We report results and modelling of an experiment performed at the Target Area West Vulcan laser facility, aimed at investigating laser–plasma interaction in conditions that are of interest for the shock ignition scheme in inertial confinement fusion (ICF), that is, laser intensity higher than ${10}^{16}$ $\mathrm{W}/{\mathrm{cm}}^2$ impinging on a hot ($T>1$ keV), inhomogeneous and long scalelength pre-formed plasma. Measurements show a significant stimulated Raman scattering (SRS) backscattering ($\sim 4\%{-}20\%$ of laser energy) driven at low plasma densities and no signatures of two-plasmon decay (TPD)/SRS driven at the quarter critical density region. Results are satisfactorily reproduced by an analytical model accounting for the convective SRS growth in independent laser speckles, in conditions where the reflectivity is dominated by the contribution from the most intense speckles, where SRS becomes saturated. Analytical and kinetic simulations well reproduce the onset of SRS at low plasma densities in a regime strongly affected by non-linear Landau damping and by filamentation of the most intense laser speckles. The absence of TPD/SRS at higher densities is explained by pump depletion and plasma smoothing driven by filamentation. The prevalence of laser coupling in the low-density profile justifies the low temperature measured for hot electrons ($7\!{-}\!12$ keV), which is well reproduced by numerical simulations.

Laser–solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging. A bright, energetic X-ray pulse can be driven from a small source, making it ideal for high resolution X-ray radiography. By limiting the lateral dimensions of the target we are able to confine the region over which X-rays are produced, enabling imaging with enhanced resolution and contrast. Using constrained targets we demonstrate experimentally a $(20\pm 3)~\unicode[STIX]{x03BC}\text{m}$ X-ray source, improving the image quality compared to unconstrained foil targets. Modelling demonstrates that a larger sheath field envelope around the perimeter of the constrained targets increases the proportion of electron current that recirculates through the target, driving a brighter source of X-rays.

The use of laser-accelerated protons as a particle probe for the detection of electric fields in plasmas has led in recent years to a wealth of novel information regarding the ultrafast plasma dynamics following high intensity laser-matter interactions. The high spatial quality and short duration of these beams have been essential to this purpose. We will discuss some of the most recent results obtained with this diagnostic at the Rutherford Appleton Laboratory (UK) and at LULI - Ecole Polytechnique (France), also applied to conditions of interest to conventional Inertial Confinement Fusion. In particular, the technique has been used to measure electric fields responsible for proton acceleration from solid targets irradiated with ps pulses, magnetic fields formed by ns pulse irradiation of solid targets, and electric fields associated with the ponderomotive channelling of ps laser pulses in under-dense plasmas.

We report spectrally resolved X-ray scattering data from shock compressed foils illustrating the feasibility of X-ray Thomson scattering experiment on a sub-kilo joule laser system. Sandwich targets consisting of CH/Al/CH were shock compressed using ∼1 ns laser pulses. Separate 270 ps laser pulses were used to generate an intense source of Ti-He-α (1s2-1s2p1P) radiation which was used as a probing source of 4.75 keV photons. The spectrum of scattered photons was recorded at a scattering angle of 82° with a CCD fitted spectrometer using a PET crystal in von-Hamos geometry. Although spectral resolution was used to separate the scatter from any background, the resolution was limited by source broadening. The relative level of scatter at different times in the sample history was measured by varying the delay between the shock driving beams and the back-lighter beams. We have compared the scatter spectra with simulations based on two different models of the L-shell bound-free contribution.

Recent experiments undertaken at the Rutherford Appleton Laboratory to produce X-ray lasing over the 5–30 nm wavelength range are reviewed. The efficiency of lasing is optimized when the main pumping pulse interacts with a preformed plasma. Experiments using double 75-ps pulses and picosecond pulses superimposed on 300-ps background pulses are described. The use of travelling wave pumping with the approximately picosecond pulse experiments is necessary as the gain duration becomes comparable to the time for the X-ray laser pulse to propagate along the target length. Results from a model taking account of laser saturation and deviations from the speed of light c of the travelling wave and X-ray laser group velocity are presented. We show that X-ray laser pulses as short as 2–3 ps can be produced with optical pumping pulses of ≈1-ps.

Frequency doubling a 140 × 110 mm 40 J sub-ps 1054 nm beam for laser matter interaction studies was investigated at the Central Laser Facility, with efficiencies greater than 60% being achieved. The conversion characteristics (efficiency, beam quality, focusability, and pulse length) for two large 157 mm diameter aperture high quality KDP crystals of thickness 2 mm and 4 mm were studied. Using a fundamental drive beam of two times diffraction limited quality, focal spots of four times the diffraction limit in the frequency doubled beam were achieved and beam degradation effects shown to be minimal.

The atomic force microscope (AFM) has previously been applied to the measurement of surface forces (including adhesion and friction) and to the investigation of material properties, such as hardness. Here we describe the modification of a commercial AFM that enables the stiffness of interaction between surfaces to be measured concurrently with the surface forces. The stiffness is described by the rheological phase difference between the response of the AFM tip to a driving oscillation of the substrate. We present the interaction between silica surfaces bearing adsorbed polymer, however, the principles could be applied to a wide variety of materials including biological samples.

The technique of Chirped Pulse Amplification (CPA) developed by Strickland and Mourou (1985) is now in common use on many laser systems [see, for instance, the review by Perry & Mourou (1994)] and has resulted in massive increases in focused intensities. This paper describes CPA implementation on the Vulcan laser system which has generated multi-Joule sub-picosecond pulses whilst maintaining beam quality to produce focused intensities of 5 × 1019 Wcm−2.