Experiments have been undertaken using the VEGA-3 petawatt laser system at the Centro de Láseres Pulsados (CLPU) facility in Salamanca to investigate electron and ion acceleration in under-dense plasma. The respective longitudinal and transverse fields of the ‘bubble’ structure of a laser wakefield accelerator (LWFA) simultaneously accelerates electrons to GeV energies, and ions to 100s keV/u to MeV/u energies. The laser is configured to produce two ultra-intense laser pulses, each with a minimum pulse duration of 30 fs and a variable inter-pulse delay up to 300 fs. The double pulses can superpose or resonantly excite the LWFA bubble to increase the accelerating fields. By focusing the laser beam into a 2.74 mm diameter supersonic jet of He gas, using an F/10.4 parabola, an initial intensity of up to ≈1019 Wcm−2 can be realized at focus. This ionises the gas to produce plasma and the imposes a ponderomotive force that creates the LWFA accelerating structures. For backing pressures of 30 – 60 bar, corresponding to plasma densities of 1–4×1019 cm−3, the fields of the LWFA can exceed 200 MV/m, which is sufficient to accelerate electrons to GeV energies, and ions to 100s keV/u. This study focuses on ion acceleration in the transverse direction. He+1 and He+2 ion spectra have been measured using a Thompson parabola spectrometer and a multi-channel plate detector. He ions with energies up to a few hundred keV/u are observed for both single pulses (5.0 J) and double pulses (5.0 J and 3.6 J, respectively), where the inter-pulse delay is varied between 0 fs and ± 300 fs. The measured spectra are consistent with numerical simulations. Ions are observed to undergo electron exchange in the neutral surrounding gas, which produces different charge states ions and neutral atoms.
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.