525 Matching Results

Search Results

Advanced search parameters have been applied.

Implications of beam phase and RFSUM measured near transition

Description: A technique using RF bucket reduction for acquiring information about the particle distribution in longitudinal phase space has been applied in the Fermilab Booster. Data sets were obtained at six important time intervals of a Booster cycle for three different beam intensities. Controlled RF bucket reduction also provides other opportunities for beam manipulation.
Date: April 7, 2004
Creator: Yang, Xi & MacLachlan, James
Partner: UNT Libraries Government Documents Department

J/psi Production in Quark-Gluon Plasma

Description: We study J/{psi} production at RHIC and LHC energies with both initial production and regeneration. We solve the coupled set of transport equation for the J/{psi} distribution in phase space and the hydrodynamic equation for evolution of quark-gluon plasma. At RHIC, continuous regeneration is crucial for the J/{psi} momentum distribution while the elliptic flow is still dominated by initial production. At LHC energy, almost all the initially created J/{psi}s are dissociated in the medium and regeneration dominates the J/{psi} properties.
Date: October 30, 2006
Creator: Yan, Li; Zhuang, Pengfei & Xu, Nu
Partner: UNT Libraries Government Documents Department

Real time correlation function in a single phase spaceintegral--beyond the linearized semiclassical initial valuerepresentation

Description: It is shown how quantum mechanical time correlation functions [defined, e.g., in Eq. (1.1)] can be expressed, without approximation, in the same form as the linearized approximation of the semiclassical initial value representation (LSC-IVR), or classical Wigner model, for the correlation function [cf. Eq. (2.1)], i.e., as a phase space average (over initial conditions for trajectories) of the Wigner functions corresponding to the two operators. The difference is that the trajectories involved in the LSC-IVR evolve classically, i.e., according to the classical equations of motion, while in the exact theory they evolve according to generalized equations of motion that are derived here. Approximations to the exact equations of motion are then introduced to achieve practical methods that are applicable to complex (i.e., large) molecular systems. Four such methods are proposed in the paper--the full Wigner dynamics (full WD) and the 2nd order WD based on 'Winger trajectories', and the full Donoso-Martens dynamics (full DMD) and the 2nd order DMD based on 'Donoso-Martens trajectories'--all of which can be viewed as generalizations of the original LSC-IVR method. Numerical tests of these four versions of this new approach are made for two anharmonic model problems, and for each the momentum autocorrelation function (i.e., operators linear in coordinate or momentum operators) and the force autocorrelation function (non-linear operators) have been calculated. These four new approximate treatments are indeed seen to be significant improvements to the original LSC-IVR approximation.
Date: July 10, 2007
Creator: Liu, Jian & Miller, William H.
Partner: UNT Libraries Government Documents Department

Recirculation in multiple wave conversions

Description: A one-dimensional multiple wave-conversion model is constructed that allows energy recirculation in ray phase space. Using a modular eikonal approach, the connection coefficients for this model are calculated by ray phase-space methods. Analytical results (confirmed numerically) show that all connection coefficients exhibit interference effects that depend on an interference phase, calculated from the coupling constants and the area enclosed by the intersecting rays. This conceptual model, which focuses on the topology of intersecting rays in phase space, is used to investigate how mode conversion between primary and secondary waves is modified by the presence of a tertiary wave.
Date: July 30, 2008
Creator: Kaufman, A. N.; Brizard, A.J.; Kaufman, A.N. & Tracy, E.R.
Partner: UNT Libraries Government Documents Department

Phase Space Dissimilarity Measures for Structural Health Monitoring

Description: A novel method for structural health monitoring (SHM), known as the Phase Space Dissimilarity Measures (PSDM) approach, is proposed and developed. The patented PSDM approach has already been developed and demonstrated for a variety of equipment and biomedical applications. Here, we investigate SHM of bridges via analysis of time serial accelerometer measurements. This work has four aspects. The first is algorithm scalability, which was found to scale linearly from one processing core to four cores. Second, the same data are analyzed to determine how the use of the PSDM approach affects sensor placement. We found that a relatively low-density placement sufficiently captures the dynamics of the structure. Third, the same data are analyzed by unique combinations of accelerometer axes (vertical, longitudinal, and lateral with respect to the bridge) to determine how the choice of axes affects the analysis. The vertical axis is found to provide satisfactory SHM data. Fourth, statistical methods were investigated to validate the PSDM approach for this application, yielding statistically significant results.
Date: November 1, 2011
Creator: Bubacz, Jacob A; Chmielewski, Hana T; Pape, Alexander E; Depersio, Andrew J; Hively, Lee M; Abercrombie, Robert K et al.
Partner: UNT Libraries Government Documents Department

Lattice Modeling and Calibration with Turn-by-Turn Orbit Data

Description: A new method that explores turn-by-turn BPM data to calibrate lattice models of accelerators is proposed. The turn-by-turn phase space coordinates at one location of the ring are first established using data from two BPMs separated by a simple section with a known transfer matrix, such as a drift space. The phase space coordinates are then tracked with the model to predict positions at other BPMs, which can be compared to measurements. The model is adjusted to minimize the difference between the measured and predicted orbit data. BPM gains and rolls are included as fitting variables. This technique can be applied to either the entire or a section of the ring. We have tested the method experimentally on a part of the SPEAR3 ring.
Date: April 5, 2011
Creator: Huang, X.; Sebek, J.; Martin, D. & /SLAC
Partner: UNT Libraries Government Documents Department

The velocity peaks in the cold dark matter spectrum on earth

Description: The cold dark matter spectrum on earth is expected to have peaks in velocity space. We obtain estimates for the sizes and locations of these peaks. To this end we have generalized the secondary infall model of galactic halo formation to include angular momentum of the dark matter particles. This new model is still spherically symmetric and it has self-similar solutions. Our results are relevant to direct dark matter search experiments.
Date: April 13, 1995
Creator: Sikivie, P.; Tkachev, I.I. & Wang, Y.
Partner: UNT Libraries Government Documents Department

Betatron motion with coupling of horizontal and vertical degrees of freedom

Description: The Courant-Snyder parameterization of one-dimensional linear betatron motion is generalized to two-dimensional coupled linear motion. To represent the 4 x 4 symplectic transfer matrix the following ten parameters were chosen: four beta-functions, four alpha-functions and two betatron phase advances which have a meaning similar to the Courant-Snyder parameterization. Such a parameterization works equally well for weak and strong coupling and can be useful for analysis of coupled betatron motion in circular accelerators as well as in transfer lines. Similarly, the transfer matrix, the bilinear form describing the phase space ellipsoid and the second order moments are related to the eigen-vectors. Corresponding equations can be useful in interpreting tracking results and experimental data.
Date: November 21, 2002
Creator: Bogacz, S. A. & Lebedev, V. A.
Partner: UNT Libraries Government Documents Department

Hybrid Ray/Wave Optics for Laser-Plasma Interaction

Description: This aim of this FY 1998 LDRD project was to create a computational tool which bridges the gap between wave and ray optical regimes, important for application areas such as laser propagation in plasma and multimode photonics. We used phase space methods, where a set of rays distributed in a particular way in position and angle retain many essential features of wave optics. To characterize and enhance our understanding of the method, we developed a GUI-based photonics tool which can analyze light propagation in systems with a variety of axial and transverse refractive index distributions.
Date: February 18, 1999
Creator: Ratowsky, R.P.; Kallman, J.S.; Afeyan, B.B. & Feit, M.D.
Partner: UNT Libraries Government Documents Department


Description: In recent years, longitudinal phase-space tomography has become a useful diagnostic tool in the domain of particle accelerators. A computer code has been developed to visualize and quantify dynamic effects in longitudinal phase space, like transition crossing and rebucketing. This code is capable of reconstructing the longitudinal phase space distribution during turn-by-turn parameter changes such as RF phase and voltage jumps. This paper describes the reconstruction code as well as recent applications at the Relativistic Heavy Ion Collider (RHIC).
Date: June 2, 2002
Partner: UNT Libraries Government Documents Department

Gyrokinetics Simulation of Energetic Particle Turbulence and Transport

Description: Progress in research during this year elucidated the physics of precession resonance and its interaction with radial scattering to form phase space density granulations. Momentum theorems for drift wave-zonal flow systems involving precession resonance were derived. These are directly generalizable to energetic particle modes. A novel nonlinear, subcritical growth mechanism was identified, which has now been verified by simulation. These results strengthen the foundation of our understanding of transport in burning plasmas
Date: September 21, 2011
Creator: Diamond, Patrick H.
Partner: UNT Libraries Government Documents Department

High precision measurements of the neutron spin structure in Hall A at Jlab

Description: Conclusions of this presentation are: (1) JLab energy upgrade will offer new exciting opportunities to study the nucleon (spin) structure such as high precision, unexplored phase space, flavor decomposition; (2) Large technological efforts is in progress to optimally exploit these opportunities; (3) HallA will be the first hall to get the new beam, first experiment expected to run in 2014; (4) A1n likely one of the first experiments to take data in the new 12 GeV era; and (5) SIDIS exp. will follow in couple of years.
Date: April 1, 2012
Creator: Annand, R M; Cates, G; Cisbani, E; Franklin, G B; Liyanage, N; Puckett, A et al.
Partner: UNT Libraries Government Documents Department

CSR Interaction for a 2D Energy-Chirped Bunch on a General Orbit

Description: When an electron bunch with initial linear energy chirp traverses a bunch compression chicane, the bunch interacts with itself via coherent synchrotron radiation (CSR) and space charge force. The effective longitudinal CSR force for such kind of 2D bunch on a circular orbit has been analyzed earlier [1]. In this paper, we present the analytical results of the effective longitudinal CSR force for a 2D energy-chirped bunch going through a general orbit, which includes the entrance and exit of a circular orbit. In particular, we will show the behavior of the force in the last bend of a chicane when the bunch is under extreme compression. This is the condition when bifurcation of bunch phase space occurs in many CSR measurements. [1] R. Li, Phys. Rev. ST Accel. Beams 11, 024401 (2008)
Date: May 1, 2009
Creator: Li, Rui
Partner: UNT Libraries Government Documents Department


Description: Detailed examination of computed particle trajectories has revealed a complexity and disorder that is of increasing interest to accelerator specialists. To introduce this topic, the author would like you to consider for a moment the analysis of synchrotron oscillations for a particle in a coasting beam, regarded as a problem in one degree of freedom. A simple analysis replaces the electric field of the RF-v cavity system by a traveling wave, having the speed of a synchronous reference particle, and leads to a pair of differential equations of the form dy/dn = -K sin {pi}x, (1A) where y measures the fractional departure of energy from the reference value {pi}x measures the electrical phase angle at which the particle traverses the cavity, and K is proportional to the cavity voltage; and dx/dn = {lambda}{prime}y, (1b) in which {lambda}{prime} is proportional to the change of revolution period with respect to particle energy. It will be recognized that these equations can be derived from a Hamiltonian function H = (1/2){lambda}{prime}y{sup 2}-(K/{pi})cos {pi}x. (2) Because this Hamiltonian function does not contain the independent variable explicitly, it will constitute a constant of the motion and possible trajectories in the x,y phase space will be just the curves defined by H = Constant, namely the familiar simple curves in phase space that are characteristic of a physical (non-linear) pendulum.
Date: May 1, 1974
Creator: Laslett, L. Jackson.
Partner: UNT Libraries Government Documents Department

Alternative approach to general coupled linear optics

Description: The Twiss parameters provide a convenient description of beam optics in uncoupled linear beamlines. For coupled beamlines, a variety of approaches are possible for describing the linear optics; here, we propose an approach and notation that naturally generalizes the familiar Twiss parameters to the coupled case in three degrees of freedom. Our approach is based on an eigensystem analysis of the matrix of second-order beam moments, or alternatively (in the case of a storage ring) on an eigensystem analysis of the linear single-turn map. The lattice functions that emerge from this approach have an interpretation that is conceptually very simple: in particular, the lattice functions directly relate the beam distribution in phase space to the invariant emittances. To emphasize the physical significance of the coupled lattice functions, we develop the theory from first principles, using only the assumption of linear symplectic transport. We also give some examples of the application of this approach, demonstrating its advantages of conceptual and notational simplicity.
Date: November 29, 2005
Creator: Wolski, Andrzej
Partner: UNT Libraries Government Documents Department

Charge Separation for Muon Collider Cooling

Description: Most schemes for six dimensional muon ionization cooling work for only one sign. It is then necessary to have charge separation prior to that cooling. Schemes of charge separation using bent solenoids are described, and their simulated performances reported. It is found that for efficient separation, it should take place at somewhat higher momenta than commonly used for the cooling. Charge separation using bent solenoids can be effective if carefully designed. Bent solenoids can generate dispersion from 'momentum drift', but can spoil emittance from 'amplitude drift'. Abrupt entry into a bent solenoid causes emittance growth, but matching using integral {lambda} lengths, or Norem's method, corrects this problem. Reverse bending removes the dispersion and reduces 'amplitude drift', but only if there is no rf until after all bending. The main problem is bunch lengthening and distortion from the long transports without rf. At 230 MeV/c, even with a higher field of 3 T, non-linearities increase the 6D emittance by 117% and give 13% loss, which is not acceptable. Raising the momentum from 230 to 300 MeV gives a 6D emittance growth of 38% and the loss 5%, which may be acceptable. Raising the momentum further to 400 MeV/c gives very good results: 6D growth of 24% and 2.5% loss. Further optimization should include the acceleration to the higher momenta prior to the separation, and the higher momentum cooling immediately after it. The longitudinal phase space prior to the separation should be rotated to minimize the total bunch lengthening.
Date: March 28, 2011
Creator: Palmer, R.B.; Fernow & R.C.
Partner: UNT Libraries Government Documents Department

Subpicosecond electron bunch train production using a phase-space exchange technique

Description: Our recent experimental demonstration of a photoinjector electron bunch train with sub-picosecond structures is reported in this paper. The experiment is accomplished by converting an initially horizontal beam intensity modulation into a longitudinal phase space modulation, via a beamline capable of exchanging phase-space coordinates between the horizontal and longitudinal degrees of freedom. The initial transverse modulation is produced by intercepting the beam with a multislit mask prior to the exchange. We also compare our experimental results with numerical simulations.
Date: March 1, 2011
Creator: Sun, Y.-E.; /Fermilab; Piot, P.; U., /Fermilab /Northern Illinois; Johnson, A.S.; Lumpkin, A.H. et al.
Partner: UNT Libraries Government Documents Department

Transverse-to-longitudinal Emittance-exchange with an Energy Chirped Beam

Description: Emittance exchange has been proposed to increase the performance of free electron lasers by tailoring the phase space of an electron beam. The principle of emittance exchange - where the transverse phase space of the electron beam is exchanged with the longitudinal phase space - has been demonstrated recently at the A0 photoinjector. The experiment used a low charge bunch (250 pC) with no energy chirp. Theory predicts an improvement in the emittance exchange scheme when the incoming beam has an energy chirp imparted on it. The energy chirp helps to overcome the thick lens effect of the deflecting mode cavity and other second order effects that might lead to an incomplete emittance exchange at higher charges. In this work, we report experimental and simulation results from operating the emittance exchange beam line using an energy chirped beam with higher charge (500 pC) at different RF-chirp settings.
Date: May 1, 2012
Creator: Thangaraj, J.; Ruan, J.; Johnson, A.S.; Thurman-Keup, R.; Lumpkin, A.H.; Santucci, J. et al.
Partner: UNT Libraries Government Documents Department

First observation of the exchange of transverse and longitudinal emittances

Description: An experimental program to demonstrate a novel phase space manipulation in which the horizontal and longitudinal emittances of a particle beam are exchanged has been completed at the Fermilab A0 Photoinjector. A new beamline, consisting of a TM{sub 110} deflecting mode cavity flanked by two horizontally dispersive doglegs has been installed. We report on the first direct observation of transverse and longitudinal emittance exchange: {l_brace}{var_epsilon}{sub x}{sup n}, {var_epsilon}{sub y}{sup n}, {var_epsilon}{sub z}{sup n}{r_brace} = {l_brace} 2.9 {+-} 0.1, 2.4 {+-} 0.1, 13.1 {+-} 1.3{r_brace} {yields} {l_brace}11.3 {+-} 1.1, 2.9 {+-} 0.5, 3.1 {+-} 0.3{r_brace} mm-mrad.
Date: February 1, 2011
Creator: Ruan, J.; Johnson, A.S.; Lumpkin, A.H.; Thurman-Keup, R.; Edwards, H.; Fliller, R.P. et al.
Partner: UNT Libraries Government Documents Department