Oxford Centre for High Energy Density Science (OxCHEDS)

Abstract:

We have focused a beam (BL3) of FLASH (Free-electron LASer in Hamburg: δ=13.5 nm, pulse length 15 fs, pulse energy 10-40 μJ, 5Hz) using a fine polished off-axis parabola having a focal length of 270 mm and coated with a Mo/Si multilayer with an initial reflectivity of 67% at 13.5 nm. The OAP was mounted and aligned with a picomotor controlled six-axis gimbal. Beam imprints on poly(methyl methacrylate) - PMMA were used to measure focus and the focused beam was used to create isochoric heating of various slab targets. Results show the focal spot has a diameter of ≤1 μm producing intensities greater than 1016 W cm-2. Observations were correlated with simulations of best focus to provide further relevant information. This focused XUV laser beam now allows us to begin exploring matter under extreme conditions.

Abstract:

A method for producing non-uniformly spaced (chirped) trains of ultrafast pulses is demonstrated, using an acousto-optic programmable dispersive filter (AOPDF). Programmable pulse trains of this type may find applications in quasi-phase matching of high-harmonic generation. © 2009 Optical Society of America.

Abstract:

The temporal resolution of existing streak cameras are limited by electron transit time dispersion. Here we present a state-of-art design compensating this to achieve a breakthrough of 100fs time resolution. © 2009 OSA/CLEO/IQEC 2009.

Abstract:

The temporal resolution of existing streak cameras are limited by electron transit time dispersion. Here we present a state-of-art design compensating this to achieve a breakthrough of 100fs time resolution. © 2009 OSA/CLEO/IQEC 2009.

Abstract:

The production of highly energetic beams of both electrons and ions is a major part of the experimental programme at the Central Laser Facility (CLF), STFC Rutherford Appleton Laboratory. Every year sees a significant number of experiments done in both areas. This has been complemented by theoretical studies that have been carried out at the CLF and UK universities. In a recent consultation on plans to build a 10 PW upgrade to the VULCAN facility, laser-driven particle acceleration formed a very significant part of the science case that emerged from this consultation. In this talk, I will review the experimental progress that has been made in particle acceleration, and I will also examine what theoretical investigations suggest the future of this field will be. Experimental studies of laser-driven ion acceleration of the CLF using both the VULCAN and ASTRA systems have looked at a number of aspects including focussing and control of the ion beam, manipulation of the energy spectrum, energy scaling with laser and target parameters, and direct use of the proton beam in both isochoric heating of secondary targets and proton radiography. Recently there has been great interest in a number of theoretical studies which indicate that it should be possible to explore radiation-pressure driven ion acceleration for intensities above 1021 Wcm-2, which will be accessible with the ASTRA-GEMINI system. This very exciting prospect will also be discussed. Electron acceleration in laser wakefields is also a well established part of the CLF programme. Experimental studies of laser-driven electron acceleration using the ASTRA laser have explored electron acceleration in both supersonic gas jets and gas-filled capillaries. This has led to the production of electron bunches with up to 1 GeV energy and a few percent energy spread. The influence of tuneable parameters such as the evolution of the plasma channel inside a capillary or the position of the laser focus with respect to the gas jet is actively being investigated. These efforts are backed up by a matching numerical campaign. Recent experiments have also shown that electron bunches trapped on a downward density ramp can have a very small absolute energy spread, and the potential consequences of these results will also be discussed. © 2011 Optical Society of America.