Plasma waveguide formation in predissociated clustering gases.

We report on the use of a novel technique to create a plasma waveguide suitable for guiding high-intensity laser pulses in underdense plasmas. A narrow channel of a clustering gas is dissociated with a low-intensity prepulse. This prepulse is followed by a high-intensity, focused laser pulse.

Radiological characterisation of photon radiation from ultra-high-intensity laser-plasma and nuclear interactions.

With the increasing number of multi-terawatt (10(12) W) and petawatt (10(15) W) laser interaction facilities being built, the need for a detailed understanding of the potential radiological hazards is required and their impact on personnel is of major concern. Experiments at a number of facilities are being undertaken to achieve this aim. This paper describes the recent work completed on the Vulcan petawatt laser system at the CCLRC Rutherford Appleton Laboratory, where photon doses of up to 43 mSv at 1 m per shot have been measured during commissioning studies.

Production of enzymatically active ketosteroid isomerase following insoluble expression in Escherichia coli.

Enzymatically active Delta(5)-3-ketosteroid isomerase (KSI) protein with a C-terminus his(6)-tag was produced following insoluble expression using Escherichia coli. A simple, integrated process was used to extract and purify the target protein. Chemical extraction was shown to be as effective as homogenization at releasing the inclusion body proteins from the bacterial cells, with complete release taking less than 20 min.

Intensified process for the purification of an enzyme from inclusion bodies using integrated expanded bed adsorption and refolding.

This work describes the integration of expanded bed adsorption (EBA) and adsorptive protein refolding operations in an intensified process used to recover purified and biologically active proteins from inclusion bodies expressed in E. coli. Delta(5)-3-Ketosteroid isomerase with a C-terminal hexahistidine tag was expressed as inclusion bodies in the cytoplasm of E.

Adsorptive refolding of histidine-tagged glutathione S-transferase using metal affinity chromatography.

Column-based protein refolding strategies are often advantageous due to their ease of integration with purification operations, improved refolding yields, and the high concentrations at which the refolded protein can be recovered. His6-tagged glutathione S-transferase (GST-(His6)) was refolded while it was adsorbed in a metal affinity chromatography column. The redox environment could be controlled during the refolding reaction by the addition of reduced and oxidized glutathione without reducing the immobilized nickel metal ions.

Refolding strategies for ketosteroid isomerase following insoluble expression in Escherichia coli.

Dilution and column-based protein refolding techniques are compared for refolding Delta 5-3-ketosteroid isomerase (KSI) with a C-terminus his6-tag. Column refolding was performed by removing the denaturant while the protein was adsorbed in an immobilized metal affinity chromatography column. Both dilution refolding and a single-step column-based refolding strategy were optimized to maximize the recovery of KSI enzyme activity, and achieved refolding yields of 87% and 70% respectively.

Screening protein refolding using surface plasmon resonance.

Surface plasmon resonance (SPR) measurements were used to screen refolding conditions to identify a physicochemical environment which gives an acceptable refolding yield for samples of glutathione-S-transferase (GST) denatured in 6 M guanidine hydrochloride and 32 mM dithiothreitol. The SPR measurements were performed on carboxymethylcellulose coated chips that could accommodate two separate flow paths. One side of the chip was derivatized with immobilized glutathione and the other with goat anti-GST antibody.

Long-pulse self-starting stimulated-Brillouin-scattering resonator.

We demonstrate, for the first time to our knowledge, a self-starting stimulated-Brillouin-scattering phaseconjugate resonator in a flash-lamp-pumped dye-laser system. The brightness of the laser is increased by a factor of 40 compared with that of an equivalent plane-]plane conventional resonator.

High-reflectivity four-wave mixing by saturable gain in Rhodamine 6G dye.

Four-wave mixing in a saturated gain medium has been modeled numerically, and the predictions for the reflectivity have been compared with experiments carried out in the laser-pumped dye Rhodamine 6G. It is demonstrated that the saturable absorption of the inversion laser pump has a dramatic influence on the intensity dependence of the four-wave-mixing reflectivity.

Measurement of 248-nm, subpicosecond pulse durations by two-photon fluorescence of xenon excimers.

A technique for measuring the duration of single ultrashort pulses at KrF(*) wavelengths has been developed that employs fluorescence from xenon excimers excited by two-photon absorption of atom pairs. Pulses of ~350-fsec duration have been measured at 248 nm.

Single-frequency phase-conjugate laser resonator using stimulated Brillouin scattering.

An experimental investigation of a phase-conjugate laser resonator using a Nd:YAG gain medium and incorporating Brillouin-enhanced four-wave mixing is reported. Phase-conjugate reflectivities of greater than unity and stable oscillation between a single laser frequency and a counterpropagating Stokes frequency are demonstrated.

Technique for measuring phase-conjugation fidelity by heterodyning signals.

A simple heterodyning technique is described that permits a rigorous measurement of the phase-conjugate fraction of a scattered beam in Brillouin scattering. A general expression for interferometry using phase-conjugate mirrors is derived. The applications of the technique to the measurement of laser phase structure and intensity-dependent phase shifts, and also for high-resolution determination of Brillouin acoustic frequencies, are discussed.

Pulse compression in a phase-conjugating Brillouin cavity.

By the formation of two Brillouin mirrors at either end of a methane chamber, a Brillouin cavity has been produced that is capable of oscillation when injected by a laser pulse. The pulse-compressing mechanisms of the Brillouin mirrors cause a train of intense short-duration pulses to be produced, and the Brillouin cavity displays the characteristic of a phase-conjugate resonator.

High-efficiency laser-pulse compression by stimulated Brillouin scattering.

Highly efficient compression of laser pulses down to 1 nsec in duration by stimulated Brillouin scattering has been demonstrated. Compression ratios of ~10 and energy-conversion efficiencies >70% have been produced. Several compressor systems have been investigated, including the use of tapered waveguides, long-focal-length geometries, and generator-amplifier systems.

Multiplate resonant reflectors for the vacuum ultraviolet.

A multiplate resonant reflector has been designed, constructed, and used in the VUV as an output mirror for an Ar excimer laser. Details of the design calculations etc. are given.

Repetitive vacuum ultraviolet xenon excimer laser.

A repetitive, tunable, high-power vacuum ultraviolet laser operating on the 172-nm bound-free transition in xenon has been developed for use in photochemistry, selective excitation spectroscopy, and in the generation of coherent radiation in the XUV spectral region. A compact high-voltage generator is employed in conjunction with a coaxial cold-cathode diode to pump high-pressure xenon at a repetition rate of up to 10 Hz, though at present gas heating limits the operation of the laser to 0.5 Hz.