First Name: R.
Middle Name:
Last Name: Narang
Full Name: R. Narang
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7 papers
| 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 |
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| 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. |
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| title: | Experiments on laser driven beatwave acceleration in a ponderomotively formed plasma channel |
| format: | journal article |
| year: | 2004 |
| 10 authors: | | | | | | | | | | |
| abstract: | A 10 ps long beam of 12 MeV electrons is externally injected into a ~3-cm long plasma beatwave excited in a laser ionized hydrogen gas. The electrons have been accelerated to 50 MeV with a gradient of ~1.3 GeV/m. It is shown that when the effective plasma wave amplitude-length product is limited by ionization-induced defocusing (IID), acceleration of electrons is significantly enhanced by using a laser pulse with a duration longer than the time required for ions to move across the laser spot size. Both experiments and two-dimensional simulations reveal that, in this case, self-guiding of the laser pulse in a ponderomotively formed plasma channel occurs. This compensates for IID and drives the beatwave over the longer length compared to when such a channel is not present. |
| keywords: | pbpl |
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| title: | Acceleration of Injected Electrons In A Laser Beatwave Experiment |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 10 authors: | | | | | | | | | | |
| abstract: | Plasma-based accelerators of particles are of great interest because plasmas can sustain very strong electric fields. They are utilizing a relativistic plasma wave with a phase velocity close to the speed of light driven by a high-power laser beam. The Neptune Laboratory at UCLA is being used for plasma beatwave acceleration of injected electrons. Here, a two-wavelength laser pulse (frequencies w1,w2) resonantly drives a longitudinal electron plasma wave of frequency equal to w1-w2, providing a field strength of GeV/m and, therefore, accelerates an injected electron beam at this very high gradient. A 10 ps beam of 12 MeV electrons is loaded in a 3-cm long plasma beatwave accelerator driven by a TW CO2 laser pulse. At the resonance condition, the electrons have been accelerated to 50 MeV with a gradient of ~1.3 GeV/m. It is shown that for large volume diffraction limited plasmas, when efficiency of the plasma wave excitation is restricted by ionization-induced refraction, acceleration of electrons is enhanced significantly by using asymmetric (fast front and slow fall) long pulses. 2D PIC simulations revealed that guiding of the laser pulse in a ponderomotive, self-induced ion channel, formed ~200 ps after the field ionization, allows compensation for the ionization-induced defocusing and efficient driving of the beatwave over the entire length. |
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| title: | Plasma source test and simulation results for the underdense plasma lens experiment at the UCLA Neptune Laboratory |
| format: | unknown |
| year: | 2000 |
| 8 authors: | | | | | | | | |
| abstract: | The planned plasma lens experiment at the UCLA Neptune Laboratory is described. In the experiment, electron beams with an energy of 16 MeV, a charge of 4 nC, and a pulse duration of 30 ps full-width at half-maximum (FWHM) are designed to be produced from the 1.625-cell photoinjector radio-frequency gun (f=2.856 GHz) and PWT linac in the Neptune. The generated beams are passed through a thin plasma with a density of low 10/sup 12/ cm/sup -3/ range and a thickness of a few centimeters. For this experiment, a LaB/sub 6/-based discharge plasma source was developed and tested. In this paper, the overview of the planned plasma lens experiment and the test results of the plasma source for various conditions are presented. In addition, computer simulations with a 2-1/2 dimensional particle-in-cell code (MAGIC) were performed and the simulation results are shown. (19 References). |
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| title: | Underdense plasma lens experiment at the UCLA Neptune Laboratory |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 10 authors: | | | | | | | | | | |
| abstract: | An underdense plasma-lens experiment is planned at the UCLA Neptune Laboratory. For this experiment, a LaB/sub 6/-based discharge plasma source was developed and tested. Test results of the plasma source show that it can provide satisfactory Ar plasma parameters for underdense plasma lens experiments, i.e., a density in the low 10/sup 12/ cm/sup -3/ range and a thickness of a few cm. In the plasma chamber a YAG slab and a Cherenkov radiator are placed for electron beam diagnostics so that both time-integrated and time-resolved information will be obtained and compared with the MAGIC code (2 and 1/2 dimensional particle-in-cell) simulations. In this paper, the planned experiment including test results of the plasma source, diagnostics and MAGIC simulation results is presented. (5 References). |
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| title: | Test results of the plasma source for underdense plasma lens experiments at the UCLA Neptune Lab |
| format: | conference procceeding |
| conference: | 8th Advanced Accelerator Concepts Workshop |
| year: | 1999 |
| 7 authors: | | | | | | | |
| abstract: | A plasma source was developed at UCLA for planned underdense plasma lens experiments, where the plasma density is less than the electron beam density. The argon plasma, produced by a discharge between a LaB_6 cathode at 1330 degrees C and a tantalum anode, is confined by a solenoidal magnetic field and flows transversely across the electron beam path. Extensive test of the plasma source is under way for various conditions before it is assembled with the UCLA photocathode-based electron linac. In particular, different longitudinal (with respect to the electron beam) plasma profiles and effective plasma lengths can be obtained by adjusting the moveable sliding door between the plasma source and the transverse beamline. Test results of the plasma source are presented. (11 References). |
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