Recently a new electron-bunch injection scheme for the laser wakefield accelerator has been proposed [JETP Lett. 74, 371 (2001); Phys. Rev. E 65, 046504 (2002)]. In this scheme, a low energy electron bunch, sent in a plasma channel just before a high-intensity laser pulse, is trapped in the laser wakefield, considerably compressed and accelerated to an ultrarelativistic energy. In this paper we show the possibility of the generation of an extremely short (on the order of 1 μm long or a few femtoseconds in duration) relativistic-electron-bunch by this mechanism. The initial electron bunch, which can be generated, for example, by a laser-driven photocathode rf gun, should have an energy of a few hundred keVs to a few MeVs, a duration in the picosecond range or less and a relatively low concentration. The trapping conditions and parameters of an accelerated bunch are investigated. The laser pulse dynamics as well as a possible experimental setup for the demonstration of the injection scheme are also considered
Recent advances in laser wakefield acceleration demonstrated the generation of extremely short (with a duration of a few femtoseconds) relativistic electron bunches with relatively low (of the order of couple of percent) energy spread. In this article we study the dynamics of such bunches in drift space (vacuum) and in channel-guided laser wakefields. Analytical solutions were found for the transverse coordinate of an electron and for the bunch envelope in the wakefield in the case of arbitrary change in the energy. Our results show strong bunch dynamics already on a millimeter scale propagation distance both in plasma and in vacuum. When the bunch propagates in vacuum, its transverse sizes grow considerably; the same is observed for the normalized bunch emittance that worsens the focusability of the bunch. A scheme of twostage laser wakefield accelerator with small drift space between the stages is proposed. It is found that fast longitudinal betatron phase mixing occurs in a femtosecond bunch when it propagates along the wakefield axis. When bunch propagates off axis, strong bunch decoherence and fast emittance degradation due to the finite bunch length was observed.
We study the effect of chirp on electromagnetic (EM) pulse interaction with a charged particle. Both the one-dimensional (1D) and 3D cases are considered. It is found that, in contrast to the case of a nonchirped pulse, the charged particle energy can be changed after the interaction with a 1D EM chirped pulse. Different types of chirp and pulse envelopes are considered. In the case of small chirp, an analytical expression is found for arbitrary temporal profiles of the chirp and the pulse envelope. In the 3D case, the interaction with a chirped pulse results in a polarization-dependent scattering of charged particles.
The effect of frequency variation (chirp) in an electromagnetic (EM) pulse on the pulse interaction with a charged particle and plasma is studied. Various types of chirp and pulse envelopes are considered. In vacuum, a charged particle receives a kick in the polarization direction after interaction with a chirped EM pulse. Interaction of a one-dimensional chirped pulse with uniform plasma is considered. We found that the amplitude of the wake wave generated in plasma by an EM pulse can be significantly higher when the pulse is chirped.
In this article we present a theoretical investigation on an experimental design of a laser wakefield accelerator in which electron bunches from a photocathode radio frequency linac are injected into a capillary discharge plasma channel just in front of a few tens of terawatt drive laser pulse. The electron bunch, with a kinetic energy of 2.9 MeV and an energy chirp imposed by the linac, is magnetically compressed by a factor of 8 to a duration of 250 fs, and is magnetically focused into the plasma channel where it matches the spot size of the drive laser (≈30 μm). The dynamics of the bunch, starting from the photocathode, through the linac, along the beam transportation line, through the magnetic compressor, and its focusing into the plasma channel are comprehensively simulated with the general particle tracer code. Further, we use our three-dimensional numerical codes to calculate the laser wakefield and to determine and optimize the trapping and acceleration of the injected bunch in the wakefield. We show that, injecting a 5 pC electron bunch of 250 fs duration, the experiment should deliver an electron bunch of approximately 744 MeV energy, with 1.1% relative energy spread, and with an extremely short duration (6 fs), after acceleration in a 5.4 cm long plasma channel.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.