David J. Spence

First demonstration of guiding of high-intensity laser pulses in a hydrogen-filled capillary discharge waveguide

The results of the first experiments to demonstrate guiding of high-intensity laser pulses through a hydrogen-filled capillary discharge waveguide are described. Measurements of the temporal behaviour during the discharge of both the pulse energy transmission and the transverse spatial profile of the beam in the exit plane of the waveguide are presented. Guiding of laser pulses with a peak input intensity of greater than 1016 W cm-2 was observed for 20 and 40 mm long waveguides with pulse energy transmissions of approximately 90% and 80%, respectively. The proportion of energy coupled into the waveguide and the propagation loss were determined to be (96±2)% and (4±1) m-1. More than 103 laser pulses were guided through the same capillary.

Shibboleth Access for Resources on the National Grid Service (SARoNGS)

The National Grid Service (NGS) provides access to compute and data resources for UK academics. Currently users are required to have an X.509 certificate from the UK e-Science Certification Authority (CA) or one of its international peers to access the NGS. The CA must satisfy the requirements for internationally agreed assurance levels and some users find the processes of obtaining and managing certificates difficult. Shibboleth, an implementation of federation identity-based authentication, has been widely deployed in academic environments in the UK. The SARoNGS project, was proposed to integrate the Shibboleth and X.509 based infrastructures, to deliver a production level service for accessing the NGS in a user-friendly way. This paper describes an architecture by which users are authenticated by the UK Access Management Federation to acquire low assurance credentials to access Grid resources on the NGS. Users can login to NGS resources via NGS Portal, using their local institution’s authentication system.

Progress in optical-field-ionization soft X-ray lasers at LOA

We give on overview of recent advances in collisionally pumped optical field-ionization soft X-ray lasers developed at LOA. Saturated amplification has been achieved on the 5d-5p transition in Xe^8+ at 41.8 nm, and on the 4d-4p transition in Kr^8+ at 32.8 nm. We demonstrate a significant increase of the energy output from the Xe^8+ laser driven within two types of wave-guide. Finally, we present results of a pioneering work aimed to set up and characterize the first true soft X-ray laser chain.

Application of the Gas‐Filled Capillary Discharge Waveguide to Laser‐Plasma Acceleration

The application of the gas‐filled capillary discharge waveguide to laser‐plasma accelerators is reviewed. The results of experiments to guide high‐intensity laser pulses in capillaries with circular or square cross‐sections are described. The relation between capillary diameter, guided spot size, and plasma density are explored, and a possible new hybrid regime of guiding is identified.

Progress on collisionally pumped optical-field-ionization soft X-ray lasers

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.

Demonstration of lasing at 41.8 nm in Xe8+ driven in a plasma waveguide

We describe the first demonstration of a collisionally-excited optical field ionisation laser driven within a gas-filled capillary waveguide. Lasing on the 4d95d - 4d95p transition at 41.8 nm in Xe8+ was observed to be closely-correlated to conditions under which the pump laser pulses were guided well by the waveguide. Simulations of the propagation of the pump laser radiation show that gain was achieved over essentially the whole 30 mm length of the waveguide.