A. Valishev

Fermi National Accelerator Laboratory (Fermilab), Batavia, Illinois, United States

Are you A. Valishev?

Claim your profile

Publications (97)143.73 Total impact

  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Beam-beam forces and collision optics can strongly affect beam lifetime, dynamic aperture, and halo formation in particle colliders. Extensive analytical and numerical simulations are carried out in the design and operational stage of a machine to quantify these effects, but experimental data is scarce. The technique of small-step collimator scans was applied to the Fermilab Tevatron collider and to the CERN Large Hadron Collider to study the effect of collisions on transverse beam halo dynamics. We describe the technique and present a summary of the first results on the dependence of the halo diffusion coefficient on betatron amplitude in the Tevatron and in the LHC.
    12/2013;
  • Source
    G. Stancari, A. Valishev, S. M. White
    [show abstract] [hide abstract]
    ABSTRACT: A system for bunch-by-bunch detection of transverse proton and antiproton coherent oscillations in the Fermilab Tevatron collider is described. It is based on the signal from a single beam-position monitor located in a region of the ring with large amplitude functions. The signal is digitized over a large number of turns and Fourier-analyzed offline with a dedicated algorithm. To enhance the signal, band-limited noise is applied to the beam for about 1 s. This excitation does not adversely affect the circulating beams even at high luminosities. The device has a response time of a few seconds, a frequency resolution of $1.6\times 10^{-5}$ in fractional tune, and it is sensitive to oscillation amplitudes of 60 nm. It complements Schottky detectors as a diagnostic tool for tunes, tune spreads, and beam-beam effects. Measurements of coherent mode spectra are presented and compared with models of beam-beam oscillations.
    12/2013;
  • Source
    A. Valishev, G. Stancari
    [show abstract] [hide abstract]
    ABSTRACT: Current wires are considered for compensation of long-range beam-beam interactions for the High Luminosity upgrade (HL-LHC) of the Large Hadron Collider at CERN. In this note, we demonstrate the advantage of using Electron Lens for this purpose instead of a conventional current-bearing wire.
    12/2013;
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: The use of nonlinear lattices with large betatron tune spreads can increase instability and space charge thresholds due to improved Landau damping. Unfortunately, the majority of nonlinear accelerator lattices turn out to be nonintegrable, producing chaotic motion and a complex network of stable and unstable resonances. Recent advances in finding the integrable nonlinear accelerator lattices have led to a proposal to construct at Fermilab a test accelerator with strong nonlinear focusing which avoids resonances and chaotic particle motion. This presentation will outline the main challenges, theoretical design solutions and construction status of the Integrable Optics Test Accelerator underway at Fermilab.
    01/2013;
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Fermilab's Integrable Optics Test Accelerator is an electron storage ring designed for testing advanced accelerator physics concepts, including implementation of nonlinear integrable beam optics and experiments on optical stochastic cooling. The machine is currently under construction at the Advanced Superconducting Test Accelerator facility. In this report we present the goals and the current status of the project, and describe the details of machine design. In particular, we concentrate on numerical simulations setting the requirements on the design and supporting the choice of machine parameters.
    01/2013;
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Experimental measurements of beam halo diffusion dynamics with collimator scans are reviewed. The concept of halo control with a hollow electron beam collimator, its demonstration at the Tevatron, and its possible applications at the LHC are discussed.
    09/2012;
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: The two Tevatron Electron Lenses (TEL1 and TEL2) are installed in Tevatron in 2001 and 2006 respectively. TEL1 is operated as the vital parts of the Tevatron for abort gap beam clearing, while TEL2 is functioning as the backup as well as the test device for beam-beam compensation, space charge compensator and soft beam collimator. Both of them are working exceptionally reliable after a few initial kinks being worked out. Their operations in Tevatron are summarized in this report.
    07/2012;
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: What prevents us from building super-high intensity accelerators? The answer is case-specific, but it often points to one of the following phenomena: machine resonances, various tune shifts (and spreads), and instabilities. These three phenomena are interdependent in all present machines. In this paper we propose a path toward alleviating these phenomena by making accelerators nonlinear. This idea is not new: Orlov (1963) and McMillan (1967) have proposed initial ideas on nonlinear focusing systems for accelerators. However, practical implementations of such ideas proved elusive, until recently.
    07/2012;
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Nonlinear optics is a promising idea potentially opening the path towards achieving super high beam intensities in circular accelerators. Creation of a tune spread reaching 50% of the betatron tune would provide strong Landau damping and make the beam immune to instabilities. Recent theoretical work has identified a possible way to implement stable nonlinear optics by incorporating nonlinear focusing elements into a specially designed machine lattice. In this report we propose the design of a test accelerator for a proof-of-principle experiment. We discuss possible studies at the machine, requirements on the optics stability and sensitivity to imperfections.
    02/2012;
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams.
    02/2012;
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams.
    02/2012;
  • Source
    G. Stancari, A. Valishev, A. Semenov
    [show abstract] [hide abstract]
    ABSTRACT: A system was developed for bunch-by-bunch detection of transverse proton and antiproton coherent oscillations based on the signal from a single beam-position monitor (BPM) located in a region of the ring with large amplitude functions. The signal is digitized over a large number of turns and Fourier-analyzed offline with a dedicated algorithm. To enhance the signal, the beam is excited with band-limited noise for about one second, and this was shown not to significantly affect the circulating beams even at high luminosity. The system is used to measure betatron tunes of individual bunches and to study beam- beam effects. In particular, it is one of the main diagnostic tools in an ongoing study of nonlinear beam-beam compensation studies with Gaussian electron lenses. We present the design and operation of this tool, together with results obtained with proton and antiproton bunches.
    02/2012;
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: High-intensity proton linacs and storage rings are essential for a) state-of-the-art neutron source user facilities, b) extending the high-energy physics intensity frontier, c) as a driver to generate pions for a future neutrino factory or muon collider, and d) for transmutation of radioactive waste and associated energy production. For example, Project X at Fermilab will deliver MW proton beams at energies ranging from 3 to 120 GeV. Nonlinear magnetic lattices with large tune spreads and with integrable, nearly integrable and chaotic dynamics have been proposed to maximize dynamic aperture and minimize particle loss. We present PyORBIT simulations of proton dynamics in such lattices, including the effects of transverse space charge for the first time.
    01/2012;
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Collimation of proton and antiproton beams in the Tevatron collider is required to protect CDF and D0 detectors and minimize their background rates, to keep irradiation of superconducting magnets under control, to maintain long-term operational reliability, and to reduce the impact of beam-induced radiation on the environment. In this article we briefly describe the design, practical implementation and performance of the collider collimation system, methods to control transverse and longitudinal beam halo and two novel collimation techniques tested in the Tevatron.
    Journal of Instrumentation 08/2011; 6(08):T08005. · 1.66 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: A novel concept of controlled halo removal for intense high-energy beams in storage rings and colliders is presented. It is based on the interaction of the circulating beam with a 5-keV, magnetically confined, pulsed hollow electron beam in a 2-m-long section of the ring. The electrons enclose the circulating beam, kicking halo particles transversely and leaving the beam core unperturbed. By acting as a tunable diffusion enhancer and not as a hard aperture limitation, the hollow electron beam collimator extends conventional collimation systems beyond the intensity limits imposed by tolerable losses. The concept was tested experimentally at the Fermilab Tevatron proton-antiproton collider. The first results on the collimation of 980-GeV antiprotons are presented.
    Physical Review Letters 08/2011; 107(8):084802. · 7.94 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: The transverse beam diffusion rate vs. particle oscillation amplitude was measured in the Tevatron using collimator scans. All collimator jaws except one were retracted. As the jaw of interest was moved in small steps, the local shower rates were recorded as a function of time. By using a diffusion model, the time evolution of losses could be related to the diffusion rate at the collimator position. Preliminary results of these measurements are presented.
    01/2011;
  • [show abstract] [hide abstract]
    ABSTRACT: Recent experimental studies at the Fermilab Tevatron collider have shown that magnetically confined hollow electron beams can act as a new kind of collimator for high-intensity beams in storage rings. In a hollow electron beam collimator, electrons enclose the circulating beam. Their electric charge kicks halo particles transversely. If their distribution is axially symmetric, the beam core is unaffected. This device is complementary to conventional two-stage collimation systems: the electron beam can be placed arbitrarily close to the circulating beam; and particle removal is smooth, so that the device is a diffusion enhancer rather than a hard aperture limitation. The concept was tested in the Tevatron collider using a hollow electron gun installed in one of the existing electron lenses. We describe some of the technical aspects of hollow-beam scraping and the results of recent measurements.
    01/2011;
  • Source
    01/2010;
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: The Fermilab Tevatron has been, until 2010, the premier high-energy physics collider in the world. The data collected over the last decade by high-energy physics experiments running at the Tevatron have been analyzed to make important measurements in fundamental areas such as B meson masses and flavor oscillation, searches for the Higgs boson, and supersymmetry. Collecting these data at the limits of detectability has required the Tevatron to operate reliably at high beam intensities to maximize the number of collisions to analyze. This impressive achievement has been assisted by the use of HPC resources and software provided through the SciDAC program. This paper describes the enhancements to the BeamBeam3d code to realistically simulate the Tevatron, the validation of these simulations, and the improvement in equipment reliability and personal safety achieved with the aid of simulations.
    Review of Modern Physics 01/2010; 13(2). · 44.98 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: We present validation and results from a simulation of the Fermilab Tevatron including multiple beam dynamics effects. The essential features of the simulation include a fully 3D strong-strong beam-beam particle-in-cell Poisson solver, interactions among multiple bunches and both head-on and long-range beam-beam collisions, coupled linear optics and helical trajectory consistent with beam orbit measurements, chromaticity and resistive wall impedance. We validate individual physical processes against measured data where possible, and analytic calculations elsewhere. Finally, we present simulations of the effects of increasing beam intensity with single and multiple bunches, and study the combined effect of long-range beam-beam interactions and transverse impedance. The results of the simulations were successfully used in Tevatron operations to support a change of chromaticity during the transition to collider mode optics, leading to a factor of two decrease in proton losses, and thus improved reliability of collider operations. Comment: 29 pages, 19 figures, submitted to Phys. Rev. ST Accel. Beams
    Physical Review Special Topics - Accelerators and Beams 06/2009; · 1.57 Impact Factor

Publication Stats

176 Citations
398 Downloads
143.73 Total Impact Points

Institutions

  • 2005–2009
    • Fermi National Accelerator Laboratory (Fermilab)
      Batavia, Illinois, United States
  • 2004–2005
    • University of Pittsburgh
      Pittsburgh, Pennsylvania, United States
  • 2000–2005
    • Yale University
      • Department of Physics
      New Haven, Connecticut, United States
  • 1998–2005
    • Budker Institute of Nuclear Physics
      Novo-Nikolaevsk, Novosibirsk, Russia
  • 1999–2004
    • Novosibirsk State University
      Novo-Nikolaevsk, Novosibirsk, Russia
  • 2002–2003
    • Russian Academy of Sciences
      Moskva, Moscow, Russia