By Topic

Particle Accelerator Conference, 1995., Proceedings of the 1995

Date 1-5 May 1995

Go

Filter Results

Displaying Results 1 - 25 of 213
  • Proceedings of the 1995 Particle Accelerator Conference Volume 5 of 5

    Publication Year: 1995
    Save to Project icon | Request Permissions | PDF file iconPDF (3903 KB)  
    Freely Available from IEEE
  • Author index

    Publication Year: 1995
    Save to Project icon | Request Permissions | PDF file iconPDF (2387 KB)  
    Freely Available from IEEE
  • Fast symplectic mapping and quasi-invariants for the Large Hadron Collider

    Publication Year: 1995 , Page(s): 2804 - 2806 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    Beginning with a tracking code for the LHC, we construct the canonical generator of the full-turn map in polar coordinates. For very fast mapping we adopt a model in which the momentum is modulated sinusoidally with a period of 130 turns (very close to the synchrotron period). We achieve symplectic mapping of 107 turns in 3.6 hours on a workstation. Quasi-invariant tori are constructed on the Poincare section corresponding to multiples of the synchrotron period. The possible use of quasi-invariants in deriving long-term bounds on the motion is discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Nonlinear dependence of synchrotron radiation on beam parameters

    Publication Year: 1995 , Page(s): 2807 - 2809 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    Synchrotron radiation has been traditionally treated as an effect which only depends on the linear beam dynamics. Electrons in advanced accelerators and storage rings, however, can lose several percent of their energy in one turn, especially when the ring incorporates synchrotron radiation sources or free electron lasers. In these machines nonlinear effects can become important, not only because of the high variation of the particle's energy around the ring, but also because of the necessity to have very good beam quality in wigglers, undulators, and free electron lasers. Since these instruments can have helical structure, a general reference frame with torsion is used and the Lorenz-Dirac radiation reaction of the charged particle is taken into account. We will utilize the differential algebra technique to compute nonlinear transfer maps of general optical elements. Applications include radiation damping in multipoles, its effect on closed orbit distortion in a storage ring, and nonlinear tune shifts due to various radiating devices. The software provided will also be useful in simulating Siberian snakes View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effects of the CHESS wigglers on a beam with an angular offset

    Publication Year: 1995 , Page(s): 2866 - 2867 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (136 KB)  

    The magnetic field due to a single pole of a wiggler is, by normal accelerator magnet standards, both very strong and very nonuniform. Because the poles alternate sign and are made to have the same strength the effects of the nonuniform fields on the beam largely cancel from one pole to another. In an ideal case where there are no mechanical or magnetic errors, the net integrated dipole field along a path parallel to the wiggler axis and on the midplane would be exactly zero. We estimate the integrated field along a path not parallel to the axis but still in the midplane. Such a path is typical of the closed orbit during electron injection or luminosity optics. When the path of integration is at an angle to the wiggler axis, the horizontal or vertical position in one pole is not precisely the same as the horizontal or vertical position in any other pole. Because of the relatively strong variation of field strength with position the integration over one pole does not cancel with the integration over another pole. Based on approximate expressions for the field in the wiggler, we show that the size of this effect is substantially smaller than the actual integrated dipole field measured parallel to the axis. This work has relevance to the CESR ring View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A study of beam-beam interactions at finite crossing angles for a B-factory

    Publication Year: 1995 , Page(s): 2883 - 2885 vol.5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    The feasibility of adopting a finite beam crossing angle at the interaction point of KEKB B-factory has been studied. Various aspects of beam behaviors, such as sensitivities to resonances and development of bunch tails, have been investigated with computer simulations. It is shown that an acceptable operating condition can be found with a suitable combination of machine parameters that are envisioned at KEKB View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Hamiltonian formalism for space charge dominated beams in a uniform focusing channel

    Publication Year: 1995 , Page(s): 3182 - 3184 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    Halo formation for a test particle in a mismatched KV beam is studied. Parametric resonances of the particle Hamiltonian due to envelope modulation are studied with particular emphasis on period 2 resonance which plays dominant role in halo formation. It is shown that the onset of global chaos exhibits a sharp transition when the amplitude of modulation is larger than a critical value which is a function of a single parameter, κ, i.e., the ratio of the space charge perveance to the focusing strength View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The description of high current beam dynamics using Lie algebraic methods

    Publication Year: 1995 , Page(s): 3232 - 3234 vol.5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    A scheme to describe a nonlaminar beam dynamics in the electromagnetic field is suggested. It is based on the Lie algebraic methods and uses the quasi-equilibrium plasma model. Numerical results are represented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Particle tracking with generating functions of magnetic fringing fields

    Publication Year: 1995 , Page(s): 2868 - 2870 vol.5
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    A construction scheme for generating functions (GFs) suitable for particle tracking across arbitrary magnetic fields is presented. The GF is approximated by a power series solution of the Hamilton-Jacobi differential equation with analytical expressions for the coefficients. This approach is applied to magnetic fringing fields, which are presented as simplified analytical expressions. A short REDUCE code transforms the vector potentials automatically into an expanded GF View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Klystron power specifications based on transient beam loading analysis in damping rings

    Publication Year: 1995 , Page(s): 3217 - 3219 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    A useful diagram is presented and used to study RF cavity voltage regulation in a damping ring or other circular accelerator where large beam currents are injected and extracted rapidly. With conventional feedback systems and high particle beam currents, the maximum beam current can be limited by the ability of the klystron to maintain constant gap voltage at high currents, low currents, or in the absence of beam. Techniques for storing high current beams are suggested when the maximum klystron output power is predetermined. Alternately, these techniques may be applied and used to specify the performance requirements of the klystron if the desired particle beam current and nominal RF cavity voltage are known View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wake field and the diffraction model due to a flat beam moving past a conducting wedge

    Publication Year: 1995 , Page(s): 3043 - 3045 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    To clean a beam of its excessive tail particles, one often uses a collimator. If the beam intensity is high enough or if the beam is brought too close to the collimator, however, the wake fields generated by the beam-collimator interaction can cause additional beam tails to grow, thus defeating, or even worsening the beamtail cleaning process. The wake field generated by a sheet beam moving past a conducting wedge has been obtained in closed form by Henke (1991) using the method of conformal mapping. This result is applied in the present work to obtain the wake force and the transverse kick received by a test charge moving with the beam. For the beam to be approximated as sheet beams, it is assumed to be flat and the collimator is assumed to have an infinite extent in the flat dimension. We derive an exact expression for the transverse wake force delivered to particles in the beam bunch. Implication of emittance growth as a beam passes closely by a collimator is discussed. We consider two idealized wedge geometries View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Halo of a high-brightness electron beam

    Publication Year: 1995 , Page(s): 3170 - 3172 vol.5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    The experimental study of transverse profile of the ELSA-linac electron beam has been undertaken in order to analyze the mechanisms of halo formation and development in the generation, acceleration and transport of a high-intensity, high-brightness charged-particle beam. Measurements are reported in which the beam profile is observed over four to five decades. They were performed using an imaging technique in which light emitted from an optical transition radiation (OTR) screen placed in the beam path is transported through conventional optics to an intensified video camera. The electron-density distribution is shown to be dependent on the beam current, through space charge effects, initial conditions and transport configuration View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Simulation of beam-beam effects in Tevatron

    Publication Year: 1995 , Page(s): 2886 - 2888 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    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 6×6 to 36×36 and finally to ~100×100 bunches. The beam dynamics of the Tevatron has been studies from the beam-beam effect point of view in a “strong-weak” representation with a single particle being tracked in the presence of the other beam. This paper describes the beam-beam effect in the 6×6 operation of the Tevatron View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Simulation studies of the LAMPF proton linac

    Publication Year: 1995 , Page(s): 3185 - 3187 vol.5
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    The work presented here is an extension of our previous work. We have attempted to do a more complete simulation by including modeling of the low-energy beam transport (LEBT). No measurements of the longitudinal structure of the beam, except phase-scans, are performed at LAMPF. Transverse measurements include slit and collector emittance measurements, and wire scans to determine beam size and centroids. Comparison of simulations to beam loss data suggest that the primary causes of beam spill are incomplete longitudinal capture and the lack of longitudinal matching. Measurements to support these claims are not presently made at LAMPF. However, agreement between measurement and simulation for the transverse beam properties and transmissions serve to benchmark the simulations View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Computation of lattice maps using modular BCH and similarity composition rules [particle accelerators]

    Publication Year: 1995 , Page(s): 2871 - 2873 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    A beam line map construction method for linear and circular high-energy colliders is described which avoids truncated power-series maps through systematic use of a two-term Baker-Campbell-Hausdorff (BCH) formula in combination with similarity transformations. The beam line map ultimately assumes the form of a product of a linear map and a single-exponential Lie-operator map. The method (i) provides insight into map generator sources, (ii) is accurate, (iii) is complete in that all effects, such as edges and soft fringes, mis-alignments and mis-powerings, multipole errors, and input beam errors can be simply included, (iv) permits faster map computation times, and (v) bypasses truncated power-series map methods allowing for higher order, and even non-polynomial generators View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Experimental study of the Duke storage ring dynamic aperture

    Publication Year: 1995 , Page(s): 2877 - 2879 vol.5
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    The Duke storage ring was designed with a large dynamic aperture for UV-VUV free electron laser operations. During commissioning of the Duke storage ring, experiments were performed to measure the horizontal, vertical, and energy apertures. The experimental methods used for the aperture measurements are presented in this paper. The measured results are discussed and compared with the computer simulations View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of parametric resonances on the bunched beam dilution mechanism

    Publication Year: 1995 , Page(s): 3337 - 3339 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    Experimental measurements of bunch dilution resulting from a modulating secondary RF cavity will be discussed. We found that parametric resonances played indeed an important role in the bunch dilution mechanism. The RMS bunch length vs. time did not satisfy the Einstein relation. Thus the bunch dilution may not be explained by a simple diffusion mechanism View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A theoretical study of the electron-proton instability in a long proton pulse

    Publication Year: 1995 , Page(s): 3143 - 3144 vol.5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (180 KB)  

    The electron-proton instability of a long, intense, and partially neutralized proton bunch is studied by numerically solving the equations of motion for the line centroid of the proton beam and the line centroid of the trapped electrons. The formalism takes into account the effects of variable line densities and alternating-gradient (AG) focusing. Good qualitative agreement between the computational results and experimental observations was obtained when applying the theory to the Los Alamos Proton Storage Ring (PSR). Both the case of a clean extraction gap and the case with a few percent of protons in the extraction gap were studied. It is found that with only a few percent neutralization, the PSR beam can become unstable in both cases. The same equations and method were used to study the stability of the proton beam in the accumulator ring of the proposed LANSCE II spallation-neutron source. The results indicate that the e-p instability can also occur in the LANSCE II accumulator ring for only a few percent neutralization View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Microwave instabilities in electron rings with negative momentum compaction factor

    Publication Year: 1995 , Page(s): 3064 - 3066 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    Bunch lengthening (or shortening) caused by the potential well distortion and the microwave instability in electron rings with negative momentum compaction factor is discussed in detail based on the resonator impedance model; further, a comparison with rings of positive momentum compaction factor is given. It was found that the bunch shape is less deformed and the current threshold of the microwave instability is higher in the rings with negative momentum compaction factor over a very wide range of the impedance parameters. The results also show that even within the range where the threshold for positive momentum compaction is higher than that for negative momentum compaction, the bunch lengthening is still less serious in most cases. Finally, an example of bunch lengthening in the case that α<0 with a real wake field of the SLC damping ring (old vacuum chamber) is given in contrast to the case in which α>0 View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The lattice of the CERN Large Hadron Collider

    Publication Year: 1995 , Page(s): 2844 - 2846 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    The lattice of the CERN Large Hadron Collider is designed with 23 regular cells per are, each containing 6 tightly packed 14.2 m long dipoles. This allows to reach 7 TeV per beam with a dipole field of 8.4 Tesla. There are four experimental insertions, two of which are devoted to high luminosity experiments with ±23 m of free space for the detector. The other two experimental insertions are combined with injection. The value of β* at the interaction points is tunable from 6 m at injection to 0.5 m in collision. The energy deposition in the inner triplets is carefully reduced to sustain the nominal luminosity of 1034 cm-2 s-1. Two insertions are devoted to collect the halo particles with large emittance and momentum spread surrounding the beam core: escaping rates of the protons are estimated to be less than 4·106 sec -1 m-1. Finally, one insertion is used to extract the particles in the vertical direction with a minimized deflecting strength View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Operating experience with high beam currents and transient beam loading in the SLC damping rings

    Publication Year: 1995 , Page(s): 3046 - 3048 vol.5
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    During the 1994 SLC run the nominal operating intensity in the damping rings was raised from 3.5×1010 to greater than 4×1010 particles per bunch (ppb). Stricter regulation of rf system parameters was required to maintain stability of the rf system and particle beam. Improvements were made in the feedback loops which control the cavity amplitude and loading angles. Compensation for beam loading was also required to prevent klystron saturation during repetition rate changes. To minimize the effects of transient loading on the rf system, the gain of the direct rf feedback loop and the loading angles were optimized View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A study of the longitudinal coupled bunch instability in the Fermilab Main Ring

    Publication Year: 1995 , Page(s): 3013 - 3015 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    Longitudinal synchrotron oscillations of proton bunches in the Fermilab Main Ring have been observed during various portions of the acceleration cycle. These oscillations have an effect upon the ability to coalesce 11 proton bunches into one bucket for subsequent transfer into the Tevatron. The oscillations appear to be caused by a longitudinal coupled bunch instability. We report measurements made to characterize the instability as well as design of a narrow-band feedback system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The dynamic beta effect in CESR

    Publication Year: 1995 , Page(s): 2889 - 2891 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    The change in beta due to the beam-beam interaction-the `dynamic beta effect'-has been observed in the Cornell Storage Ring CESR by comparing the observed luminosity with the observed vertical beam heights. Under current colliding beam conditions, the resulting changes in horizontal beta around the ring have exceeded Δβx x=0.5 and the horizontal tune shift parameter ξx has exceeded 0.05 View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Advanced photon source insertion device field quality and multipole error specification

    Publication Year: 1995 , Page(s): 3409 - 3411 vol.5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    The Advanced Photon Source (APS) storage ring is a 7-GeV light source with forty straight sections. Intense X-ray beams will be delivered by insertion devices installed in these straight sections. Installation of insertion devices in the APS storage ring produces several effects which can degrade overall performance. Rigid ring performance requirements exist which can be used to set limits on insertion device field quality, i.e. the first- and second-field integrals of the transverse magnetic field. Individual multipole error specifications can be determined by considering the lifetime of the beam. For nominal operation of the APS storage ring, the vertical aperture corresponding to a 10-hour lifetime is approximately 3.35 mm, which limits the level of multipole error. We find that the skew-octupole error has the most significant effect on the reduction of the aperture; the reasons are discussed in this paper View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Damping rate measurements in the SLC damping rings

    Publication Year: 1995 , Page(s): 3073 - 3075 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    The transverse damping rates of the SLC electron and positron damping rings have been measured during the high current physics run at, I=3.5×1010 particles per bunch. The measurements, done over a period of two months, show large fluctuations exceeding the statistical uncertainty of each measurement. The longitudinal damping rate of the positron damping was also measured View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.