First Name: W
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Last Name: Gai
Full Name: W. Gai
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14 papers
| title: | Observation and analysis of self-amplified spontaneous emission at the APS low-energy undulator test line |
| format: | conference procceeding |
| conference: | 22nd International Free Electron Laser Conference |
| year: | 2001 |
| 153 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | Exponential growth of self-amplified spontaneous emission at 530 nm was first experimentally observed at the Advanced Photon Source low-energy undulator test line in December 1999. Since then, further detailed measurements and analysis of the results have been made. Here, we present the measurements and compare these with calculations based on measured electron beam properties and theoretical expectations. (31 References). |
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| title: | Observation of plasma wakefield acceleration in the underdense regime |
| format: | unknown |
| year: | 2000 |
| 5 authors: | | | | | |
| abstract: | Initial experiments which have explored the physics of the underdense (blowout) regime of the plasma wakefield accelerator (PWFA) at the Argonne Wakefield Accelerator facility are reported. In this regime, the relativistic electron beam is denser than the plasma, causing the beam channel to completely rarefy, and leaving a high quality accelerating region which also contains a uniform ion column. This ion column in turn allows the drive and accelerating beams to be well guided over many initial beam beta-function lengths. The results of these experiments, which have taken place over several years, are reviewed. Notable achievements in the course of these studies include the creation and measurement of drive and witness beam generated in an rf photoinjector, as well as previously published studies on drive beam guiding in the underdense regime. In addition, these experiments allowed measurement of both beam energy loss and gain, at a maximum average rate of 25 MeV/m in this regime of the PWFA, which is consistent with a peak acceleration gradient of 62 MeV/m in the excited waves. Difficulties associated with this type of experiment are discussed, as are prospects for mitigating these difficulties and achieving high gradient acceleration in planned future experiments. |
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| title: | Propagation of short electron pulses in a plasma channel |
| format: | unknown |
| year: | 1998 |
| 4 authors: | | | | |
| abstract: | We report the near-steady-state propagation over long distance of a 25 psec, tightly focused relativistic electron beam which creates, by radial ejection of plasma electrons, a focusing ion channel in a plasma of electron density smaller than the beam. A dense beam core, close in radius to the injected beam, which was nearly matched to the ion focusing strength, is observed at the plasma exit. Time-resolved imaging confirms that this core is situated in the trailing half of the beam, as predicted by analytical and computer models. We discuss the impact of these results on plasma wake field acceleration schemes. (16 References). |
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| title: | Results of blowout regime propagation experiments of an electron beam in a plasma |
| format: | conference procceeding |
| conference: | 1997 Particle Accelerator Conference |
| year: | 1998 |
| 4 authors: | | | | |
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| title: | Wakefields In Planar Dielectric-Loaded Structures |
| format: | conference procceeding |
| conference: | Summer Study on New Directions for High Energy Physics |
| year: | 1997 |
| 4 authors: | | | | |
| abstract: | Several promising schemes for high-gradient acceleration of charged particles in planar electromagnetic structures have been recently proposed. In this paper we investigate, by both computer simulation and theoretical analysis, the longitudinal and transverse wake-fields experienced a relativistic charged particle in a planar structure. We show that, in the limit of a large aspect ratio beam, the net deflecting wake-fields vanishes. Practical implications of this result for short wavelength advanced accelerators are discussed. |
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| title: | Measurements of plasma wake-fields in the blow-out regime |
| format: | conference procceeding |
| conference: | 1995 Particle Accelerator Conference |
| year: | 1995 |
| 9 authors: | | | | | | | | | |
| abstract: | Initial results from nonlinear plasma wake-field experiments at the Argonne Wakefield Accelerator (AWA) test facility are reported. This nonlinear "blow-out" regime is characterized by the complete ejection of the plasma electrons from the beam channel. The wake-fields in this case are of notably high quality for acceleration of electrons, as the acceleration is independent of transverse position, and the focusing is linear and independent of longitudinal position within the electron depleted region, allowing self-consistent guiding of the majority of the driving electron beam. Initial measurements of the energy gain in a witness beam indicate a positive shift in its energy distribution of at least 0.5 MeV. (9 References). |
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| title: | Demonstration of Electron-Beam Self-Focusing in Plasma Wake Fields |
| format: | unknown |
| year: | 1990 |
| 10 authors: | | | | | | | | | | |
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| title: | Experimental studies of plasma wake-field acceleration and focusing |
| format: | unknown |
| year: | 1990 |
| 10 authors: | | | | | | | | | | |
| abstract: | The Plasma Wake-field Accelerator (PWFA) continues to be the object of much investigation, due to the promise of the ultra-high accelerating gradients that can exist in relativistic plasma waves driven in the wake of charged particle beams. These large amplitude plasma wake-fields are of interest in the laboratory, both for the wealth of basic nonlinear plasma wave phenomena which can be studied, as well as for the applications of acceleration and focusing of electrons and positrons in linear colliders. Plasma wake-field waves are also of importance in nature, due to their possible role in direct cosmic ray acceleration. The purpose of the present work is to review the experimental advances made in PWFA research at Argonne National Laboratory, in which many interesting beam and plasma phenomena have been observed. Emphasis is given to discussion of the nonlinear aspects of the PWFA beam-plasma interaction. (29 References). |
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| title: | Demonstration of electron beam self-focusing in plasma wake fields |
| format: | conference procceeding |
| conference: | Annual Meeting of the Division of Plasma Physics of the APS |
| year: | 1990 |
| 10 authors: | | | | | | | | | | |
| abstract: | The direct observation of wake-field self-focusing of an electron beam in plasma is reported. The dynamics of beam self-pinching and the fast collisionless evolution of a Bennett-like, near-equilibrium profile are examined theoretically and computationally. The experimental results are compared to predictions of the analysis and discussed in the context of application to the plasma lens and the plasma wake-field accelerator. (19 References). |
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| title: | Experimental Measurement of Nonlinear Plasma Wake-Fields |
| format: | conference procceeding |
| conference: | 1989 Particle Accelerator Conference |
| year: | 1989 |
| 7 authors: | | | | | | | |
| abstract: | We report direct high resolution observation of nonlinear steepened plasma waves excited in the wake of an intense, self-pinched electron beam. Oscillations in both accelerating and deflecting fields are measured, and analyzed in the context of linear and nonlinear plasma wave theory. The degree of nonlinearity in the wake-fields is shown to be consistent with analytical predictions of the beam self-pinching. The impact of these results on plasma acceleration and focusing schrmrs is discussed. |
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| title: | Argonne plasma wake-field acceleration experiments |
| format: | conference procceeding |
| conference: | 1989 Workshop on Advanced Accelerator Concepts |
| year: | 1989 |
| 7 authors: | | | | | | | |
| abstract: | Four years after the initial proposal of the Plasma Wake-field Accelerator (PWFA), it continues to be the object of much investigation, due to the promise of the ultra-high accelerating gradients that can exist in relativistic plasma waves driven in the wake of charged particle beams. These wake-fields are of interest both in the laboratory, for acceleration and focusing of electrons and positrons in future linear colliders, and in nature as a possible cosmic ray acceleration mechanism. The authors review the recent experimental advances made in PWFA research at Argonne National Laboratory. (25 References). |
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| title: | Experimental measurement of nonlinear plasma wake fields |
| format: | unknown |
| year: | 1989 |
| 7 authors: | | | | | | | |
| abstract: | We report direct high-resolution observation of nonlinear steepened plasma waves excited in the wake of an intense, self-pinched electron beam. Oscillations in both accelerating and deflecting fields are measured, and analyzed in the context of linear and nonlinear plasma-wave theory. The degree of nonlinearity in the wake fields is shown to be consistent with analytical predictions of the beam self-pinching. The impact of these results on plasma acceleration and focusing schemes is discussed. |
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| title: | Experimental observation of plasma wake-field acceleration |
| format: | unknown |
| year: | 1988 |
| 9 authors: | | | | | | | | | |
| abstract: | The authors report the first experimental test of the physics of plasma wake-field acceleration performed at the Argonne National Laboratory Advanced Accelerator Test Facility. Megavolt-per-meter plasma wake fields are excited by a intense 21-MeV, multipicosecond bunch of electrons in a plasma of density n/sub e/ approximately=10/sup 13/ cm/sup -3/, and probed by a low-intensity 15-MeV witness pulse with a variable delay time behind the intense bunch. Accelerating and deflecting wake-field measurements are presented, and the results compared to theoretical predictions. (8 References). |
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| title: | Experimental Demonstration of Wake-Field Effects in Dielectric Structures |
| format: | unknown |
| year: | 1988 |
| 7 authors: | | | | | | | |
| abstract: | We have measured the wake fields induced by short, intense relativistic electron bunches in a slow-wave structure consisting of a dielectric-lined tube, as a test of the dielectric wake-field acceleration mechanism. These fields were used to accelerate a second electron bunch which followed the driving bunch at a variable distance. Results are presented for different dielectrics and beam intensities, and are compared with theoretical predictions. |
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