A   B   C   D   E   F   G   H   I   K   L   M   O   P   Q   R   S   T   U   V   W    


Paper Title Other Keywords Page
MOPC007 Anisotropy-Driven Instability in Intense Charged Particle Beams betatron, simulation, focusing, dipole 558
  • E. Startsev, R.C. Davidson, H. Qin
    PPPL, Princeton, New Jersey
  Funding: Research supported by the U.S. Department of Energy.

In electrically neutral plasmas with strongly anisotropic distribution functions, free energy is available to drive different collective instabilities such as the electrostatic Harris instability and the transverse electromagnetic Weibel instability. Such anisotropies develop naturally in particle accelerators and may lead to a detoriation of beam quality. We have generalized the analysis of the classical Harris and Weibel instabilities to the case of a one-component intense charged particle beam with anisotropic temperature including the important effects of finite transverse geometry and beam space-charge. For a long costing beam, the delta-f particle-in-cell code BEST and the eighenmode code bEASt have been used to determine detailed 3D stability properties over a wide range of temperature anisotropy and beam intensity. A theoretical model is developed which describes the essential features of the linear stage of these instabilities. Both, the simulations and analytical theory, clearly show that moderately intense beams are linearly unstable to short-wavelength perturbations, provided the ratio of the longitudinal temperature to the transverse temperature is smaller than some threshold value.

MPPE034 Symmetries and Invariants of the Time-dependent Oscillator Equation and the Envelope Equation focusing, lattice 2315
  • H. Qin, R.C. Davidson
    PPPL, Princeton, New Jersey
  Funding: Research supported by the U.S. Department of Energy.

Single-particle dynamics in a time-dependent focusing field is examined. The existence of the Courant-Snyder invariant* is fundamentally the result of the corresponding symmetry admitted by the oscillator equation with time-dependent frequency.** A careful analysis of the admitted symmetries reveals a deeper connection between the nonlinear envelope equation and the oscillator equation. A general theorem regarding the symmetries and invariants of the envelope equation, which includes the existence of the Courant-Snyder invariant as a special case, is demonstrated. The symmetries of the envelope equation enable a fast algorithm for finding matched solutions without using the conventional iterative shooting method.

*E.D. Courant and H.S. Snyder, Ann. Phys. 3, 1 (1958). **R.C. Davidson and H. Qin, Physics of Intense Charged Particle Beams in High Energy Accelerators (World Scientific, 2001).

MOPB002 High Intensity High Charge State ECR Ion Sources ion, ion-source, electron, emittance 179
  • D. Leitner, C.M. Lyneis
    LBNL, Berkeley, California
  Funding: This work was supported by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Nuclear Physics Division of the U.S. Department of Energy under Contract DE AC03-76SF00098.

The next-generation heavy ion beam accelerators such as the proposed Rare Isotope Accelerator (RIA), the Radioactive Ion Beam Factory at RIKEN, the GSI upgrade project, the LHC-upgrade, and IMP in Lanzhou require a great variety of high charge state ion beams with a magnitude higher beam intensity than currently achievable. High performance Electron Cyclotron Resonance (ECR) ion sources can provide the flexibility since they can routinely produce beams from hydrogen to uranium. Over the last three decades, ECR ion sources have continued improving the available ion beam intensities by increasing the magnetic fields and ECR heating frequencies to enhance the confinement and the plasma density. With advances in superconducting magnet technology, a new generation of high field superconducting sources is now emerging, designed to meet the requirements of these next generation accelerator projects. The talk will briefly review the field of high performance ECR ion sources and the latest developments for high intensity ion beam production. The currently most advanced next-generation superconducting source ECR ion source VENUS will be described in more detail.

MOPB005 Advances in the Performance of the SNS Ion Source ion, ion-source, SNS, linac 472
  • R.F. Welton, S.N. Murray, M.P. Stockli
    ORNL, Oak Ridge, Tennessee
  • R. Keller
    LBNL, Berkeley, California
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.

The ion source developed for the Spallation Neutron Source* (SNS) is a radio frequency, multi-cusp source designed to produce ~ 40 mA of H- with a normalized rms emittance of less than 0.2 pi mm mrad. To date the source has been utilized in the commissioning of the SNS accelerator, delivering beams of 10-50 mA with duty-factors of typically ~0.1% for operational periods of several weeks and availabilities now ~99%. Ultimately the SNS facility will require beam duty-factors of 6% (1 ms pulse length, 60 Hz repetition rate, 21 day run-period). Over the last year, several experiments were performed in which the ion source was continuously operated at full duty-factor and maximum beam current on a dedicated test stand. Recently, a breakthrough in our understanding of the Cs release process has led to the development of a new source conditioning technique which resulted in a dramatic increase in beam persistence with time. Average H- beam attenuation rates have been improved from ~5 mA/day to ~0.4 mA/day, allowing beams in excess of 30 mA to be delivered continuously at full duty factor for periods of ~20 days. Prior to this development, full duty factor beams could only be sustained for periods of several hours.

TPAE001 Experiments on Wake Field Acceleration in Plasma and the Program of the Further Works in YerPhI electron, acceleration, laser, vacuum 752
  • M.L. Petrosyan, M. Akopov, Y.A. Garibyan, E.M. Laziev, R.A. Melikian, Y. Nazaryan, M.K. Oganesyan, G.M. Petrosyan, L.M. Petrosyan, V.S. Pogosyan, G.K. Tovmasyan
    YerPhI, Yerevan
  Funding: ISTC, Project A-405.

The use of wake field acceleration basically is aimed to obtaining of high acceleration rate in comparison with traditional methods of acceleration. Meantime in the last years in YerPhI it was offered to use wake field acceleration for acceleration of high-current electron bunches on energy about 100 MeV. Experimental installation for research of formation of high-current electron bunches of the given configuration, necessary for wake field acceleration and acceleration of these bunches in plasma is created. The installation is intended for acceleration of electron bunches with a current of few tens amperes and up to energy 1-2 MeV. For excitation of wake waves in plasma the electron accelerator of direct action with use of high-voltage pulse transformer is used. Results of researches have revealed some properties of formation of high-current bunches, especially restrictions of a electron current because of space charge effects at sub-picoseconds duration of bunches. The basic parameters of the wake field acceleration project on energy about 100 MeV are given, taking into account results of researches on experimental installation.

TPAE002 The Project PLASMONX for Plasma Acceleration Experiments and a Thomson X-Ray Source at SPARC laser, electron, acceleration, simulation 820
  • L. Serafini, F. Alessandria, A. Bacci, I. Boscolo, S. Cialdi, C. De Martinis, D. Giove, C. Maroli, M. Mauri, V. Petrillo, R. Pozzoli, M. Rome
    INFN-Milano, Milano
  • D. Alesini, M. Bellaveglia, S. Bertolucci, M.E. Biagini, R. Boni, M. Boscolo, M. Castellano, A. Clozza, G. Di Pirro, A. Drago, A. Esposito, M. Ferrario, L. Ficcadenti, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, A. Ghigo, S. Guiducci, M. Incurvati, C. Ligi, F. Marcellini, M.  Migliorati, A. Mostacci, L. Palumbo, L. Pellegrino, M.A. Preger, R. Ricci, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, A. Stecchi, A. Stella, F. Tazzioli, C. Vaccarezza, M. Vescovi, C. Vicario
    INFN/LNF, Frascati (Roma)
  • W. Baldeschi, A. Barbini, M. Galimberti, A. Giulietti, A. Gizzi, P. Koester, L. Labate, A. Rossi, P. Tommasini
    CNR/IPP, Pisa
  • R. Bonifacio, N. Piovella
    Universita' degli Studi di Milano, MILANO
  • U. Bottigli, B. Golosio, P.N. Oliva, A. Poggiu, S. Stumbo
    INFN-Cagliari, Monserrato (Cagliari)
  • F. Broggi
    INFN/LASA, Segrate (MI)
  • C.A. Cecchetti, D. Giulietti
    UNIPI, Pisa
  We present the status of the activity on the project PLASMONX, which foresees the installation of a multi-TW Ti:Sa laser system at the CNR-ILIL laboratory to conduct plasma acceleration experiments and the construction of an additional beam line at SPARC to develop a Thomson X-ray source at INFN-LNF. After pursuing self-injection experiments at ILIL, when the electron beam at SPARC will be available the SPARC laser system will be upgraded to TW power level in order to conduct either external injection plasma acceleration experiments and ultra-bright X-ray pulse generation with the Thomson source. Results of numerical simulations modeling the interaction of the SPARC electron beam and the counter-propagating laser beam are presented with detailed discussion of the monochromatic X-ray beam spectra generated by Compton backscattering: X-ray energies are tunable in the range 20 to 1000 keV, with pulse duration from 30 fs to 20 ps. Preliminary simulations of plasma acceleration with self-injection are illustrated, as well as external injection of the SPARC electron beam. The proposed time schedule for this initiative is finally shown, which is tightly correlated with the progress of the SPARC project.  
TPAE003 Numerical Study of Injection Mechanisms for Generation of Mono-Energetic Femtosecond Electron Bunch from the Plasma Cathode electron, laser, injection, acceleration 859
  • T. Ohkubo, M. Uesaka, G. Zhidkov
    UTNL, Ibaraki
  Acceleration gradients of up to the order of 100GV/m and mono-energetic electron bunch up to 200MeV have recently been observed in several plasma cathode experiments. However, mechanisms of self-injection in plasma are not sufficiently clarified, presently. In this study, we carried out 2D PIC simulation to reveal the mechanisms of mono-energetic femtosecond electron bunch generation. We found two remarkable conditions for the generation: electron density gradient at vacuum-plasma interface and channel formation in plasma. Steep electron density gradient (~ plasma wave length) causes rapid injection and produces an electron bunch with rather high charge and less than 100fs duration. The channel formation guides an injected laser pulse and decreases the threshold of laser self-focusing, which leads to high electric field necessary for wave-breaking injection.  
TPAE005 Generation of Small Energy Spread Electron Beam from Self-Modulated Laser Wakefield Accelerator electron, laser, ion, space-charge 976
  • C. Kim, I.S. Ko
    POSTECH, Pohang, Kyungbuk
  • N. Hafz, G.-H. Kim, H. Suk
    KERI, Changwon
  Funding: The authors are grateful for financial support from the Korean Ministry of Science and Technology through the Creative ResearchInitiatives Program.

Laser and plasma based accelerators have been studied for a next generation particle accelerator. Still, there are some problems to solve for real applications. For example, it has been observed that the accelerated electron beam from laser and plasma based accelerators has a 100% energy spread. Thus, the generation of small energy spread beam is an important issue in the laser and plasma based accelerator study. In this work, we introduce a method to control the energy spread. From a basic theory and simulation, it is found that the transverse electron distribution is changed from the Gaussian to a Maxwell-Boltzmann distribution and low energy electrons spread out more rapidly than high energy electrons as they propagate in vacuum. Thus, a small size collimator is installed to remove the small energy electrons and it is conformed that the small energy spread can be obtained from an experiment.

TPAE017 Progress on High Power Tests of Dielectric-Loaded Accelerating Structures vacuum, impedance, acceleration, simulation 1566
  • C.-J. Jing, W. Gai, R. Konecny, J.G. Power
    ANL, Argonne, Illinois
  • S.H. Gold
    NRL, Washington, DC
  • A.K. Kinkead
  Funding: This work was supported by the U.S. Dept of Energy, High Energy Physics Division and Office of Naval Research.

This paper presents a progress report on a series of high-power rf experiments that were carried out to evaluate the potential of the Dielectric-Loaded Accelerating (DLA) structure for high-gradient accelerator operation. Since the last PAC meeting in 2003, we have tested DLA structures loaded with two different ceramic materials: Alumina (Al2O3) and MCT (MgxCa1-xTiO3). The alumina-based DLA experiments have concentrated on the effects of multipactor in the structures under high-power operation, and its suppression using TiN coatings, while the MCT experiments have investigated the dielectric joint breakdown observed in the structures due to local field enhancement. In both cases, physical models have been set up, and the potential engineering solutions are being investigated.

TPAE022 Analytical and Numerical Calculations of Two-Dimensional Dielectric Photonic Band Gap Structures and Cavities for Laser Acceleration simulation, lattice, laser, acceleration 1793
  • K.R. Samokhvalova, C. Chen
    MIT/PSFC, Cambridge, Massachusetts
  • B.L. Qian
    National University of Defense Technology, Hunan
  Funding: Research supported in part by Department of Energy, Office of High Energy Physics, Grant No. DE-FG02-95ER40919 and in part by Department of Defense, Joint Technology Office, under a subcontract with University of Arizona.

Dielectric photonic band gap (PBG) structures have many promising applications in laser acceleration. For these applications, accurate determination of fundamental and high order band gaps is critical. We present the results of our recent work on analytical calculations of two-dimensional (2D) PBG structures in rectangular geometry. We compare the analytical results with computer simulation results from the MIT Photonic Band Gap Structure Simulator (PBGSS) code, and discuss the convergence of the computer simulation results to the analytical results. Using the accurate analytical results, we design a mode-selective 2D dielectric cylindrical PBG cavity with the first global band gap in the frequency range of 8.8812 THz to 9.2654 THz. In this frequency range, the TM01-like mode is shown to be well confined.

TPAE023 3D Metallic Lattices for Accelerator Applications lattice, simulation, photon, vacuum 1838
  • M.A. Shapiro, J.R. Sirigiri, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts
  • G. Shvets
    The University of Texas at Austin, Austin, Texas
  Funding: DOE-HEP

We present the results of research on 3D metallic lattices operating at microwave frequencies for application in (1) accelerator structures with higher order mode suppression, (2) Smith-Purcell radiation beam diagnostics, and (3) polaritonic materials for laser acceleration. Electromagnetic waves in a 3D simple cubic lattice formed by metal wires are calculated using HFSS. The bulk modes in the lattice are determined using single cell calculations with different phase advances in all three directions. The Brillouin diagram for the bulk modes is presented and indicates the absence of band gaps in simple lattices except the band below the cutoff. Lattices with thin wires as well as with thick wires have been analyzed. The Brillouin diagram also indicates the presence of low frequency 3D plasmon mode as well as the two degenerate photon modes analogous to those in a 2D lattice. Surface modes for a semi-infinite cubic lattice are modeled as a stack of cells with different phase advances in the two directions along the surface. The surface modes are found for both the thin and thick wire lattices in the band below the cutoff. They demonstrate that the lattice acts as a negative dielectric constant material.

TPAE024 Determination of Longitudinal Phase Space in SLAC Main Accelerator Beams simulation, electron, acceleration, radiation 1856
  • C.D. Barnes, F.-J. Decker, P. Emma, M.J. Hogan, R.H. Iverson, P. Krejcik, C.L. O'Connell, R. Siemann, D.R. Walz
    SLAC, Menlo Park, California
  • C.E. Clayton, C. Huang, D.K. Johnson, C. Joshi, W. Lu, K.A. Marsh
    UCLA, Los Angeles, California
  • S. Deng, T.C. Katsouleas, P. Muggli, E. Oz
    USC, Los Angeles, California
  In the E164 Experiment at that Stanford Linear Accelerator Center (SLAC), we seek to drive plasma wakes for electron acceleration using 28.5 GeV bunches from the main accelerator. These bunches can now be made with an RMS length of less than 20 microns, and direct measurement is not feasible. Instead, we use an indirect technique, measuring the energy spectrum at the end of the linac and comparing with detailed simulations of the entire machine. We simulate with LiTrack, a 2D code developed at SLAC which includes wakefields, synchrotron radiation and all second order optical aberrations. Understanding the longitudinal profile allows a better understanding of acceleration in the plasma wake, as well as investigation of possible destructive transverse effects. We present results from the July 2004 experimental run and show how this technique aids in data analysis. We also discuss accuracy and validation of phase space determinations.  
TPAE025 Field Ionization of Neutral Lithium Vapor using a 28.5 GeV Electron Beam electron, acceleration, diagnostics, radiation 1904
  • C.L. O'Connell, C.D. Barnes, F.-J. Decker, M.J. Hogan, R.H. Iverson, P. Krejcik, R. Siemann, D.R. Walz
    SLAC, Menlo Park, California
  • C.E. Clayton, C. Huang, D.K. Johnson, C. Joshi, W. Lu, K.A. Marsh, W.B. Mori, M. Zhou
    UCLA, Los Angeles, California
  • S. Deng, T.C. Katsouleas, P. Muggli, E. Oz
    USC, Los Angeles, California
  The E164/E164X plasma wakefield experiment studies beam-plasma interactions at the Stanford Linear Acceleration Center (SLAC). Due to SLAC recent ability to variably compress bunches longitudinally from 650 microns down to 20 microns, the incoming beam is sufficiently dense to field ionize the neutral Lithium vapor. The field ionization effects are characterized by the beam’s energy loss through the Lithium vapor column. Experimental results are presented.  
TPAE026 Wakefields in a Dielectric Tube with Frequency Dependent Dielectric Constant resonance, impedance, laser, damping 1916
  • R. Siemann, A. Chao
    SLAC, Menlo Park, California
  Funding: U.S. Department of Energy.

Dielectric laser driven accelerators could operate at a fundamental mode frequency where consideration must be given to the frequency dependence of the dielectric constant when calculating wakefields. Wakefields are calculated for a frequency dependence that arises from a single atomic resonance. Causality is considered, and the effect on the short range wakefield is calculated.

TPAE031 Simulations of Laser Pulse Coupling and Transmission Efficiency in Plasma Channels laser, simulation, diagnostics, coupling 2179
  • R. Giacone, D.L. Bruhwiler, J.R. Cary, D.A. Dimitrov, P. Messmer
    Tech-X, Boulder, Colorado
  • E. Esarey, C.G.R. Geddes, W. Leemans
    LBNL, Berkeley, California
  Funding: Work supported by U.S. DOE under contracts DE-FG03-02ER83557, DE-FC02-01ER41178, DE-AC03-76SF00098, DE-FG03-95ER40926 and use of NERC supercomputer facilities.

Optical guiding of the laser pulse in a laser wakefield accelerator (LWFA) via plasma channels can greatly increase the interaction length and, hence, the maximun energy of trapped electrons.* Energy efficient coupling of laser pulses from vacuum into plasma channels is very important for optimal LWFA performance. We present 2D particle-in-cell simulations of this problem using the VORPAL code.** Some of the mechanisms considered are enhanced leakage of laser energy transversely through the channel walls, enhanced refraction due to tunneling ionization of neutral gas on the periphery of the gas jet, ionization of neutral gas by transverse wings of the laser pulse and effect of the pulse being off axis of the channel. Using power spectral diagnostics,*** we are able to differentiate between pump depletion and leakage from the channel. The results from our simulations show that for short (≈λp) plasma ramp, very little leakage and pump depletion is seen. For narrow channel walls and long ramps, leakage increases significantly.

*C. G. R. Gedes et al., Nature 431 (2004), p. 538. **C. Nieter and J. R. Cary, J. Comp. Phys. 196 (2004), p. 448.***D. A. Dimitrov et al., Proc. Advanced Accel. Concepts Workshop (2004).

TPAE032 Particle-in-Cell Simulations of Lower-Density CM-Scale Capillary Channels laser, simulation, electron, vacuum 2248
  • P. Messmer, D.L. Bruhwiler, D.A. Dimitrov, P. Stoltz
    Tech-X, Boulder, Colorado
  • E. Esarey, C.G.R. Geddes, W. Leemans
    LBNL, Berkeley, California
  Funding: This work is funded by DOE under contracts DE-FC02-01ER41178, DE-FG02-04ER84097, DE-AC03-76SF00098 and DE-FG03-95ER40926, including the SciDAC Accelerator Project and use of NERSC.

Capillary channels of cm-length and at plasma density low compared to gas jets are promising setups for low noise laser wakefield acceleration. Computationally, however, the large discrepancy of the length scales of the plasma and the laser are a big challenge. Methods are therefore sought that relax the need to concurrently resolve both length scales. Moving windows allow to reduce the size of the computational box to a few plasma wave-lengths, which can already be a big gain compared to the full length of the capillary. On the other hand, average methods allow to relax the constraint to resolve the laser wavelength. These methods split the laser induced current into a fast varying part and a slowly varying envelope. The average over the fast timescales is performed in a semi analytic way, leaving the evolution of the envelope to be modeled. Such an envelope model is currently being incorporated into the VORPAL code.* Preliminary results show considerable time savings compared to fully resolved simulations. The status of this ongoing work will be presented.

*C. Nieter and J. R. Cary, J. Comp. Phys. 196 (2004), p. 448.

TPAE034 Developing a Multi-Timescale PIC Code for Plasma Accelerators simulation, betatron, laser 2324
  • S. Deng, T.C. Katsouleas, X. Wang
    USC, Los Angeles, California
  • W.B. Mori
    UCLA, Los Angeles, California
  Funding: DOE: DE-FG02-92ER40745, DOE-SCIDAC: DE-FC02-01ER41192.

An idea for advancing beam and plasma particles with different time scales in a full PIC model of plasma accelerators is proposed. Because beam particles usually respond much slower than plasma particles, large time steps can be used to update beam particles to save computation time. In this paper, we will describe how to apply this multi-timescale method in a particle-in-cell (PIC) [1] code OSIRIS [2]. Simulation results for SLAC E164 [3] experimental parameters are given and show a high degree of accuracy while gaining a factor of 4-6 in computing time. The limitations of this method are also studied. The maximum time saving is determined by driver beam energy and size of simulation box.

TPAE039 The Effects of Ion Motion in Very Intense Beam-Driven Plasma Wakefield Accelerators ion, emittance, electron, collider 2562
  • J.B. Rosenzweig, A.M. Cook, M.C. Thompson, R.B. Yoder
    UCLA, Los Angeles, California
  Funding: This work is supported by U.S. Dept. of Energy grant DE-FG03-92ER40693.

Recent proposals for using plasma wakefield accelerators in the blowout regime as a component of a linear collider have included very intense driver and accelerating beams, which have densities many times in excess of the ambient plasma density. The electric fields of these beams are widely known to be large enough to completely expel plasma electrons from the beam path; the expelled electrons often attain relativistic velocities in the process. We examine here another aspect of this high-beam density scenario: the motion of ions. In the lowest order analysis, for both cylindrically symmetric and "flat" beams, it is seen that for the recently discussed "after-burner" scenario the ions completely collapse inside of the electron beam. In this case the ion density is significantly increased, with a large increase in the beam emittance expected as a result. Particle-in-cell simulations of ion-collapse in the nonlinear regime are discussed.

TPAE041 Modeling TeV Class Plasma Afterburners simulation, acceleration, collider, emittance 2666
  • C. Huang, C.E. Clayton, D.K. Johnson, C. Joshi, W. Lu, W.B. Mori, M. Zhou
    UCLA, Los Angeles, California
  • C.D. Barnes, F.-J. Decker, M.J. Hogan, R.H. Iverson
    SLAC, Menlo Park, California
  • S. Deng, T.C. Katsouleas, P. Muggli, E. Oz
    USC, Los Angeles, California
  Funding: Work supported by DOE and NSF.

Plasma wakefield acceleration can sustain acceleration gradients three orders of magnitude larger than conventional RF accelerator. In the recent E164X experiment, substantial energy gain of about 3Gev has been observed. Thus, a plasma afterburner, which has been proposed to double the incoming beam energy for a future linear collider, is now of great interest. In an afterburner, a particle beam drives a plasma wave and generates a strong wakefield which has a phase velocity equal to the velocity of the beam. This wakefield can then be used to accelerate part of the drive beam or a trailing beam. Several issues such as the efficient transfer of energy and the stable propagation of both the drive and trailing beams in the plasma are critical to the afterburner concept. We investigate the nonlinear beam-plasma interaction in such scenario using the 3D computer modeling code QuickPIC. We will report the latest simulation results of both 50 GeV and 1 TeV plasma afterburner stages for electrons including the beam-loading of a trailing beam. Analytic analysis of hosing instability in this regime will be presented.

TPAE042 Beam Matching to a Plasma Wake Field Accelerator Using a Ramped Density Profile at the Plasma Boundary synchrotron, emittance, focusing, ion 2702
  • K.A. Marsh, C.E. Clayton, C. Huang, D.K. Johnson, C. Joshi, W. Lu, W.B. Mori, M. Zhou
    UCLA, Los Angeles, California
  • C.D. Barnes, F.-J. Decker, M.J. Hogan, R.H. Iverson, P. Krejcik, C.L. O'Connell, R. Siemann, D.R. Walz
    SLAC, Menlo Park, California
  • S. Deng, T.C. Katsouleas, P. Muggli, E. Oz
    USC, Los Angeles, California
  Funding: DOE Grant No. DE-FG03-92ER40727.

An important aspect of plasma wake field accelerators (PWFA) is stable propagation of the drive beam. In the under dense 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. 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 PWFA experiments at SLAC.

TPAE043 Production of Terahertz Seed Radiation for FEL/IFEL Microbunchers for Second Generation Plasma Beatwave Experiments at Neptune radiation, laser, electron, beat-wave 2780
  • J.E. Ralph, C. Joshi, J.B. Rosenzweig, C. Sung, S. Tochitsky
    UCLA, Los Angeles, California
  Funding: This work was supported by the DOE Contract No. DE-FG03-92ER40727.

To achieve phase locked injection of short electron bunches in a plasma beatwave accelerator, the Neptune Laboratory will utilize microbunching in an FEL or IFEL system. These systems require terahertz (THz) seed radiation on the order of 10 kW for the FEL and 10 MW for the IFEL bunchers. We report results of experiments on THz generation using nonlinear frequency mixing of CO2 laser lines in GaAs. A two-wavelength laser beam was split and sent onto a 2.5 cm long GaAs crystal cut for noncollinear phase matching. Low power measurements achieved ~1 W of 340 ?m radiation using 200 ns CO2 pump pulses with wavelengths 10.3?m and 10.6?m. We also demonstrated tunability of difference frequency radiation, producing 240?m by mixing two different CO2 laser lines. By going to shorter laser pulses and higher intensities, we were able to increase the conversion efficiency while decreasing the surface damage threshold. Using 200ps pulses we produced ~2 MW of 340 ?m radiation. Future studies in this area will focus on developing large diameter Quasi-Phase matched structures for production of high power THz radiation.

TPAE044 Terahertz IFEL/FEL Microbunching for Plasma Beatwave Accelerators electron, undulator, radiation, laser 2812
  • C. Sung, C.E. Clayton, C. Joshi, P. Musumeci, C. Pellegrini, J.E. Ralph, S. Reiche, J.B. Rosenzweig, S. Tochitsky
    UCLA, Los Angeles, California
  Funding: Work supported by the U.S. Department of Energy under Contract No. DE-FG03-92ER40727.

In order to obtain monoenergetic acceleration of electrons, phase-locked injection using electron microbunches shorter than the accelerating structure is necessary. For a laser-driven plasma beatwave accelerator experiment, we propose to microbunch the electrons by interaction with terahertz (THz) radiation in an undulator via two mechanisms– free electron laser (FEL) and inverse free electron laser (IFEL). Since the high power FIR radiation will be generated via difference frequency mixing in GaAs by the same CO2 beatwave used to drive the plasma wave, electrons could be phase-locked and pre-bunched into a series of microbunches separated with the same periodicity. Here we examine the criteria for undulator design and present simulation results for both IFEL and FEL approaches. Using different CO2 laser lines, electrons can be microbunched with different periodicity 300 – 100 mm suitable for injection into plasma densities in the range 1016 – 1017 cm-3, respectively. The requirement on the THz radiation power and the electron beam qualities are also discussed.

TPAE046 Modeling Self-Ionized Plasma Wakefield Acceleration for Afterburner Parameters Using QuickPIC simulation, electron, betatron, acceleration 2905
  • M. Zhou, C.E. Clayton, V.K. Decyk, C. Huang, D.K. Johnson, C. Joshi, W. Lu, W.B. Mori, F.S. Tsung
    UCLA, Los Angeles, California
  • F.-J. Decker, R.H. Iverson, C.L. O'Connell, D.R. Walz
    SLAC, Menlo Park, California
  • S. Deng, T.C. Katsouleas, P. Muggli, E. Oz
    USC, Los Angeles, California
  Funding: DOE

A plasma wakefield accelerator (PWFA) has been proposed as a way to double the energy of a future linear collider. This afterburner concept will require meter long uniform plasmas. For the parameters envisaged in possible afterburner stages, the self-fields of the particle beam are intense enough to tunnel ionize some neutral gases such as lithium. Tunnel ionization has been investigated as a way for the beam itself to create the plasma.* Furthermore, tunnel ionization in a neutral or partially pre-ionized gas may create new plasma electrons and alter the plasma wake.*,** Unfortunately, it is not possible to model a PWFA with afterburner parameters using the models described in Bruhwiler et al. and Deng et al. Here we describe the addition of a tunnel ionization package using the ADK model into QuickPIC, a highly efficient quasi-static particle in cell (PIC) code which can model a PWFA with afterburner parameters. There is excellent agreement between QuickPIC and OSIRIS(a full PIC code) for pre-ionized plasmas. Effects of self-ionization on hosing instability –one of the most critical issues to overcome to make an afterburner a reality – for a bunch propagating in a plasma hundreds of betatron oscillations long will be discussed.

*D. L. Bruhwiler et al., Phys. Plasmas 10 (2003), p. 2022. **S. Deng et al., Phys. Rev. E, 68, 047401 (2003).

TPAE048 The UCLA/FNPL Time Resolved Underdense Plasma Lens Experiment electron, focusing, quadrupole, space-charge 3013
  • M.C. Thompson, H. Badakov, J.B. Rosenzweig, G. Travish
    UCLA, Los Angeles, California
  • H. Edwards, R.P. Fliller, G.M. Kazakevich, P. Piot, J.K. Santucci
    Fermilab, Batavia, Illinois
  • J.L. Li, R. Tikhoplav
    Rochester University, Rochester, New York
  Funding: Work Supported by U.S. Dept. of Energy grant DE-FG03-92ER40693.

An underdense plasma lens experiment is planned as a collaboration between UCLA and the Fermilab NICADD Photoinjector Laboratory (FNPL). The experiment will focus on measuring the variation of the plasma focusing along the longitudinal beam axis and comparing these results with theory and simulation. The experiment will utilize a thin gaussian underdense plasma lens with peak density 6 x 1012 cm-3 and a FWHM length of 1.6 cm. This plasma lens will have a focusing strength equivalent to a quadrupole magnet with a 180 T/m field gradient. A 15 MeV, 8nC electron beam with nominal dimensions sr = 400 μm and sz = 2.1 mm will be focused by this plasma lens onto an OTR screen approximately 2 cm downstream of the lens. The light from the OTR screen will be imaged into a streak camera in order to directly measure the correlation between z and sr within the beam. Status and progress on the experiment are reported.

TPAE053 Near-GeV Electron Beams from the Laser Wakefield Accelerator in the “Bubble” Regime electron, laser, simulation, vacuum
  • N. Hafz, H. Suk
    KERI, Changwon
  • D.-K. Ko, J. Lee
    APRI-GIST, Gwangju
  Funding: This research was funded by the Korean Ministry Science and Technology through the Creative Research Initiative (CRI) Program.

This Communication describes a 2D-PIC simulation of a laser wakefield accelerator in which an ultrashort, petawatt-class laser is focused and propagated through an underdense preformed plasma. We are looking at the phase-spaces of a large number of background plasma electrons that are accelerated to very high energies by the laser-induced plasma bubble. The result shows the possibility of generating a GeV-level electron beam in a few millimeters plasma size. As a future work, we will use a 500 TW laser system, that is under construction at APRI-GIST in Korea, for laser-plasma based accelerator researches to which the current simulation is relevant.

TPAE054 Ultraintense and Ultrashort Laser Pulses from Raman Amplification in Plasma for Laser-Plasma Accelerators simulation, laser, electron, resonance 3274
  • M.S. Hur, G.-H. Kim, H. Suk
    KERI, Changwon
  • A.E. Charman, R.R. Lindberg, J.S. Wurtele
    LBNL, Berkeley, California
  Funding: Korea Electrotechnology Research Institute, Korea; Creative Research Initiatives, Korea.

We present analysis and simulations of kinetic effects in the Raman pulse amplification in plasma. An ultraintense and ultrashort laser pulse is a very essential part in an advanced acceleration scheme using laser and plasma. To make strong pulses, a noble scheme of using Raman backscatter in plasma was proposed and has been studied intensively.* The Raman amplification in plasma does not have a restriction in material damage threshold. However, for the new amplifier to be a promising alternative of the CPA technique, more extensive studies on various issues are required. One of the fundamental issues is the electron kinetic effect such as particle trapping or wavebreaking. We present a theoretical analysis of the kinetic effect; a new kinetic term is derived to be added to the fluid model and the effect of the new term is verified by averaged-PIC (aPIC)** simulations. Various one dimensional and semi-two dimensional aPIC simulations of pulse amplification are presented. We discuss the future application of the Raman scheme to upgrading the laser pulse of the Center of Advanced Accelerator in KERI, which are currently 2 TW and 700 fs, into a few more TW and less than 100 fs.

*V. M. Malkin, G. Shvets, and N. J. Fisch, Phys. Rev. Lett. vol. 82, 4448 (1999).**M. S. Hur, G. Penn, J. S. Wurtele, and R. Lindberg, Phys. Plasmas vol. 11, 5204 (2004).

TPAE056 Acceleration of Charged Particles by High Intensity Few-Cycle Laser Pulses electron, laser, acceleration, undulator 3337
  • U. Schramm, F. Gruener, D. Habs, J. Schreiber
    LMU, München
  • S. Becker, M. Geissler, S. Karsch, F. Krausz, J. Meyer-ter-Vehn, K. Schmid, G. Tsakiris, L. Veisz, K. Witte
    MPQ, Garching, Munich
  Funding: Funded by the german DFG (TR18) and BMBF (06ML184).

Only recently a breakthrough in laser plasma acceleration has been achieved with the observation of intense (nC) mono-energetic (10% relative width) electron beams in the 100MeV energy range.* Above the wave-breaking threshold the electrons are trapped and accelerated in a single wake of the laser pulse, called bubble, according to PIC simulations.** However, pulse energis varied from shot-to-shot in the experiments. At the MPQ Garching we prepare the stable acceleration of electrons by this bubble regime by the use of 10TW few-cycle laser pulse. As the pulse lenght of 5-10fs remains below the plasma period also at higher plama densities, we expect the scheme to be more stable and efficient. The status of the experiment will be reported. Further, we exploit a colliding beam setup existing at the Jena multi TW laser system for the investigation of the positron generation in the electron-electron collision or in the collision of hard X-rays resulting from Thomson backscattering. The presentation of results on heavy ion acceleration from laser-irradiated thin foils will round up this summary of the Munich activities.

*See ‘dream beams' in Nature 431 (2004).**A. Pukhov, J. Meyer-ter-Vehn, Appl. Phys. B 74, 355 (2002).

TPAE057 A Multibunch Plasma Wakefield Accelerator electron, laser, simulation, background 3384
  • E.K. Kallos, T.C. Katsouleas, P. Muggli
    USC, Los Angeles, California
  • M. Babzien, I. Ben-Zvi, K. Kusche, P.I. Pavlishin, I. Pogorelsky, V. Yakimenko
    BNL, Upton, Long Island, New York
  • W.D. Kimura
    STI, Washington
  • F. Zhou
    UCLA, Los Angeles, California
  We investigate a plasma wakefield acceleration scheme where a train of electron microbunches feeds into a high density plasma. When the microbunch train enters such a plasma that has a corresponding plasma wavelength equal to the microbunch separation distance, a strong wakefield is expected to be resonantly driven to an amplitude that is at least one order of magnitude higher than that using an unbunched beam. PIC simulations have been performed using the beamline parameters of the Brookhaven National Laboratory Accelerator Test Facility operating in the configuration of the STELLA inverse free electron laser (IFEL) experiment. A 65 MeV electron beam is modulated by a 10.6 um CO2 laser beam via an IFEL interaction. This produces a train of ~90 microbunches separated by the laser wavelength. In this paper, we present both a simple theoretical treatment and simulation results that demonstrate promising results for the multibunch technique as a plasma-based accelerator.  
TPAE058 Plasma Dark Current in Self-ionized Plasma Wake Field Accelerators (PWFA) electron, radiation, diagnostics, space-charge 3444
  • E. Oz, S. Deng, T.C. Katsouleas, P. Muggli
    USC, Los Angeles, California
  • C.D. Barnes, F.-J. Decker, M.J. Hogan, R.H. Iverson, P. Krejcik, C.L. O'Connell, R. Siemann, D.R. Walz
    SLAC, Menlo Park, California
  • C.E. Clayton, C. Huang, D.K. Johnson, C. Joshi, W. Lu, K.A. Marsh, W.B. Mori, M. Zhou
    UCLA, Los Angeles, California
  Particle trapping is investigated with experiment, theory and simulations for conditions relevant to beam driven Plasma Wake Field Accelerators. Such trapping produces plasma dark current when the wakefield aplitude is above a threshold values and may place a limit on the maximum acceleration gradient in a PWFA. Trapping and dark current are enhanced when in an ionizing plasma, that is self-ionized by the beam as well as in gradual density gradients. In the E164X conducted at the Stanford Linear Accelerator Center by a collaboration of USC, UCLA and SLAC, evidence of trapping has been observed. Here we present experimental results and a simplified analytical model of the particle trapping threshold which is compared to simulations done with an object oriented fully parallel 3-D PIC code OSIRIS.  
TPAE064 Externally Controlled Injection of Electrons by a Laser Pulse in a Laser Wakefield Electron Accelerator electron, injection, laser, scattering 3644
  • S.-Y. Chen, C.-L. Chang, W.-T. Chen, T.-Y. Chien, C.-H. Lee, J.-Y. Lin, J. Wang
    IAMS, Taipei
  Funding: National Science Council, Taiwan

Spatially and temporally localized injection of electrons is a key element for development of plasma-wave electron accelerator. Here we report the demonstration of two different schemes for electron injection in a self-modulated laser wakefield accelerator (SM-LWFA) by using a laser pulse. In the first scheme, by implementing a copropagating laser prepulse with proper timing, we are able to control the growth of Raman forward scattering and the production of accelerated electrons. We found that the stimulated Raman backward scattering of the prepulse plays the essential role of injecting hot electrons into the fast plasma wave driven by the pump pulse. In the second scheme, by using a transient density ramp we achieve self-injection of electrons in a SM-LWFA with spatial localization. The transient density ramp is produced by a prepulse propagating transversely to drill a density depression channel via ionization and expansion. The same mechanism of injection with comparable efficiency is also demonstrated with a transverse plasma waveguide driven by Coulomb explosion.

TPAE066 Robust Autoresonant Excitation in the Plasma Beat-Wave Accelerator: A Theoretical Study laser, resonance, electron, beat-wave 3688
  • A.E. Charman, R.R. Lindberg, J.S. Wurtele
    UCB, Berkeley, California
  • L. Friedland
    The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem
  Funding: Division of High Energy Physics, U.S. Department of Energy, DARPA, U.S. Department of Defense.

A modified version of the Plasma Beat-Wave Accelerator scheme is introduced and analyzed, which is based on autoresonant phase-locking of the nonlinear Langmuir wave to the slowly chirped beat frequency of the driving lasers via adiabatic passage through resonance. This new scheme is designed to overcome some of the limitations of previous approaches, namely relativistic detuning and nonlinear modulations in the driven Langmuir wave amplitude, and sensitivity to frequency mismatch from density fluctuations. As in previous schemes, instabilities of the ionic background ultimately limit the useful interaction time, but nevertheless peak electric fields approaching the wave-breaking limit seem readily attainable. Compared to traditional approaches, the autoresonant scheme achieves larger accelerating electric fields for given laser intensity; the plasma wave excitation is more robust to variations in plasma density; it is largely insensitive to the choice of chirp rate, provided that chirping is sufficiently slow; and the quality and uniformity of the resulting plasma wave and its suitability for accelerator applications may be superior.

TPAT034 Manipulations of Double Electron Beams within One RF Period for Seeded SM-LWFA Experiment laser, electron, emittance, linac 2312
  • F. Zhou, D. Cline
    UCLA, Los Angeles, California
  • M. Babzien, V. Yakimenko
    BNL, Upton, Long Island, New York
  • W.D. Kimura
    STI, Washington
  Funding: Work supported by U.S. DOE.

Although seeded SM-LWFA only requires one electron beam to initiate the laser wakefield, it would be highly desirable to have a second electron beam traveling after the first one to probe the accelerated electrons. To create and preserve significant amount of wakefield in the STELLA SM-LWFA experiment, the first e-beam needs to be tiny (<40 microns FWHM) in size and short in length within the plasma. To probe the wakefield which is damped within 10 ps for certain plasma density, the separation between the first and second beams needs to be within one RF period and the second e-beam must have smaller energy spread and smaller size. Design of double beams in one RF period to meet the strict requirements and the preliminary beam study at BNL-ATF facility are presented. The scheme of double beams with ATF bunch compressor is also discussed.

TPAT036 Ferroelectric Plasma Source for Heavy Ion Beam Charge Neutralization ion, electron, heavy-ion, focusing 2452
  • P. Efthimion, R.C. Davidson, E.P. Gilson, L. Grisham
    PPPL, Princeton, New Jersey
  • B. G. Logan, W. Waldron, S. Yu
    LBNL, Berkeley, California
  Funding: Research supported by the U.S. Department of Energy.

Plasmas are employed as a medium for charge neutralizing heavy ion beams to allow them to focus to a small spot size. Calculations suggest that plasma at a density of 1-100 times the ion beam density and at a length ~ 0.1-1 m would be suitable. To produce 1 meter plasma, large-volume plasma sources based upon ferroelectric ceramics are being considered. These sources have the advantage of being able to increase the length of the plasma and operate at low neutral pressures. The source will utilize the ferroelectric ceramic BaTiO3 to form metal plasma. The drift tube inner surface of the Neutralized Drift Compression Experiment (NDCX) will be covered with ceramic. High voltage (~ 1-5 kV) is applied between the drift tube and the front surface of the ceramic by placing a wire grid on the front surface. A prototype ferroelectric source 20 cm long produced plasma densities ~ 5x1011 cm-3. The source was integrated into the experiment and successfully charge neutralized the K ion beam. Presently, the 1 meter source is being fabricated. It will be characterized and integrated into NDCX for charge neutralization experiments. Experimental results will be presented.

TPAT037 Simulating the Long-Distance Propagation of Intense Beams in the Paul Trap Simulator Experiment ion, simulation, focusing, lattice 2491
  • E.P. Gilson, M. Chung, R.C. Davidson, P. Efthimion, R. M. Majeski, E. Startsev
    PPPL, Princeton, New Jersey
  Funding: Research supported by the U.S. Department of Energy.

The Paul Trap Simulator Experiment (PTSX) makes use of a compact Paul trap configuration with quadrupolar oscillating wall voltages to simulate the propagation of intense charged particle beams over distances of many kilometers through magnetic alternating-gradient transport systems. The simulation is possible because of the similarity between the transverse dynamics of particles in the two systems. One-component pure cesium ion plasmas have been trapped that correspond to normalized intensity parameters s < 0.8, where s is the ratio of the square of the plasma frequency to twice the square of the average transverse focusing frequency. The PTSX device confines the plasma for hundreds of milliseconds, which is equivalent to beam propagation over tens of kilometers. Results are presented for experiments in which the amplitude of the oscillating confining voltage waveform has been modified as a function of time. A comparison is made between abrupt changes in amplitude and adiabatic changes in amplitude. The effects of varying the frequency are also discussed. A barium ion source and a laser system have been installed and initial measurements made with this system are presented.

TPAT039 Wavelet-Based Poisson Solver for Use in Particle-in-Cell Simulations simulation, diagnostics, vacuum, electron 2601
  • B. Terzic, C.L. Bohn, D. Mihalcea
    Northern Illinois University, DeKalb, Illinois
  • I.V. Pogorelov
    LBNL, Berkeley, California
  Funding: Work of B.T., D.M. and C.L.B. is supported by Air Force contract FA9471-040C-0199. Work of I.V.P. is supported by the U.S. Department of Energy contract DE-AC03-76SF00098.

We report on a successful implementation of a wavelet-based Poisson solver for use in 3D particle-in-cell simulations. One new aspect of our algorithm is its ability to treat the general (inhomogeneous) Dirichlet boundary conditions. The solver harnesses advantages afforded by the wavelet formulation, such as sparsity of operators and data sets, existence of effective preconditioners, and the ability simultaneously to remove numerical noise and further compress relevant data sets. Having tested our method as a stand-alone solver on two model problems, we merged it into IMPACT-T to obtain a fully functional serial PIC code. We present and discuss preliminary results of application of the new code to the modelling of the Fermilab/NICADD and AES/JLab photoinjectors.

Corresponding author: B.T. (bterzic@nicadd.niu.edu)

TPAT040 Actual Stationary State for Plasma Lens electron, ion, acceleration, heavy-ion 2619
  • V. Zadorozhny
    NASU/IOC, Kiev
  • A. Goncharov
    NSC/KIPT, Kharkov
  • Z.P. Parsa
    BNL, Upton, Long Island, New York
  The electrostatic plasma lens (PL) provides an attractive and unique tool for manipulating high-current heavy ion beams. The fundamental concept of the PL is based on the use of magnetically insulated electrons and equipotentialization of magnetic field lines. Rigorous application of PL is, however, limited. The reason is the estimation behaviour of electrons for complicated magnetic fields runs into severe difficults.We show that there are specific conditions that admit steady-state of a longitudinal motion, and consider a question of it stability. These results are needed to develop an optimized PL with minimal spherical aberation, in party by optimization of the magnetic field conficuration in the low-magnetic-field range.  
TPAT068 A Fast Faraday Cup for the Neutralized Drift Compression Experiment ion, simulation, electron, target 3765
  • A.B. Sefkow, R.C. Davidson, P. Efthimion, E.P. Gilson
    PPPL, Princeton, New Jersey
  • F.M. Bieniosek, J.E. Coleman, S. Eylon, W.G. Greenway, E. Henestroza, J.W. Kwan, P.K. Roy, D.L. Vanecek, W. Waldron, S. Yu
    LBNL, Berkeley, California
  • D.R. Welch
    ATK-MR, Albuquerque, New Mexico
  Funding: Research supported by the U.S. Department of Energy.

Heavy ion drivers for high energy density physics applications and inertial fusion energy use space-charge-dominated beams which require longitudinal bunch compression in order to achieve sufficiently high beam intensity at the target. The Neutralized Drift Compression Experiment-1A (NDCX-1A) at Lawrence Berkeley National Laboratory (LBNL) is used to determine the effective limits of neutralized drift compression. NDCX-1A investigates the physics of longitudinal drift compression of an intense ion beam, achieved by imposing an initial velocity tilt on the drifting beam and neutralizing the beam's space-charge with background plasma. Accurately measuring the longitudinal compression of the beam pulse with high resolution is critical for NDCX-1A, and an understanding of the accessible parameter space is modeled using the LSP particle-in-cell (PIC) code. The design and preliminary experimental results for an ion beam probe which measures the total beam current at the focal plane as a function of time are summarized.

TPAT069 Numerical Studies of Electromagnetic Instabilities in Intense Charged Particle Beams with Large Energy Anisotropy focusing, simulation, heavy-ion, vacuum 3780
  • E. Startsev, R.C. Davidson, W.L. Lee
    PPPL, Princeton, New Jersey
  Funding: Research supported by the U.S. Department of Energy.

In intense charged particle beams with large energy anisotropy, free energy is available to drive transverse electromagnetic Weibel-type instabilities. Such slow-wave transverse electromagnetic instabilities can be described by the so-called Darwin model, which neglects the fast-wave portion of the displacement current. The Weibel instability may also lead to an increase in the longitudinal velocity spread, which would make the focusing of the beam difficult and impose a limit on the minimum spot size achievable in heavy ion fusion experiments. This paper reports the results of recent numerical studies of the Weibel instability using the Beam Eigenmode And Spectra (bEASt) code for space-charge-dominated, low-emittance beams with large tune depression. To study the nonlinear stage of the instability, the Darwin model is being developed and incorporated into the Beam Equilibrium Stability and Transport(BEST) code.

TPAT092 Numerical Studies of the Friction Force for the RHIC Electron Cooler electron, ion, simulation, space-charge 4278
  • A.V. Fedotov, I. Ben-Zvi, V. Litvinenko
    BNL, Upton, Long Island, New York
  • D.T. Abell, D.L. Bruhwiler, R. Busby, P. Schoessow
    Tech-X, Boulder, Colorado
  Funding: Work performed under the auspices of the U.S. Department of Energy.

Accurate calculation of electron cooling times requires an accurate description of the dynamical friction force. The proposed RHIC cooler will require ~55 MeV electrons, which must be obtained from an RF linac, leading to very high transverse electron temperatures. A strong solenoid will be used to magnetize the electrons and suppress the transverse temperature, but the achievable magnetized cooling logarithm will not be large. Available formulas for magnetized dynamical friction are derived in the logarithmic approximation, which is questionable in this regime. In this paper, we explore the magnetized friction force for parameters of the RHIC cooler, using the VORPAL code.* VORPAL can simulate dynamical friction and diffusion coefficients directly from first principles.** Various aspects of the friction force, such as dependence on magnetic field, scaling with ion charge number and others, are addressed for the problem of high-energy electron cooling in the RHIC regime.

*C. Nieter & J.R. Cary, J. Comp. Phys. 196 (2004), p. 448. **D.L. Bruhwiler et al., Proc. 33rd ICFA Advanced Beam Dynamics Workshop (2004).

TOAD005 Observation of Frequency Locked Coherent Transition Radiation radiation, electron, vacuum, single-bunch 452
  • R.A. Marsh, A.S. Kesar, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts
  Funding: This work was supported by the Department of Energy, High Energy Physics, under contract DE-FG02-91ER40648.

Measurements of frequency locked, coherent transition radiation (CTR) were performed at the 17 GHz high-gradient accelerator facility built by Haimson Research Corporation at MIT PSFC. CTR produced from a metallic foil placed in the beam path was extracted through a window, and measured with a variety of detectors, including: diode, Helium cooled Si Bolometer, and double heterodyne receiver system. The angular energy distribution measured by the diode and bolometer are in agreement and consistent with calculations for a 15 MeV 200 mA 110 ns beam of 1 ps bunches. Heterodyne receiver measurements were able to show frequency locking, namely inter-bunch coherence at integer multiples of the accelerator RF frequency of 17.14 GHz. At the locked frequencies the power levels are enhanced by the number of bunches in a single beam pulse. The CTR was measured as a comb of locked frequencies up to 240 GHz, with a bandwidth of 50 MHz.

TPPE001 The HERA Volume H- Source electron, extraction, emittance, vacuum 788
  • J. Peters
    DESY, Hamburg
  Funding: The support of EEC (Contract HPRI-CT-2001-50021) is gratefully acknowledged.

The HERA RF-Volume Source is the only source that delivers routinely a H – current of 40 mA without Cs. It has been running for years without interruption for maintenance. The production mechanism for H – ions in this type of source is still under discussion. Laser photodetachment measurements have been done at DESY in order to measure the H – distribution in the source. The measurements were done also under extraction conditions at high voltage. The dependency of the quality of the Hminus beam on the frequency was investigated. A frequency range of 1.65 – 9 Mhz was scanned and the emittance was measured for several Hminus currents up to 40 mA. The results of our investigations make further source improvements possible. Recently currents of 60 mA were reached.

TPPE003 Analysis of Multigrid Extraction Plasma Meniscus Formation electron, ion, extraction, proton 862
  • M. Cavenago
    INFN/LNL, Legnaro, Padova
  • V. Antoni, F. Sattin
    CNR/RFX, Padova
  • A. Tanga
    MPI/IPP, Garching
  Funding: INFN-LNL, CNR-RFX.

Effects of plasma meniscus on the emittance in negative ion source proposed for spallation sources or neutral beam injectors (NBI) for tokamaks are particularly interesting to study with fluid models because: 1) at least three different charged fluid can be recognised: the thermalized and fully magnetized electrons; the slightly magnetized and roughly thermalized positive ions; the negative ions, typically formed within few cm from meniscus; 2) different implementation of the magnetic filter system need to be compared; 3) optimization of electron dump and outlet electrode strongly depends on plasma meniscus contact point. With reasonable assumption on system geometry, 2D and 3D charged fluid quation for the selfconsistent electrostatic field can be written and effect of grid aperture is investigated. Moreover, these equations are easily implemented into a multiphysics general purpose program. Preliminary results are described, and compared to existing codes.

TPPE011 A Compact High-Brightness Heavy-Ion Injector emittance, ion, heavy-ion, extraction 1263
  • G.A. Westenskow, D.P. Grote, E. F. Halaxa
    LLNL, Livermore, California
  • F.M. Bieniosek, J.W. Kwan
    LBNL, Berkeley, California
  Funding: This work has been performed under the auspices of the U.S. DOE by UC-LBNL under contract DE-AC03-76SF00098 and by UC-LLNL under contract W-7405-ENG-48, for the Heavy Ion Fusion Virtual National Laboratory.

To provide compact high-brightness heavy-ion beams for Heavy Ion Fusion (HIF) accelerators, we have been experimenting with merging multi-beamlets in an injector which uses an RF plasma source. In an 80-kV 20-microsecond experiment, the RF plasma source has produced up to 5 mA of Ar+ in a single beamlet. An extraction current density of 100 mA/cm2 was achieved, and the thermal temperature of the ions was below 1 eV. More than 90% of the ions were in the Ar+ state, and the energy spread from charge exchange was found to be small. We have tested at full voltage gradient the first 4 gaps of a 61-beamlet injector design. Einzel lens were used to focus the beamlets while reducing the beamlet to beamlet space charge interaction. We will report on a converging 119 multi-beamlet source. Although the source has the same optics as a full 1.6 MV injector system, the test will be carried out at 400 kV due to the test stand HV limit. We will measure the beam’s emittance after the beamlets are merged and have been transported through an electrostatic quadrupole. Our goal is to confirm the emittance growth and to demonstrate the technical feasibility of building a driver-scale HIF injector.

TPPE012 Using the Orbit Tracking Code Z3CYCLONE to Predict the Beam Produced by a Cold Cathode PIG Ion Source for Cyclotrons under DC Extraction emittance, ion, ion-source, cyclotron 1297
  • E.R. Forringer, H.G. Blosser
    NSCL, East Lansing, Michigan
  Experimental measurements of the emittance and luminosity of beams produced by a cold-cathode Phillips Ionization Guage (PIG) ion source for cyclotrons under dc extraction are reviewed. (The source being studied is of the same style as ones that will be used in a series of 250 MeV proton cyclotrons being constructed for cancer therapy by ACCEL Inst, Gmbh, of Bergisch Gladbach, Germany.) The concepts of 'plasma boundary' and 'plasma temperature' are presented as a useful set of parameters for describing the initial conditions used in computational orbit tracking. Experimental results for r-pr and z-pz emittance are compared to predictions from the MSU orbit tracking code Z3CYCLONE with results indicating that the code is able to predict the beam produced by these ion sources with adequate accuracy such that construction of actual cyclotrons can proceed with reasonably prudent confidence that the cyclotron will perform as predicted.  
TPPE018 Characterization of a Tubular Hot-Cavity Surface Ionization Source ion, target, ion-source, emittance 1581
  • Y. Liu, H. Z. Bilheux, Y. Kawai
    ORNL, Oak Ridge, Tennessee
  Funding: Managed by UT-Battelle, LLC, for the U.S. DOE under contract DE-AC05-00OR22725.

Elements with low ionization potentials can be efficiently ionized by positive surface ionization. It has been experimentally observed and theoretically shown that the ionization efficiency in a hot-cavity can be significantly higher than expected for the surface ionization mechanism. This is explained by the existence of a thermal plasma inside the cavity consisting of surface ionized ions and thermionic electrons. We have investigated the suggested ioniation mechanisms in a tubular hot-cavity surface ionization source where the area of the exit aperture is small compared with the tube inner surface. Thermal analyses of the tubular cavity and calculated mean number of wall collisions of a neutral particle in the cavity before escaping through the exit aperture are presented. Measured emittance and ionization efficiencies of various elements as a function of the cavity temperature for different cavity materials are discussed.

TPPE022 First Results on the Path Towards a Microwave-Assisted H- Ion Source ion, ion-source, electron, SNS 1784
  • R. Keller, P.A. Luft, M. T. Monroy, A. Ratti, M.J. Regis, D. L. Syversrud, J.G. Wallig
    LBNL, Berkeley, California
  • D.E. Anderson, R.F. Welton
    ORNL, Oak Ridge, Tennessee
  Funding: This work supported by Office of Basic Energy Sciences, U.S. Department of Energy under Contract No. DE-AC03-76SF00098.

A novel concept for creating intense beams of negative hydrogen ion beams is presented. In this approach, an ECR ion source operating at 2.45 GHz frequency is utilized as a primary plasma generator and coupled to an SNS-type multi-cusp H- ion source. The secondary source is driven by chopped dc power avoiding the use of filaments or of an internal rf antenna. The development of the new ion source is aimed at the future beam-power goal of 3 MW for the Spallation Neutron Source (SNS) that will be pursued after the start of SNS operations, but application to other proton driver accelerators that include an accumulator ring is feasible as well. The first two phases of this development effort have been successfully completed: assembly of a test stand and verification of the performance of an rf-driven SNS ion-source prototype; and extraction of electrons with more than 350 mA current from a 2.45-GHz ECR ion source obtained on loan from Argonne National Laboratory. The next goal is the demonstration of actual H- ion production by this novel, hybrid ion source. This paper describes the source principle and design in detail and reports on the current status of the development work.

TPPE027 Properties of Laser-Produced Highly Charged Heavy Ions for Direct Injection Scheme laser, ion, target, rfq 1976
  • K. Sakakibara, T. Hattori, N. Hayashizaki, T. Ito
    RLNR, Tokyo
  • H. Kashiwagi
    JAERI/ARTC, Gunma-ken
  • M. Okamura
    RIKEN, Saitama
  To accelerate highly charged intense ion beam, we have developed the Direct Plasma Injection Scheme (DPIS) with laser ion source. In this scheme an ion beam from a laser ion source is injected directly to a RFQ linac without a low energy beam transport (LEBT) and the beam loss in the LEBT can be avoided. We achieved high current acceleration of carbon ions (60mA) by DPIS with the high current optimized RFQ. As the next setp we will use heavier elements like Ag, Pb, Al and Cu as target in LIS (using CO2, Nd-YAG or other laser) for DPIS and will examine properties of laser-produced plasma (the relationship of between charge state and laser power density, the current dependence of the distance from the target, etc).  
TPPE028 In-Situ Electron Cyclotron Resonance (ECR) Plasma Potential Determination Using an Emissive Probe electron, ion, ion-source, monitoring 2035
  • F.W. Meyer, Y. Liu
    ORNL, Oak Ridge, Tennessee
  • H.J. You
    Hanyang University, Seoul
  Funding: This research was sponsored by the U.S. DOE under contract No. DE-AC05-00OR22725 with UT-Battelle, LLC. HJY acknowledges support from the Korean Science Education Foundation (KOSEF).

In this paper, real-time, in-situ, plasma potential measurements are reported for an ECR ion source and correlated with extracted beam characteristics. The local real-time plasma potential of the ORNL CAPRICE ECR ion source was measured using an emissive probe, which was inserted perpendicularly from the plasma chamber wall at the mid-plane of the ECR zone between one of the six radial loss cones of the magnetic field structure, where perturbation of the main ECR plasma is expected to be small. Slots machined through the plasma- and puller-electrodes at the plasma chamber wall radius permitted insertion of the probe from the extraction side of the ECR source without perturbation of the coaxial microwave injection. The emissive probe technique permits plasma potential determination independent of plasma conditions and avoids problems related to probe geometry. The probe loop tip was pointed toward the chamber center in a radial plane and was located about 5 mm outside of the ECR zone. Details of the measurements, and a comparison with an external-beam-deceleration-based plasma potential determination will be presented.

TPPE031 60 mA Carbon Beam Acceleration with DPIS rfq, ion, laser, injection 2206
  • M. Okamura, R.A. Jameson, K. Sakakibara, J. Takano
    RIKEN, Saitama
  • T. Fujimoto, S. Shibuya, T. Takeuchi
    AEC, Chiba
  • Y. Iwata, K. Yamamoto
    NIRS, Chiba-shi
  • H. Kashiwagi
    JAERI/ARTC, Gunma-ken
  • A. Schempp
    IAP, Frankfurt-am-Main
  We have studied "direct plasma injection scheme (DPIS)" since 2000. This new scheme is for producing very intense heavy ions using a combination of an RFQ and a laser ion source. An induced laser plasma goes directly into the RFQ without an extraction electrode nor any focusing devices. Obtained maximum peak current of Carbon 4+ beam reached 60 mA with this extremely simple configuration. The details of the experimental result will be presented.  
TPPE037 Relative Contribution of Volume and Surface-Plasma Generation of Negative Ions in Gas Discharges ion, electron, ion-source, cathode 2482
  • V.G. Dudnikov
    BTG, New York
  The relative contribution of volume and surface-plasma generation of extracted ?- ions in gas discharge sources will be analyzed. At the present time, it is well known that surface-plasma generation of extracted ?- ion is dominate above volume processes in discharges with admixture of cesium or other catalysts with low ionization potential. We will attract attention to evidences, that surface-plasma generation can be enhanced in high density discharges without cesium after electrode activation by high temperature conditioning in discharge. A diffusion of impurity with a low ionization potential can be a reason of observed enhancement of H- emission. For the effective generation of ?- ion beams in discharge without cesium, it is necessary to optimize surface-plasma generation of extracted ?- ion. Such optimization allows considerable improvement of ?-/D- sources characteristics.  
TPPT033 Simulations Using the VORPAL Code of Electron Impact Ionization Effects in Waveguide Breakdown Processes electron, simulation, ion, space-charge 2298
  • P. Stoltz, J.R. Cary, P. Messmer, C. Nieter
    Tech-X, Boulder, Colorado
  Funding: Supported by Department of Energy SBIR Grant No. DE-FG03-02ER83554.

We present results of three-dimensional simulations using the VORPAL code of power absorbtion by stray electrons in X-band waveguides. These simulations include field emission from the waveguide surfaces, impact ionization of background gas, and secondary emission from the walls. We discuss the algorithms used for each of these electron effects. We show the power abosrbed as a function of background gas density. Finally, we present scaling results for running these simulations on Linux Clusters.

TPPT084 Surface Study of Nb/Cu Films for Cavity Deposition by ECR Plasma ion, vacuum, electron, superconductivity 4153
  • A.T. Wu, R.C. Ike, H.L. Phillips, A-M. Valente, H. Wang, G. Wu
    Jefferson Lab, Newport News, Virginia
  Funding: This manuscript has been authorized by SURA, Inc. under Contract No. DE-AC05-84ER-40150 with the U.S. Department of Energy.

Deposition of thin niobium (Nb) films on copper (Cu) cavities, using an electron cyclotron resonance (ECR) plasma appears to be an attractive alternative technique for fabricating superconducting radio frequency cavities to be used in particle accelerators. The performance of these Nb/Cu cavities is expected to depend on the surface characteristics of the Nb films. In this paper, we report on an investigation of the influence of deposition energy on surface morphology, microstructure, and chemical composition of Nb films deposited on small Cu disks employing a metallographic optical microscope, a 3-D profilometer, a scanning electron microscope, and a dynamic secondary ion mass spectrometer. The results will be compared with those obtained on Nb surfaces treated by buffered chemical polishing, electropolishing, and buffered electropolishing. Possible implications from this study for Nb deposition on real Cu cavities will be discussed.

TPPT085 Niobium Thin Film Coating on a 500-MHz Copper Cavity by Plasma Deposition vacuum, superconductivity, power-supply, ion 4167
  • H. Wang, H.L. Phillips, R.A. Rimmer, A-M. Valente, A.T. Wu, G. Wu
    Jefferson Lab, Newport News, Virginia
  Funding: This work was supported by DOE contract DE-AC05-84ER40150 Modification No. M175, under which the Southeastern Universities Research Association (SURA) operates the Thomas Jefferson National Accelerator Facility.

A system for the deposition, using an ECR plasma source, of a thin film of niobium inside a copper cavity for superconducting accelerator applications has been designed and is being constructed. The system uses a 500-MHz copper cavity as the substrate and the vacuum chamber. The ECR plasma will be created to produce direct niobium ion deposition. The central cylindrical grid is biased to realize the energy controlled deposition. This report describes the design of several subcomponents including the vacuum chamber, RF supply, biasing grid and magnet coils. Operational parameters are compared between a working small-sample deposition system and this system. Initial plasma simulation also suggested that plasma ignition in this cavity system is feasible.

TPPT098 VORPAL as a Tool for Three-Dimensional Simulations of Multipacting in Superconducting RF Cavities electron, simulation, radio-frequency, resonance 4332
  • C. Nieter, J.R. Cary, P. Stoltz
    Tech-X, Boulder, Colorado
  • G.R. Werner
    CIPS, Boulder, Colorado
  Considerable resources are required to run three dimensional simulations of multipacting in superconducting rf cavities. Three dimensional simulations are needed to understand the possible roles of non-axisymmetric features such as the power couplers. Such simulations require the ability to run in parallel. We consider the versatile plasma simulation code VORPAL* as a possible platform to study such effects. VORPAL has a general 3D domain decomposition and can run in any physical dimension. VORPAL uses the CMEE library** to model the secondary emission of electrons from metal surfaces. We will present a three dimensional simulation of a simple pillbox rf cavity to demonstrate the potential of VORPAL to be a major simulation tool for superconducting rf cavities.

*C. Nieter and J.R. Cary, J. Comp. Phys. 196 (2004), p. 448. **P.H. Stoltz, ICFA electron cloud work shop, Napa, CA (2004).

TOPA001 Mono Energetic Beams from Laser Plasma Interactions laser, electron, injection, simulation 69
  • C.G.R. Geddes, E. Esarey, W. Leemans, C.B. Schroeder, C. Toth
    LBNL, Berkeley, California
  • J.R. Cary, C. Nieter
    Tech-X, Boulder, Colorado
  • J. Van Tilborg
    TUE, Eindhoven
  Funding: Supported by U.S. Dept. of Energy contracts DE-AC03-76SF00098, DE-FG03-95ER40926, DE-FG02-01ER41178, DE-FG02-03ER83857, SciDAC, and NSF 0113907. C. Geddes is also supported by the Hertz foundation.

A laser driven wakefield accelerator has been tuned to produce high energy electron bunches with low emittance and energy spread by extending the interaction length using a plasma channel. Wakefield accelerators support gradients thousands of times those achievable in RF accelerators, but short acceleration distance, limited by diffraction, has resulted in low energy beams with 100% electron energy spread. In the present experiments on the L’OASIS laser,* the relativistically intense drive pulse was guided over 10 diffraction ranges by a plasma channel. At a drive pulse power of 9 TW, electrons were trapped from the plasma and beams of percent energy spread containing >200pC charge above 80 MeV and with normalized emittance estimated at < 2 pi -mm-mrad were produced.** Data and simulations (VORPAL***) show the high quality bunch was formed when beam loading turned off injection after initial trapping, and when the particles were extracted as they dephased from the wake. Up to 4TW was guided without trapping, potentially providing a platform for controlled injection. The plasma channel technique forms the basis of a new class of accelerators, with high gradients and high beam quality.

*W.P. Leemans et al., Phys. Plasmas 5, 1615-23 (1998). **C.G.R. Geddes et al., Nature 431, 538-41 (2004). ***C. Nieter et al., J. Comp. Phys. 196, 448-73 (2004).

TOPA005 Left-Handed Metamaterials Studies and their Application to Accelerator Physics radiation, electron, dipole, diagnostics 458
  • S.P. Antipov, W. Liu, J.G. Power
    ANL, Argonne, Illinois
  • L.K. Spentzouris
    Illinois Institute of Technology, Chicago, Illinois
  Funding: DOE grant NSF grant

Recently, there has been a growing interest in applying artificial materials, known as Left-Handed Metamaterials (LHM), to accelerator physics. These materials have both negative permittivity and permeability and therefore possess several unusual properties: the index of refraction is negative and the direction of the group velocity is antiparallel to the direction of the phase velocity (along k). These properties lead to a reverse Cherenkov effect, which has potential beam diagnostic applications, in addition to accelerator applications. Several LHM devices with different configurations are being experimentally and theoretically studied at Argonne. In this paper, we describe permittivity and permeability retrieval techniques that we have developed and applied to these devices. We have also investigated the possibility of building a Cherenkov detector based on LHM and propose an experiment to observe the reverse radiation generated by an electron beam passing through a LHM. The potential advantage of a LHM detector is that the radiation in this case is emitted in the direction reversed to the direction of the beam, so it could be easier to get a clean measurement.

WPAP027 RF Electron Gun with Driven Plasma Cathode cathode, gun, electron, extraction 1991
  • I.V. Khodak, V.A. Kushnir
    NSC/KIPT, Kharkov
  It’s known that RF guns with plasma cathodes based on solid-state dielectrics are able to generate an intense electron beam. In this paper we describe results of experimental investigation of the single cavity S-band RF gun with driven plasma cathode. The experimental sample of the cathode based on ferroelectric ceramics has been designed. Special design of the cathode permits to separate spatially processes of plasma development and electron acceleration. It has been obtained at RF gun output electron beam with particle energy ~500 keV, pulse current of 4 A and pulse duration of 80 ns. Results of experimental study of beam parameters are referred in. The gun is purposed to be applied as the intense electron beam source for electron linacs.  
WPAT027 Recent Results from the X-Band Pulsed Magnicon Amplifier electron, target, gun, vacuum 1979
  • O.A. Nezhevenko, V.P. Yakovlev
    Omega-P, Inc., New Haven, Connecticut
  • A.W. Fliflet, S.H. Gold
    NRL, Washington, DC
  • J.L. Hirshfield, M.A. LaPointe
    Yale University, Physics Department, New Haven, CT
  • A.K. Kinkead
  Funding: Research supported by the Department of Energy, Office of High Energy Physics, and the Office of Naval Research.

A frequency-doubling magnicon amplifier at 11.4 GHz has been designed and built as the prototype of an alternative microwave source for the Next Linear Collider project, and to test high power RF components and accelerating structures. The tube is designed to produce ~60 MW, ~1.2 microsecond pulses at 58% efficiency and 59 dB gain, using a 470 kV, 220 A, 2 mm-diameter beam. In the first tests the output power was limited to a level of 26 MW in a 200 nsec pulse. This limitation was caused by the oscillations in the tube collector. Experimental results of the magnicon tests with the new collector are presented in this paper

RPAE019 Positron Source from Betatron X-Rays Emitted in a Plasma Wiggler electron, positron, radiation, wiggler 1625
  • D.K. Johnson, C.E. Clayton, C. Huang, C. Joshi, W. Lu, K.A. Marsh, W.B. Mori, M. Zhou
    UCLA, Los Angeles, California
  • C.D. Barnes, F.-J. Decker, M.J. Hogan, R.H. Iverson, P. Krejcik, C.L. O'Connell, R. Siemann, D.R. Walz
    SLAC, Menlo Park, California
  • S. Deng, T.C. Katsouleas, P. Muggli, E. Oz
    USC, Los Angeles, California
  In the E-167 plasma wakefield accelerator (PWFA) experiments in the Final Focus Test Beam (FFTB) at the Stanford Linear Accelerator Center (SLAC), an ultra-short, 28.5 GeV electron beam field ionizes a neutral column of Lithium vapor. In the underdense regime, all plasma electrons are expelled creating an ion column. The beam electrons undergo multiple betatron oscillations leading to a large flux of broadband synchrotron radiation. With a plasma density of 3x1017 cm-3, the effective focusing gradient is near 9 MT/m with critical photon energies exceeding 50 MeV for on-axis radiation. A positron source is the initial application being explored for these X-rays, as photo-production of positrons eliminates many of the thermal stress and shock wave issues associated with traditional Bremsstrahlung sources. Photo-production of positrons has been well-studied; however, the brightness of plasma X-ray sources provides certain advantages. In this paper, we present results of the simulated radiation spectra for the E-167 experiments, and compute the expected positron yield.  
RPAP039 Accelerator and Ion Beam Tradeoffs for Studies of Warm Dense Matter ion, target, emittance, chromatic-effects 2568
  • J.J. Barnard, D. A. Callahan, A. Friedman, R.W. Lee, M. Tabak
    LLNL, Livermore, California
  • R.J. Briggs
    SAIC, Alamo, California
  • R.C. Davidson, L. Grisham
    PPPL, Princeton, New Jersey
  • E. P. Lee, B. G. Logan, P. Santhanam, A. Sessler, J.W.  Staples, J.S. Wurtele, S. Yu
    LBNL, Berkeley, California
  • C. L. Olson
    Sandia National Laboratories, Albuquerque, New Mexico
  • D. Rose, D.R. Welch
    ATK-MR, Albuquerque, New Mexico
  Funding: Work performed under the auspices of the U.S. Department of Energy under University of California contract W-7405-ENG-48 at LLNL, University of California contract DE-AC03-76SF00098 at LBNL, and contract DEFG0295ER40919 at PPPL.

One approach to heat a target to "Warm Dense Matter" conditions (similar, for example, to the interiors of giant planets or certain stages in Inertial Confinement Fusion targets), is to use intense ion beams as the heating source. By consideration of ion beam phase space constraints, both at the injector, and at the final focus, and consideration of simple equations of state, approximate conditions at a target foil may be calculated. Thus target temperature and pressure may be calculated as a function of ion mass, ion energy, pulse duration, velocity tilt, and other accelerator parameters. We examine the variation in target performance as a function of various beam and accelerator parameters, in the context of several different accelerator concepts, recently proposed for WDM studies.

RPAP040 Design of a Fast Neutral He Beam System for Feasibility Study of Charge-Exchange Alpha-Particle Diagnostics in a Thermonuclear Fusion Reactor ion, ion-source, diagnostics, extraction 2630
  • K. Shinto, S. Kitajima, M. Sasao, H. Sugawara, Takenaga, M. Takenaga, S. Takeuchi
    Graduate School of Engineering, Tohoku University, Sendai
  • O. Kaneko, M. Nishiura
    NIFS, Gifu
  • S. Kiyama
    AIST, Tsukuba
  • M. Wada
    Doshisha University, Graduate School of Engineering, Kyoto
  For alpha-particle diagnostics in a thermonuclear fusion reactor, neutralization using a fast (~2 MeV) neutral He beam produced by the spontaneous electron detachment of a He- is considered most promising. However, the beam transport of produced fast neutral He has not been studied, because of difficulty for producing high-brightness He- beam. Double-charge-exchange He- sources and simple beam transport systems were developed and their results were reported in the PAC99* and other papers.** To accelerate an intense He- beam and verify the production of the fast neutral He beam, a new test stand has been designed. It consists of a multi-cusp He+ source, alkali metal gas cell for double charge exchange, a stigmatic 90 degree bending magnet as an ion separator, an accelerating tube and a free-flight tube to produce fast neutral He beam by autodetachment. The beam parameters of the He- beam are planed to be 150 keV of the beam energy and 10 uA of the beam current. A He+ beam of about 10 mA is extracted from the ion source and accelerated up to 15~25 keV for the effective charge exchange. Details of the design of the test stand and the brief result of the beam optics will be presented.

*M. Sasao et al., Proc. of PAC99, pp. 1306-1308. **M. Sasao et al., Rev. Sci. Instr. Vol.69, pp.1063-1065 (1998).

RPAT078 Bunch Length Measurements Using Coherent Radiation radiation, electron, vacuum, acceleration 4027
  • R. Ischebeck, C.D. Barnes, I. Blumenfeld, F.-J. Decker, M.J. Hogan, R.H. Iverson, P. Krejcik, R. Siemann, D.R. Walz
    SLAC, Menlo Park, California
  • C.E. Clayton, C. Huang, D.K. Johnson, W. Lu, K.A. Marsh
    UCLA, Los Angeles, California
  • S. Deng, E. Oz
    USC, Los Angeles, California
  • N.A. Kirby
    Stanford University, Stanford, Califormia
  Funding: Work supported by Department of Energy contracts DE-AC02-76SF00515 (SLAC), DE-FG03-92ER40745, DE-FG03-98DP00211, DE-FG03-92ER40727, DE-AC-0376SF0098, and National Science Foundation grants No. ECS-9632735, DMS-9722121 and PHY-0078715.

The accelerating field that can be obtained in a beam-driven plasma wakefield accelerator depends on the current of the electron beam that excites the wake. In the E-167 experiment, a peak current above 10kA will be delivered at a particle energy of 28GeV. The bunch has a length of a few ten micrometers and several methods are used to measure its longitudinal profile. Among these, autocorrelation of coherent transition radiation (CTR) is employed. The beam passes a thin metallic foil, where it emits transition radiation. For wavelengths greater than the bunch length, this transition radiation is emitted coherently. This amplifies the long-wavelength part of the spectrum. A scanning Michelson interferometer is used to autocorrelate the CTR. However, this method requires the contribution of many bunches to build an autocorrelation trace. The measurement is influenced by the transmission characteristics of the vacuum window and beam splitter. We present here an analysis of materials, as well as possible layouts for a single shot CTR autocorrelator.

RPAT079 Resolution of Transverse Electron Beam Measurements Using Optical Transition Radiation radiation, electron, acceleration, target 4042
  • R. Ischebeck, F.-J. Decker, M.J. Hogan, R.H. Iverson, P. Krejcik, R. Siemann, D.R. Walz
    SLAC, Menlo Park, California
  • C.E. Clayton, C. Huang, W. Lu
    UCLA, Los Angeles, California
  • S. Deng, E. Oz
    USC, Los Angeles, California
  • M. Lincoln
    Stanford University, Stanford, Califormia
  Funding: Work supported by Department of Energy contracts DE-AC02-76SF00515 (SLAC), DE-FG03-92ER40745, DE-FG03-98DP00211, DE-FG03-92ER40727, DE-AC-0376SF0098, and National Science Foundation grants No. ECS-9632735, DMS-9722121 and PHY-0078715.

In the plasma wakefield acceleration experiment E-167, optical transition radiation is used to measure the transverse profile of the electron bunches before and after the plasma acceleration. The distribution of the electric field from a single electron does not give a point-like distribution on the detector, but has a certain extension. Additionally, the resolution of the imaging system is affected by aberrations. The transverse profile of the bunch is thus convolved with a point spread function (PSF). Algorithms that deconvolve the image can help to improve the resolution. Imaged test patterns are used to determine the modulation transfer function of the lens. From this, the PSF can be reconstructed. The Lucy-Richardson algorithm is used to deconvolute this PSF from test images.

ROAB003 Highly Compressed Ion Beams for High Energy Density Science ion, target, heavy-ion, acceleration 339
  • A. Friedman, J.J. Barnard, D. A. Callahan, G.J. Caporaso, D.P. Grote, R.W. Lee, S.D. Nelson, M. Tabak
    LLNL, Livermore, California
  • R.J. Briggs
    SAIC, Alamo, California
  • C.M. Celata, A. Faltens, E. Henestroza, E. P. Lee, M. Leitner, B. G. Logan, G. Penn, L. R. Reginato, A. Sessler, J.W.  Staples, W. Waldron, J.S. Wurtele, S. Yu
    LBNL, Berkeley, California
  • R.C. Davidson, L. Grisham, I. Kaganovich
    PPPL, Princeton, New Jersey
  • C. L. Olson, T. Renk
    Sandia National Laboratories, Albuquerque, New Mexico
  • D. Rose, C.H. Thoma, D.R. Welch
    ATK-MR, Albuquerque, New Mexico
  Funding: Work performed under auspices of USDOE by U. of CA LLNL & LBNL, PPPL, and SNL, under Contract Nos. W-7405-Eng-48, DE-AC03-76SF00098, DE-AC02-76CH03073, and DE-AC04-94AL85000, and by MRC and SAIC.

The Heavy Ion Fusion Virtual National Laboratory (HIF-VNL) is developing the intense ion beams needed to drive matter to the High Energy Density (HED) regimes required for Inertial Fusion Energy (IFE) and other applications. An interim goal is a facility for Warm Dense Matter (WDM) studies, wherein a target is heated volumetrically without being shocked, so that well-defined states of matter at 1 to 10 eV are generated within a diagnosable region. In the approach we are pursuing, low to medium mass ions with energies just above the Bragg peak are directed onto thin target "foils," which may in fact be foams or "steel wool" with mean densities 1% to 100% of solid. This approach complements that being pursued at GSI, wherein high-energy ion beams deposit a small fraction of their energy in a cylindrical target. We present the requirements for warm dense matter experiments, and describe suitable accelerator concepts, including novel broadband traveling wave pulse-line, drift-tube linac, RF, and single-gap approaches. We show how neutralized drift compression and final focus optics tolerant of large velocity spread can generate the necessarily compact focal spots in space and time.

ROAB006 Pulsed Power Drivers and Diodes for X-Ray Radiography pulsed-power, electron, impedance, vacuum 510
  • K.J. Thomas
    AWE, Reading
  Flash radiography has been used as a diagnostic for explosively driven hydrodynamics experiments for several decades following the pioneering work of J C Martin and his group at AWE. Relatively simple pulsed power drivers operating between 1 and 10 MV coupled to experimentally optimised electron beam diodes have achieved great success in a number of different classes of these experiments. The next generation of radiographic facilities will aim to improve even further the radiographic performance achievable by developing both the electron beam diodes used and the accelerators that drive them. The application of the rod-pinch diode to an Inductive Voltage Adder at 2 MV in the US has already advanced the quality of radiography available for relatively thin objects. For the thickest objects accelerators operating at up to 15 MV and diodes capable of focusing electron beams to intensities of ~ 1 MA/cm2 for tens of nanoseconds will be required in the future. Since the various candidate diode configurations operate in both high and low impedance regimes there is a further challenge to design and engineer an accelerator capable of driving whichever one, or more, are eventually used.  
ROPA004 CEBAF Control Room Renovation controls, monitoring, linac, synchrotron 378
  • M. Spata, A. Cuffe, H. Fanning, T.C.O. Oren
    Jefferson Lab, Newport News, Virginia
  The Machine Control Center at Jefferson Lab's Continuous Electron Beam Accelerator Facility was initially constructed in the early 1990s and based on proven technology of that era. Through our experience over the last 15 years and in our planning for the facilities 12 GeV upgrade we reevaluated the control room environment to capitalize on emerging visualization and display technologies and improve on workflow processes and ergonomic attributes. This effort also sets the foundation for the redevelopment of the accelerator's control system to deliver high reliability performance with improvements in beam specifications management and information flow. The complete renovation was performed over a three-week period with no interruption to beam operations. We present the results of this effort.  
FPAE071 Initial Results on Neutralized Drift Compression Experiments (NDCX-IA) for High Intensity Ion Beam ion, diagnostics, simulation, induction 3856
  • P.K. Roy, A. Anders, D. Baca, F.M. Bieniosek, J.E. Coleman, S. Eylon, W.G. Greenway, E. Henestroza, M. Leitner, B. G. Logan, D. Shuman, D.L. Vanecek, W. Waldron, S. Yu
    LBNL, Berkeley, California
  • R.C. Davidson, P. Efthimion, E.P. Gilson, I. Kaganovich, A.B. Sefkow
    PPPL, Princeton, New Jersey
  • D. Rose, C.H. Thoma, D.R. Welch
    ATK-MR, Albuquerque, New Mexico
  • W.M. Sharp
    LLNL, Livermore, California
  Funding: This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098.

Ion beam neutralization and compression experiments are designed to determine the feasibility of using compressed high intensity ion beams for high energy density physics (HEDP) experiments and for inertial fusion power. To quantitatively ascertain the various mechanisms and methods for beam compression, the Neutralized Drift Compression Experiment (NDCX) facility is being constructed at Lawrence Berkeley National Laboratory (LBNL). In the first compression experiment, a 260 KeV, 25 mA, K+ ion beam of centimeters size is radially compressed to a mm size spot by neutralization in a meter-long plasma column and beam peak current is longitudinally compressed by an induction velocity tilt core. Instrumentation, preliminary results of the experiments, and practical limits of compression are presented. These include parameters such as emittance, degree of neutralization, velocity tilt time profile, and accuracy of measurements (fast and spatially high resolution diagnostic) are discussed.

FPAE077 LSP Simulations of the Neutralized Drift Compression Experiment ion, simulation, focusing, emittance 4006
  • C.H. Thoma, D.R. Welch
    ATK-MR, Albuquerque, New Mexico
  • S. Eylon, E. Henestroza, P.K. Roy, S. Yu
    LBNL, Berkeley, California
  • E.P. Gilson
    PPPL, Princeton, New Jersey
  Funding: Work supported by the VNL for HIF through PPPL and LBNL.

The Neutralized Drift Compression Experiment (NDCX) at Lawrence Berkeley National Laboratory involves the longitudinal compression of a singly-stripped K ion beam with a mean energy of 250 keV in a meter long plasma. We present simulation results of compression of the NDCX beam using the PIC code LSP. The NDCX beam encounters an acceleration gap with a time-dependent voltage that decelerates the front and accelerates the tail of a 500 ns pulse which is to be compressed 110 cm downstream. The simulations model both ideal and experimental voltage waveforms. Results show good longitudinal compression without significant emittance growth.

FPAP011 New Vortices in Axisymmetric Beams in Inhomogeneous Magnetic Field electron, vacuum, cyclotron
  • Y. Golub
    MRTI RAS, Moscow
  We analyzed localized vortices in non-neutral inhomogeneous by density and velocity electron beams propagating in vacuum along the inhomogeneous external magnetic field. These vortices distinguish from vortices, which used in Golub Yu.Ya. et al. and Golub Yu.Ya. because of inhomogeneous external magnetic field. Also new types of vortex are obtained by new solution method of nonlinear equations.** The new method is development of a method described in Golub Yu.Ya. That method distinguish from standard Larichev-Reznik or Reznik method, which used in Golub Yu.Ya. et al. It has been found new expression for electric field potential of vortex in a wave frame. The expression is axisymmetric in a wave frame. New vortices are new solitons in the inhomogeneous external magnetic field.

*Golub Yu.Ya. et al., in Nonlinear world: IV Intern. Workshop on Nonlin. and Turbul. Proc. in Phys., (ed. by V.G. Bar'yakhtar et al.) World Scientific Publishing Co. Pte. Ltd., Singapore, 1990, vol. 2, p. 857. **Golub Yu.Ya., Proceedings of EPAC 2002, Paris, France, p. 1253.

FPAP026 Multispecies Weibel Instability for Intense Ion Beam Propagation Through Background Plasma ion, background, electron, heavy-ion 1952
  • R.C. Davidson, S.R. Hudson, I. Kaganovich, H. Qin, E. Startsev
    PPPL, Princeton, New Jersey
  Funding: Research supported by the U.S. Department of Energy.

In application of heavy ion beams to high energy density physics and fusion, background plasma is utilized to neutralize the beam space charge during drift compression and/or final focus of the ion beam. It is important to minimize the deleterious effects of collective instabilities on beam quality associated with beam-plasma interactions. Plasma electrons tend to neutralize both the space charge and current of the beam ions. It is shown that the presence of the return current greatly modifies the electromagnetic Weibel instability (also called the filamentation instability), i.e., the growth rate of the filamentation instability greatly increases if the background ions are much lighter than the beam ions and the plasma density is comparable to the ion beam density. This may preclude using underdense plasma of light gases in heavy ion beam applications. It is also shown that the return current may be subject to the fast electrostatic two-stream instability.

FPAP027 Hybrid Quantum Mechanical–Quasi-Classical Model for Evaluating Ionization and Stripping Cross Sections in Atom-Ion Collisions ion, target, electron, heavy-ion 1988
  • I. Kaganovich, R.C. Davidson, E. Startsev
    PPPL, Princeton, New Jersey
  Funding: Research supported by the U.S. Department of Energy.

Ion-atom ionization cross sections are needed in many applications employing the propagation of fast ions through matter. When experimental data or full-scale theoretical calculations are non-existent, approximate methods must be used. The most robust and easy-to-use approximations include the Born approximation of quantum mechanics and the quasi-classical approach utilizing classical mechanics together with the Bohr-Sommerfeld quantization rule.* The simplest method to extend the validity of both approaches is to combine them, i.e., use the two different approaches but only for the regions of impact parameters in which they are valid, and sum the results to obtain the total cross section. We have recently investigated theoretically and experimentally the stripping of more than 18 different pairs of projectile and target atoms in the range of 3-38 MeV/amu to study the range of validity of various approximations. The results of the modified approach agree better with the experimental data than either the Born approximation or the quasi-classical approach, applied separately.

*I. D. Kaganovich et al., "Formulary and scaling cross sections for ion-atom impact ionization," http://arxiv.org/abs/physics/0407140.

FPAP028 Ion Beam Pulse Interaction with Background Plasma in a Solenoidal Magnetic Field ion, electron, background, target 2062
  • I. Kaganovich, R.C. Davidson, E. Startsev
    PPPL, Princeton, New Jersey
  Funding: Research supported by the U.S. Department of Energy.

Background plasma can be used as an effective neutralization scheme to transport and compress intense ion beam pulses, and the application of a solenoidal magnetic field allows additional control and focusing of the beam pulse. Ion beam pulse propagation in a background plasma immersed in an applied solenoidal magnetic field has been studied both analytically and numerically with three different particle-in-cell codes (LSP, OOPIC-Pro and EDPIC) to cross-check the validity of the results. Very good charge and current neutralization is observed for high values of the solenoidal magnetic field.* However, for intermediate values of the solenoidal magnetic field, current neutralization is a complex process, and a sizable self-magnetic field is generated at the head of the beam. Collective wave excitations are also generated ahead of the beam pulse.

*I. D. Kaganovich, E. A. Startsev and R. C. Davidson, Nuclear Instruments and Methods in Physics Research A, in press (2004).

FPAT025 Electron Dynamics of the Rod-Pinch Diode in the Cygnus Experiment at Los Alamos electron, cathode, simulation, ion 1901
  • L. Yin, K. J. Bowers, R.C. Carlson, BG.D. DeVolder, J. T. Kwan, JR.S. Smith, CM.S. Snell
    LANL, Los Alamos, New Mexico
  • MJ.B. Berninger
    Bechtel Nevada, Los Alamos, New Mexico
  In this work, two-dimensional particle-in-cell simulations are used to examine the electron physics in the rod-pinch diode, a device that can be used to produce a relatively low-energy (a few MeV) radiographic electron source. It is found that with diode parameters for which the electrons' dominant dynamics are approximated well as a magnetized fluid, the diode produces an electron source with a desired small spot size as the electrons drift to and impinge on the anode tip. However, for a large cathode-to-anode radius ratio, a population of electrons that consists predominantly of electrons emitted from the downstream surface of the cathode is found to propagate in the upstream direction and the diode may perform anomalously as a consequence. A method is proposed for improving the quality of the electron source by suppressing electron emission from the downstream cathode surface to reduce the presence of unmagnetized electrons.  
FPAT080 Simulations of Beam Injection and Extraction into Ion Sources ion, injection, simulation, background 4069
  • M. Cavenago
    INFN/LNL, Legnaro, Padova
  Funding: INFN-LNL

Charge breeding, consistiting of injecting singly charged ion into ECRIS(Electron Cyclotron Resonance Ion Sources) to extract an highly charged ion beam, is a promising technique for rare or radioactive ion beam. Efficiency and extracted beam temperature are dominated by the strong collisional diffusion of charged ion inside source. A computer code, named BEAM2ECR, written to simulate details of the injection, ionization, collision and extraction processes is described.* A model of injection plasma sheath and of source fringe field were recently added. Neutral injection is also supported, for comparison with other techniques, like gas feeding or metal vapor injection. Results, clearly favouring near axis injection for most cases are described. Code is written in C-language and possibility of concurrent execution over a Linux cluster was recently added.

*M. Cavenago, O. Kester, T. Lamy and P. Sortais, Rev. Sci. Instrum. 73, 537 (2002).

FOAB001 Compact Neutron Generators for Medical, Home Land Security, and Planetary Exploration ion, ion-source, target, electron 49
  • J.P. Reijonen
    LBNL, Berkeley, California
  Funding: This work is being support by U.S. Department of Energy under contract No. DE-AC03-76SF00098.

The Plasma and Ion Source Technology Group at Lawrence Berkeley National Laboratory has developed various types of advanced D-D (neutron energy 2.5 MeV), D-T (14 MeV) and T-T (0 – 9 MeV) neutron generators for wide range of applications. These applications include medical (Boron Neutron Capture Therapy), homeland security (Prompt Gamma Activation Analysis, Fast Neutron Activation Analysis and Pulsed Fast Neutron Transmission Spectroscopy) and planetary exploration in form of neutron based, sub-surface hydrogen detection systems. These neutron generators utilize RF induction discharge to ionize the deuterium/tritium gas. This discharge method provides high plasma density for high output current, high atomic species from molecular gases, long life operation and versatility for various discharge chamber geometries. Three main neutron generator developments are discussed here: high neutron output co-axial neutron generator for BNCT applications, point neutron generator for security applications, compact and sub-compact axial neutron generator for elemental analysis applications. Current status of the neutron generator development with experimental data will be presented.

FOAD002 Ultra-High Density Electron Beams for Beam Radiation and Beam Plasma Interaction electron, emittance, focusing, simulation 145
  • S.G. Anderson, J. Brown, D.J. Gibson, F.V. Hartemann, J.S. Jacob, A.M. Tremaine
    LLNL, Livermore, California
  • P. Frigola, J. Lim, J.B. Rosenzweig, G. Travish
    UCLA, Los Angeles, California
  • P. Musumeci
    INFN-Roma, Roma
  Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48.

Current and future applications of high brightness electron beams, which include advanced accelerators such as the plasma wake-field accelerator (PWFA) and beam-radiation interactions such as inverse-Compton scattering (ICS), require both transverse and longitudinal beam sizes on the order of tens of microns. Ultra-high density beams may be produced at moderate energy (50 MeV) by compression and subsequent strong focusing of low emittance, photoinjector sources. We describe the implementation of this method used at LLNL’s PLEIADES ICS x-ray source in which the photoinjector-generated beam has been compressed to 300 fsec duration using the velocity bunching technique and focused to 20 μm rms size using an extremely high gradient, permanent magnet quadrupole (PMQ) focusing system.