The first demonstration of laser action in ruby was made in 1960 by T. H. Maiman of Hughes Research Laboratories, USA. Many laboratories worldwide began the search for lasers using different materials, operating at different wavelengths. In the UK, academia, industry and the central laboratories took up the challenge from the earliest days to develop these systems for a broad range of applications. This historical review looks at the contribution the UK has made to the advancement of the technology, the development of systems and components and their exploitation over the last 60 years.

D.C. ice-resistivity measurements on the polar Paris Gletscher in East Greenland are presented. It is found that the observed profile is well described by a four-layer system. Near the surface there are two layers resulting from the penetration of the summer temperatures into the polar ice. Below this the ice has constant resistivity until the bed is reached, where contrary to expectation a high-resistivity layer is found.

The results of measurements of surface flow and ablation on the glacier Bersækerbræ, in the Staunings Alper, East Greenland, are presented. A correlation is shown between the rate of flow and rate of ablation, as suggested by current theory.

The theory of plasma ablation by laser irradiation of a solid target is considered when thermal conduction is weak and the absorption is dominated by inverse bremsstrahlung (the self-regulating model). Analytic solutions are identified to treat both steady and time-dependent flows in limiting cases. The intermediate behaviour is explored by numerical modelling. The models are presented for planar, cylindrical and spherical geometries with both tight and weak focused beams. A brief investigation of the applicability of analytic models to the heating of thin foil systems is also presented.

The theory of plasma ablation by laser irradiation from cylindrical and spherical solid targets is considered when thermal conduction is dominant and absorption is local at the critical density. Analytic solutions for both inhibited and uninhibited heat fluxes are developed, but only investigated in detail when flux limiting does not introduce a step discontinuity. In most cases it is found that only a restricted region of flow is steady, and must be terminated by a rarefaction wave. The transition from quasi-planar to strongly divergent flow is shown to depend on a characteristic parameter, which represents the ratio of the thermal conduction length to the target radius.

The clarification of models of laser ablation by plasma heating is examined using a general dimensional argument and introducing a set of universal parameters. The regime of laser-plasma interaction in which collisional absorption and thermal conduction dominate is examined for spherical systems. Detailed scaling relations are derived for uninhibited and flux-limited thermal conduction. The complete set of regimes for steady spherical flow are examined, and it is found that the most important flows are thin collisional and thick local absorption.

Analytic modelling of laser-produced plasmas has generally been restricted to one-dimensional flow. Multi-dimensional hydrodynamic approximations are available, and are explored in this paper. Two configurations are examined. The explosive mode in which the entire body of material is uniformly heated is treated by the self-similar form, and the aspect ratio of the resulting expansion is determined. Ablative flows can be approximated by the hybrid model, and the self-regulating flow from a solid target can be calculated in this way.

The structure of deflagrations in one-dimensional flow is examined in detail. It is shown that the rule that deflagrations be weak or Chapman-Jouget must be obeyed unless a non-hydrodynamic discontinuity occurs. Such flows are shown to be unique and stable, once the downstream expansion is specified. It is shown that non-hydrodynamic discontinuities, if strong, are accompanied by a compression leading to a weak termination. The application to plasmas produced by laser irradiation of a solid is investigated and the flow structure in the presence of flux limitation evaluated.

Dimensional analysis is used to predict the functional relationships amongst the characteristic variables of the ablation of a cold dense fluid by an imposed external heat source. From these relations, self-similar limiting forms are identified and evaluated. Numerical simulation is used to investigate the interpolation between these limits. Self-similar forms generalizing well-known existing solutions of relevance to laser-plasma are demonstrated and include a general proof of Nemchinov's hypothesis for the heating of small targets of limited mass.

The generation of magnetic fields by currents driven by the electron pressure gradient in non-uniform plasmas is considered. The equations for field generation and energy balance are derived under the MHD approximation. It is shown that there exists a class of waves, thermal magnetic waves, which propagate along surfaces of constant density. The properties of such waves are examined. In addition, a class of self-similar solutions are presented. These represent an unstable growth of magnetic field in localized plasma regions, i.e. magnetic hot spots.

University research in the UK with high power lasers is carried out at the SERC's Central Laser Facility with a multi-terawatt neodymium glass laser, VULCAN, and a developmental KrF laser, SPRITE. These systems are briefly described together with the design of a new KrF laser to supersede VULCAN. The new laser design, SUPERSPRITE, is based on optical and Raman multiplexing which is being developed with the present SPRITE system. The specification of SUPERSPRITE is for 3.5 kJ in 1 ns and a peak power of 300 TW in short pulses. The new technology is seen as highly cost effective in relation to neodymium glass lasers. A resume of the development of XUV lasers in the UK in collaboration with laboratories overseas is given. The work is based on laser action through recombination in highly ionized ions and recent progress includes collaborative experiments on the GEKKO XII facility in Japan which have demonstrated laser action at the shortest wavelength to date at 45 A in Mg XII. The physics of energy transport in short pulses is fundamental to the extrapolation of recombination lasers to shorter wavelengths and is being studied from a more basic standpoint using both the VULCAN and SPRITE facilities. Some details of this work are given.

The free expansion of a heated mass of uniform gas (e.g. a laser produced plasma) can be modelled by self-similar motion with a linear velocity gradient. Using a series of numerical solutions we have shown that a reasonable representation is obtained by the use of a matching parameter relating the scale lengths in the prototype and its model, and that the representation improves as the ratio of the heating and disassembly times increases. In this paper we re-examine these two inferred results, and re-derive them on an analytic basis. The extension of the theory to multi-structured bodies shows that such systems of symmetric form allow self-similar motion, as does the particular case of an asymmetric one-dimensional foil. The case of isothermal foils is examined in detail to illustrate the derivation of the matching conditions.

Intense and stable laser operation with Ni-like Zr and Ag was demonstrated at pump energies between 2 J and 5 J energy from the PHELIX pre-amplifier section. A novel single mirror focusing scheme for the TCE x-ray laser (XRL) has been successfully implemented by the LIXAM/MBI/GSI collaboration under different pump geometries. This shows potential for an extension to shorter XRL wavelength. Generation of high quality XRL beams for XRL spectroscopy of highly charged ions is an important issue within the scientific program of PHELIX. Long range perspective is the study of nuclear properties of radioactive isotopes within the FAIR project.

The existence of modes of compressible fluid flow involving a separation of variables into a similarity solution in two dimensions and one-dimensional flow in the third is demonstrated. The numerical integration of such flows by a modified von Neumann–Richtmyer scheme is proposed, and the stability conditions investigated, showing that a generalized Courant–Friedrichs–Lewy condition is necessary. The inclusion of dissipation in the forms of artificial viscosity and thermal conduction into the model is discussed. The results of some test calculations are presented to demonstrate the behaviour of this model.

The self-similar motion of a polytropic gas with a linear velocity distribution is considered in an arbitrary ν-dimensional space. It is shown that if the initial state of the gas is isotropic the flow has a characteristic ellipsoidal form. Both expanding and compressing flows are shown to exist. The application of such flows as models for the expansion of an initially uniform mass of gas into vacuum is considered by comparison with computationally modelled expansions in one-dimensional cylindrical and spherical geometries. It is found that the accuracy of the representation increases when the heating time is long compared with the characteristic time of expansion.