arXiv subjects

P. L. Colestock

Publications and source records attributed to P. L. Colestock.

6 recordsLinked to original sources

arXiv2000

Electro-Optic Sampling of Transient Fields from the passage of High-Charge Electron Bunches

When a relativistic electron bunch traverses a structure, strong electric fields are induced in its wake. We present measurements of the electric field as a function of time as measured at a fixed location in the beam line. For a 12 nC bunch of duration 4.2 ps FWHM, the peak field is measured >0.5 MV/m. Time resolution of ~5 ps is achieved using electro-optic sampling with a lithium tantalate (LiTaO_3) crystal and a short-pulse infrared laser synchronized to the beam. We present measurements under several different experimental conditions and discuss the influence of mode excitation in the structure.

physics.acc-ph↗

arXiv2000

The Beam Halo Experiment at the LEDA Facility

Due to the potentially adverse effects of the generation of halo particles in intense proton beams, it is imperative to have a clear understanding of the mechanisms that can lead to halo formation for current and proposed high- intensity linacs. To this end a theoretical model has been developed, which indicates that protons under the combined influence of strong space charge forces and periodic focussing in a linear transport channel can be kicked into halo orbits. However, no experimental measurements of beam halo in proton beams have yet been carried out. In this paper we report the progress of an effort to carry out an experiment to measure beam-halo using the existing high- intensity proton beam of the LEDA facility. A linear transport channel has been assembled with the appropriate diagnostics for measuring the expected small beam component in the beam halo as a function of beam parameters. The experiment is based on the use of an array of high-dynamic-range wire and beam scrapers to determine the halo and core profiles along the transport channel. Details of the experimental design, the expected halo measurement properties will be presented.

physics.acc-ph↗

arXiv1999

A Search for Disoriented Chiral Condensate at the Fermilab Tevatron

We present results from MiniMax (Fermilab T-864), a small test/experiment at the Tevatron designed to search for the production of disoriented chiral condensate (DCC) in $p - \bar p$ collisions at $\sqrt{s} = 1.8$ TeV in the forward direction, $\sim 3.4 < η< \sim 4.2$. Data, consisting of $1.3 \times 10^6$ events, are analyzed using the robust observables developed in an earlier paper. The results are consistent with generic, binomial-distribution partition of pions into charged and neutral species. Limits on DCC production in various models are presented.

hep-ex↗

arXiv1998

Coherent Nonlinear Phenomena in High Energy Synchrotrons: Observations and Theoretical Models

Nonlinear waves have been observed in synchrotrons for years but have received little attention in the literature. While pathological, these phenomena are worth studying on at least two accounts. First, the formation of solitary waves may lead to droplet formation that causes significant beam halo to develop. Secondly, a variety of nonlinear processes are likely involved in the normal saturation of unstable oscillations, leading to the possibility that low-level, but potentially broadband fluctuation spectra may develop. Both features carry indirectly the signature of the machine impedance. In this work we review a number of observations of nonlinear longitudinal waves made in Fermilab accelerators, and make a first attempt to develop appropriate theoretical models to explain these observations.

physics.acc-ph↗

arXiv1998

Solitary Waves on a Coasting High-Energy Stored Beam

In this work we derive evolution equations for the nonlinear behavior of a coasting beam under the influence of a resonator impedance. Using a renormalization group approach we find a set of coupled nonlinear equations for the beam density and the resonator voltage. Under certain conditions, these may be analytically solved yielding solitary wave behavior, even in the presence of significant dissipation in the resonator. We find long-lived perturbations, i.e. droplets, which separate from the beam and decelerate towards a quasi-equilibrium state, in good agreement with simulation results.

physics.acc-ph↗

arXiv1996

Preliminary Results from a Search for Disoriented Chiral Condensates at MiniMax

We report on the progress of a search for disoriented chiral condensates (DCCs) in the far forward region at sqrt(s)=1.8 TeV. MiniMax is a small collider experiment situated at the C0 interaction region of the Tevatron and has been designed to measure the ratio of charged to neutral pions produced at eta near 4.1. The distribution of this ratio is expected to be very different for the generic binomial and DCC particle production models. We present a method used for the search using the factorial moments of particle generating functions, which can be extracted directly from the data. A preliminary comparison of robust ratios of measured values and those expected from the different models is also presented.

hep-ex↗