Laser-plasma accelerator group

Abstract:

The results of the first experimental demonstration of a short-wavelength laser driven within a gas-filled capillary-discharge waveguide were described. The xenon gas was mixed with the hydrogen and strong lasing on the 4d ⁹5d-4d⁹5p transition in Xe⁸⁺ at 41.8 nm was observed. Analysis shows that lasing was strongly correlated with good guiding of the pump pulse and numerical simulations indicate that gain is likely to have been achieved over a significant fraction of the 30 mm length of the capillary. The success of this proof-of-principle experiment suggests that this and other short-wavelength lasers could be driven within waveguides of this type, leading to increased energy output and reduced beam divergence.

Abstract:

Cross sections for e+ p neutral current deep inelastic scattering have been measured at a center-of-mass energy of √s = 318 GeV with the ZEUS detector at HERA using an integrated luminosity of 63.2 pb -1. The double-differential cross section, d2σ/ dxdQ2, is presented for 200 GeV2 < Q2 < 30 000 GeV2 and for 0.005 < x < 0.65. The single-differential cross sections dσ/dQ2, dσ/dx and dσ/dy are presented for Q2 > 200 GeV2. The effect of Z-boson-exchange is seen in dσ/dx measured for Q2 > 10 000 GeV2. The data presented here were combined with ZEUS e+ p neutral current data taken at √s = 300 GeV and the structure function F2em was extracted. All results agree well with the predictions of the Standard Model.

Abstract:

Inclusive Ks⁰Ks⁰ production in deep inelastic ep scattering at HERA has been studied with the ZEUS detector using an integrated luminosity of 120 pb^-1. Two states are observed at masses of 1537-8^-9 MeV and 1726 ± 7 MeV, as well as an enhancement around 1300 MeV. The state at 1537 MeV is consistent with the well established f′2(1525). The state at 1726 MeV may be the glueball candidate f0(1710). However, it's width of 38 -14^-20 MeV is narrower than 125 ± 10 MeV observed by previous experiments for the f0(1710). © 2003 Elsevier B.V. All rights reserved.

Abstract:

We present the status of optical field ionization soft X-ray lasers. The amplifying medium is generated by focusing a high-energy circularly polarized 30-fs 10-Hz Ti: sapphire laser system in a gaseous medium. Using xenon or krypton, strong laser emission at 41.8 and 32.8 nm, respectively, has been observed. After presenting the basis of the physics, we present recent characterization of the sources as well as dramatic improvement of their performances using the waveguiding technique.

Abstract:

In many cases the length over which particles can be accelerated in a laser-driven plasma accelerator is limited by refraction or diffraction of the driving laser pulse. In order to overcome this limitation the driving pulse must be guided or channeled through the plasma, In this paper we briefly review of the techniques used to guide laser pulses with peak intensities up to 10(19) W cm(-2), and describe recent experimental results.