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Exclusive processes and the exclusive-inclusive connection in quantum chromodynamics

Description: An outline of a new analysis of exclusive processes and quantum chromodynamics is presented. The main elements of this work involve a consistent Fock space decomposition of the hadronic wave function, plus evolution equations for wave functions which allow an exact evaluation of hadronic matrix elements in the asymptotic short distance limit. 77 references. (JFP)
Date: March 1, 1979
Creator: Brodsky, S.J. & Lepage, G.P.
Partner: UNT Libraries Government Documents Department

Large momentum transfer electron scattering from few-nucleon systems

Description: A review is given of the experimental results from a series of measurements at SLAC of large momentum transfer (Q/sup 2/ > 20 fm/sup -2/) electron scattering at forward angles from nuclei with A less than or equal to 4. Theoretical interpretations of these data in terms of traditional nuclear physics models and in terms of quark constituent models are described. Some physics questions for future experiments are explored, and a preview of possible future measurements of magnetic structure functions of light nuclei at large Q/sup 2/ is given.
Date: August 1, 1979
Creator: Arnold, R.G.
Partner: UNT Libraries Government Documents Department

Meson radiative decays. [Review, rates]

Description: The status of decays of the kind V ..-->.. P..gamma.. and P ..-->.. V..gamma..viewed with special emphasis on the work done by the authors in this field. The low experimental value of GAMMA(rho ..-->.. ..pi gamma..) remains the outstanding problem. The lastest preliminary numbers from a Fermi Laboratory experiment go in the right direction but not far enough. 15 references.
Date: April 1, 1979
Creator: Edwards, B.J. & Kamal, A.N.
Partner: UNT Libraries Government Documents Department

Polarized beams in high energy circular accelerators

Description: In recent years, high energy physicists have become increasingly interested in the possible spin effects at high energies. To study those spin effects, it is desirable to have beams with high energy, high intensity and high polarization. In this talk, we briefly review the present status and the prospects for the near future of high energy polarized beams. 30 refs.
Date: May 1, 1979
Creator: Chao, A.W.
Partner: UNT Libraries Government Documents Department

Linac beam colliding with a stored beam revisited

Description: A system was suggested to collide an accelerator beam, such as a linac electron beam, with the stored positron beam in a storage ring, and a simple theory of the performance of the system was worked out in terms of the beam parameters of the linac and the storage ring. In cases where the available accelerator can deliver beam energies greater than those which can be stored in the ring, a higher center-of-mass energy can be attained with this system than with the storage ring alone. This is the situation we now find ourselves in at SLAC with the linac capable of supplying beams of about twice the energy of those we can store in PEP and with developments in progress to raise the linac energy still more. 2 refs.
Date: November 1, 1979
Creator: Rees, J.R. & Wiedemann, H.
Partner: UNT Libraries Government Documents Department

On setting magnets in the PEP beam-transport line

Description: This paper discusses magnets in the PEP beam-transport line. Topics discussed are: conditioning, direction of excitation, rate of excitation; determination of the excitation current for the principal bend magnets; steering mechanisms; bump magnets; and determination of excitation currents of the quadrupole magnets. (LSP)
Date: June 11, 1979
Creator: Peterson, J.M.
Partner: UNT Libraries Government Documents Department

Energy calibration of SPEAR by g-2 precession

Description: We have checked the absolute energy calibration of SPEAR near 3.6 GeV to an accuracy of +- 0.02% by measuring the g-2 precession frequency of a stored positron beam at a fixed machine energy. This is considerably more accurate than the +- 0.01% systematic uncertainty assigned to the energy calibration on the basis field measurements of the SPEAR magnets. Alternatively, these results can be interpreted as a large-..gamma.. (..gamma.. /approximately/ 7055) measurement of the positron magnetic anomaly a/sub e+/ = (1.1599 +- 0.0012) /times/ 10/sup /minus/3/. 6 refs., 2 figs., 1 tab.
Date: September 1, 1979
Creator: Fischer, G.E.; Gustavson, D.B.; Johnson, J.R.; Murray, J.J.; Phillips, T.J.; Prepost, R. et al.
Partner: UNT Libraries Government Documents Department

Frequencies of small oscillations in the vicinity of a fixed point: Application to sextupole insertions

Description: The stability criterion of A.C. Bountis for the periodic orbits of a dynamical mapping is applied to the horizontal motion of a particle in a storage ring with sextupole magnets. The approach developed takes into account any number of non-linear ''kicks'' in one superperiod of the ring, non-equal spacing between nonlinear elements and a strong focusing magnet system. The stability criterion for a fixed point is given provided such a fixed point is found. The formula for the tune of the small oscillations for any stable fixed point is derived. 2 refs.
Date: January 10, 1979
Creator: Kheifets, S.
Partner: UNT Libraries Government Documents Department

Linear electronic phase shifter design

Description: The rf systems for linear accelerators or storage rings use electronically variable phase shifters as control elements in feedback loops or to set reference phases. A variety of electronic phase shifters has been described in literature. One desirable feature of these devices is a linear response of the phase shift as a function of their control voltage. This report describes the design of 180/degrees/ phase shifters at 1300 MHz and 353 MHz using voltage variable capacitance diodes as terminations in transmission lines. The optimization of paramenters is discussed with emphasis on linearity, power handling capability and temperature stability. 9 refs., 9 figs.
Date: November 1, 1979
Creator: Schwarz, H.
Partner: UNT Libraries Government Documents Department

Modeling a horizontal wiggler in an electron storage ring

Description: The effects of a wiggler on the beam parameters depend on several integrals involving the machine functions and the field distribution in the wiggler. It is shown that these integrals are separable into sums of products of terms containing only the initial values of the machine functions, and terms containing integrals over the wiggler fields. The field-dependent integrals may be determined by numerical integrations based on measured field distribution. In typical wiggler designs, the energy and excitation dependencies of the integrals may be modeled mathematically by simple power series.
Date: February 1, 1979
Creator: Helm, R.H.
Partner: UNT Libraries Government Documents Department

Single feedback systems for simultaneous damping of horizontal and longitudinal coherent oscillations

Description: A complete analysis of the Type (x, delta) feedback system is presented using a matrix method. The analyses of other types are similar to that of Type (x, delta) and only the results are included. Some comparisons of these types of feedback schemes in terms of power consumptions and the effectiveness in damping the horizontal-betatron and synchrotron oscillations are included. Some effects of position measuring errors on the performance of the feedback systems are also discussed.
Date: January 1, 1979
Creator: Chao, A.W.; Morton, P.L. & Rees, J.R.
Partner: UNT Libraries Government Documents Department

A users guide to Poisson

Description: This writeup describes the POISSON program package in operation at SLAC. The program can be used to solve two-dimensional or cylindrical magnetostatic or electrostatic problems. The program uses an irregular triangular mesh of up to 6600 points in the finite difference approximation to Poisson's equation. Symmetry properties of a problem are taken advantage of so that usually, only part of a given problem has to be set up. For example: only a 45 degree segment of a symmetrical quadrupole is solved in order to obtain a complete solution. Successive over-relaxation (SOR) is used to find values of the vector potential at the mesh points from the boundary conditions and input currents. Non-linear regions (iron) are treated in a quasi-linear manner by holding the permeabilities constant during a relaxation cycle, computing local fields at the end of a cycle, performing a table lookup and under-correcting the permeability to keep the problem stable. 10 figs.
Date: November 1, 1979
Creator: Early, R.A.
Partner: UNT Libraries Government Documents Department

Single feedback systems for simultaneous damping of horizontal and longitudinal coherent oscillations

Description: To describe the horizontal motion of the bunch, we need four coordinates, x and z are the horizontal and longitudinal displacements of the bunch center relative to the ideal trajectory; x' is the angle between the bunch's direction of motion and the ideal trajectory; and delta=..delta..E/E is relative energy error of the bunch. Among the four variables, x and z are easy to measure by position monitors, while x' and delta are easy to change by electromagnetic devices. In combination, this suggests four possible types of feedback systems. In the following, we will present a complete analysis of the Type (x, delta) feedback system, using a matrix method. The analyses of other types are similar to that of Type (x, delta) and only the results are included. We then include some comparisons of these types of feedback schemes in terms of power consumptions and the effectiveness in damping the horizontal-betatron and synchrotron oscillations. We will also discuss some effects of position measuring errors on the performance of the feedback system. 2 refs., 3 tabs.
Date: March 1, 1979
Creator: Chao, A.W.; Morton, P.L. & Rees, J.R.
Partner: UNT Libraries Government Documents Department

Transverse resonances of periodically widened cyclindrical tubes with circular cross section

Description: The transverse resonances of the electromagnetic field in periodic cylindrical cavities connected by concentric side tubes are calculated for arbitrary azimuthal mode numbers by expansion of the Hertz potentials in subregions bounded by coordinate surfaces. The expansion coefficients are determined by matching of the tangential field components across the common surfaces of the subregions. Resonances are characterized by the existence of solutions of the homogeneous wave equation in the absence of source terms, and the resonant frequencies are given by the vanishing of the determinant of an infinite matrix. They can be calculated on a computer by truncating the matrix. Expressions for the stored energy, the loss-factor, and for R/Q are then obtained by integration over the fields at resonance. These results are of interest for the determination of the energy loss and the stability of the beam in high-energy particle accelerators and storage rings when cavities are formed by pairs of cross section variations of the vacuum chamber. 7 refs., 1 fig.
Date: September 1, 1979
Creator: Zotter, B. & Bane, K.
Partner: UNT Libraries Government Documents Department

Transverse instability excited by rf deflecting modes for PEP

Description: We have looked at the possible transverse instability effects which are caused by the deflecting modes of the rf cavities in PEP. The results are obtained by applying the expression of the instability damping rate. We have assumed that there equal bunches equally spaced in PEP. We have worked out the equivalent for a single bunch beam. The effect of chromaticity xi is included as a frequency shift in the bunch mode spectra. We rewrite this result in terms of the transverse wake field instead of the impedance. We include an application of the Sacherer formalism to the case of resistive wall. The resulting expression of the damping rate contains two terms. The first term corresponds to the effect of the short wake fields; it agrees with the result of the head-tail instability as derived by Sands. A numerical estimate of this resistive-wall head tail case for PEP is given. It re-confirms that the resistive wall instability is not a serious problem for PEP. The second term gives the effect of long wake fields and it agrees with the result of Courant and Sessler. 10 refs., 2 figs.
Date: November 1, 1979
Creator: Chao, A.W. & Yao, C.Y.
Partner: UNT Libraries Government Documents Department

Properties of a linac-storage ring stretcher system

Description: Some of the design characteristics and costs of a matched system comprising a pulsed linac and a storage ring to be used as a beam stretcher are discussed. The goal is to obtain a 2 GeV, 0.1 mA quasi-continuous stream of electrons. Within this goal, some optimization criteria will be examined and some technological difficulties will be indicated.
Date: February 1, 1979
Creator: Loew, G.A.
Partner: UNT Libraries Government Documents Department

Wakefields in a pillbox cavity

Description: The wakefields due to a bunch in a pillbox cavity can be found by mode-expansion of the fields given by the wave-equation. Usually one considers first the wakefield due to an infinitely short pulse and then integrates over the current distribution. Since the series for the delta function pulse converge rather poorly, it is preferable to use the wakefield due to a step-function current, which can also be integrated to give the result for an arbitrary current distribution. For the most important case of fields with azimuthal symmetry, the results are expressed as double series over the radial mode number n, and the longitudinal mode number p. For a beam traveling with light-velocity, these series have been summed analytically. However, the results are restricted to observation times before reflections from the cylindrical side-wall reach the axis, i.e., they are actually valid only for a parallel-plate geometry. In order to find the wakefields in cylindrical cavities of finite radius we have to re-examine the infinite series. Although no closed-form expression could be found for the sidewall reflections, they can be determined from a function defined by a single infinite sum with only one variable. Extension to modes with azimuthal variation is straightforward. However, extension to beam velocities smaller than light-velocity is more complicated and again would require the use of functions defined by infinite series. The influence of finite holes in the end-walls has not been investigated in this report, since no analytic solutions are known for this case. However, the character of the solutions for the closed cavity should help in understanding the numerical results obtained for this case. 7 refs., 7 figs.
Date: December 1, 1979
Creator: Zotter, B.
Partner: UNT Libraries Government Documents Department

Scaling of colliding-beam rings based on pulsed rf

Description: This note examines the cost-scaling of electron-positron storage rings based on pulsed RF systems. The first section uses the nomenclature of P. Wilson to obtain the basic relations between efficiency of power transfer and structure lengths required. The second section uses these properties to obtain the cost equations as a function of energy for an ''optimized'' machine. The optimized radius goes as the 1.7 power of the peak energy. 3 figs., 1 tab.
Date: March 1, 1979
Creator: Ritson, D.
Partner: UNT Libraries Government Documents Department

Steady state distribution for unbunched beams colliding in a drift space

Description: A self-consistent time-independent solution of the system of coupled equations for the distribution of two colliding unbunched beams of opposite charges is found. The solution for each beam contains an arbitrary constant which characterizes the lateral size of the beam. On the other hand, the angular divergence is uniquely determined by the line charge density of the opposite beam in case the beams have cylindrical symmetry. The possible implications of this solution for a linac collider are discussed. Further work on the stability of this solution is needed. 6 refs., 9 figs., 2 tabs.
Date: December 1, 1979
Creator: Kheifets, S. & Chao, A.W.
Partner: UNT Libraries Government Documents Department

Is it possible to improve the eventrate for narrow resonances in SPEAR and PEP

Description: The eventrate at narrow resonances, like the /psi//J and /Tau/ resonances, is not only determined by the luminosity of the e/sup +/ and e /sup /minus// storage ring but also by the energy spread in the beam due to synchrotron radiation. This energy spread is much larger than the width of the resonances. Therefore, if the energy spread could be reduced by a factor F the eventrate would increase by the same factor.
Date: October 15, 1979
Creator: Wiedemann, H.
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

Emittance in a FODO-cell lattice

Description: Several PEP Notes give formulas and curves for the variation of beam parameters in a FODO lattice as functions of focal length. However, because of approximations, the results for emittance are not accurate when the focusing is too strong. We give here the emittance calculation correct for any phase advance per cell between 0 and . 3 refs., 1 fig.
Date: May 1, 1979
Creator: Helm, R.H. & Wiedemann, H.
Partner: UNT Libraries Government Documents Department

What is Centauro. [High-Z nuclear matter blob in primary cosmic radiation]

Description: Another interpretation of the Centauro event is given in which the primary object initiating the collision is a glob of nuclear matter of very high density. The kinetics of this glob are described, and the experimental implications set forth. Among the latter are the horizontal air shower rate and the mean quark density on earth, both within experimental limits according to the glob interpretation. 7 references. (JFP)
Date: January 1, 1979
Creator: Bjorken, J.D. & McLerran, L.D.
Partner: UNT Libraries Government Documents Department

Stability of the higher order longitudinal modes for PEP

Description: The theory of longitudinal instabilities of bunched beams is well known. Application to PEP has recently been considered by Pellegrini and Sands, who were mainly concerned with the rigid bunch oscillation of three bunches (i.e. the dipole mode with mode number m = 1). In this note, we will look at the stability of modes with arbitrary mode number m, first for a single-bunch beam and then or a beam consisting of three equally spaced bunches. The method of analysis is essentially that of Sacherer's, whose main result is an integral equation for the eigenmodes and eigenfrequencies of the longitudinal bunch oscillations. It turns out that the integral equation can be solved if the unperturbed beam has a uniform distribution inside an ellipse in the longitudinal phase space (the water-bag model). We study the impedance of a parallel resonator circuit representing the rf accelerating cavity and obtain expressions for the damping rates and frequency shifts for mode number m. In deriving these expressions, we have included contributions from the tails of the impedance and not only from its peak. The importance of these contributions has been pointed out by Zotter. For m = 1, our expression for the damping rate is the same as that for Robinson damping. We also find that the damping rate of a higher order mode (m />=/ 2) is small compared with that of the dipole mode (m = 1)--- this is expected since the rf wavelength is much longer than the bunch length. On the other hand, due to the contribution from the impedance tail, the mode frequency shift does not decrease with m rapidly. We have also included an estimate of the damping rates of the quadrupole modes using the PEP parameters. 4 refs., 1 fig.
Date: July 1, 1979
Creator: Chao, A.W.
Partner: UNT Libraries Government Documents Department