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Correction of the field in the SSC dipoles using superconductor on the wedges

Description: The SSC colliding beam storage ring requires superconducting magnets capable of producing a magnetic field of 6.6 T which has very high accuracy. For many of the multipoles, that multipole must be reduced (at a radius of 1 centimeter) to the order of 0.2 parts in 10,000. This field accuracy is dictated by the physics of storing very small high-current proton beams at energies ranging from 1 TeV to 20 TeV. Magnetization of the superconductor can cause sextupole field errors of up to 6 parts in 10,000 at an injection field of 0.33 T at a radius of 1 centimeter. Saturation of the magnet iron can induce sextupole field errors of 1 to 2 parts in 10,000 at the full field of 6.6 T. Manufacturing errors can induce other multipole components, both normal and skew. The SSC coil has three wedges separating the superconducting coil blocks on the inner layer of the coil. These wedges must be accurately located. If the wedges have superconductors attached, one can correct all of the magnetic field multipoles (both normal and skew) from N = 1 (dipole) to N = 6 (12 pole). This paper describes this method of correction as it pertains to the SSC dipole magnet. 9 refs., 5 figs., 3 tabs.
Date: September 1, 1987
Creator: Green, M.A. & Talman, R.M.
Partner: UNT Libraries Government Documents Department

Theorem on magnet fringe field

Description: Transverse particle motion in particle accelerators is governed almost totally by non-solenoidal magnets for which the body magnetic field can be expressed as a series expansion of the normal (b{sub n}) and skew (a{sub n}) multipoles, B{sub y} + iB{sub x} = {summation}(b{sub n} + ia{sub n})(x + iy){sup n}, where x, y, and z denote horizontal, vertical, and longitudinal (along the magnet) coordinates. Since the magnet length L is necessarily finite, deflections are actually proportional to ``field integrals`` such as {bar B}L {equivalent_to} {integral} B(x,y,z)dz where the integration range starts well before the magnet and ends well after it. For {bar a}{sub n}, {bar b}{sub n}, {bar B}{sub x}, and {bar B}{sub y} defined this way, the same expansion Eq. 1 is valid and the ``standard`` approximation is to neglect any deflections not described by this expansion, in spite of the fact that Maxwell`s equations demand the presence of longitudinal field components at the magnet ends. The purpose of this note is to provide a semi-quantitative estimate of the importance of {vert_bar}{Delta}p{sub {proportional_to}}{vert_bar}, the transverse deflection produced by the ion-gitudinal component of the fringe field at one magnet end relative to {vert_bar}{Delta}p{sub 0}{vert_bar}, the total deflection produced by passage through the whole magnet. To emphasize the generality and simplicity of the result it is given in the form of a theorem. The essence of the proof is an evaluation of the contribution of the longitudinal field B{sub x} from the vicinity of one magnet end since, along a path parallel to the magnet axis such as path BC.
Date: December 31, 1995
Creator: Wei, Jie & Talman, R.
Partner: UNT Libraries Government Documents Department


Description: The Unified Accelerator Libraries (UAL) provide a modularized environment for applying diverse accelerator simulation codes. Development of UAL is strongly prejudiced toward1 importing existing codes rather than developing new ones. This guide provides instructions for using this environment. This includes instructions for acquiring and building the codes, then for launching and interpreting some of the examples included with the distribution. In some cases the examples are general enough to be applied to different accelerators by mimicking input files and input parameters. The intention is to provide just enough computer language discussion (C++ and Perl) to support the use and understanding of the examples and to help the reader gain a general understanding of the overall architecture. Otherwise the manual is ''documentation by example.'' Except for an appendix concerning maps, discussion of physics is limited to comments accompanying the numerous code examples. Importation of codes into UAL is an ongoing enterprise and when a code is said to have been Imported it does not necessarily mean that all features are supported. Other than this, the original documentation remains applicable (and is not duplicated here.)
Date: January 9, 2003
Creator: Malitsky, N. & Talman, R.
Partner: UNT Libraries Government Documents Department

Optimal focusing for a linac-based hard x-ray source

Description: In spite of having a small average beam current limit, a linac can have features that make it attractive as an x-ray source: high energy, ultralow emittance and energy spread, and flexible beamline optics. Unlike a storage ring, in which an (undulator) radiation source is necessarily short and positioned at an electron beam waist, in a linac the undulator can be long and the electron beam can be adjusted to have a (virtual) waist far downstream toward the x-ray target. Using a planned CEBAF beamline as an example, this paper shows that a factor of 2000 in beam current can be overcome to produce a monochromatic hard x-ray source comparable with, or even exceeding, the performance of an x-ray line at a third generation storage ring. Optimal electron beam focusing conditions for x-ray flux density and brilliance are derived, and are verified by simulations using the SRW code.
Date: March 28, 2011
Creator: Liu, C.; Krafft, G. & Talman, R.
Partner: UNT Libraries Government Documents Department


Description: A general scaling law can be derived for the relative momentum deflection produced on a particle beam by fringe fields, to leading order. The formalism is applied to two concrete examples, for magnets having dipole and quadrupole symmetry. During recent years, the impact of magnet fringe fields is becoming increasingly important for rings of relatively small circumference but large acceptance. A few years ago, following some heuristic arguments, a scaling law was proposed [1], for the relative deflection of particles passing through a magnet fringe-field. In fact, after appropriate expansion of the magnetic fields in Cartesian coordinates, which generalizes the expansions of Steffen [2], one can show that this scaling law is true for any multipole magnet, at leading order in the transverse coefficients [3]. This paper intends to provide the scaling law to estimate the impact of fringe fields in the special cases of magnets with dipole and quadrupole symmetry.
Date: June 30, 2000
Partner: UNT Libraries Government Documents Department

Simulation of beam-beam effects in tevatron

Description: The Fermilab accelerator complex is in the middle of an upgrade plan Fermilab III. In the last phase of this upgrade the luminosity of the Tevatron will increase by at least one order of magnitude. In order to keep the number of interactions per crossing manageable for experiments, the number of bunches will be increased from 6 {times} 6 to 36 {times} 36 and finally to {approximately}100 {times} 100 bunches. The beam dynamics of the Tevatron has been studied from Beam-Beam effect point of view in a ``Strong-Weak`` representation with a single particle being tracked in presence of other beam. This paper describes the beam-beam effect in 6 {times} 6 operation of Tevatron.
Date: August 1, 1995
Creator: Mishra, C.S.; Assadi, S. & Talman, R.
Partner: UNT Libraries Government Documents Department

Nonlinear dynamics experiment in the Tevatron

Description: Results of the continuing analysis of the nonlinear dynamics experiment E778 are presented. Sixteen special sextupoles introduced nonlinearities in the Tevatron. 'Smear,' which is one of the parameters used to quantify the degree of nonlinearity, was extracted from the data and compared with calculation. Injection efficiency in the presence of nonlinearities was studied. Measurements of the dynamic aperture were performed. The final results in one degree of freedom of the smear, the injection efficiency and the dynamic aperture are presented. Particles captured on nonlinear resonance islands were directly observed and measurements were performed. The capture efficiency was extracted from the data and compared with prediction. The influence of tune modulation on the stability of these islands was investigated. Plans for future measurements are discussed. 4 refs., 6 figs.
Date: January 1, 1989
Creator: Merminga, N.; Edwards, D.; Finley, D.; Gerig, R.; Gelfand, N.; Harrison, M. et al.
Partner: UNT Libraries Government Documents Department