure. This effectively increases the repetition rate by an order of magnitude. In the next several sections, we trace the beam through the collider to review the research program at SLAC. 41 refs., 1 fig.
Date: June 1, 1990
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Test facilities for future linear colliders

Description: During the past several years there has been a tremendous amount of progress on Linear Collider technology world wide. This research has led to the construction of the test facilities described in this report. Some of the facilities will be complete as early as the end of 1996, while others will be finishing up around the end 1997. Even now there are extensive tests ongoing for the enabling technologies for all of the test facilities. At the same time the Linear Collider designs are quite mature now and the SLC is providing the key experience base that can only come from a working collider. All this taken together indicates that the technology and accelerator physics will be ready for a future Linear Collider project to begin in the last half of the 1990s.
Date: December 1, 1995
Creator: Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Transverse and longitudinal coupled bunch instabilities in trains of closely spaced bunches

Description: Damping rings for the next generation of linear collider may need to contain several bunch trains within which the bunches are quire closely spaced (1 or 2 RF wavelengths). Methods are presented for studying the transverse and longitudinal coupled bunch instabilities, applicable to this problem and to other cases in which the placement of the bunches is not necessarily symmetric. 5 refs., 1 fig.
Date: March 1, 1989
Creator: Thompson, K.A. & Ruth, R.D.
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

Study of invariant surfaces and their break-up by the Hamilton-Jacobi method

Description: A method is described to compute invariant tori in phase space for calssical non-integrable Hamiltonian systems. Our procedure is to solve the Hamilton-Jacobi equation stated as a system of equations for Fourier coefficients of the generating function. The system is truncated to a finite number of Fourier modes and solved numerically by Newton's method. The resulting canonical transformation serves to reduce greatly the non-integrable part of the Hamiltonian. In examples studied to date the convergence properties of the method are excellent, even near chaotic regions and on the separatrices of isolated broad resonances. We propose a criterion for breakup of invariant surfaces, namely the vanishing of the Jacobian of the canonical transformation to new angle variables. By comparison with results from tracking, we find in an example with two nearly overlapping resonances that this criterion can be implemented with sufficient accuracy to determine critical parameters for the breakup ('transition to chaos') to an accuracy of 5 to 10%.
Date: August 1, 1986
Creator: Warnock, R.L. & Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Plasma laser accelerator: longitudinal dynamics, the plasma/laser interaction, and a qualitative design

Description: In this paper we present our studies on a plasma laser accelerator. First we look at the longitudinal dynamics and the trapping of particles in the potential well due to the longitudinal electric field in a plasma density wave. Next we study the plasma/laser interaction to obtain power requirements. Lastly, we qualitatively design a plasma/laser accelerator with parameters somewhat more modest than existing suggestions.
Date: April 1, 1982
Creator: Ruth, R.D. & Chao, A.W.
Partner: UNT Libraries Government Documents Department

Bounds on nonlinear motion for a finite time

Description: Recent improvements in numerical methods to compute canonical transformations make it feasible to set interesting bounds on the motion of nonlinear Hamiltonian systems over a finite interval of time. 7 refs.
Date: June 1, 1989
Creator: Warnock, R.L. & Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Bunch lengthening calculations for the SLC (Stanford Linear Collider) damping rings

Description: The problem of bunch lengthening in electron storage rings has been treated by many people, and there have been many experiments. In the typical experiment, the theory is used to determine the impedance of the ring. What has been lacking thus far, however, is a calculation of bunch lengthening that uses a carefully calculated ring impedance (or wakefield). In this paper we begin by finding the potential well distortion due to some very simple impedance models, in order to illustrate different types of bunch lengthening behavior. We then give a prescription for extending potential well calculations into the turbulent regime once the threshold is known. Then finally, using the wakefield calculated for the SLC damping rings, combined with the measured value of the threshold, we calculate bunch lengthening for the damping rings, and compare the results with the measurements. 9 refs., 6 figs.
Date: March 1, 1989
Creator: Bane, K.L.F. & Ruth, R.D.
Partner: UNT Libraries Government Documents Department