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Observation of B0 -> chi_c0 K*0 and Evidence of B+ -> chi_c0 K*+

Description: The authors present the observation of the decay B{sup 0} {yields} {chi}{sub c0}K*{sup 0} as well as evidence of B{sup +} {yields} {chi}{sub c0}K*{sup +}, with an 8.9 and a 3.6 standard deviation significance, respectively, using a data sample of 454 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II B meson factory located at the Standard Linear Accelerator Center (SLAC). The measured branching fractions are: {Beta}(B{sup 0} {yields} {chi}{sub c0}K*{sup 0}) = (1.7 {+-} 0.3 {+-} 0.2) x 10{sup -4} and {Beta}(B{sup +} {yields} {chi}{sub c0}K*{sup +}) = (1.4 {+-} 0.5 {+-} 0.2) x 10{sup -4}, where the first quoted errors are statistical and the second are systematic. They obtain a branching fraction upper limit of {Beta}(B{sup +} {yields} {chi}{sub c0}K*{sup +}) < 2.1 x 10{sup -4} at the 90% confidence level.
Date: August 13, 2008
Creator: Aubert, : B.
Partner: UNT Libraries Government Documents Department

Hosing Instability in the Blow-Out Regime for Plasma-Wakefield Acceleration

Description: The electron hosing instability in the blow-out regime of plasma-wakefield acceleration is investigated using a linear perturbation theory about the electron blow-out trajectory in Lu et al. [in Phys. Rev. Lett. 96, 165002 (2006)]. The growth of the instability is found to be affected by the beam parameters unlike in the standard theory Whittum et al. [Phys. Rev. Lett. 67, 991 (1991)] which is strictly valid for preformed channels. Particle-in-cell simulations agree with this new theory, which predicts less hosing growth than found by the hosing theory of Whittum et al.
Date: February 13, 2008
Creator: Huang, C.; Lu, W.; Zhou, M.; Clayton, C.E.; Joshi, C.; Mori, W.B. et al.
Partner: UNT Libraries Government Documents Department

Intelligent Detector Design

Description: At a future e+e- linear collider, precision measurements of jets will be required in order to understand physics at and beyond the electroweak scale. Calorimetry will be used with other detectors in an optimal way to reconstruct particle 4-vectors with unprecedented precision. This Particle Flow Algorithm (PFA) approach is seen as the best way to achieve particle mass resolutions from dijet measurements in the range of {approx} 30%/{radical}E, resulting in innovative methods for choosing the calorimeter technology and optimizing the detector design.
Date: February 13, 2007
Creator: Graf, N.; Cassell, R.; Johnson, T.; McCormick, J.; /SLAC; Magill, S. et al.
Partner: UNT Libraries Government Documents Department

Evidence for D(0)-Dbar(0) Mixing

Description: We present evidence for D{sup 0}-{bar D}{sup 0} mixing in D{sup 0} {yields} K{sup +}{pi}{sup -} decays from 384 fb{sup -1} of e{sup +}e{sup -} colliding-beam data recorded near {radical}s = 10.6GeV with the BABAR detector at the PEP-II storage rings at SLAC. We find the mixing parameters x{prime}{sup 2} = [-0.22 {+-} 0.30 (stat.) {+-} 0.21 (syst.)] x 10{sup -3} and y{prime} = [9.7 {+-} 4.4(stat.) {+-} 3.1(syst.)] x 10{sup -3}, and a correlation between them of -0.94. This result is inconsistent with the no-mixing hypothesis with a significance of 3.9 standard deviations. We measure R{sub D}, the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates, to be [0.303 {+-} 0.016 (stat.) {+-} 0.010 (syst.)]%. We find no evidence for CP violation.
Date: March 13, 2007
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department

Failure Scenarios and Mitigations and for the BaBar Superconducting Solenoid

Description: The cryogenic department at the Stanford Linear Accelerator Center is responsible for the operation, troubleshooting, and upgrade of the 1.5 Tesla superconducting solenoid detector for the BABAR B-factory experiment. Events that disable the detector are rare but significantly impact the availability of the detector for physics research. As a result, a number of systems and procedures have been developed over time to minimize the downtime of the detector, for example improved control systems, improved and automatic backup systems, and spares for all major components. Together they can prevent or mitigate many of the failures experienced by the utilities, mechanical systems, controls and instrumentation. In this paper we describe various failure scenarios, their effect on the detector, and the modifications made to mitigate the effects of the failure. As a result of these modifications the reliability of the detector has increased significantly with only 3 shutdowns of the detector due to cryogenics systems over the last 2 years.
Date: December 13, 2005
Creator: Thompson, EunJoo; Candia, A.; Craddock, W.W.; Racine, M.; Weisend, J.G., II & /SLAC
Partner: UNT Libraries Government Documents Department

Faint Radio Sources in the NOAO Bootes Field. VLBA Imaging And Optical Identifications

Description: As a step toward investigating the parsec-scale properties of faint extragalactic radio sources, the Very Long Baseline Array (VLBA) was used at 5.0 GHz to obtain phase-referenced images of 76 sources in the NOAO Booetes field. These 76 sources were selected from the FIRST catalog to have peak flux densities above 10 mJy at 5'' resolution and deconvolved major diameters of less than 3'' at 1.4 GHz. Fifty-five of these faint radio sources were identified with accretion-powered radio galaxies and quasars brighter than 25.5 mag in the optical I band. On VLA scales at 1.4 GHz, a measure of the compactness of the faint sources (the ratio of the peak flux density from FIRST to the integrated flux density from the NVSS catalog) spans the full range of possibilities arising from source-resolution effects. Thirty of the faint radio sources, or 39{sub -7}{sup +9}%, were detected with the VLBA at 5.0 GHz with peak flux densities above 6 {sigma} {approx} 2 mJy at 2 mas resolution. The VLBA detections occur through the full range of compactness ratios. The stronger VLBA detections can themselves serve as phase-reference calibrators, boding well for opening up much of the radio sky to VLBA imaging. For the adopted cosmology, the VLBA resolution corresponds to 17 pc or finer. Most VLBA detections are unresolved or slightly resolved but one is diffuse and five show either double or core-jet structures; the properties of these latter six are discussed in detail. Eight VLBA detections are unidentified and fainter than 25.5 mag in the optical I band; their properties are highlighted because they likely mark optically-obscured active nuclei at high redshift.
Date: June 13, 2005
Creator: Wrobel, J.M.; /NRAO, Socorro; Taylor, Greg B.; /NRAO, Socorro /KIPAC, Menlo Park; Rector, T.A.; /NRAO, Socorro /Alaska U. et al.
Partner: UNT Libraries Government Documents Department

Analysis of KEK-ATF Optics And Coupling Using Orbit Response Matrix Analysis

Description: LOCO is a code for analysis of the linear optics in a storage ring based on the closed orbit response to steering magnets. The analysis provides information on focusing errors, BPM gain and rotation errors, and local coupling. Here, we report the results of an application of LOCO to the KEK-ATF. Although the analysis appears to have provided useful information on the optics of the machine, it appears that one of the main aims of the study--to reduce the vertical emittance by correcting the local coupling--was not successful, and we discuss some possible reasons for this.
Date: October 13, 2006
Creator: Wolski, A.; /LBL, Berkeley; Nelson, J.; Ross, M.; Woodley, M.; /SLAC et al.
Partner: UNT Libraries Government Documents Department

Chrysolcolla Redefined as Spertiniite

Description: XAFS and {mu}-XAFS spectra were collected at the Cu K-edge for seven chrysocolla samples (Peru, USA, and Congo). The results suggest that the local structure around Cu is similar to that in Cu(OH){sub 2} (spertiniite). Cu-L{sub 3} STXM imaging and spectroscopy confirm that the chrysocolla samples examined here consist of mesoscopic Cu(II)-rich domains surrounded by Si-rich domains (in agreement with results from infra-red spectroscopy). Hence, we suggest that chrysocolla, which is generally considered to be orthorhombic with composition (Cu,Al){sub 2}H{sub 2}Si{sub 2}O{sub 5}(OH){sub 4} {center_dot} nH{sub 2}O, is in actually a mesoscopic assemblage composed dominantly of spertiniite (Cu(OH){sub 2}), water and amorphous silica (SiO{sub 2}).
Date: December 13, 2006
Creator: Farges, Francois; /Museum Nat. Hist., Paris /Stanford U., Geo. Environ. Sci.; Benzerara, Karim; /Paris U., VI-VII, LMCP; Brown, Gordon E., Jr. & /Stanford U., Geo. Environ. Sci. /SLAC, SSRL
Partner: UNT Libraries Government Documents Department

Unexpected Cancellations in Gravity Theories

Description: Recent computations of scattering amplitudes show that N = 8 supergravity is surprisingly well behaved in the ultraviolet and may even be ultraviolet finite in perturbation theory. The novel cancellations necessary for ultraviolet finiteness first appear at one loop in the guise of the ''no-triangle hypothesis''. We study one-loop amplitudes in pure Einstein gravity and point out the existence of cancellations similar to those found previously in N = 8 supergravity. These cancellations go beyond those found in the one-loop effective action. Using unitarity, this suggests that generic theories of quantum gravity based on the Einstein-Hilbert action may be better behaved in the ultraviolet at higher loops than suggested by naive power counting, though without additional (supersymmetric) cancellations they diverge. We comment on future studies that should be performed to support this proposal.
Date: July 13, 2007
Creator: Bern, Z.; Carrasco, J.J.; /UCLA; Forde, D.; /SLAC, /UCLA; Ita, H. et al.
Partner: UNT Libraries Government Documents Department

Accelerator Structure Bead Pull Measurement at SLAC

Description: Microwave measurement and tuning of accelerator structures are important issues for the current and next generation of high energy physics machines. Application of these measurements both before and after high power processing can reveal information about the structure but may be misinterpreted if measurement conditions are not carefully controlled. For this reason extensive studies to characterize the microwave measurements have been made at SLAC. For the bead pull a reproducible measurement of less than 1 degree of phase accuracy in total phase drift is needed in order to resolve issues such as phase changes due to structure damage during high power testing. Factors contributing to measurement errors include temperature drift, mechanical vibration, and limitations of measurement equipment such as the network analyzer. Results of this continuing effort will be presented.
Date: May 13, 2005
Creator: Lewandowski, J.R.; Bowden, G.; Miller, R.H.; Wang, J.W. & /SLAC
Partner: UNT Libraries Government Documents Department

A 3D Parallel Beam Dynamics Code for Modeling High Brightness Beams in Photoinjectors

Description: In this paper we report on IMPACT-T, a 3D beam dynamics code for modeling high brightness beams in photoinjectors and rf linacs. IMPACT-T is one of the few codes used in the photoinjector community that has a parallel implementation, making it very useful for high statistics simulations of beam halos and beam diagnostics. It has a comprehensive set of beamline elements, and furthermore allows arbitrary overlap of their fields. It is unique in its use of space-charge solvers based on an integrated Green function to efficiently and accurately treat beams with large aspect ratio, and a shifted Green function to efficiently treat image charge effects of a cathode. It is also unique in its inclusion of energy binning in the space-charge calculation to model beams with large energy spread. Together, all these features make IMPACT-T a powerful and versatile tool for modeling beams in photoinjectors and other systems. In this paper we describe the code features and present results of IMPACT-T simulations of the LCLS photoinjectors. We also include a comparison of IMPACT-T and PARMELA results.
Date: February 13, 2006
Creator: Qiang, Ji; Lidia, S.; Ryne, R.D.; /LBL, Berkeley; Limborg, C. & /SLAC
Partner: UNT Libraries Government Documents Department

The work function of sub-monolayer cesium-covered gold: A photoelectronspectroscopy study

Description: Using visible and X-ray photoelectron spectroscopy we measured the work function of a Au(111) surface at a well-defined sub-monolayer coverage of Cs. For a Cs coverage producing a photoemission maximum with a He-Ne laser, the work function is 1.61 {+-} 0.08 eV consistent with previous assumptions used to analyze vibrationally promoted electron emission. A discussion of possible Cs layer structures is also presented.
Date: June 13, 2008
Creator: LaRue, J.L.; White, J.D.; Nahler, N.H.; Liu, Z.; Sun, Y.; Pianetta, P.A. et al.
Partner: UNT Libraries Government Documents Department

Analysis of D0 -> K+ pi- pi0 Decays: Search for D0-D0bar Mixing, and Measurements of the Doubly Cabibbo-Suppressed Decay Rate and Resonance Contributions

Description: Analyzing D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} decays, herein are presented the methods and results of a search for D{sup 0}-{bar D}{sup 0} mixing, a measurement of the branching ratio R {equivalent_to} {Lambda}(D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0})/{Lambda}(D{sup 0} {yields} K{sup -}{pi}{sup +}{pi}{sup 0}), and measurements of the contributions from D{sup 0} {yields} K{sup +}{rho}{sup -}, K*{sup +}{pi}{sup -}, K*{sup 0}{pi}{sup 0}; 230.4 fb{sup -1} of data collected from the BABAR detector at the PEP-II collider during 2000-2004 (Runs 1-4) are analyzed. An event-level tagging technique is developed, which facilitates the accurate determination of doubly Cabibbo-suppressed resonance contributions by suppressing background from Cabibbo-favored decays. The branching ratio is measured as R = (0.214 {+-} 0.008 (stat) {+-} 0.008 (syst))%, with (46.1 {+-} 3.3 (stat) {+-} 2.9 (syst))% of D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} decays proceeding through the channel D{sup 0} {yields} K*{sup +}{pi}{sup -}. The data are consistent with the null-D-mixing hypothesis at a confidence level of 10%, and the expected value of {+-} {radical}(x{sup 2} + y{sup 2}) is measured as -0.013 {+-} 0.010 (stat), indicating negative interference between mixing and doubly Cabibbo-suppressed decay. The expected value of the integrated mixing rate is (x{sup 2} + y{sup 2})/2 = (0.013 {+-} 0.013 (stat))%.
Date: December 13, 2005
Creator: Wilson, Michael Galante
Partner: UNT Libraries Government Documents Department

Hadron Spectroscopy and Wavefunctions in QCD and the AdS/CFT Correspondence

Description: The AdS/CFT correspondence has led to important insights into the properties of quantum chromodynamics even though QCD is a broken conformal theory. We have recently shown how a holographic model based on a truncated AdS space can be used to obtain the hadronic spectrum of light q{bar q}, qqq and gg bound states. Specific hadrons are identified by the correspondence of string modes with the dimension of the interpolating operator of the hadron's valence Fock state, including orbital angular momentum excitations. The predicted mass spectrum is linear M {proportional_to} L at high orbital angular momentum, in contrast to the quadratic dependence M{sup 2} {proportional_to} L found in the description of spinning strings. Since only one parameter, the QCD scale LQCD, is introduced, the agreement with the pattern of physical states is remarkable. In particular, the ratio of D to nucleon trajectories is determined by the ratio of zeros of Bessel functions. The light-front quantization of gauge theories in light-cone gauge provides a frame-independent wavefunction representation of relativistic bound states, simple forms for current matrix elements, explicit unitarity, and a trivial vacuum. The light-front Fock-state wavefunctions encode the bound state properties of hadrons in terms of their quark and gluon degrees of freedom at the amplitude level. One can also use the extended AdS/CFT space-time theory to obtain a model for hadronic light-front wavefunctions, thus providing a relativistic description of hadrons in QCD at the amplitude level. The model wavefunctions display confinement at large inter-quark separation and conformal symmetry at short distances. In particular, the scaling and conformal properties of the LFWFs at high relative momenta agree with perturbative QCD. These AdS/CFT model wavefunctions could be used as an initial ansatz for a variational treatment of the light-front QCD Hamiltonian. We also show how hadron form factors in both the space-like ...
Date: October 13, 2005
Creator: Brodsky, Stanley J.; de Teramond, Guy F. & U., /SLAC /Costa Rica
Partner: UNT Libraries Government Documents Department

MAXI and GLAST Studies of Jets in Active Galaxies

Description: The recent launch of GLAST--coinciding with the MAXI workshop--opens a new era for studies of jet-dominated active galaxies, known as blazars. While the emission processes operating in various spectral bands in blazars are reasonably well understood, the knowledge of the details of the structure of the jet, location of the dissipation region with respect to the accreting black hole, and coupling of the jet to the accretion process are known only at a rudimentary level. Blazars are variable, and this provides an opportunity to use the variability in various bands--and in particular, the relationship of respective time series to each other--to explore the relative location of regions responsible for emission in the respective bands. Observationally, this requires well-sampled time series in as many spectral bands as possible. To this end, with its all-sky, sensitive monitoring capability, the recently launched GLAST, and MAXI, to be deployed in 2009, are the most promising instruments bound to provide good sampling in respectively the energetic gamma-ray, and the soft X-ray band. This paper highlights the inferences regarding blazar jets that can be gleaned from such joint observations.
Date: October 13, 2008
Creator: Madejski, Greg; Kataoka, Jun & Sikora, Marek
Partner: UNT Libraries Government Documents Department

Measurement of \mathcal{B}(\tau^{-}\-->\bar{K^{0}}\pi^{-}\nu_{\tau}) Using the \babar Detector

Description: A preliminary measurement of the branching fraction {Beta}({tau}{sup -} {yields} K{sub S}{sup 0}{pi}{sup -}{nu}{sub {tau}}) is made using 384.6 fb{sup -1} of e{sup +}e{sup -} collision data provided by the PEP-II collider, operating primarily at {radical}s = 10.58 GeV, and recorded using the BABAR detector. From this they measure: {Beta}({tau}{sup -} {yields} {bar K}{sup 0}{pi}{sup -}{nu}{sub {tau}}) = (0.840 {+-} 0.004(stat) {+-} 0.023(syst))%. This result is the most precise measurement to date and is consistent with the world average.
Date: August 13, 2008
Creator: Wren, A
Partner: UNT Libraries Government Documents Department

Lattice and Collective Effects for PEP-X

Description: This is a more comprehensive report of the accelerator physics in the white paper 'PEP-X Light Source at SLAC'. A new light source called 'PEP-X' would reside in the 2.2-km PEP-II tunnel. It has a hybrid lattice where two of its six arcs contain DBA cells that provide a total of 30 straight sections for insertion device beam lines and the remaining arcs contain TME cells for an extremely low emittance. Using 90 meter damping wigglers the horizontal emittance at 4.5 GeV is further reduced to 0.1 nm-rad. Many collective effects including intra-beam scattering, Touschek lifetime, and fast ion instability are studied. We expect that PEP-X will produce photon beams having brightnesses near 10{sup 22} (ph/s/mm{sup 2}/mrad{sup 2}/0.1% BW) at 10 keV and 10{sup 21} at 35 keV.
Date: May 13, 2008
Creator: Bane, Karl; Cai, Yunhai; Chao, Alex; Hettel, Robert; Huang, Zhirong; Nosochkov, Yuri et al.
Partner: UNT Libraries Government Documents Department

The Inside Story: Quasilocal Tachyons and Black Holes

Description: We analyze the fate of excitations in regions of closed string tachyon condensate, a question crucial for understanding unitarity in a class of black holes in string theory. First we introduce a simple new example of quasilocal tachyon condensation in a globally stable AdS/CFT background, and review tachyons' appearance in black hole physics. Then we calculate forces on particles and fields in a tachyon phase using a field theoretic model with spatially localized exponentially growing time dependent masses. This model reveals two features, both supporting unitary evolution in the bulk of spacetime. First, the growing energy of fields sourced by sets of (real and virtual) particles in the tachyon phase yields outward forces on them, leaving behind only combinations which do not source any fields. Secondly, requiring the consistency of perturbative string theory imposes cancellation of a BRST anomaly, which also yields a restricted set of states. Each of these effects supports the notion of a black hole final state arising from string-theoretic dynamics replacing the black hole singularity.
Date: January 13, 2006
Creator: Horowitz, Gary T.; /UC, Santa Barbara; Silverstein, Eva & /SLAC /Stanford U., Phys. Dept.
Partner: UNT Libraries Government Documents Department

Chandra Reveals Twin X-ray Jets in the Powerful FR-II Radio Galaxy 3C353

Description: We report X-ray imaging of the powerful FR II radio galaxy 3C 353 using the Chandra X-ray Observatory. 3C 353's two 4-inch wide and 2-feet long jets allow us to study in detail the internal structure of the large-scale relativistic outflows at both radio and X-ray photon energies with the sub-arcsecond spatial resolution provided by the VLA and Chandra instruments. In a 90 ks Chandra observation, we have detected X-ray emission from most radio structures in 3C 353, including the nucleus, the jet and the counterjet, the terminal jet regions (hotspots), and one radio lobe. We show that the detection of the X-ray emission associated with the radio knots and counterknots, which is most likely non-thermal in origin, puts several crucial constraints on the X-ray emission mechanisms in powerful large-scale jets of quasars and FR II sources. In particular, we show that this detection is inconsistent with the inverse-Compton model proposed in the literature, and instead implies a synchrotron origin of the X-ray jet photons. We also find that the width of the X-ray counterjet is possibly narrower than that measured in radio bands, that the radio-to-X-ray flux ratio decreases systematically downstream along the jets, and that there are substantial (kpc-scale) offsets between the positions of the X-ray and radio intensity maxima within each knot, whose magnitudes increase away from the nucleus. We discuss all these findings in the wider context of the physics of extragalactic jets, proposing some particular though not definitive solutions or interpretations for each problem. In general, we find that the synchrotron X-ray emission of extragalactic large-scale jets is not only shaped by the global hydrodynamical configuration of the outflows, but is also likely to be very sensitive to the microscopic parameters of the jet plasma. A complete, self-consistent model for the X-ray emission of extragalactic ...
Date: June 13, 2008
Creator: Kataoka, J.; Stawarz, L.; Harris, D.E.; Siemiginowska, A.; Ostrowski, M.; Swain, M.R. et al.
Partner: UNT Libraries Government Documents Department

Bounds on Masses of Bulk Fields in String Compactifications

Description: In string compactification on a manifold X, in addition to the string scale and the normal scales of low-energy particle physics, there is a Kaluza-Klein scale 1/R associated with the size of X. We present an argument that generic string models with low-energy supersymmetry have, after moduli stabilization, bulk fields with masses which are parametrically lighter than 1/R. We discuss the implications of these light states for anomaly mediation and gaugino mediation scenarios.
Date: February 13, 2006
Creator: Kachru, Shamit; McGreevy, John; Svrcek, Peter & /Stanford U., Phys. Dept. /SLAC
Partner: UNT Libraries Government Documents Department

The Diffuse Galactic Gamma-Ray Emission Model for GLAST LAT

Description: Diffuse emission from the Milky Way dominates the gamma-ray sky. About 80% of the high-energy luminosity of the Milky Way comes from processes in the interstellar medium. The Galactic diffuse emission traces interactions of energetic particles, primarily protons and electrons, with the interstellar gas and radiation field, thus delivering information about cosmic-ray spectra and interstellar mass in distant locations. Additionally, the Galactic diffuse emission is the celestial foreground for the study of gamma-ray point sources and the extragalactic diffuse gamma-ray emission. We will report on the latest developments in the modeling of the Galactic diffuse emission, which will be used for the Gamma Ray Large Area Space Telescope (GLAST) investigations.
Date: June 13, 2007
Creator: Porter, T.A.; /UC, Santa Cruz; Digel, S.W.; /SLAC /KIPAC, Menlo Park; Grenier, I.A.; /Saclay et al.
Partner: UNT Libraries Government Documents Department

Development of a 20 MeV Dielectric-Loaded Test Accelerator

Description: This paper presents a progress report on a joint project by the Naval Research Laboratory (NRL) and Argonne National Laboratory (ANL), in collaboration with the Stanford Linear Accelerator Center (SLAC), to develop a dielectric-loaded test accelerator in the magnicon facility at NRL. The accelerator will be powered by an experimental 11.424-GHz magnicon amplifier that presently produces 25 MW of output power in a {approx}250-ns pulse at up to 10 Hz. The accelerator will include a 5-MeV electron injector originally developed at the Tsinghua University in Beijing, China, and can incorporate DLA structures up to 0.5 m in length. The DLA structures are being developed by ANL, and shorter test structures fabricated from a variety of dielectric materials have undergone testing at NRL at gradients up to {approx}8 MV/m. SLAC has developed components to distribute the power from the two magnicon output arms to the injector and to the DLA accelerating structure with separate control of the power ratio and relative phase. RWBruce Associates, Inc., working with NRL, has investigated means to join short ceramic sections into a continuous accelerator tube by a brazing process using an intense 83-GHz beam. The installation and testing of the first dielectric-loaded test accelerator, including injector, DLA test structure, and spectrometer, should take place within the next year.
Date: April 13, 2007
Creator: Gold, S.H.; Kinkead, A.K.; Gai, W.; Power, J.G.; Konecny, R.; Jing, C. et al.
Partner: UNT Libraries Government Documents Department

The Status of Normal Conducting RF (NCRF) Guns, a Summary of the ERL2005 Workshop

Description: The 32nd Advanced ICFA Beam Dynamics Workshop on Energy Recovering Linacs (ERL2005) was held at Jefferson Laboratory, March 20 to 23, 2005. A wide range of ERL-related topics were presented and discussed in several working groups with Working Group 1 concentrated upon the physics and technology issues for DC, superconducting RF (SRF) and normal conducting RF (NCRF) guns. This paper summarizes the NCRF gun talks and reviews the status of NCRF gun technology. It begins with the presentations made on the subject of low-frequency, high-duty factor guns most appropriate for ERLs. One such gun at 433MHz was demonstrated at 25%DF in 1992, while the CW and much improved version is currently being constructed at 700MHz for LANL. In addition, the idea of combining the NCRF gun with a SRF linac booster was presented and is described in this paper. There was also a talk on high-field guns typically used for SASE free electron lasers. In particular, the DESY coaxial RF feed design provides rotationally symmetric RF fields and greater flexibility in the placement of the focusing magnetic field. While in the LCLS approach, the symmetric fields are obtained with a dual RF feed and racetrack cell shape. Although these guns cannot be operated at high-duty factor, they do produce the best quality beams. With these limitations in mind, a section with material not presented at the workshop has been included in the paper. This work describes a re-entrant approach which may allow NCRF guns to operate with simultaneously increased RF fields and duty factors. And finally, a novel proposal describing a high-duty factor, two-frequency RF gun using a field emission source instead of a laser driven photocathode was also presented.
Date: March 13, 2006
Creator: Dowell, D.H.; /SLAC; Lewellen, J.W.; /Argonne; Nguyen, D.; Alamos, /Los et al.
Partner: UNT Libraries Government Documents Department