tags:
Potential Duplicate Authors:
view citation format
21 papers
| title: | An Inverse Compton Scattering Radiation Source via Self-Guiding in a Plasma |
| format: | conference procceeding |
| conference: | |
| year: | 2006 |
| 2 authors: | | |
| abstract: | In an inverse-Compton scattering source, in which a relativistic electron beam collides with a high-power laser pulse, the x-ray flux produced is proportional to the brightness of the two beams and the size of their overlap region in three-dimensional space. In vacuum, this overlap is limited by the diffraction of the two beams, but the diffraction limit can be overcome by confining both beams in a plasma guiding channel. A dense, bunched electron beam injected into an underdense plasma will self-guide via ``blowout,'' in which the beam head creates a focusing ion channel through which the body of the beam is guided; this same channel can also guides a counterpropagating laser beam. Constraints include the need for long laser wavelength (1 to 10 μm) and high beam densities. We present a possible configuration for a gamma-ray source using 180° Compton scattering in a uniform plasma, including 2D simulation results. Estimated photon yields are up to a factor of 5 larger than in vacuum scattering, with production of nearly 1010 photons per nanocoulomb of electron beam charge. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | High Energy Gain of Trapped Electrons in a Tapered, Diffraction-Dominated Inverse-Free-Electron Laser |
| format: | preprint |
| year: | 2005 |
| 17 authors: | | | | | | | | | | | | | | | | | |
| abstract: | Energy gain of trapped electrons in excess of 20 MeV has been demonstrated in an Inverse-Free- Electron-Laser (IFEL) accelerator experiment. A 14.5 MeV electron beam is copropagated with a 400 GW CO2 laser beam in a 50 cm long undulator strongly tapered in period and ¯eld amplitude. The Rayleigh range of the laser, » 1.8 cm, is much shorter than the undulator length yielding a di®raction-dominated interaction. Experimental results on the dependence of the acceleration on injection energy, laser focus position, and laser power are discussed. Simulations, in good agreement with the experimental data, show that most of the energy gain occurs in the ¯rst half of the undulator at a gradient of 70 MeV/m and that the structure in the measured energy spectrum arises because of higher harmonic IFEL interaction in the second half of the undulator. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Effects of Ion Motion in Intense Beam-Driven Plasma Wakefield Accelerators |
| format: | journal article |
| year: | 2005 |
| 5 authors: | | | | | |
| abstract: | Recent proposals for using plasma wakefield accelerators (PWFA) as a component of a linear collider have included intense electron beams with densities many times in excess of the plasma density. The beam’s electric fields expel the plasma electrons from the beam path to many beam radii in this regime. We analyze here the motion of plasma ions under the beam fields, and find for a proposed PWFA collider scenario that the ions completely collapse inside of the beam. Simulations of ion collapse are presented. Implications of ion motion on the feasibility of the PWFA-based colliders are discussed. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Side-Coupled Slab-Symmetric Structure for High-Gradient Acceleration using Terahertz Power |
| format: | journal article |
| year: | 2005 |
| 2 authors: | | |
| abstract: | A slab-symmetric dielectric-loaded accelerator structure, consisting of a vacuum gap between dielectric-lined conducting walls, is described. The device is resonantly excited by an external drive laser which is side coupled into the acceleration region; a novel coupling scheme, which consists of an array of narrow, equally spaced slots in the upper structure boundary, is presented and analyzed in detail. This structure partakes of the advantages of earlier slab-symmetric optical acceleration proposals, but will use a terahertz-frequency external radiation source ( 340 m), allowing realistic electron beams to be used in a proof-of-principle experiment. Two- and three-dimensional electromagnetic simulations are used to verify the mode patterns and study the effects of the couplers, including time-dependent calculations of the filling of the structure and particle-in-cell computations of the beam wakefields. Details of the resonance are found to be highly sensitive to the coupling slot geometry: the presence of the couplers can lead to frequency detuning, changes in the field breakdown limits and overall Q factor, and distortions of the field pattern. Beam wakefields are enhanced by the presence of the slots, but found to have no significant effect on the beam transport. The resonant accelerating fields, which are nearly constant along the short transverse direction, are found to have between 10 and 15 times the amplitude of the driving radiation, with only a small ( < 10%) admixture of other nonaccelerating modes. Field gradients are computed to be near 100 MV=m when the structure is driven with 100MWof terahertz laser power. Possible manufacturing methods for a prototype device are discussed. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Side-coupled slab-symmetric structure for high-gradient acceleration using terahertz power |
| format: | journal article |
| year: | 2005 |
| 2 authors: | | |
| abstract: | A slab-symmetric dielectric-loaded accelerator structure, consisting of a vacuum gap between dielectric-lined conducting walls, is described. The device is resonantly excited by an external drive laser which is side coupled into the acceleration region; a novel coupling scheme, which consists of an array of narrow, equally spaced slots in the upper structure boundary, is presented and analyzed in detail. This structure partakes of the advantages of earlier slab-symmetric optical acceleration proposals, but will use a terahertz-frequency external radiation source ( 340 m), allowing realistic electron beams to be used in a proof-of-principle experiment. Two- and three-dimensional electromagnetic simulations are used to verify the mode patterns and study the effects of the couplers, including time-dependent calculations of the filling of the structure and particle-in-cell computations of the beam wakefields. Details of the resonance are found to be highly sensitive to the coupling slot geometry: the presence of the couplers can lead to frequency detuning, changes in the field breakdown limits and overall Q factor, and distortions of the field pattern. Beam wakefields are enhanced by the presence of the slots, but found to have no significant effect on the beam transport. The resonant accelerating fields, which are nearly constant along the short transverse direction, are found to have between 10 and 15 times the amplitude of the driving radiation, with only a small ( < 10%) admixture of other nonaccelerating modes. Field gradients are computed to be near 100 MV=m when the structure is driven with 100MWof terahertz laser power. Possible manufacturing methods for a prototype device are discussed. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | The Effects of Ion Motion in Very Intense Beam-driven Plasma Wakefield Accelerators |
| format: | conference procceeding |
| conference: | |
| year: | 2004 |
| 4 authors: | | | | |
| abstract: | 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 |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | An Optimal Design for a THz Dielectric-Loaded Slab-Symmetric Accelerator |
| format: | conference procceeding |
| conference: | |
| year: | 2004 |
| 2 authors: | | |
| abstract: | A slab-symmetric dielectric-loaded accelerator structure, consisting of a vacuum gap between dielectric-lined conducting walls, is analyzed theoretically and computationally. The device is to be resonantly excited by an external laser source of wavelength 340 |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Enhanced Acceleration of Injected Electrons in a Laser Beatwave Induced Plasma Channel |
| format: | preprint |
| year: | 2004 |
| 10 authors: | | | | | | | | | | |
| abstract: | Enhanced energy gain of externally injected electrons by a ~3-cm long, high-gradient relativistic plasma wave (RPW) is demonstrated. Using a CO2 laser-beatwave of duration longer than the ion motion time across the laser spot size, a laser self-guiding process is initiated in a plasma channel. Guiding compensates for ionization-induced defocusing (IID) creating a longer plasma, which extends the interaction length between electrons and the RPW. In contrast to a maximum energy gain of 10 MeV when IID is dominant, the electrons gain up to 38 MeV energy in a laser beatwave induced plasma channel. PACS: 52.35Mw, 52.38Hb, 52.38Kd |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | An Ultra-High Gradient Cerenkov Wakefield Acceleration Experiment at SLAC FFTB |
| format: | conference procceeding |
| conference: | |
| year: | 2004 |
| 7 authors: | | | | | | | |
| abstract: | The creation of ultra-high current, ultra-short pulse beams (Q=3 nC, ) at the SLAC FFTB has opened the way for very high gradient plasma wakefield acceleration experiments. We study here the use of these beams in a proposed Cerenkov wakefield experiment, where one may excite electromagnetic wakes in a simple dielectric tube with inner diameter of few100 microns that exceed the GV/m level. We discuss the scaling of the fields with design geometric design parameters, and choice of dielectric. We also examine measurable aspects of the experiment, such as the total coherent Cerenkov radiation energy one may collect, and the expected aspects of dielectric breakdown at high fields. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Energy Loss of a High Charge Bunched Electron Beam in Plasma: Simulations, Scaling, and Accelerating Wakefields |
| format: | preprint |
| year: | 2004 |
| 4 authors: | | | | |
| abstract: | The energy loss and gain of a beam in the nonlinear, ‘‘blowout’’ regime of the plasma wakefield accelerator, which features ultrahigh accelerating fields, linear transverse focusing forces, and nonlinear plasma motion, has been asserted, through previous observations in simulations, to scale linearly with beam charge. Additionally, from a recent analysis by Barov et al., it has been concluded that for an infinitesimally short beam, the energy loss is indeed predicted to scale linearly with beam charge for arbitrarily large beam charge. This scaling is predicted to hold despite the onset of a relativistic, nonlinear response by the plasma, when the number of beam particles occupying a cubic plasma skin depth exceeds that of plasma electrons within the same volume. This paper is intended to explore the deviations from linear energy loss using 2D particle-in-cell simulations that arise in the case of experimentally relevant finite length beams. The peak accelerating field in the plasma wave excited behind the finite-length beam is also examined, with the artifact of wave spiking adding to the apparent persistence of linear scaling of the peak field amplitude into the nonlinear regime. At large enough normalized charge, the linear scaling of both decelerating and accelerating fields collapses, with serious consequences for plasma wave excitation efficiency. Using the results of parametric particle-in-cell studies, the implications of these results for observing severe deviations from linear scaling in present and planned experiments are discussed. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Non-Resonant Beat-Wave Excitation of Constant Phase-Velocity, Relativistic Plasma Waves for Charged-Particle Acceleration |
| format: | journal article |
| year: | 2004 |
| 10 authors: | | | | | | | | | | |
| abstract: | The nonresonant beat-wave excitation of relativistic plasma waves is studied in two-dimensional simulations and experiments. It is shown through simulations that, as opposed to the resonant case, the accelerating electric fields associated with the nonresonant plasmons are always in phase with the beat-pattern of the laser pulse. The excitation of such nonresonant relativistic plasma waves is shown to be possible for plasma densities as high as 14 times the resonant density. The density fluctuations and the fields associated with these waves have significant magnitudes, facts confirmed experimentally using collinear Thomson scattering and electron injection, respectively. The applicability of these results towards eventual phase-locked acceleration of prebunched and externally injected electrons is discussed. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Velocity Bunching Experiment at the Neptune Laboratory |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 3 authors: | | | |
| abstract: | In this paper we describe the rectilinear compression experiment at the Neptune photoinjector at UCLA. The electron bunches have been shortened to sub-ps pulse length by chirping the beam energy spectrum in a short S-band high gradient standing wave RF cavity and then letting the electrons undergo velocity compression in the following rectilinear drift. Using a standard Martin Puplett interferometer to characterize coherent transition radiation from the beam, we measured bunch lengths as short as 0.4 ps with compression ratio in excess of 10 for an electron beam of 7 MeV energy and charge up to 300 pC. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Energy Loss and Accelerating Field in the Plasma Wakefield Accelerator |
| format: | preprint |
| year: | 2003 |
| 4 authors: | | | | |
| abstract: | |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | A Plasma-Assisted High-Brightness X-Ray Source via Inverse Compton Scattering |
| format: | preprint |
| year: | 2003 |
| 3 authors: | | | |
| abstract: | |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | A Slab-Symmetric Dielectric-Loaded Structure for High-Gradient Acceleration at THz |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 2 authors: | | |
| abstract: | We present a design for a slab-symmetric accelerating structure to be resonantly excited at terahertz frequencies. The device, consisting of a vacuum gap between dielectric-lined walls, combines the advantages of a slab geometry (including strong suppression of transverse beam wakefields and low power density) with the existence of a resonant mode having phase synchronism with relativistic electrons. Accelerating fields of hundreds of MeV/m are predicted when the structure is powered by a high-power FIR radiation source in development at UCLA. Simulation of the structure fields is described and compared with theory, and an experimental program is discussed. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | A Resonant, THz Slab-Symmetric Dielectric-Based Accelerator |
| format: | conference procceeding |
| conference: | ICFA Workshop on Physics and Applications of High Brightness Electron Beams |
| year: | 2003 |
| 2 authors: | | |
| abstract: | Slab-symmetric dielectric-loaded structures, consisting of a vacuum gap between dielectric-lined conducting walls, have become a subject of interest for highgradient acceleration of high-charge beams due to their simplicity, relatively low power density, and advantageous beam dynamics. Such a structure can be resonantly excited by an external power source and is known to strongly suppress transverse wakefields. Motivated by the prospect of a high-power FIR radiation source, currently under construction at UCLA, we investigate a high-gradient slabsymmetric accelerator powered by up to 100 MW of laser power at 340 ?m, with a predicted gradient near 100 MeV/m. Theory and simulation studies of the structure fields and wakes are presented, with an outline of a future experiment. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | A Resonant, THz Slab-Symmetric Dielectric-Based Accelerator |
| format: | conference procceeding |
| conference: | 10th Advanced Accelerator Concepts Workshop |
| year: | 2002 |
| 2 authors: | | |
| abstract: | Slab-symmetric dielectric-loaded structures, consisting of a vacuum gap between dielectric-lined conducting walls, have become a subject of interest for short-wavelength acceleration due to their simplicity, relatively low power density, and advantageous beam dynamics. Such a structure can be resonantly excited by an external power source and is known to strongly suppress transverse wakefields. Motivated by the prospect of a high-power FIR radiation source, currently under construction at UCLA, we investigate a high-gradient slab- symmetric accelerator powered by up to 100 MW of laser power at 340 um, with a predicted gradient near 100 MeV/m. Three-dimensional simulation studies of the structure fields and wakes are presented and compared with theory, and a future experiment is discussed. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Energy Loss of a High Charge Bunched Electron Beam in Plasma: Nonlinear plasma response and linear scaling |
| format: | conference procceeding |
| conference: | 10th Advanced Accelerator Concepts Workshop |
| year: | 2002 |
| 4 authors: | | | | |
| abstract: | |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Velocity bunching experiment at the Neptune Laboratory |
| format: | conference procceeding |
| conference: | 10th Advanced Accelerator Concepts Workshop |
| year: | 2002 |
| 5 authors: | | | | | |
| abstract: | |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | High Energy Gain of Trapped Electrons in a Tapered, Diffraction-Dominated Inverse-Free-Electron Laser |
| format: | journal article |
| year: | |
| 17 authors: | | | | | | | | | | | | | | | | | |
| abstract: | Energy gain of trapped electrons in excess of 20 MeV has been demonstrated in an inverse-freeelectron-laser (IFEL) accelerator experiment. A 14.5 MeVelectron beam is copropagated with a 400 GW CO2 laser beam in a 50 cm long undulator strongly tapered in period and field amplitude. The Rayleigh range of the laser, 1:8 cm, is much shorter than the undulator length yielding a diffraction-dominated interaction. Experimental results on the dependence of the acceleration on injection energy, laser focus position, and laser power are discussed. Simulations, in good agreement with the experimental data, show that most of the energy gain occurs in the first half of the undulator at a gradient of 70 MeV=m and that the structure in the measured energy spectrum arises because of higher harmonic IFEL interaction in the second half of the undulator. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | LASER-POWERED DIELECTRIC STRUCTURE AS A MICRON-SCALE ELECTRON SOURCE |
| format: | preprint |
| year: | |
| 3 authors: | | | |
| abstract: | We describe a resonant laser-powered structure, measur- ing 1 mm or less in every dimension, that is capable of generating and accelerating electron beams to low ener- gies ( 1–2 MeV). Like several other recently investigated dielectric-based accelerators, the device is planar and res- onantly excited with a side-coupled laser; however, exten- sive modifications are necessary for synchronous accelera- tion and focusing of nonrelativistic particles. Electrons are generated within the device via a novel ferroelectric-based cathode. The accelerator is constructed from dielectric ma- terial using conventional microfabrication techniques and powered by a 1- m gigawatt laser. The electron beams pro- duced are suitable for a number of existing industrial and medical applications. |
| keywords: | |
| Download | View | Details | edit | delete | |