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100 years of elementary particles [Beam Line, vol. 27, issue 1, Spring 1997]

Description: This issue of Beam Line commemorates the 100th anniversary of the April 30, 1897 report of the discovery of the electron by J.J. Thomson and the ensuing discovery of other subatomic particles. In the first three articles, theorists Abraham Pais, Steven Weinberg, and Chris Quigg provide their perspectives on the discoveries of elementary particles as well as the implications and future directions resulting from these discoveries. In the following three articles, Michael Riordan, Wolfgang Panofsky, and Virginia Trimble apply our knowledge about elementary particles to high-energy research, electronics technology, and understanding the origin and evolution of our Universe.
Date: April 1, 1997
Creator: Pais, Abraham; Weinberg, Steven; Quigg, Chris; Riordan, Michael; Panofsky, Wolfgang K.H. & Trimble, Virginia
Partner: UNT Libraries Government Documents Department

Borel summation and momentum-plane analyticity in perturbative QCD

Description: We derive a compact expression for the Borel sum of a QCD amplitude in terms of the inverse Mellin transform of the corresponding Borel function. The result allows us to investigate the momentum-plane analyticity properties of the Borel-summed Green functions in perturbative QCD. An interesting connection between the asymptotic behavior of the Borel transform and the Landau singularities in the momentum plane is established. We consider for illustration the polarization function of massless quarks and the resummation of one-loop renormalon chains in the large-{beta}{sub 0} limit, but our conclusions have a more general validity.
Date: February 5, 1999
Creator: Neubert, Matthias
Partner: UNT Libraries Government Documents Department

A brief review of nuclear electronics standards . . . Past, present and future

Description: Modular Nuclear Instrument Standards have played a key role in U. S. Department of Energy National Laboratories and similar scientific laboratories worldwide for more than three decades. The scientific and engineering efficiency and economic benefits have been well documented. Standards are constantly evolving with the introduction of new technologies and the present is a time of rapid change. This report is based on an invited talk presented at the Joint Meeting of the U.S. Nuclear Instrument Module (NIM) and European Standards for Norms in Electronics (ESONE) Standards Committees, Lyon, France, October 20, 2000. It provides a brief overview of past developments and attempts to identify areas of possible opportunities for renewed standardization efforts to meet future challenges.
Date: November 1, 2000
Creator: Larsen, R.S.
Partner: UNT Libraries Government Documents Department

Bunch compression at the Stanford Linear Collider

Description: The production and measurement of short electron and positron bunches in the Stanford Linear Collider (SLC) will be presented in this paper. The bunches are compressed in a transport line between the damping rings and the linac. The electron and positron bunch distributions in the SLC linac have been measured using a Hamamatsu, model N3373-02, 500-femtosecond streak camera. The distributions were measured at the end of the SLC linac versus the bunch compressor RF voltage. The measurements are compared with simulations.
Date: August 1, 1995
Creator: Holtzapple, R.L.; Decker, F.J. & Simopoulos, C.
Partner: UNT Libraries Government Documents Department

A bunch compressor for the Next Linear Collider

Description: A bunch compressor design for the Next Linear Collider (NLC) is described. The compressor reduces the bunch length by a factor of 40 in two stages. The first stage at 2 GeV consists of an rf section and a wiggler. The second stage at 10 GeV is formed by an arc, an rf section, and a chicane. The final bunch phase is insensitive to initial phase errors and to beam loading in the intermediate S-band pre-linac. Residual longitudinal aberrations of the system are partially compensated. The bunch compressor encompasses a solenoid spin-rotator system at 2 GeV that allows complete control over the spin orientation.
Date: June 1, 1995
Creator: Emma, P.; Raubenheimer, T. & Zimmermann, F.
Partner: UNT Libraries Government Documents Department

Bunch heating by coherent synchrotron radiation

Description: The authors discuss here effects which define the steady-state rms energy spread of a microbunch in a storage ring. It is implied that the longitudinal microwave instability is controlled by low {alpha} lattice. In this case the coherent synchrotron radiation, if exists, may be the main factor defining the bunch temperature. Another effect comes from the fact that a nonlinear momentum compaction of such lattices makes Haissinskii equation not applicable, and the coherent synchrotron radiation may effect not only bunch lengthening but the energy spread as well.
Date: October 1, 1995
Creator: Heifets, S.A. & Zolotorev, M.
Partner: UNT Libraries Government Documents Department

Calculating scattering amplitudes efficiently

Description: We review techniques for more efficient computation of perturbative scattering amplitudes in gauge theory, in particular tree and one- loop multi-parton amplitudes in QCD. We emphasize the advantages of (1) using color and helicity information to decompose amplitudes into smaller gauge-invariant pieces, and (2) exploiting the analytic properties of these pieces, namely their cuts and poles. Other useful tools include recursion relations, special gauges and supersymmetric rearrangements. 46 refs., 11 figs.
Date: January 1996
Creator: Dixon, L.
Partner: UNT Libraries Government Documents Department

Calculation of muon background in electron accelerators using the Monte Carlo computer program MUCARLO

Description: The Program MUCARLO is a computer code developed at the Stanford Linear Accelerator Center (SLAC) to study the muon flux generated from beams of electrons and positrons on various targets. The MUCARLO program has been modified extensively in recent years; this paper describes the latest version. Preliminary results from this code are presented, and compared with results from another (TOMCAT) and with experimental data.
Date: November 1, 1995
Creator: Rokni, S.H.; Keller, L.P. & Nelson, W.R.
Partner: UNT Libraries Government Documents Department

Calculations of the giant-dipole-resonance photoneutrons using a coupled EGS4-morse code

Description: The production and transport of the photoneutrons from the giant-dipoleresonance reaction have been implemented in a coupled EGS4-MORSE code. The total neutron yield (including both the direct neutron and evaporation neutron components) is calculated by folding the photoneutron yield cross sections with the photon track length distribution in the target. Empirical algorithms based on the measurements have been developed to estimate the fraction and energy of the direct neutron component for each photon. The statistical theory in the EVAP4 code, incorporated as a MORSE subroutine, is used to determine the energies of the evaporation neutrons. These represent major improvements over other calculations that assumed no direct neutrons, a constant fraction of direct neutrons, monoenergetic direct neutron, or a constant nuclear temperature for the evaporation neutrons. It was also assumed that the slow neutrons (< 2.5 MeV) are emitted isotropically and the fast neutrons are emitted anisotropically in the form of 1+Csin{sup 2}{theta}, which have a peak emission at 900. Comparisons between the calculated and the measured photoneutron results (spectra of the direct, evaporation and total neutrons; nuclear temperatures; direct neutron fractions) for materials of lead, tungsten, tantalum and copper have been made. The results show that the empirical algorithms, albeit simple, can produce reasonable results over the interested photon energy range.
Date: October 1, 1995
Creator: Liu, J.C.; Nelson, W.R.; Kase, K.R. & Mao, X.S.
Partner: UNT Libraries Government Documents Department

Calculations on Cylindrical Metal Vacuum Chambers in Pulsed Magnetic Fields

Description: It has been suggested that metallic vacuum chambers might be suitable for pulsed magnets operating at audio frequencies, with pulse widths nominally 1/360 sec. In the present note calculations are given for a simple model of such a system, in order to estimate the effects of field attenuation and eddy current losses. The results of the calculation may be summarized briefly as follows, where the results apply to a cylindrical chamber of non-maeyletic stainless steel, 3.0 cm in inside diameter and 0.15 an wall thickness: (1) With steady-state harmonic excitation, the field in the interior Is reduced by a factor of {approximately} 1.03 at 2,000 cps compared to dc; (2) With transient operation, the exponential decay time is about 0.021 millisecond; (3) With square-wave excitation, at 200 gauss and 180 pps, the power dissipation in the stainless steel is about 24 watts/foot, or about a factor of 20 less if half-sine-wave pulses are used instead of square pulses. These results seem encouraging enough to warrant experimental investigation of this type of vacuum chamber for pulsed steering.
Date: October 8, 1964
Partner: UNT Libraries Government Documents Department

Can lepton flavor violating interactions explain the atmospheric neutrino anomaly

Description: We investigate whether flavor changing neutrino interactions (FCNIs) can be sufficiently large to provide a viable solution to the atmospheric neutrino problem. Effective operators induced by heavy boson exchange that allow for flavor changing neutrino scattering off quarks or electrons are related by an SU(2){sub L} rotation to operators that induce anomalous tau decays. Since SU(2){sub L} violation is small for New Physics at or above the weak scale, one can use the upper bounds on lepton flavor violating tau decays or on lepton universality violation to put severe, model-independent bounds on the relevant non-standard neutrino interactions. Also Z-induced flavor changing neutral currents, due to heavy singlet neutrinos, are too small to be relevant for the atmospheric neutrino anomaly. We conclude that the FCNI solution to the atmospheric neutrino problem is ruled out.
Date: September 16, 1999
Creator: Grossman, yuval
Partner: UNT Libraries Government Documents Department

Can TMAE photocathode be used for high rate applications?

Description: The paper explores the problems associated with wire aging, charging effects and self-sustaining cathode currents in the TMAE based photo-detectors. It is generally believed that anode wire aging is the most serious problem encountered in TMAE (tetrakis dimethylamino ethylene)-based Cherenkov ring imaging detectors. Although charging effects and self-sustaining cathod currents have not been studied systematically, there is concern that they too could become significant over a long period of time.
Date: March 1, 1995
Creator: Va`vra, J.
Partner: UNT Libraries Government Documents Department

Channeling acceleration: A path to ultrahigh energy colliders

Description: Acceleration of charged particles along crystal channels has been proposed earlier in an attempt to achieve high acceleration gradient while at the same time to suppress excessive emittance growth. Recently the authors demonstrated that a particle in a generic focusing channel can in principle absolutely damp to its transverse ground state without any quantum excitation. This yields the minimum beam emittance that one can ever attain, {gamma}{epsilon}{sub min} = {h_bar}/2mc, limited only by the uncertainty principle. In this paper they discuss sources of excitation when a more realistic channel is considered, including bremsstrahlung and multiple Coulomb scattering. They investigate the possibility of colliding ultrahigh energy particles in such strong focusing channels without the need of a final focusing system, where the concept of luminosity departs from the conventional approach. They show that a high luminosity can be attained with a rather modest beam power.
Date: May 1, 1995
Creator: Chen, P.; Huang, Z. & Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Chaos in Accelerators

Description: Chaos is a general phenomenon in nonlinear dynamical systems. Accelerators--storage rings in particular--in which particles are stored for 10{sup 10} revolutions constitute a particularly intricate nonlinear dynamical system. (In comparison, the earth has revolved around the sun for only 10{sup 9} turns.) Storage rings therefore provide an ideal testing ground for chaos physics. In fact, it is the chaos phenomenon that imposes one of the key design criteria for these accelerators. One might arguably say that the demise of the Superconducting Super Collider project originated from a misjudgement in its chaos analysis at one point along its design path, leading to its first substantial cost escalation. This talk gives an elementary introduction to the study of chaos in accelerators.
Date: May 11, 1999
Creator: Chao, Alex
Partner: UNT Libraries Government Documents Department

Chiral Boson Theory on the Light-Front

Description: The framework for describing the quantized theory of chiral boson is discussed. It avoids the conflict with the requirement of the principle of microcausality as is found in the conventional treatment. The discussion of the Floreanini-Jackiw model and its modified version for describing the chiral boson becomes very transparent on the light-front.
Date: September 16, 1999
Creator: Srivastava, Prem P.
Partner: UNT Libraries Government Documents Department

A code to compute the action-angle transformation for a particle in an abritrary potential well

Description: For a Vlasov treatment of longitudinal stability under an arbitrary wake field, with the solution of the Haiessinski equation as the unperturbed distribution, it is important to have the action-angle transformation for the distorted potential well in a convenient form. The authors have written a code that gives the transformation q,p {yields} J, {phi}, with q(J,{phi}) as a Fourier series in {phi}, the Fourier coefficients and the Hamiltonian H(J) being spline functions of J in C{sup 2} (having continuous second derivatives).
Date: June 1, 1995
Creator: Berg, J.S. & Warnock, R.L.
Partner: UNT Libraries Government Documents Department

Beam dynamics in SLC

Description: Beam dynamics issues affect many different aspects of the SLC performance. This paper concentrates on the multi-particle beam dynamics in the linac and the associated limitations that are imposed on the overall SLC performance. The beam behavior in the presence of strong wakefields has been studied in order to optimize the performance and to predict the expected emittances in high performance linacs. Emittance measurements and simulations are presented for the SLAC linac and are compared in detail. As the overall SLC performance depends on the accelerator stability, the tuning stability is discussed. Measurements are shown and the consequences for the performance of the SLC are discussed.
Date: July 1, 1997
Creator: Assmann, R.W.
Partner: UNT Libraries Government Documents Department

Beam loading compensation in the NLCTA

Description: In the design of the Next Linear Collider (NLC), multi-bunch operation is employed to improve efficiency at the cost of substantial beam loading. The RF pulse that powers the accelerator structures will be shaped to compensate for the effect of the transient loading along the bunch train. This scheme has been implemented in the Next Linear Collider Test Accelerator (NLCTA), a facility built to test the key accelerator technology of the NLC. In this paper the authors describe the compensation method, the techniques used to measure the energy variation along the bunch train, and results from tests with NLC-like beam currents.
Date: May 1, 1997
Creator: Adolphsen, C.; Lavine, T.; Nantista, C.; Ruth, R.; Wang, J. & Yeremian, D.
Partner: UNT Libraries Government Documents Department

Beam Profile Measurement at 30 GeV Using Optical Transition Radiation

Description: We present results of measurements of spot size and angular divergence of a 30 GeV electron beam through use of optical transition radiation (OTR). The OTR near field pattern and far field distribution are measured as a function of beam spot size and divergence at wavelengths of 441, 532, and 800 nm, for both the single and double foil configurations. Electron beam spot sizes of 50 {micro}m rms have been resolved, demonstrating the utility of OTR for measurement of small beam spot sizes of high energy (30 GeV) electron beams. Two-foil interference was clearly observed and utilized electron beam angular divergences of {approximately} 100 {micro}rad.
Date: July 10, 1999
Creator: Whittum, David H
Partner: UNT Libraries Government Documents Department

Beam profile monitors in the NLCTA

Description: The transverse current profile in the Next Linear Collider Test Accelerator (NLCTA) electron beam can be monitored at several locations along the beam line by means of profile monitors. These consist of insertable phosphor screens, light collection and transport systems, CID cameras, a frame-grabber, and PC and VAX based image analysis software. In addition to their usefulness in tuning and steering the accelerator, the profile monitors are utilized for emittance measurement. A description of these systems and their performance is presented.
Date: May 1, 1997
Creator: Nantista, C.; Adolphsen, C.; Brown, R.L.; Fuller, R. & Rifkin, J.
Partner: UNT Libraries Government Documents Department

Beam Test of Gamma-ray Large Area Space Telescope Components

Description: A beam test of GLAST (Gamma-ray Large Area Space Telescope) components was performed at the Stanford Linear Accelerator Center in October, 1997. These beam test components were simple versions of the planned light hardware. Results on the performance of the tracker, calorimeter, and anticoincidence charged particle veto are presented.
Date: May 27, 1999
Creator: Bloom, Elliott D
Partner: UNT Libraries Government Documents Department

Beam trajectory jitter in the SLC linac

Description: We present model-independent measurements of the vertical trajectory jitter of the positron beam in the Stanford Linear Collider (SLC) linac and discuss the results of studies aimed at isolating its source.
Date: May 1, 1995
Creator: Adolphsen, C. & Slaton, T.
Partner: UNT Libraries Government Documents Department

Beamline stability measurements with a stretched wire system in the FFTB

Description: Beamline stability is of great importance for future linear colliders where tolerances generally are in the micron to sub-micron range. A stretched wire system in the sealed FFTB tunnel at SLAC was used to monitor beamline motion with a sub-micron resolution. In future linear colliders low frequency changes of the beamline alignment (< 0.1 Hz) lead to untolerable quasistatical misalignments and betatron oscillations. Since it requires time to correct those errors, it is very important to determine how often corrections are needed. The authors present the measurements, discuss the systematics of the stretched wire system and compare the observations with the ATL-model for ground motion.
Date: September 1, 1996
Creator: Assmann, R.; Salsberg, C. & Montag, C.
Partner: UNT Libraries Government Documents Department

Bellows design for the PEP-II High Energy Ring arc chambers

Description: An overview of the current bellows module design and performance parameters is presented. Performance requirements based on external chamber design constraints, and operational needs are discussed. Parameters include beam impedance of the RF shield, and electrical resistance of the shield gap joint. Also discussed is the analysis of the high-current thermal management, and structural and cyclic behavior of the bellows and RF shield. Experiments of the tribology and electrical resistance of the shield sliding joint are summarized, and their results presented. Existing and new design options are discussed in light of the analyses and experiments. The final design is presented as the optimal compromise between the varying parameters.
Date: August 1, 1995
Creator: Nordby, M.E.; Kurita, N. & Ng, C.K.
Partner: UNT Libraries Government Documents Department