In 2014, electron beams with energy up to 4.3 GeV were obtained using 9 cm-long capillary discharge plasma waveguides and laser pulses with peak power 310 TW [1]. Although the laser power available was 1 PW, at that time it was not possible to increase the electron beam energy further since effective laser-guiding of the 60 micron focal spot at lower density was not possible. Usually the capillary radius would be reduced to increase the plasma channel depth and achieve matched guiding of the laser, but for PW laser pulses significant capillary damage would typically occur. The concept of inverse bremsstrahlung heating inside a capillary waveguide was proposed to address this problem [2]. Results will be shown on the optimization of heating and laser-guiding, which has allowed for guiding of laser pulses with PW peak power and 60 micron radius over tens of centimeters, and the generation of electron beams with energy up to 8GeV.
The work was supported by the Office of Science, US DOE under Contract DE-AC02-05CH11231 and the NSF. [1] W. P. Leemans et al., Phys. Rev. Lett. 113, 245002 (2014). [2] N.A. Bobrova et al., Phys. Plasmas 20, 020703 (2013).
Laser-plasma accelerators (LPAs) rely on intense laser fields that create wakes in plasmas. Advancement in the field of LPAs depends on extending the laser-plasma interaction length. State-of-the-art accelerators make use of laser guiding by capillary discharge channels. The transverse density profile (channel depth) of such channels confines the laser, and the on-axis density determines the energy transfer to the wake. The transverse profile can be controlled by choosing the radius of the capillary, but laser-induced capillary damage occurs when the radius is reduced to achieve the required channel depth. Both the on-axis density and the transverse profile depend on the pressure inside the capillary before discharge. As the pressure is reduced to increase the interaction length, confinement of the laser beam is reduced. A scheme to improve laser guiding at low densities by locally heating the plasma with a secondary, nanosecond-scale heater laser has been implemented, and preliminary results are presented here. Heating of the plasma and modified confinement of the main laser pulse have been demonstrated.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.