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Real-time applications of neural nets

Description: Producing, accelerating and colliding very high power, low emittance beams for long periods is a formidable problem in real-time control. As energy has grown exponentially in time so has the complexity of the machines and their control systems. Similar growth rates have occurred in many areas, e.g., improved integrated circuits have been paid for with comparable increases in complexity. However, in this case, reliability, capability and cost have improved due to reduced size, high production and increased integration which allow various kinds of feedback. In contrast, most large complex systems (LCS) are perceived to lack such possibilities because only one copy is made. Neural nets, as a metaphor for LCS, suggest ways to circumvent such limitations. It is argued that they are logically equivalent to multi-loop feedback/forward control of faulty systems. While complimentary to AI, they mesh nicely with characteristics desired for real-time systems. Such issues are considered, examples given and possibilities discussed. 21 refs., 6 figs.
Date: May 1, 1989
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Magnets for high energy colliders

Description: The problem of producing, preserving and stably colliding low emittance bunches for long periods of time is a formidable problem involving questions of jitter, dynamic alignment and reproducibility associated with magnetic and mechanically hysteresis. Permanent magnets provide ideal solutions for lower capital and operating costs. Because they are light in weight, compact and require no power or cooling they are easy to use, stable and uniquely reliable. With their low permeability this implies a minimal impact on the surrounding environment and vice versa. For example, they are ideal for final focus systems embedded in particle detectors with strong solenoidal fields while their strength and compactness minimizes the solid angle they subtend around the interaction point (IP) as well as their target thickness along the beam line. We discuss calculations there /rvec B/ is a nonlinear, anisotropic function of /rvec H/. The results explain discrepancies observed measurement and calculation of permanent magnet systems and indicate good multipoles are possible with far higher strengths than previously obtained. We extend previous calculations on the obtainable gradients for different types of quadrupoles down to 1 mm bore radii where 2000 T/m appears possible with conventional designs and available materials. We discuss why much higher gradients are possible by the same means. Additional specifications for PM manufacturers are recommended. 14 refs., 5 figs.
Date: March 1, 1989
Creator: Spencer, J. & Stucki, H.
Partner: UNT Libraries Government Documents Department

Accelerator diagnosis and control by Neural Nets

Description: Neural Nets (NN) have been described as a solution looking for a problem. In the last conference, Artificial Intelligence (AI) was considered in the accelerator context. While good for local surveillance and control, its use for large complex systems (LCS) was much more restricted. By contrast, NN provide a good metaphor for LCS. It can be argued that they are logically equivalent to multi-loop feedback/forward control of faulty systems, and therefore provide an ideal adaptive control system. Thus, where AI may be good for maintaining a 'golden orbit,' NN should be good for obtaining it via a quantitative approach to 'look and adjust' methods like operator tweaking which use pattern recognition to deal with hardware and software limitations, inaccuracies or errors as well as imprecise knowledge or understanding of effects like annealing and hysteresis. Further, insights from NN allow one to define feasibility conditions for LCS in terms of design constraints and tolerances. Hardware and software implications are discussed and several LCS of current interest are compared and contrasted. 15 refs., 5 figs.
Date: January 1, 1989
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Higher luminosities via alternative incident channels

Description: We show that PEP provides some unique opportunities for one and two photon physics with real photons as well as for QCD studies with internal targets. Photon beams would avoid the major limitation on the luminosity of present machines and could provide PEP an ideal b-physics factory producing the full range of J/sub c//sup PC/ and J/sub b//sup PC/ states that may not be observable otherwise as well as allow a whole new class of ''missing-mass'' experiments. These latter particles are the pseudo-Goldstone bosons and their supersymmetric counterparts. These and related possibilities like a single-pass, ''free electron laser'' facility or even synchrotron radiation beam lines all favor a mini-maxi configuration for the low-beta insertions in PEP. This allows more diverse experiments without excluding any ongoing experimental programs. Such possibilities have interesting implications for a number of proposed facilities including the SSC. Some systematic machine physics studies over a range of energies are suggested. 24 refs., 6 figs.
Date: April 1, 1985
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Some optics alternatives for the FFS

Description: The evolution of the SLC Final Focus System (FFS) has been discussed in the SLC Red Books and various collider notes. Bulos and Brown and Murray were able to achieve small ..beta..'s with large l/sub 1/'s (the distance between the IP and the effective field boundary of the first quad). However, all current solutions which are compatible with the known constraints of the total path length, aperture and spot size require high gradient, superconducting quads. Such quads cannot be expected to provide very good inherent field quality (i.e., without correction windings) but can be expected to be comparatively expensive to build and operate simply. The purpose of this note is to present a more general solution for the FFS telescope which is compatible with the known constraints of detectors, magnet types, available space and the ingoing and outgoing phase space expectations. While a number of different solutions were found, the ones presented provide comparable performance, simpler operation and lower costs. The gradients are sufficiently low to allow the use of conventional electromagnets, intrinsic or cryostable superconducting or rare earth permanent (REP) magnets or any arbitary combination of all of these magnet types. 8 references, 9 figures, 1 table.
Date: March 7, 1984
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Some uses of REPMM's in storage rings and colliders

Description: Improvements for existing rings and techniques for building new rings composed entirely of passive, Rare Earth Permanent Magnet Multipoles (REPMM's) are considered using circular dipoles, quadrupoles and sextupoles. Over the past few years we have made such magnets using a single size SmCo/sub 5/ block with up to five easy-axis orientations. The final production scheme is modular in that magnets are built-up from quantized layers. All multipole layers are made in exactly the same way using algorithms differing only by the desired multipole symmetry. The method is simple, efficient and inexpensive and allows a ''do-it-yourself'' approach to constructing new magnetic elements. For rings these might include focusing optical klystrons, rotatable multipoles for diagnostics, correction or extraction, or possibly combined function systems for the unit cells. A high quality, low-beta, PMQ insertion which can change beta, tune and energy is described as well as the PMS's for the SD and SF elements of the North SLC damping ring. Because these sextupoles will be the first optical use of PM's in storage rings they are discussed in detail together with the advantages, problems and requirements of such applications. 8 refs., 4 figs.
Date: April 1, 1985
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Present optics options for TeV colliders

Description: A practical approach for implementing TeV collider optics with high luminosities pounds approx. = 10/sup 33/ (cm/sup 2/ s)/sup -1/ but without large pinch effects is given using current alternatives. Characteristics are considered that constrain the optics and the types and orders of magnets required. A modified linac FoDo cell based on permanent magnet hybrid quadrupoles is discussed. Similarly, a demagnifying, permanent magnet telescopic system that allows variation of beta, eta and energy is suggested for the final focus. The basic cell for low emittance damping rings can also be constructed solely from permanent magnets. Small diameter, low permeability, high field permanent magnets have proven useful for injection and extraction lines and are also compatible with the large particle near the interaction regions as well as with exotic experiments for production and use of secondary beams or for multi-bunch coalescing schemes for control of longitudinal bunch distribution. An 8-10 GeV prototype cell and final focus experiment is proposed to verify and study such systems as well as do some interesting physics tests. One example, which could be used with the PEP storage ring, would convert an external electron beam into a photon beam to avoid beamstrahlung effects - a major problem for high energy e+- colliders.
Date: May 1, 1986
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Exact transfer functions for the PEP storage ring magnets and some general characteristics and techniques

Description: The exact, ion-optical transfer functions for the dipoles, quadrupoles and sextupoles of the PEP standard PODC cell are calculated for any single particle with initial coordinates (r, p, s). Modifications resulting from radiative energy loss are also calculated and discussed. These functions allow one to characterize individual magnets or classes of magnets by their aberrations and thereby simplify their study and correction. In contrast to high-energy spectrometers where aberrations are often analyzed away, those in storage rings drive series of high order resonances, even for perfect magnets (2), that can produce stop bands and other effects which can seriously limit performance. Thus, one would like to eliminate them altogether or failing this to develop local and global correction schemes. Even then, one should expect higher order effects to influence injection, extraction or single-pass systems either because of orbit distortions or overly large phase spece distortions such as may occur in low-beta insertions or any final-focus optics. The term exact means that the results here are based on solving the relativistic Lorentz force equation with accurate representations of measured magnetostatic fields. Such fields satisfy Maxwell's equations and are the actual fields seen by a particle as it propagates around a real storage ring. This is discussed in detail and illustrated with examples that show that this is possible, practical and may even be useful.
Date: May 1, 1982
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Storage rings, internal targets and PEP

Description: Storage rings with internal targets are described, using PEP as an example. The difference between electrons and heavier particles such as protons, antiprotons, and heavy ions is also discussed because it raises possibilities of bypass insertions for more exotic experiments. PEP is compared to other rings in various contexts to verify the assertion that it is an ideal ring for many fundamental and practical applications that can be carried on simultaneously. (LEW)
Date: November 1, 1986
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Permanent magnet sextupole protocol and tolerances for the damping rings

Description: Response is given to various questions on alignment tolerances for the permanent magnet sextupoles (PMS's) in the damping rings. Consideration is given to rotational errors, strength/longitudinal placement errors, transverse placement errors, pitch/yaw or tilt errors, and harmonic field errors. Resulting error limits can be specified in terms of the maximum errors allowed in the distribution. (LEW)
Date: September 5, 1985
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Harmonic strengths of PEP dipoles and some related effects and lessons

Description: The harmonic content of magnets such as the standard PEP bend is (among other things) a function of excitation current, the way the current is set and even the magnetization history. For instance, harmonic strengths generally vary not only with the magnitude of the current but the direction and rate at which the current is approached and set. The field distribution resulting from different procedures can vary markedly depending on both the mechanical and magnetic design and the degree to which eddy current effects are emphasized. Variations among magnets of the same design result from variations in the iron as well as overall magnet fabrication procedures. Because the field distribution may also depend in the previous history of a magnet, all PEP dipoles were subjected to what are called ''magnetization'' and ''standardization'' cycles before measurement---the latter depending on the former and intended to set the initial conditions of the magnet to a reproducible standard. The primary goal of the magnetic measurements was then to determine the dipole strength as a function of current for each magnet based on a practical setting algorithm. The main constraints on the algorithm were reproducibility of the integrated field, speed, power and reduction of higher harmonics. Quadrupole and sextupole strengths were also measured on about one-half of the magnets at one current. This note presents the data and discusses it from the the viewpoint of subsequent measurements with stored beams. The most important conclusion is that inability to fully distribute laminations according to heat number and/or strike number results in ''magnetic personalities'' among the magnets which are quite difficult to deal with afterwards although one can distribute ''non-standard'' magnets to minimize orbit distributions. 26 refs., 8 figs., 3 tabs.
Date: September 1, 1981
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Wigglers: the newest profession

Description: Wiggler systems have been used in storage rings within the last year to increase the intensity of synchrotron radiation available for experiments as well as to increase the reaction rates in high energy physics experiments. Multiperiod wigglers or undulators have also been used recently to make quasi-monochromatic photon beams as well as amplify existing photon beams such as in the free electron laser. If one defines a wiggler to be any system of transverse, periodic electromagnetic fields, then recent results on photon production via charged particle channeling in crystals also fall within this sphere. Of course, any periodic modulation of a charge or magnetic moment (e.g., by a laser) could produce coherent radiation or, conversely, passage through a periodic aperture (e.g., a metal bellows). This discussion is limited to a typical, active, macroscopic device and how it provides some unique advantages which are practical to achieve in storage rings. As implied, the subject divides into two basic parts - one related to the radiation from the wiggler and the other related to machine physics applications, e.g., tailoring the phase space of the particle beam, modifying its damping rates or possibly optimizing a ring for production of radiation. Neither area is exhausted nor hopefully the reader, since our goal is only to present enough information to allow one to make reasonable estimates of some important effects.
Date: January 1, 1981
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Internal targets in storage rings

Description: While fixed-target experiments in storage rings were suggested more than twenty-five years ago, little work has been done and virtually none in this country although interest seems to be growing. We survey the advantages, limitations and possibilities. Luminosities of L approx. = 10/sup 33/cm/sup -2/s/sup -1/ for electrons up to 15 GeV should be achievable now with the PEP storage ring at SLAC with good beam lifetime and emittance for target thicknesses n/sub t/ approx. 10/sup 15//cm/sup 2/. This is thin but ideal for optically pumped, polarized gas targets. Providing longitudinally polarized beams at such targets would provide a unique facility for high luminosity polarized e/sub +-/ + polarized ..gamma.., polarized e/sub +-/ + polarized A and polarized ..gamma.. + polarized A experiments. Other possibilities include the production of both external and internal beams for basic and applied science. Multiple bypass insertions are considered for thicker targets as well as production and storage of exotic, short-lived beams or for production of photon beams with undulators. The related question of multi-turn injection and extraction is also considered in such a context. Several systematic machine physics studies are suggested, e.g., ion-induced, multi-bunch instabilities with e/sub +-/ beams. The SLAC storage ring PEP is used as an example because it is ideal for simultaneous production of internal target, external target and colliding beam luminosities. The differences between electrons and heavier particles such as protons, antiprotons or heavy ions are discussed where possible.
Date: November 1, 1986
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Ideal of the perfect magnet-superconducting systems

Description: In this report, we study an iron-free, superconducting, elliptical coil quadrupole which has been proposed by General Atomics for use in the SLC final focus system. Beth has shown that such coils might provide a pure quadrupole field ignoring 3-D effects. Similarly, recent studies of rare earth permanent magnets have shown that, at least in principle, these magnets can also be made arbitrarily pure. Since similar claims can be made for conventional iron-core electromagnets either by demanding pure hyperbolic pole contours or using tricks, it is interesting to consider just how wide the gulf between principle and practice really is for each type of magnet and what it takes to bridge it (and where one is most likely to fall off). Here we consider only the superconducting option because its greater strength, variability and linearity make it potentially useful for the SLC and the low-beta insertions of the high energy storage rings such as PEP.
Date: April 1, 1983
Creator: Shoaee, H. & Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Beam-beam effects and generalized luminosity

Description: The assumption is made that before an NLC is approved, a prototype will be necessary that demonstrates the feasibility of a general purpose linear collider capable of {rvec e}{sup {+-}}{rvec e}{sup {+-}}, {rvec {gamma}}{rvec e} and {rvec {gamma}}{rvec {gamma}} incident channels. At an upgraded SLC, such channels could provide new physics over a range of energies upwards of a few GeV. Effects that limit the luminosity of a GLC are discussed together with their possible mitigations. The expected luminosities in the different channels are then predicted in a consistent way for {radical}s{sub ee} = 0.5 TeV.
Date: January 1, 1996
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

The SLC as a second generation linear collider

Description: With enough luminosity, the SLC could contribute to most of the high energy physics of current interest such as new hadrons, quark molecules, gluebaus and studies of the Standard Model and Minimal Supersymmetric SM in the form of particle searches for the lowest mass Higgs or selectron or tests of the point-like predictions for the W, Z or {tilde e}{sub R}. Some experiments require alternative incident channels such as e{gamma} and {gamma}{gamma} but only modest increases in energy. Just as the SLC was a prototype for the NLC, it could also be a prototype for a general or {gamma} linear collider -- a GLC. Because the main problem is luminosity, we give a scaling relation based on multiple bunches per R-F pulse. We then ask what is possible for the SLC in terms of bunch and train current, emittance and energy at the IP. The results suggest a phased development with the Higgs as a possible last step requiring a luminosity L{ge}10{sup 32}.
Date: May 1, 1995
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

High brightness sources for colliders

Description: Different possible sources are considered and the importance of the gun for linear colliders discussed. Low emittance electron guns suitable for SLC are available now and we discuss current work that could also provide high polarization. The relative merits of {rvec {gamma}}, {rvec e}{sup {plus minus}} and {rvec p}{sup {plus minus}} are discussed and how the next linear collider (NLC) naturally provides both {rvec e}{sup {plus minus}} and {rvec {gamma}}. Particular emphasis was placed on stability demands of LC's without sacrificing flexibility. A general purpose, versatile source is described that can collimate and/or tailor the bunch shape. Finally, some interesting experiments for SLC are discussed that could provide good physics while testing such ideas for the next generation machine. At 0.5--1.0 TeV such a machine would be complementary and competitive with LHC. 18 refs., 2 figs., 1 tab.
Date: May 1, 1991
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Optimal, real-time control--colliders

Description: With reasonable definitions, optimal control is possible for both classical and quantal systems with new approaches called PISC(Parallel) and NISC(Neural) from analogy with RISC (Reduced Instruction Set Computing). If control equals interaction, observation and comparison to some figure of merit with interaction via external fields, then optimization comes from varying these fields to give design or operating goals. Structural stability can then give us tolerance and design constraints. But simulations use simplified models, are not in real-time and assume fixed or stationary conditions, so optimal control goes far beyond convergence rates of algorithms. It is inseparable from design and this has many implications for colliders. 12 refs., 3 figs.
Date: May 1, 1991
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Some applications of AI (Artificial Intelligence) to the problems of accelerator physics

Description: Failure of orbit correction schemes to recognize betatron oscillation patterns obvious to any machine operator is a good problem with which to analyze the uses of Artificial Intelligence and the roles and relationships of operators, control systems and machines. Because such error modes are very common, their generalization could provide an efficient machine optimization and control strategy. A set of first-order, unitary transformations connecting canonical variables through measured results are defined which can either be compared to design for commissioning or to past results for 'golden orbit' operation. Because these relate directly to hardware variables, the method is simple, fast and direct. It has implications for machine design, controls, monitoring and feedback. Chronological analysis of such machine signatures can predict or provide a variety of information such as mean time to failure, failure modes and fast feedback or feedforward for optimizing figures of merit such as luminosity or current transmission. The use of theoretical and empirical scaling relations for such problems is discussed in terms of various figures of merit, the variables on which they depend as well as their functional dependences.
Date: September 1, 1986
Creator: Higo, T.; Shoaee, H. & Spencer, J.E.
Partner: UNT Libraries Government Documents Department

Breeding new light into old machines (and new)

Description: Photons produced by lasers or wigglers backscattered on high energy electron or proton beams can provide high energy, high luminosity photon-electron, photon-photon or photon-proton collisions. This allows the study of short-distance QCD processes such as high transverse momentum photon-photon and photo-production reactions, deep inelastic Compton scattering, the photon structure function, direct photon reactions, or searches for pseudo-Goldstone bosons and supersymmetry particles like the photino or goldstino. The relative reaction rates should be quite high since (1) photo-production cross sections are significantly larger than the corresponding electro-production cross sections and (2) absence of the conventional beam-beam interaction allows significantly higher currents and smaller interaction areas. It thus seems possible to have photon luminosities much larger than for electrons. Examples are given using the PEP storage ring with the SLAC linac beam.
Date: April 1, 1985
Creator: Spencer, J.E. & Brodsky, S.J.
Partner: UNT Libraries Government Documents Department

Single wavelength standard wiggler for PEP

Description: A 1lambda planar wiggler has been designed that will be used for the initial operation of the 4 to 18 GeV storage ring PEP. Three of these wigglers will be installed symmetrically around the ring at 120/sup 0/ intervals in three of six available 5 m straight sections with the purpose of providing: (1) beam size control to obtain better luminosities below 15 GeV, and (2) decreased damping times to obtain better injection rates at lower energies. Design goals are discussed and a description of the final system including cost estimates is given. Expected results and usage in PEP are discussed. Some possibilities for production of synchrotron radiation and beam monitoring with shorter wavelength, multiple-period wigglers at PEP energies are also discussed. Comparison to a wiggler now operating in SPEAR is given.
Date: March 1, 1979
Creator: Brunk, W.; Fischer, G. & Spencer, J.
Partner: UNT Libraries Government Documents Department

Test of QED using a laser at the SLAC final focus test beam

Description: Experiment {number sign}144 at SLAC has three parts: the search for low-mass states excited in {gamma}{gamma} collisions and observed in pair decay, the study of nonlinear, nonperturbative QED in {gamma}e and {gamma}{gamma} collisions, and its possible applications to general purpose linear colliders. Such colliders could produce the full range of J{sub q{center dot}{center dot}{bar q}}/{sup PC} states, leptoquarks J{sub l{center dot}{center dot}{bar q}}/{sup PC}, the particles of supersymmetry, the top quark or Higgs. However, to realize them a number of technical problems need resolution that are addressed in E144 together with interesting possibilities for highly polarized, high brightness {gamma}/{sup {yields}} e{sup {yields}{plus minus}} beams that are needed for electroweak studies.
Date: April 1, 1992
Creator: Spencer, J.E.
Partner: UNT Libraries Government Documents Department