scholarly journals Enhanced relativistic-electron beam collimation using two consecutive laser pulses

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Sophia Malko ◽  
Xavier Vaisseau ◽  
Frederic Perez ◽  
Dimitri Batani ◽  
Alessandro Curcio ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electron Beam ◽  
Laser Pulse ◽  
Relativistic Electron ◽  
Relativistic Electron Beam ◽  
Laser Pulses ◽  
Spot Size ◽  
High Energy ◽  
The Magnetic Field ◽  
Beam Collimation

Abstract The double laser pulse approach to relativistic electron beam (REB) collimation in solid targets has been investigated at the LULI-ELFIE facility. In this scheme two collinear laser pulses are focused onto a solid target with a given intensity ratio and time delay to generate REBs. The magnetic field generated by the first laser-driven REB is used to guide the REB generated by a second delayed laser pulse. We show how electron beam collimation can be controlled by properly adjusting the ratio of focus size and the delay time between the two pulses. We found that the maximum of electron beam collimation is clearly dependent on the laser focal spot size ratio and related to the magnetic field dynamics. Cu-Kα and CTR imaging diagnostics were implemented to evaluate the collimation effects on the respectively low energy (≤100 keV) and high energy (≥MeV) components of the REB.

Fast-wave interaction with a relativistic electron beam

1974 ◽  
Vol 11 (2) ◽  
pp. 299-309 ◽  
Author(s):  
P. Sarangle
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Electron Beam ◽  
Relativistic Electron ◽  
Microwave Radiation ◽  
Relativistic Electron Beam ◽  
Parametric Instability ◽  
Travelling Wave ◽  
Fast Wave ◽  
Coupled Modes

The excitation of a relativistic electron beam, by means of a fast waveguide structure, is examined. Here the beam is injected into a modified waveguide, and interacts with the modes of the guide in such a way as to transform some of its energy into microwave radiation. This microwave generation device, called the Ubitron, is based upon a fast-wave excitation of a magnetically modulated relativistic electron beam. The beam is modulated by injecting it into a small spatially periodic magnetic field region within the guide. Analysis of this interaction shows that the slow space charge beam mode couples actively to the fast transverse electric guide mode. The result is parametric instability of the coupled modes. Synchronism between the doppler-shifted transverse travelling wave and the undulating electron beam results in a transfer of energy from the beam to the transverse field. The parametrically growing field can be a source of microwave radiation. The period magnetic field, together with the beam density, provide the coupling media between the unstable waves. The growth rate of the instability is shown to depend, in a nonlinear manner, on the product of the beam plasma frequency and the strength of the applied rippled magnetic field. The growth rate is obtained as a function of the system parameters.

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