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E-Beam Driven Accelerators: Working Group Summary (open access)

E-Beam Driven Accelerators: Working Group Summary

The working group has identified the parameters of an afterburner based on the design of a future linear collider. The new design brings the center of mass energy of the collider from 1 to 2 TeV. The afterburner is located in the final focus section of the collider, operates at a gradient of {approx}4 GeV/m, and is only about 125 m long. Very important issues remain to be addressed, and include the physics and design of the positron side of the afterburner, as well as of the final focus system. Present plasma wakefield accelerator experiments have reached a level of maturity and of relevance to the afterburner, that make it timely to involve the high energy physics and accelerator community in the afterburner design process. The main result of this working group is the first integration of the designs of a future linear collider and an afterburner.
Date: July 12, 2005
Creator: Muggli, P.; U., /Southern California & Ng, J.S.T.
System: The UNT Digital Library
Pentaquark Searches And Properties of D/SJ Resonances at BaBar (open access)

Pentaquark Searches And Properties of D/SJ Resonances at BaBar

Preliminary results from inclusive searches for strange pentaquark production in e{sup +}e{sup -} interactions at {radical}s = 10.58 GeV using 123 fb{sup -1} of data collected with the BABAR detector are presented. In addition new mass estimates for the D*{sub sJ}(2317){sup +} and D{sub sJ}(2460){sup +} mesons are given. The mesons are studied in e{sup +}e{sup -} {yields} c{bar c} data using 125 fb{sup -1} for the decay to the D{sub s}{sup +} s meson along with one or more {pi}{sup 0}, {pi}{sup +}, or {gamma} particles. A search is also performed for neutral and doubly-charged partners.
Date: October 12, 2005
Creator: Halyo, V.
System: The UNT Digital Library
The growth of epitaxial uranium oxide observed by micro-Raman spectroscopy (open access)

The growth of epitaxial uranium oxide observed by micro-Raman spectroscopy

Raman spectroscopy can be performed with micrometer resolution and can thus be used to determine the dependence of oxide thickness on the substrate's grain structure or local impurity inclusions. The Raman signal amplitude emitted from an epitaxial uranium oxide layer as a function of oxide thickness has been modeled for light of 632.8 nm wavelength incident on the oxide and reflected from the uranium substrate using the optical properties determined by spectrophotometry. The model shows that the Raman signal increases with oxide thickness and saturates at about 150 nm thickness. The model was compared with the measured Raman signal amplitude of an epitaxial uranium oxide layer growing in air with a known time dependence of oxide growth.
Date: December 12, 2005
Creator: Caculitan, N & Siekhaus, W J
System: The UNT Digital Library
Evidence for B+ to K0barK+ and B0 to K0K0bar, and Measurement of the Branching Fraction and Search for Direct CP Violation in B+ to K0pi+ (open access)

Evidence for B+ to K0barK+ and B0 to K0K0bar, and Measurement of the Branching Fraction and Search for Direct CP Violation in B+ to K0pi+

The authors present evidence for the b {yields} d penguin-dominated decays B{sup +} {yields} {bar K}{sup 0}K{sup +} and B{sup 0} {yields} K{sup 0}{bar K}{sup 0} with significances of 3.5 and 4.5 standard deviations, respectively. The results are based on a sample of 227 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at SLAC. We measure the branching fractions {Beta}(B{sup +} {yields} {bar K}{sup 0}K{sup +}) = (1.5 {+-} 0.5 {+-} 0.1) x 10{sup -6} (< 2.4 x 10{sup -6}) and {Beta}(B{sup 0} {yields} K{sup 0}{bar K}{sup 0}) = (1.19{sub -0.35}{sup +0.40} {+-} 0.13) x 10{sup -6}, where the uncertainties are statistical and systematic, respectively, and the upper limit on the branching fraction for {bar K}{sup 0}K{sup +} is at the 90% confidence level. They also present improved measurements of the charge-averaged branching fraction {Beta}(B{sup +} {yields} K{sup 0}{pi}{sup +}) = (26.0 {+-} 1.3 {+-} 1.0) x 10{sup -6} and CP-violating charge asymmetry {Alpha}{sub CP} (K{sup 0}{pi}{sup +}) = -0.09 {+-} 0.05 {+-} 0.01, where the uncertainties are statistical and systematic, respectively.
Date: July 12, 2005
Creator: Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
System: The UNT Digital Library
Two Rounds of Whole Genome Duplication in the Ancestral Vertebrate (open access)

Two Rounds of Whole Genome Duplication in the Ancestral Vertebrate

The hypothesis that the relatively large and complex vertebrate genome was created by two ancient, whole genome duplications has been hotly debated, but remains unresolved. We reconstructed the evolutionary relationships of all gene families from the complete gene sets of a tunicate, fish, mouse, and human, then determined when each gene duplicated relative to the evolutionary tree of the organisms. We confirmed the results of earlier studies that there remains little signal of these events in numbers of duplicated genes, gene tree topology, or the number of genes per multigene family. However, when we plotted the genomic map positions of only the subset of paralogous genes that were duplicated prior to the fish-tetrapod split, their global physical organization provides unmistakable evidence of two distinct genome duplication events early in vertebrate evolution indicated by clear patterns of 4-way paralogous regions covering a large part of the human genome. Our results highlight the potential for these large-scale genomic events to have driven the evolutionary success of the vertebrate lineage.
Date: April 12, 2005
Creator: Dehal, Paramvir & Boore, Jeffrey L.
System: The UNT Digital Library
Introduction to the Workshop, and a Brief Review of the Early Experiments on Multiple Crossing Laser Beams (open access)

Introduction to the Workshop, and a Brief Review of the Early Experiments on Multiple Crossing Laser Beams

The purpose of the workshop is to review recent experiments on the laser plasma interactions of multiple laser beams, and encourage interaction and collaboration on future experiments in this exciting emerging area. The format is a series of nine, 10 minute talks followed by a 5 minute question period covering the major topics of (1) scattering and transfer of power by multiple beams in ICF experiments; (2) basic studies of KEEN wave physics especially as facilitated by multi-beam interaction; and (3) compression of laser pulses by multi-beam interactions.
Date: June 12, 2005
Creator: Kirkwood, R K
System: The UNT Digital Library
First Results with the Prototype Detectors of the Si/W ECAL (open access)

First Results with the Prototype Detectors of the Si/W ECAL

Measurements on the prototype silicon sensors for use with an electromagnetic calorimeter with tungsten absorber are reported. The prototype sensors are based on a hexagonal geometry that optimally utilizes the space available on 6 inch silicon wafers. The sensors are segmented into approximately 750 5mm hexagonal pixels, which are connected to a bump-bonding array located at the center of the sensors. We report on those properties of the sensors that are important for linear collider applications including depletion voltage, stray capacitance and series resistance.
Date: July 12, 2005
Creator: Strom, D; Frey, R.; Breidenbach, M.; Deng, J.; Freytag, D.; Graf, N. et al.
System: The UNT Digital Library
Amplification of 1 ps Pulse Length Beam by Stimulated Raman Scattering of a 1 ns Beam in a Low Density Plasma (open access)

Amplification of 1 ps Pulse Length Beam by Stimulated Raman Scattering of a 1 ns Beam in a Low Density Plasma

The compression of a laser pulse by amplification of an ultra short pulse beam which seeds the stimulated Raman scatter of the first beam has been long been discussed in the context of solid and gas media. We investigate the possibility of using intersecting beams in a plasma to compress nanosecond pulses to picosecond duration by scattering from driven electron waves. Recent theoretical studies have shown the possibility of efficient compression with large amplitude, non-linear Langmuir waves driven either by SRS [1] or non-resonantly [2]. We describe experiments in which a plasma suitable for pulse compression is created, and amplification of an ultra short pulse beam is demonstrated.
Date: June 12, 2005
Creator: Dewald, E.; Kirkwood, R. K.; Niemann, C.; Meezan, N.; Wilks, S. C.; Divol, L. et al.
System: The UNT Digital Library
Single Bunch Monopole Instability (open access)

Single Bunch Monopole Instability

We study single bunch stability with respect to monopole longitudinal oscillations in electron storage rings. Our analysis is different from the standard approach based on the linearized Vlasov equation. Rather, we reduce the full nonlinear Fokker-Planck equation to a Schroedinger-like equation which is subsequently analyzed by perturbation theory. We show that the Haissinski solution [3] may become unstable with respect to monopole oscillations and derive a stability criterion in terms of the ring impedance.
Date: September 12, 2005
Creator: Podobedov, B. & Heifets, S.
System: The UNT Digital Library
Alighment and Vibration Issues in TeV Linear Collider Design (open access)

Alighment and Vibration Issues in TeV Linear Collider Design

The next generation of linear colliders will require alignment accuracies and stabilities of component placement at least one, perhaps two, orders of magnitude better than can be achieved by the conventional methods and procedures in practice today. The magnitudes of these component-placement tolerances for current designs of various linear collider subsystems are tabulated. In the micron range, long-term ground motion is sufficiently rapid that on-line reference and mechanical correction systems are called for. Some recent experiences with the upgraded SLAC laser alignment systems and examples of some conceivable solutions for the future are described. The so called ''girder'' problem is discussed in the light of ambient and vibratory disturbances. The importance of the quality of the underlying geology is stressed. The necessity and limitations of particle-beam-derived placement information are mentioned.
Date: August 12, 2005
Creator: Fischer, G. E.
System: The UNT Digital Library
Development and Testing of a 6-Cylinder HCCI Engine for Distributed Generation (open access)

Development and Testing of a 6-Cylinder HCCI Engine for Distributed Generation

This paper describes the technical approach for converting a Caterpillar 3406 natural gas spark ignited engine into HCCI mode. The paper describes all stages of the process, starting with a preliminary analysis that determined that the engine can be operated by preheating the intake air with a heat exchanger that recovers energy from the exhaust gases. This heat exchanger plays a dual role, since it is also used for starting the engine. For start-up, the heat exchanger is preheated with a natural gas burner. The engine is therefore started in HCCI mode, avoiding the need to handle the potentially difficult transition from SI or diesel mode to HCCI. The fueling system was modified by replacing the natural gas carburetor with a liquid petroleum gas (LPG) carburetor. This modification sets an upper limit for the equivalence ratio at {phi} {approx} 0.4, which is ideal for HCCI operation and guarantees that the engine will not fail due to knock. Equivalence ratio can be reduced below 0.4 for low load operation with an electronic control valve. Intake boosting has been a challenge, as commercially available turbochargers are not a good match for the engine, due to the low HCCI exhaust temperature. Commercial introduction …
Date: July 12, 2005
Creator: Flowers, D. L.; Martinez-Frias, J.; Espinosa-Loza, F.; Killingsworth, N.; Aceves, S. M.; Dibble, R. et al.
System: The UNT Digital Library
Magnet Fiducialization with Coordinate Measuring Machines (open access)

Magnet Fiducialization with Coordinate Measuring Machines

One of the fundamental alignment problems encountered when building a particle accelerator is the transfer of a component's magnetic centerline position to external fiducials. This operation, dubbed fiducialization, is critical because it can contribute significantly to the alignment error budget. The fiducialization process requires two measurements: (1) from magnetic centerline to mechanical centerline, and (2) from mechanical centerline to external fiducials. This paper will focus on methods for observing the second measurement. Two Stanford Linear Collider (SLC) examples are presented. The object of magnet fiducialization is to relate the magnet-defined beamline position to exterior reference surfaces. To be useful for later component alignment, this relationship must be established in a manner consistent with overall positioning tolerances. The error budget for the SLC's {+-} 100 {micro}m component to component alignment tolerance is as follows: magnetic centerline to mechanical centerline--{sigma} = {+-}30 {micro}m; mechanical centerline to fiducial marks--{sigma} = {+-}50 {micro}m; and fiducial marks to adjacent components--{sigma} = {+-}80 {micro}m; the TOTAL {sigma} = {+-}100 {micro}m. The offset between the mechanical and magnetic centerlines of well-known magnets is generally smaller than the {+-}30 {micro}m measurement tolerance. It is commonly assumed to be zero without measurement. When this tiny value must be measured, …
Date: August 12, 2005
Creator: Friedsam, H.; Oren, W. & Pietryka, M.
System: The UNT Digital Library
The Pathogenomic Sequence Analysis of B. cereus and B. Thuringiensis isolates closely related to Bacillus anthracis (open access)

The Pathogenomic Sequence Analysis of B. cereus and B. Thuringiensis isolates closely related to Bacillus anthracis

The sequencing and analysis of two close relatives of Bacillus anthracis are reported. AFLP analysis of over 300 isolates of B. cereus, B. thuringiensis and B. anthracis identified two isolates as being very closely related to B. anthracis. One, a B. cereus, BcE33L, was isolated from a zebra carcass in Nambia; the second, a B. thuringiensis, 97-27, was isolated from a necrotic human wound. The B. cereus appears to be the closest anthracis relative sequenced to date. A core genome of over 3,900 genes was compiled for the Bacillus cereus group, including B anthracis. Comparative analysis of these two genomes with other members of the B. cereus group provides insight into the evolutionary relationships among these organisms. Evidence is presented that differential regulation modulates virulence, rather than simple acquisition of virulence factors. These genome sequences provide insight into the molecular mechanisms contributing to the host range and virulence of this group of organisms.
Date: October 12, 2005
Creator: Han, C. S.; Xie, G.; Challacombe, J. F.; Altherr, M. R.; Bhotika, S. S.; Bruce, D. et al.
System: The UNT Digital Library
Ion Implantation with Scanning Probe Alignment (open access)

Ion Implantation with Scanning Probe Alignment

We describe a scanning probe instrument which integrates ion beams with the imaging and alignment function of a piezo-resistive scanning probe in high vacuum. The beam passes through several apertures and is finally collimated by a hole in the cantilever of the scanning probe. The ion beam spot size is limited by the size of the last aperture. Highly charged ions are used to show hits of single ions in resist, and we discuss the issues for implantation of single ions.
Date: July 12, 2005
Creator: Persaud, A.; Liddle, J. A.; Schenkel, T.; Bokor, J.; Ivanov, Tzv. & Rangelow, I. W.
System: The UNT Digital Library
Survey and Alignment for the ALS Project at LBL Berkeley (open access)

Survey and Alignment for the ALS Project at LBL Berkeley

The Advanced Light Source (ALS), now under construction at Lawrence Berkeley Laboratory, is a synchrotron radiation source of the third generation designed to produce extremely bright photon beams in the UV and soft X-ray regions. Its main accelerator components are a 1-1.9 GeV electron storage ring with 196.8 m circumference and 12 super-periods, a 1.5 GeV booster synchrotron with 75.0 m circumference and 4 super-periods, and a 50 MeV linac, as shown in Fig. 1. The storage ring has particularly tight positioning tolerances for lattice magnets and other components to assure the required operational characteristics. The general survey and alignment concept for the ALS is based on a network of fixed monuments installed in the building floor, to which all component positions are referred. Measurements include electronic distance measurements and separate sightings for horizontal and vertical directions, partially with automated electronic data capture. Most of the data processing is accomplished by running a customized version of PC-GEONET. It provides raw data storage, data reduction, and the calculation of adjusted coordinates, as well as an option for error analysis. PC-GEONET has also been used to establish an observation plan for the monuments and calculate their expected position accuracies, based on approximate …
Date: August 12, 2005
Creator: Keller, R.; Lauritzen, T. & Friedsam, H.
System: The UNT Digital Library
X-ray Emission from Megamaser Galaxy IC 2560 (open access)

X-ray Emission from Megamaser Galaxy IC 2560

Observation of the H{sub 2}O megamaser galaxy IC 2560 with the Chandra Observatory reveals a complex spectrum composed of soft X-ray emission due to multi-temperature thermal plasma, and a hard continuum with strong emission lines. The continuum is most likely a Compton reflection (reprocessing) of primary emission that is completely absorbed at least up to 7 keV. The lines can be identified with fluorescence from Si, S and Fe in the lowest ionization stages. The equivalent widths of the Si and S lines are broadly compatible with those anticipated for reprocessing by optically thick cold plasma of Solar abundances, while the large equivalent width of the Fe line requires some overabundance of iron. A contribution to the line from a transmitted component cannot be ruled out, but the limits on the strength of the Compton shoulder make it less likely. From the bolometric luminosity of the nuclear region, we infer that the source radiates at 1-10% of its Eddington luminosity, for an adopted central mass of 3 x 10{sup 6} M{sub {circle_dot}}. The overall spectrum is consistent with the hypotheses that the central engines powering the detected megamsers in accretion disks are obscured from direct view by the associated accretion …
Date: September 12, 2005
Creator: Madejski, Greg; /SLAC /KIPAC, Menlo Park; Done, Chris; U., /Durham; Zycki, Piotr; /Warsaw, Copernicus Astron. Ctr. et al.
System: The UNT Digital Library
A 90-GHz Photoinjector (open access)

A 90-GHz Photoinjector

Photocathode rf guns depend on mode locked laser systems to produce an electron beam at a given phase of the rf. In general, the laser pulse is less than {sigma}{sub z} = 10{sup o} of rf phase in length and the required stability is on the order of {Delta}{phi} = 1{sup o}. At 90 GHz (W-band), these requirements correspond to {sigma}{sub z} = 333 fsec and {Delta}{phi} = 33 fsec. Laser system with pulse lengths in the fsec regime are commercially available, the timing stability is a major concern. We propose a multi-cell W-band photoinjector that does not require a mode locked laser system. Thereby eliminating the stability requirements at W-band. The laser pulse is allowed to be many rf periods long. In principle, the photoinjector can now be considered as a thermionic rf gun. Instead of using an alpha magnet to compress the electron bunch, which would have a detrimental effect on the transverse phase space quality due to longitudinal phase space mixing, we propose to use long pulse laser system and a pair of undulators to produce a low emittance, high current, ultra-short electron bunch for beam dynamics experiments in the 90 GHz regime.
Date: September 12, 2005
Creator: Palmer, D. T.; Hogan, M. J.; Ferrario, M. & Serafini, L.
System: The UNT Digital Library
Practical Twistor Spinoffs: On-Shell Tree and Loop Recursion Relations (open access)

Practical Twistor Spinoffs: On-Shell Tree and Loop Recursion Relations

I briefly review how on-shell recursion relations, whose development was stimulated by recent twistor-space approaches, have been applied to compute tree and one-loop amplitudes in QCD.
Date: July 12, 2005
Creator: Dixon, Lance J.
System: The UNT Digital Library
X-ray Light Curves and Accretion Disk Structure of EX Hydrae (open access)

X-ray Light Curves and Accretion Disk Structure of EX Hydrae

We present X-ray light curves for the cataclysmic variable EX Hydrae obtained with the Chandra High Energy Transmission Grating Spectrometer and the Extreme Ultraviolet Explorer Deep Survey photometer. We confirm earlier results on the shape and amplitude of the binary light curve and discuss a new feature: the phase of the minimum in the binary light curve, associated with absorption by the bulge on the accretion disk, increases with wavelength. We discuss several scenarios that could account for this trend and conclude that, most likely, the ionization state of the bulge gas is not constant, but rather decreases with binary phase. We also conclude that photoionization of the bulge by radiation originating from the white dwarf is not the main source of ionization, but that it is heated by shocks originating from the interaction between the in-flowing material from the companion and the accretion disk. The findings in this paper provide a strong test for accretion disk models in close binary systems.
Date: April 12, 2005
Creator: Hoogerwerf, R; Brickhouse, N S & Mauche, C W
System: The UNT Digital Library
CIRCE, the Proposed Coherent Infrared Center at the LawrenceBerkeley National Laboratory (open access)

CIRCE, the Proposed Coherent Infrared Center at the LawrenceBerkeley National Laboratory

At the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory (LBNL), we are proposing the construction of CIRCE (Coherent InfraRed Center), a ring-based photon source completely optimized for the generation of coherent synchrotron radiation (CSR) in the terahertz frequency range [1]. CIRCE exploits the full complement of the CSR-production mechanisms presently available for obtaining top performance, including a photon flux exceeding by more than nine orders of magnitude that of existing ''conventional'' broadband terahertz sources.
Date: July 12, 2005
Creator: Byrd, John M.; Martin, Michael M. & Sannibale, Fernando
System: The UNT Digital Library
The High Energy Asymptotics of Scattering Processes in QCD (open access)

The High Energy Asymptotics of Scattering Processes in QCD

High energy scattering in the QCD parton model was recently shown to be a reaction-diffusion process, and thus to lie in the universality class of the stochastic Fisher-Kolmogorov-Petrovsky-Piscounov equation. We recall that the latter appears naturally in the context of the parton model. We provide a thorough numerical analysis of the mean field approximation, given in QCD by the Balitsky-Kovchegov equation. In the framework of a simple stochastic toy model that captures the relevant features of QCD, we discuss and illustrate the universal properties of such stochastic models. We investigate in particular the validity of the mean field approximation and how it is broken by fluctuations. We find that the mean field approximation is a good approximation in the initial stages of the evolution in rapidity.
Date: May 12, 2005
Creator: Enberg, Rikard; Golec-Biernat, K. & Munier, S.
System: The UNT Digital Library
Flash X-ray (FXR) Accelerator Optimization Injector Voltage-variation Compensation via Beam-induced Gap Voltage (open access)

Flash X-ray (FXR) Accelerator Optimization Injector Voltage-variation Compensation via Beam-induced Gap Voltage

Lawrence Livermore National Laboratory (LLNL) is evaluating design alternatives to improve the voltage regulation in our injector and accelerator cells of our Flash X-Ray (FXR) machine. The operational peak electron beam current and energy at the x-ray generating target are 3.2 kA and 17 MeV. The goal is to create a more mono-energetic electron beam with variation of less than 1%-root-mean-squared (rms). This would allow the beam to be focused more tightly and create an x-ray source with a smaller spot-size. Our injector appears to have significant voltage-variation, and this report describes a technique to appreciably correct the deviations. When an electron beam crosses the energized gap of an accelerator cell, the energy increases. However, the beam with the associated electromagnetic wave also loses a small amount of energy because of the increased impedance seen across each gap. The phenomenon is sometimes called beam loading. It can also be described as a beam-induced voltage at the gap which is time varying. The polarity of this induced voltage is the opposite of the voltage in the injector. The time varying profiles of the injector and induced gap voltage are related through the beam current. However, while the change in magnitude is …
Date: May 12, 2005
Creator: Ong, M. M.
System: The UNT Digital Library
Laser Beam Propagation through Long Ignition Scale Plasmas on NIF (open access)

Laser Beam Propagation through Long Ignition Scale Plasmas on NIF

Experiments on the National Ignition Facility (NIF) have employed the first four beams to measure propagation and laser backscattering losses in large ignition-size plasmas. Gas-filled targets between 2 mm and 7 mm length have been heated from one side by overlapping the focal spots of the four beams from one quad operated at 351 nm (3{omega}) with a total intensity of 2 x 10{sup 15}W cm{sup -2}. The targets were filled with 1 atm of CO{sub 2} producing of up to 7 mm long homogeneously heated plasmas with densities of n{sub e} = 5 x 10{sup 20} cm{sup -3} and temperatures of T{sub e} = 2 keV. The high energy in a NIF quad of beams of 16kJ, illuminating the target from one direction, creates unique conditions for the study of laser plasma interactions at scale lengths not previously accessible. The propagation through the large-scale plasma was measured with a gated x-ray imager that was filtered for 3.5 keV x rays. These data indicate that the beams interact with the full length of this ignition-scale plasma during the last {approx}1 ns of the experiment when applying full laser beam smoothing consisting of phase plates, smoothing by spectral dispersion and polarization …
Date: June 12, 2005
Creator: Glenzer, S H
System: The UNT Digital Library
MIP Reconstruction Techniques and Minimum Spanning Tree Clustering (open access)

MIP Reconstruction Techniques and Minimum Spanning Tree Clustering

The development of a tracking algorithm for minimum ionizing particles in the calorimeter and of a clustering algorithm based on the Minimum Spanning Tree approach are described. They do not depend on information from the central tracking system. Both are important components of a particle flow algorithm currently under development.
Date: September 12, 2005
Creator: Mader, Wolfgang F.
System: The UNT Digital Library