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Observation of the Exclusive Reaction e^+e^-\ to \phi\eta at \sqrt{s}=10.58 GeV

Description: The authors report the observation of e{sup +}e{sup -} {yields} {phi}{eta} near {radical}s = 10.58 GeV with 6.5 {sigma} significance in the K{sup +}K{sup -}{gamma}{gamma} final state in a data sample of 224 fb{sup -1} collected by the BABAR experiment at the PEP-II e{sup +}e{sup -} storage rings. They measure the restricted radiation-corrected cross section to be {sigma}(e{sup +}e{sup -} {yields} {phi}{eta}) = 2.1 {+-} 0.4(stat) {+-} 0.1(syst) fb within the range |cos{theta}*| < 0.8, where {theta}* is the center-of-mass polar angle of the {phi} meson. The {phi} meson is required to be in the invariant mass range of 1.008 < m{sub {phi}} < 1.035 GeV/c{sup 2}. The radiation corrected cross section in the full cos {theta}* range is extrapolated to be 2.9 {+-} 0.5(stat) {+-} 0.1(syst) fb.
Date: November 17, 2006
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department

The GLAST Background Model

Description: In order to estimate the ability of the GLAST/LAT to reject unwanted background of charged particles, optimize the on-board processing, size the required telemetry and optimize the GLAST orbit, we developed a detailed model of the background particles that would affect the LAT. In addition to the well-known components of the cosmic radiation, we included splash and reentrant components of protons, electrons (e+ and e-) from 10 MeV and beyond as well as the albedo gamma rays produced by cosmic ray interactions with the atmosphere. We made estimates of the irreducible background components produced by positrons and hadrons interacting in the multilayered micrometeorite shield and spacecraft surrounding the LAT and note that because the orbital debris has increased, the shielding required and hence the background are larger than were present in EGRET. Improvements to the model are currently being made to include the east-west effect.
Date: October 17, 2007
Creator: Ormes, J.F.; U., /Denver; Atwood, W.; /UC, Santa Cruz; Burnett, T.; /Washington U., Seattle et al.
Partner: UNT Libraries Government Documents Department

Investigation of Microwave Instability on Electron Storage Ring TLS

Description: With the planned installation of a superconducting rf system, the new operation mode of TLS, the electron storage ring at NSRRC, is expected to double the beam intensity. Several accelerator physics topics need to be examined. Beam instability of single-bunch longitudinal microwave instability is one of these topics. We consider two approaches to measure the effective broad band impedance. We compare these measurement results with each other and to old data [Ref.1]. We calculate the threshold current of microwave instability with a mode-mixing analysis code written by Dr. K. Oide of KEK [Ref.2]. We also develop a multi-particle tracking code to simulate the instability. The results of simulation and measurement are compared and discussed. We conclude that doubling of beam current from 200 mA (1.5 mA/bunch) to 400 mA (3 mA/bunch) will not trigger the microwave instability even without a Landau cavity to lengthen the bunch. The benefit of Landau cavity is mainly for beam life time.
Date: May 17, 2005
Creator: Wang, M.-H. & Chao, A.
Partner: UNT Libraries Government Documents Department

Implications of the Early X-Ray Afterglow Light Curves of Swift GRBs

Description: According to current models, gamma-ray bursts (GRBs) are produced when the energy carried by a relativistic outflow is dissipated and converted into radiation. The efficiency of this process, {epsilon}{sub {gamma}}, is one of the critical factors in any GRB model. The X-ray afterglow light curves of Swift GRBs show an early stage of flattish decay. This has been interpreted as reflecting energy injection. When combined with previous estimates, which have concluded that the kinetic energy of the late ({approx}> 10 hr) afterglow is comparable to the energy emitted in {gamma}-rays, this interpretation implies very high values of {epsilon}{sub {gamma}}, corresponding to {approx}> 90% of the initial energy being converted into {gamma}-rays. Such a high efficiency is hard to reconcile with most models, including in particular the popular internal-shocks model. We re-analyze the derivation of the kinetic energy from the afterglow X-ray flux and re-examine the resulting estimates of the efficiency. We confirm that, if the flattish decay arises from energy injection and the pre-Swift broad-band estimates of the kinetic energy are correct, then {epsilon}{sub {gamma}} {approx}> 0.9. We discuss various issues related to this result, including an alternative interpretation of the light curve in terms of a two-component outflow model, which we apply to the X-ray observations of GRB 050315. We point out, however, that another interpretation of the flattish decay--a variable X-ray afterglow efficiency (e.g., due to a time dependence of afterglow shock microphysical parameters)--is possible. We also show that direct estimates of the kinetic energy from the late X-ray afterglow flux are sensitive to the assumed values of the shock microphysical parameters and suggest that broad-band afterglow fits might have underestimated the kinetic energy (e.g., by overestimating the fraction of electrons that are accelerated to relativistic energies). Either one of these possibilities implies a lower {gamma}-ray efficiency, and ...
Date: January 17, 2006
Creator: Granot, Jonathan; /KIPAC, Menlo Park; Konigl, Arieh; /Chicago U., Astron. Astrophys. Ctr. /Chicago U., EFI; Piran, Tsvi & U., /Hebrew
Partner: UNT Libraries Government Documents Department

Diagnostics for the LCLS Photoinjector Beamline

Description: Two spectrometers have been added to the LCLS photoinjector beamline. The first one will be located close to the exit of the Photoinjector RF gun. With this diagnostic, we will measure beam energy, energy spread (correlated and uncorrelated), possibly deleterious structure in the longitudinal phase space induced by longitudinal space charge force, and slice thermal emittance ... This extensive characterization of the 5MeV electron bunch will be made possible by combining this spectrometer with other diagnostics (YAG screens and Cerenkov Radiator). A second spectrometer located at the end of the beamline has been designed to characterize the 6 dimensional phase space of the 135MeV beam to be injected in the main accelerator. At that second spectrometer station, we will measure energy, energy spread (correlated and uncorrelated), longitudinal phase space, slice emittances ... Those last two measurements require using this spectrometer in combination with the transverse RF deflecting cavity and with the quadrupole scan emittance station. The designs of these two spectrometers have been supported by simulations from MAD and PARMELA.
Date: March 17, 2006
Creator: Limborg-Deprey, C.; Dowell, D.; Schmerge, J.F. & /SLAC
Partner: UNT Libraries Government Documents Department

Evidence for a Canonical GRB Afterglow Light Curve in the Swift/XRT Data

Description: We present new observations of the early X-ray afterglows of the first 27 gamma-ray bursts (GRBs) detected with the Swift X-ray Telescope (XRT). The early X-ray afterglows show a canonical behavior, where the light curve broadly consists of three distinct power law segments: (1) an initial very steep decay ({infinity} t{sup -a} with 3 {approx}< a{sub 1} {approx}< 5) , followed by (2) a very shallow decay (0.2 {approx}< a{sub 2} {approx}< 0.8), and finally (3) a somewhat steeper decay (1 {approx}< a{sub 3} {approx}< 1.5). These power law segments are separated by two corresponding break times, 300 s {approx}< t{sub break,1} {approx}< 500 s and 10{sup 3} s {approx}< t{sub break,2} {approx}< 10{sup 4} s. On top of this canonical behavior of the early X-ray light curve, many events have superimposed X-ray flares, which are most likely caused by internal shocks due to long lasting sporadic activity of the central engine, up to several hours after the GRB. We find that the initial steep decay is consistent with it being the tail of the prompt emission, from photons that are radiated at large angles relative to our line of sight. The first break in the light curve (t{sub break,1}) takes place when the forward shock emission becomes dominant, with the intermediate shallow flux decay (a{sub 2}) likely caused by the continuous energy injection into the external shock. When this energy injection stops, a second break is then observed in the light curve (t{sub break,2}). This energy injection increases the energy of the afterglow shock by at least a factor of f {approx}> 4, and augments the already severe requirements for the efficiency of the prompt gamma-ray emission.
Date: August 17, 2005
Creator: Nousek, J.A.; Kouveliotou, C.; Grupe, D.; Page, K.; Granot, J.; Ramirez-Ruiz, E. et al.
Partner: UNT Libraries Government Documents Department

Beam Characterizations at Femtosecond Electron Beam Facility

Description: The SURIYA project at the Fast Neutron Research Facility (FNRF) has been established and is being commissioning to generate femtosecond (fs) electron bunches. Theses short bunches are produced by a system consisting of an S-band thermionic cathode RF-gun, an alpha magnet (a-magnet) serving as a magnetic bunch compressor, and a SLAC-type linear accelerator (linac). The characteristics of its major components and the beam characterizations as well as the preliminary experimental results will be presented and discussed in this paper.
Date: March 17, 2006
Creator: Rimjaem, S.; Jinamoon, V.; Kangrang, M.; Kusoljariyakul, K.; Saisut, J.; Thongbai, C. et al.
Partner: UNT Libraries Government Documents Department

Analysis of Laser-Driven Particle Acceleration fromPlanar Infinite Conductive Boundaries

Description: This article explores the energy gain for a single relativistic electron from a monochromatic linearly polarized plane wave incident on a planar reflective boundary oriented at an arbitrary oblique angle, and compares the prediction for the energy gain from Inverse Transition Radiation method and the electric field path integral method. It is found that both methods predict the same energy gain regardless of the orientation of the boundary. A brief analysis on partially reflecting surfaces is presented.
Date: February 17, 2006
Creator: Plettner, T. & /Stanford U., Ginzton Lab.
Partner: UNT Libraries Government Documents Department

The B -> pi Form Factor from Light-cone Sum Rules in Soft-collinear Effective Theory

Description: Recently, we have derived light-cone sum rules for exclusive B-meson decays into light energetic hadrons from correlation functions within soft-collinear effective theory [1]. In these sum rules the short-distance scale refers to ''hard-collinear'' interactions with virtualities of order {Lambda}{sub QCD}m{sub b}. Hard scales (related to virtualities of order m{sub b}{sup 2}) are integrated out and enter via external coefficient functions in the sum rule. Soft dynamics is encoded in light-cone distribution amplitudes for the B-meson, which describe both the factorizable and non-factorizable contributions to exclusive B-meson decay amplitudes. Factorization of the correlation function has been verified to one-loop accuracy. Thus, a systematic separation of hard, hard-collinear, and soft dynamics in the heavy-quark limit is possible.
Date: October 17, 2005
Creator: Hurth, Tobias; /SLAC, /CERN; De Fazio, Fulvia; /INFN, Bari; Feldmann, Thorsten & U., /Siegen
Partner: UNT Libraries Government Documents Department

Virialization Heating in Galaxy Formation

Description: In a hierarchical picture of galaxy formation virialization continually transforms gravitational potential energy into kinetic energies in the baryonic and dark matter. For the gaseous component the kinetic, turbulent energy is transformed eventually into internal thermal energy through shocks and viscous dissipation. Traditionally this virialization and shock heating has been assumed to occur instantaneously allowing an estimate of the gas temperature to be derived from the virial temperature defined from the embedding dark matter halo velocity dispersion. As the mass grows the virial temperature of a halo grows. Mass accretion hence can be translated into a heating term. We derive this heating rate from the extended Press Schechter formalism and demonstrate its usefulness in semi-analytical models of galaxy formation. Our method is preferable to the traditional approaches in which heating from mass accretion is only modeled implicitly through an instantaneous change in virial temperature. Our formalism can trivially be applied in all current semi-analytical models as the heating term can be computed directly from the underlying merger trees. Our analytic results for the first cooling halos and the transition from cold to hot accretion are in agreement with numerical simulations.
Date: January 17, 2007
Creator: Wang, P. (KIPAC, Menlo Park) & Abel, T. (Santa Barbara, KITP)
Partner: UNT Libraries Government Documents Department

Wakefields in the LCLS Undulator Transitions

Description: For a short bunch in an elliptical collimator we demonstrate that, as in a purely round collimator, the wake can be estimated from the primary fields of the beam alone. We obtain the wakes in the LCLS rectangular-to-round, undulator transitions using a hybrid method that includes indirect numerical (field) integration and an analytical potential energy term. For the LCLS 1 nC bunch charge configuration, we find the wake-induced energy change in the transitions to be small compared to that due to the resistance of the beam pipe walls.
Date: July 17, 2006
Creator: Bane, K.L.F.; /SLAC; Zagorodov, I. & /DESY
Partner: UNT Libraries Government Documents Department

X-ray Spectroscopy of Cooling Cluster

Description: We review the X-ray spectra of the cores of clusters of galaxies. Recent high resolution X-ray spectroscopic observations have demonstrated a severe deficit of emission at the lowest X-ray temperatures as compared to that expected from simple radiative cooling models. The same observations have provided compelling evidence that the gas in the cores is cooling below half the maximum temperature. We review these results, discuss physical models of cooling clusters, and describe the X-ray instrumentation and analysis techniques used to make these observations. We discuss several viable mechanisms designed to cancel or distort the expected process of X-ray cluster cooling.
Date: January 17, 2006
Creator: Peterson, J.R.; /SLAC; Fabian, A.C. & /Cambridge U., Inst. of Astron.
Partner: UNT Libraries Government Documents Department

XMM-Newton Spectroscopy of the Cluster of Galaxies 2a 0335+096

Description: We present here the results of a deep (130 ks) XMM-Newton observation of the cluster of galaxies 2A 0335+096. The deep exposure allows us to study in detail its temperature structure and its elemental abundances. We fit three different thermal models and find that the multi-temperature wdem model fits our data best. We find that the abundance structure of the cluster is consistent with a scenario where the relative number of Type Ia supernovae contributing to the enrichment of the intra-cluster medium is {approx}25%, while the relative number of core collapse supernovae is {approx}75%. Comparison of the observed abundances to the supernova yields does not allow us to put any constrains on the contribution of Pop III stars to the enrichment of the ICM. Radial abundance profiles show a strong central peak of both Type Ia and core collapse supernova products. Both the temperature and iron abundance maps show an asymmetry in the direction of the elongated morphology of the surface brightness. In particular the temperature map shows a sharp change over a brightness edge on the southern side of the core, which was identified as a cold front in the Chandra data. This suggests that the cluster is in the process of a merger with a subcluster. Moreover, we find that the blobs or filaments discovered in the core of the cluster by Chandra are, contrary to the previous results, colder than the ambient gas and they appear to be in pressure equilibrium with their environment.
Date: January 17, 2006
Creator: Werner, Norbert; /SRON, Utrecht; de Plaa, J.; /SRON, Utrecht /Utrecht U.; Kaastra, J.S.; /SRON, Utrecht et al.
Partner: UNT Libraries Government Documents Department

Properties of Ellipticity Correlation with Atmospheric Structure From Gemini South

Description: Cosmic shear holds great promise for a precision independent measurement of {Omega}{sub m}, the mass density of the universe relative to the critical density. The signal is expected to be weak, so a thorough understanding of systematic effects is crucial. An important systematic effect is the atmosphere: shear power introduced by the atmosphere is larger than the expected signal. Algorithms exist to extract the cosmic shear from the atmospheric component, though a measure of their success applied to a range of seeing conditions is lacking. To gain insight into atmospheric shear, Gemini South imaging in conjunction with ground condition and satellite wind data were obtained. We find that under good seeing conditions Point-Spread-Function (PSF) correlations persist well beyond the separation typical of high-latitude stars. Under these conditions, ellipticity residuals based on a simple PSF interpolation can be reduced to within a factor of a few of the shot-noise induced ellipticity floor. We also find that the ellipticity residuals are highly correlated with wind direction. Finally, we correct stellar shapes using a more sophisticated procedure and generate shear statistics from stars. Under all seeing conditions in our data set the residual correlations lie everywhere below the target signal level. For good seeing we find that the systematic error attributable to atmospheric turbulence is comparable in magnitude to the statistical error (shape noise) over angular scales relevant to present lensing surveys.
Date: January 17, 2007
Creator: Asztalos, Stephen J.; /LLNL, Livermore; de Vries, W.H.; /UC, Davis /LLNL, Livermore; Rosenberg, L.J; Treadway, T. et al.
Partner: UNT Libraries Government Documents Department

Beam Position Monitoring using the HOM-Signals from a Damped and Detuned Accelerating Structure

Description: The Next and Global Linear Collider (NLC/GLC) designs require precision alignment of the beam in the accelerator structures to reduce short range wakefields. The moderately damped and detuned structures themselves provide suitable higher order mode (HOM) signals to measure this alignment. The modes in the lowest dipole band, whose frequencies range from 14-16 GHz, provide the strongest signals. To determine the position resolution they provide, an NLC/GLC prototype structure that was installed in the ASSET facility of the SLAC Linac was instrumented to downmix and digitize these signals. The beam position within the structure was determined by simultaneously measuring the signals at three frequencies (14.3, 15, 15.7 GHz) corresponding to modes localized at the beginning, the middle and the end of the 60 cm long structure. A resolution of 1 micron was achieved even with 28 dB signal attenuation, which is better than the 5 micron resolution required for the NLC/GLC.
Date: May 17, 2005
Creator: Dobert, S; Adolphsen, C.; Jones, R.; Lewandowski, J.; Li, Z.; Pivi, M. et al.
Partner: UNT Libraries Government Documents Department

Beam Matching to a Plasma Wakefield Accelerator Using a Ramped Density Profile at the Plasma Boundary

Description: An important aspect of plasma wake field accelerators (PWFA) is stable propagation of the drive beam. In the under dense plasma regime, the drive beam creates an ion channel which acts on the beam as a strong thick focusing lens. The ion channel causes the beam to undergo multiple betatron oscillations along the length of the plasma. There are several advantages if the beam size can be matched to a constant radius. First, simulations have shown that instabilities such as hosing are reduced when the beam is matched [1]. Second, synchrotron radiation losses are minimized when the beam is matched. Third, an initially matched beam will propagate with no significant change in beam size in spite of large energy loss or gain. Coupling to the plasma with a matched radius can be difficult in some cases. This paper shows how an appropriate density ramp at the plasma entrance can be useful for achieving a matched beam. Additionally, the density ramp is helpful in bringing a misaligned trailing beam onto the drive beam axis. A plasma source with boundary profiles useful for matching has been created for the E-164X PWFA experiments at SLAC.
Date: February 17, 2006
Creator: Marsh, K.A.; Clayton, C.E.; Huang, C.; Johnson, D.K.; Joshi, C.; Lu, W. et al.
Partner: UNT Libraries Government Documents Department

Active Damping of the E-P Instability at the Los Alamos Proton Storage Ring

Description: A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos Proton Storage Ring (PSR). This system was able to improve the instability threshold by approximately 30% (as measured by the change in RF buncher voltage at instability threshold). The feedback system configuration, setup procedures, and optimization of performance are described. Results of several experimental tests of system performance are presented including observations of instability threshold improvement and grow-damp experiments, which yield estimates of instability growth and damping rates. A major effort was undertaken to identify and study several factors limiting system performance. Evidence obtained from these tests suggests that performance of the prototype was limited by higher instability growth rates arising from beam leakage into the gap at lower RF buncher voltage and the onset of instability in the horizontal plane, which had no feedback.
Date: March 17, 2008
Creator: Macek, R.J.; Alamos, /Los; Assadi, S.; Ridge, /Oak; Byrd, J.M.; /LBL, Berkeley et al.
Partner: UNT Libraries Government Documents Department

Optical Phase Locking of Modelocked Lasers for Particle Accelerators

Description: Particle accelerators require precise phase control of the electric field through the entire accelerator structure. Thus a future laser driven particle accelerator will require optical synchronism between the high-peak power laser sources that power the accelerator. The precise laser architecture for a laser driven particle accelerator is not determined yet, however it is clear that the ability to phase-lock independent modelocked oscillators will be of crucial importance. We report the present status on our work to demonstrate long term phaselocking between two modelocked lasers to within one degree of optical phase and describe the optical synchronization techniques that we employ.
Date: February 17, 2006
Creator: Plettner, T.; Sinha, S.; Wisdom, J.; /Stanford U., Phys. Dept.; Colby, E.R. & /SLAC
Partner: UNT Libraries Government Documents Department

Positron Beam Propagation in a Meter Long Plasma Channel

Description: Recent experiments and simulations have shown that positron beams propagating in plasmas can be focused and also create wakes with large accelerating gradients. For similar parameters, the wakes driven by positron beams are somewhat smaller compared to the case of an electron beam. Simulations have shown that the wake amplitude can be increased if the positron beam is propagated in a hollow plasma channel (Ref. 1). This paper, compares experimentally, the propagation and beam dynamics of a positron beam in a meter scale homogeneous plasma, to a positron beam hollow channel plasma. The results show that positron beams in hollow channels are less prone to distortions and deflections. Hollow channels were observed to guide the positron beam onto the channel axis. Beam energy loss was also observed implying the formation of a large wake amplitude. The experiments were carried out as part of the E-162 plasma wakefield experiments at SLAC.
Date: March 17, 2008
Creator: Marsh, K.A.; Blue, B.E.; Clayton, C.E.; Joshi, C.; Mori, W.B.; /UCLA et al.
Partner: UNT Libraries Government Documents Department

General Relativistic Effects in Atom Interferometry

Description: Atom interferometry is now reaching sufficient precision to motivate laboratory tests of general relativity. We begin by explaining the non-relativistic calculation of the phase shift in an atom interferometer and deriving its range of validity. From this we develop a method for calculating the phase shift in general relativity. This formalism is then used to find the relativistic effects in an atom interferometer in a weak gravitational field for application to laboratory tests of general relativity. The potentially testable relativistic effects include the non-linear three-graviton coupling, the gravity of kinetic energy, and the falling of light. We propose experiments, one currently under construction, that could provide a test of the principle of equivalence to 1 part in 10{sup 15} (300 times better than the present limit), and general relativity at the 10% level, with many potential future improvements. We also consider applications to other metrics including the Lense-Thirring effect, the expansion of the universe, and preferred frame and location effects.
Date: March 17, 2008
Creator: Dimopoulos, Savas; /Stanford U., Phys. Dept.; Graham, Peter W.; /SLAC /Stanford U., Phys. Dept.; Hogan, Jason M.; Kasevich, Mark A. et al.
Partner: UNT Libraries Government Documents Department

Fully Coherent X-ray Pulses from a Regenerative Amplifier Free Electron Laser

Description: We propose and analyze a novel regenerative amplifier free electron laser (FEL) to produce fully coherent x-ray pulses. The method makes use of narrow-bandwidth Bragg crystals to form an x-ray feedback loop around a relatively short undulator. Self-amplified spontaneous emission (SASE) from the leading electron bunch in a bunch train is spectrally filtered by the Bragg reflectors and is brought back to the beginning of the undulator to interact repeatedly with subsequent bunches in the bunch train. The FEL interaction with these short bunches not only amplifies the radiation intensity but also broadens its spectrum, allowing for effective transmission of the x-rays outside the crystal bandwidth. The spectral brightness of these x-ray pulses is about two to three orders of magnitude higher than that from a single-pass SASE FEL.
Date: February 17, 2006
Creator: Huang, Zhirong & Ruth, Ronald D.
Partner: UNT Libraries Government Documents Department

First Observations of Laser-Driven Acceleration of Relativistic Electrons in a Semi-Infinite Vacuum Space

Description: We have observed acceleration of relativistic electrons in vacuum driven by a linearly polarized visible laser beam incident on a thin gold-coated reflective boundary. The observed energy modulation effect follows all the characteristics expected for linear acceleration caused by a longitudinal electric field. As predicted by the Lawson-Woodward theorem the laser driven modulation only appears in the presence of the boundary. It shows a linear dependence with the strength of the electric field of the laser beam and also it is critically dependent on the laser polarization. Finally, it appears to follow the expected angular dependence of the inverse transition radiation process. experiment as the Laser Electron Accelerator Project (LEAP).
Date: February 17, 2006
Creator: Plettner, T.; Byer, R.L.; Smith, T.I.; /Stanford U., Phys. Dept.; Colby, E.; Cowan, B. et al.
Partner: UNT Libraries Government Documents Department

Fast Neutron Damage Studies on NdFeB Materials

Description: Many materials and electronics need to be tested for the radiation environment expected at linear colliders (LC) since both accelerator and detectors will be subjected to large fluences of hadrons, leptons and {gamma}'s over the life of the facility [1]. While the linacs will be superconducting, there are still many uses for NdFeB in the damping rings, injection and extraction lines and final focus. Our understanding of the situation for rare earth, permanent magnet materials was presented at PAC03 [2]. Our first measurements of fast neutron, stepped doses at the UC Davis McClellan Nuclear Reactor Center (UCD MNRC) were presented at EPAC04 [3]. We have extended the doses, included other manufacturer's samples, and measured induced radioactivities which are discussed in detail.
Date: May 17, 2005
Creator: Anderson, S.; Spencer, J.; Wolf, Z.; /SLAC; Baldwin, A.; Pellett, D. et al.
Partner: UNT Libraries Government Documents Department

Ion Effects in the Electron Damping Ring of the International Linear Collider

Description: Ion-induced beam instabilities and tune shifts are critical issues for the electron damping ring of the International Linear Collider (ILC). To avoid conventional ion trapping, a long gap is introduced in the electron beam by omitting a number of successive bunches out of a long train. However, the beam can still suffer from the fast ion instability, driven by ions that last only for a single passage of the electron bunches. Our study shows that the ion effects can be significantly mitigated by using multiple gaps, so that the stored beam consists of a number of relatively short bunch trains. The ion effects in the ILC damping rings are investigated using both analytical and numerical methods.
Date: July 17, 2006
Creator: Wang, L.; Raubenheimer, T.; /SLAC; Wolski, A. & U., /Liverpool
Partner: UNT Libraries Government Documents Department