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Long term prediction and the SSC (Superconducting Super Collider)

Description: Successful operation of the Superconducting Supercollider (SSC) will depend on the stable circulation of particles for tens of millions of turns around the rings, in the presence of small nonlinear deflecting fields. One design challenge is to set specifications for the maximum allowable field imperfections of this sort, consistent with the required. stability. Another challenge is to plan for the inclusion of field compensating elements that will ameliorate the effects of errors. The tools'' available for projecting the long term stability are theoretical, both analytic and numerical, and experimental. These aspects are reviewed. 19 refs.
Date: September 1, 1990
Creator: Talman, R.
Partner: UNT Libraries Government Documents Department

Elementary principles of linear accelerators

Description: These lectures come in five sections. The first is this introduction. The second is a short chronology of what are viewed as important milestones in the field. The third covers proton linacs. It introduces elementary concepts such as transit time, shunt impedance, and Q. Critical issues such as phase stability and transverse forces are discussed. The fourth section contains an elementary discussion of waveguide accelerating structures. It can be regarded as an introduction to some of the more advanced treatments of the subject. The final section is devoted to electron accelerators. Taking SLAC as an example, various topics are discussed such as structure design, choice of parameters, frequency optimization, beam current, emittance, bunch length and beam loading. Recent developments and future challenges are mentioned briefly. 41 figures, 4 tables.
Date: September 1, 1983
Creator: Loew, G.A. & Talman, R.
Partner: UNT Libraries Government Documents Department

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

Million revolution accelerator beam instrument for logging and evaluation

Description: A data acquisition and analysis instrument for the processing of accelerator beam position monitor (BPM) signals has been assembled and used preliminarily for beam diagnosis of the Fermilab accelerators. Up to eight BPM (or other analogue) channels are digitized and transmitted to an acquisition Sun workstation and from there both to a monitor workstation and a workstation for off-line (but immediate) data analysis. A coherent data description format permits fast data object transfers to and from memory, disk and tape, across the Sun ethernet. This has helped the development of both general purpose and experiment-specific data analysis, presentation and control tools. Flexible software permits immediate graphical display in both time and frequency domains. The instrument acts simultaneously as a digital oscilloscope, as a network analyzer and as a correlating, noise-reducing spectrum analyzer. 2 refs., 3 figs.
Date: March 1, 1988
Creator: Peggs, S.; Saltmarsh, C. & 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

Early instrumentation projects at the SSC

Description: Conceptual designs for some SSC instrumentation is given. Stripline beam position monitors, appropriate for cryogenic operation are described, along with plans for their A/D conversion and recording. A global timing system based on fibre optics is described; it is to be capable of {plus minus}100 psec accuracy over many tens of kilometers. Stabilization is patterned after a scheme in use at CERN. Timing pulses (roughly 60 MHz) as well as pulses synchronized to the various frequency modulated RF systems are distributed and scaled by digital clocks situated at those locations where accurate timing is required. Finally, a digital control circuit to be used for synchronizing beam transfer the Low Energy Booster to the Medium Energy Booster is described. It is based on controlling the relative phases of the two RF systems even though one of the frequencies is variable. 4 refs., 10 figs.
Date: April 1, 1990
Creator: Martin, D.J.; Mestha, L.K.; Miller, S.A. & Talman, R.
Partner: UNT Libraries Government Documents Department

Computing requirements for S. S. C. accelerator design and studies

Description: We estimate the computational hardware resources that will be required for accelerator physics studies during the design of the Superconducting SuperCollider. It is found that both Class IV and Class VI facilities (1) will be necessary. We describe a user environment for these facilities that is desirable within the context of accelerator studies. An acquisition scenario for these facilities is presented.
Date: January 1, 1984
Creator: Dragt, A.; Talman, R.; Siemann, R.; Dell, G.F.; Leemann, B.; Leemann, C. et al.
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

An experimental study of the SSC (Superconducting Super Collider) magnet aperture criterion

Description: A beam dynamics experiment, performed in the Fermilab Tevatron, that was mainly motivated by planning for the Superconducting Super Collider (SSC) is described. Nonlinearities are introduced in the Tevatron by special sextupoles in order to stimulate the SSC environment. ''Smear'' is one of the parameters used to characterize the deviation from linear behavior. Smear is extracted from experimental data and compared with calculation over a wide range of conditions. The agreement is excellent. The closed orbit at injection trajectory reveal no deterioration even at the highest sextupole excitations. Measurements of the dynamic aperture are in general agreement with prediction. Particles captured on nonlinear resonance islands are directly observed and measurements are performed for the first time. The stability of the islands under tune modulation is investigated. 4 refs., 8 figs.
Date: June 7, 1988
Creator: Merminga, N.; Edwards, D.; Finley, D.; Gerig, R.; Gelfand, N.; Harrison, M. et al.
Partner: UNT Libraries Government Documents Department