Imperial College London
Alternate

Professor Roland A Smith

Faculty of Natural Sciences, Department of Physics

Professor of Laser Physics
 
 
 
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Contact

 

+44 (0)20 7594 7866r.a.smith Website

 
 
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Location

 

745Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

157 results found

Rodriguez R, Espinosa G, Gil JM, Rubiano JG, Mendoza MA, Martel P, Minguez E, Symes DR, Hohenberger M, Smith RAet al., 2015, Time-dependent and radiation field effects on collisional-radiative simulations of radiative properties of blast waves launched in clusters of xenon, High Energy Density Physics, Vol: 17, Pages: 119-128, ISSN: 1878-0563

Radiative shock waves are ubiquitous throughout the universe and play a crucial role in the transport of energy into the interstellar medium. This fact has led to many efforts to scale the astrophysical phenomenato accessible conditions. In some laboratory experiments radiative blast waves are launched in clusters of gases by means of the direct deposition of the laser energy. In this work, by using a ollisionalradiativemodel, we perform an analysis of the plasma level populations and radiative properties of a blast wave launched in a xenon cluster. In particular, for both the shocked and unshocked material, westudy the influence of different effects such as LTE, steady-state or time-dependent NLTE simulations, plasma self-absorption or external radiation field in the determination of those properties and also in thediagnosis of the electron temperature of the blast wave.

Journal article

Swadling GF, Lebedev SV, Harvey-Thompson AJ, Rozmus W, Burdiak G, Suttle L, Patankar S, Smith RA, Bennett M, Hall GN, Suzuki-Vidal F, Bland S, Yuan Jet al., 2015, Interpenetration and deflection phenomena in collisions between supersonic, magnetized, tungsten plasma flows diagnosed using high resolution optical Thomson scattering, PHYSICS OF PLASMAS, Vol: 22, ISSN: 1070-664X

Journal article

Swadling GF, Lebedev SV, Harvey-Thompson AJ, Rozmus W, Burdiak G, Suttle L, Patankar S, Smith RA, Bennett M, Hall GN, Suzuki-Vidal F, Yuan Jet al., 2015, Erratum: Interpenetration, Deflection, and Stagnation of Cylindrically Convergent Magnetized Supersonic Tungsten Plasma Flows [Phys. Rev. Lett. 113, 035003 (2014)], Physical Review Letters, Vol: 114, ISSN: 0031-9007

Journal article

Price CJ, Donnelly TD, Giltrap S, Stuart NH, Parker S, Patankar S, Lowe HF, Drew D, Gumbrell ET, Smith RAet al., 2015, An in-vacuo optical levitation trap for high-intensity laser interaction experiments with isolated microtargets, Review of Scientific Instruments, Vol: 86, ISSN: 0034-6748

We report on the design, construction, and characterisation of a new class of in-vacuo optical levitation trap optimised for use in high-intensity, high-energy laser interaction experiments. The system uses a focused, vertically propagating continuous wave laser beam to capture and manipulate micro-targets by photon momentum transfer at much longer working distances than commonly used by optical tweezer systems. A high speed (10 kHz) optical imaging and signal acquisition system was implemented for tracking the levitated droplets position and dynamic behaviour under atmospheric and vacuum conditions, with ±5 μm spatial resolution. Optical trapping of 10 ± 4 μm oil droplets in vacuum was demonstrated, over timescales of >1 h at extended distances of ∼40 mm from the final focusing optic. The stability of the levitated droplet was such that it would stay in alignment with a ∼7 μm irradiating beam focal spot for up to 5 min without the need for re-adjustment. The performance of the trap was assessed in a series of high-intensity (1017 W cm−2) laser experiments that measured the X-ray source size and inferred free-electron temperature of a single isolated droplet target, along with a measurement of the emitted radio-frequency pulse. These initial tests demonstrated the use of optically levitated microdroplets as a robust target platform for further high-intensity laser interaction and point source studies.

Journal article

Bennett MJ, Lebedev SV, Hall GN, Suttle L, Burdiak G, Suzuki-Vidal F, Hare J, Swadling G, Patankar S, Bocchi M, Chittenden JP, Smith R, Frank A, Blackman E, Drake RP, Ciardi Aet al., 2015, Formation of radiatively cooled, supersonically rotating, plasma flows in Z-pinch experiments: Towards the development of an experimental platform to study accretion disk physics in the laboratory, High Energy Density Physics, Vol: 17, Pages: 63-67, ISSN: 1878-0563

We present data from the first Z-pinch experiments aiming to simulate aspects of accretion disk physics in the laboratory. Using off axis ablation flows from a wire array z-pinch we demonstrate the formation of a supersonically (M ∼ 2) rotating hollow plasma cylinder of height ∼4 mm and radius 2 mm. Using a combination of diagnostics we measure the rotation speed (∼60 kms−1), electron density (1019 cm−3), ion temperature (Ti ∼ 60 eV) and the product of electron temperature and average ionisation (ZTe ∼ 150 to 200 eV). Using these parameters we calculate the Reynolds number for the plasma on the order 105 and magnetic Reynolds number as 10 – 100. The plasma flow is maintained for 150 ns, corresponding to one rotation period, which should allow for studying fast instabilities which develop on this time-scale.

Journal article

Stuart NH, Bigourd D, Hill RW, Robinson TS, Mecseki K, Patankar S, New GHC, Smith RAet al., 2015, Direct fluorescence characterisation of a picosecond seeded optical parametric amplifier, Optics Communications, Vol: 336, Pages: 319-325, ISSN: 0030-4018

The temporal intensity contrast of high-power lasers based on optical parametric amplification (OPA) can be limited by parametric fluorescence from the non-linear gain stages. Here we present a spectroscopic method for direct measurement of unwanted parametric fluorescence widely applicable from unseeded to fully seeded and saturated OPA operation. Our technique employs simultaneous spectroscopy of fluorescence photons slightly outside the seed bandwidth and strongly attenuated light at the seed central wavelength. To demonstrate its applicability we have characterised the performance of a two-stage picosecond OPA pre-amplifier with 2.8×105 gain, delivering pulses at 1054 nm. We show that fluorescence from a strongly seeded OPA is reduced by ~500× from the undepleted to full pump depletion regimes. We also determine the vacuum fluctuation driven noise term seeding this OPA fluorescence to be 0.7±0.4 photons ps−1 nm−1 bandwidth. The resulting shot-to-shot statistics highlights a 1.5% probability of a five-fold and 0.3% probability of a ten-fold increase of fluorescence above the average value. Finally, we show that OPA fluorescence can be limited to a few-ps pedestal with 3×10−9 temporal intensity contrast 1.3 ps ahead of an intense laser pulse, a level highly attractive for large scale chirped-pulse OPA laser systems.

Journal article

Swadling GF, Lebedev SV, Burdiak G, Suttle L, Patankar S, Smith R, Bennett M, Hall GN, Suzuki-Vidal F, Yuan J, Harvey-Thompson AJ, Rozmus Wet al., 2015, Thomson scattering measurements of supersonic tungsten plasma flow interpenetration in wire array z-pinches

Conference paper

Swadling GF, Lebedev SV, Hall GN, Patankar S, Stewart NH, Smith RA, Harvey-Thompson AJ, Burdiak GC, de Grouchy P, Skidmore J, Suttle L, Suzuki-Vidal F, Bland SN, Kwek KH, Pickworth L, Bennett M, Hare JD, Rozmus W, Yuan Jet al., 2014, Diagnosing collisions of magnetized, high energy density plasma flows using a combination of collective Thomson scattering, Faraday rotation, and interferometry, REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 85, ISSN: 0034-6748

Journal article

Hall GN, Burdiak GC, Suttle L, Stuart NH, Swadling GF, Lebedev SV, Smith RA, Patankar S, Suzuki Vidal F, de Grouchy P, Harvey-Thompson AJ, Bennett M, Bland SN, Pickworth L, Skidmore Jet al., 2014, Monochromatic radiography of high energy density physics experiments on the MAGPIE generator, Review of Scientific Instruments, Vol: 85, ISSN: 1089-7623

A monochromatic X-ray backlighter based on Bragg reflection from a spherically bent quartzcrystal has been developed for the MAGPIE pulsed power generator at Imperial College (1.4 MA,240 ns) [I. H. Mitchell et al., Rev. Sci. Instrum. 67, 1533 (2005)]. This instrument has been usedto diagnose high energy density physics experiments with 1.865 keV radiation (Silicon He-α) froma laser plasma source driven by a ∼7 J, 1 ns pulse from the Cerberus laser. The design of thediagnostic, its characterisation and performance, and initial results in which the instrument was usedto radiograph a shock physics experiment on MAGPIE are discussed.

Journal article

Swadling GF, Lebedev SV, Harvey-Thompson AJ, Rozmus W, Burdiak GC, Suttle L, Patankar S, Smith RA, Bennett M, Hall GN, Suzuki-Vidal F, Yuan Jet al., 2014, Interpenetration, Deflection, and Stagnation of Cylindrically Convergent Magnetized Supersonic Tungsten Plasma Flows, PHYSICAL REVIEW LETTERS, Vol: 113, ISSN: 0031-9007

Journal article

Lebedev SV, Suttle L, Swadling GF, Bennett M, Bland SN, Burdiak GC, Burgess D, Chittenden JP, Ciardi A, Clemens A, de Grouchy P, Hall GN, Hare JD, Kalmoni N, Niasse N, Patankar S, Sheng L, Smith RA, Suzuki-Vidal F, Yuan J, Frank A, Blackman EG, Drake RPet al., 2014, The formation of reverse shocks in magnetized high energy density supersonic plasma flows, PHYSICS OF PLASMAS, Vol: 21, ISSN: 1070-664X

Journal article

Mecseki K, Bigourd D, Patankar S, Stuart NH, Smith RAet al., 2014, Flat-top picosecond pulses generated by chirped spectral modulation from a Nd:YLF regenerative amplifier for pumping few-cycle optical parametric amplifiers, APPLIED OPTICS, Vol: 53, Pages: 2229-2235, ISSN: 1559-128X

Journal article

Bennett MJ, Lebedev SV, Hall GN, Suttle L, Burdiak G, Suzuki-Vidal F, Hare J, Swadling G, Patankar S, Bocchi M, Chittenden JP, Smith R, Frank A, Blackman E, Drake RP, Ciardi Aet al., 2014, Rotating Plasma Disks in Dense Z-pinch Experiments, 9th International Conference on Dense Z Pinches, Publisher: AMER INST PHYSICS, Pages: 71-75, ISSN: 0094-243X

Conference paper

Swadling GF, Lebedev SV, Harvey-Thompson AJ, Rozmus W, Burdiak GC, Suttle L, Patankar S, Smith RA, Bennett M, Hall GN, Suzuki-Vidal F, Yuan Jet al., 2014, Calculation of Thomson Scattering Spectral Fits for Interpenetrating Flows, 9th International Conference on Dense Z Pinches, Publisher: AMER INST PHYSICS, Pages: 118-121, ISSN: 0094-243X

Conference paper

Suzuki Vidal F, Patankar S, Lebedev SV, Bland SN, Doyle H, Bigourd D, Burdiak G, de Grouchy P, Hall GN, Harvey Thompson AJ, Khoory E, Pickworth L, Skidmore J, Smith RA, Swadling GFet al., 2013, Observation of energetic protons trapped in laboratory magnetic-tower jets, New Journal of Physics, Vol: 15, ISSN: 1367-2630

Preliminary results of the self-emission of charged particles frommagnetically driven plasma jets has been investigated. The jets were launchedand driven by a toroidal magnetic field generated by introducing a ∼1.4 MA,250 ns electrical current pulse from the MAGPIE generator into a radialwire array. This configuration has shown to reproduce some aspects of theastrophysical magnetic-tower jet launching model, in which a jet is collimatedby a toroidal magnetic field inside a magnetic cavity. The emission of ions andprotons from the plasma was recorded onto Columbia Resin 39 plates using timeintegratedpinhole cameras. In addition a fly-eye camera, an array of 25–496cylindrical apertures allowed estimating the location of the ion emitting source.The results show the ion emission comes from both the jet and its surroundingmagnetic cavity, with the emission extending to a height of at least ∼9 cm fromthe initial position of the wires. The emission of ions is consistent with the dynamics of the jet obtained from time-resolved imaging diagnostics, i.e. opticallaser probing and self-emission of the plasma in the extreme ultra-violet. Thesepreliminary results suggest the ions are trapped inside the cavity due to the strongtoroidal magnetic field which drives the jet. In addition these studies providefirst estimates of the energy and fluence of protons for future laser-driven protonprobing diagnostics aimed at measuring the magnetic field in these experiments.

Journal article

Bigourd D, Patankar S, Robbie SIO, Doyle HW, Mecseki K, Stuart N, Hadjicosti K, Leblanc N, New GHC, Smith RAet al., 2013, Spectral enhancement in optical parametric amplifiers in the saturated regime, APPLIED PHYSICS B-LASERS AND OPTICS, Vol: 113, Pages: 627-633, ISSN: 0946-2171

Journal article

Rodriguez R, Espinosa G, Gil JM, Florido R, Rubiano JG, Mendoza MA, Martel P, Minguez E, Symes DR, Hohenberger M, Smith RAet al., 2013, Analysis of microscopic magnitudes of radiative blast waves launched in xenon clusters with collisional-radiative steady-state simulations, JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, Vol: 125, Pages: 69-83, ISSN: 0022-4073

Journal article

Suzuki-Vidal F, Lebedev SV, Krishnan M, Skidmore J, Swadling GF, Bocchi M, Harvey-Thompson AJ, Patankar S, Burdiak GC, de Grouchy P, Pickworth L, Stafford SJP, Suttle L, Bennett M, Bland SN, Chittenden JP, Hall GN, Khoory E, Smith RA, Ciardi A, Frank A, Madden RE, Wilson-Elliot K, Coleman Pet al., 2013, Interaction of radiatively cooled plasma jets with neutral gases for laboratory astrophysics studies, HIGH ENERGY DENSITY PHYSICS, Vol: 9, Pages: 141-147, ISSN: 1574-1818

Journal article

Lebedev SV, Suzuki-Vidal F, Bocchi M, Swadling GF, Burdiak G, Bland SN, de Grouchy P, Harvey-Thompson AJ, Khoory E, Patankar S, Pickworth L, Skidmore J, Smith R, Chittenden JP, Krishnan M, Madden R, Wilson-Elliot K, Ciardi A, Frank Aet al., 2013, University of Rochester, Rochester, NY, USA EXPERIMENTAL STUDIES OF SUPERSONIC RADIATIVELY COOLED PLASMA JETS, ECLA: European Conference on Laboratory Astrophysics, Publisher: E D P SCIENCES, Pages: 133-+, ISSN: 1633-4760

Conference paper

Harvey-Thompson AJ, Lebedev SV, Patankar S, Bland SN, Burdiak G, Chittenden JP, Colaitis A, De Grouchy P, Doyle HW, Hall GN, Khoory E, Hohenberger M, Pickworth L, Suzuki-Vidal F, Smith RA, Skidmore J, Suttle L, Swadling GFet al., 2012, Optical Thomson Scattering Measurements of Plasma Parameters in the Ablation Stage of Wire Array Z Pinches, Physical Review Letters, Vol: 108, Pages: 145002-1-145002-5

Journal article

Rodriguez R, Gil JM, Espinosa G, Florido R, Rubiano JG, Mendoza MA, Martel P, Minguez E, Symes DR, Hohenberger M, Smith RAet al., 2012, Determination and analysis of plasma parameters for simulations of radiative blast waves launched in clusters of xenon and krypton, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 54, ISSN: 0741-3335

Journal article

Harvey-Thompson AJ, Lebedev SV, Patankar S, Bland SN, Burdiak G, Chittenden JP, Colaitis A, De Grouchy P, Hall GN, Khoory E, Hohenberger M, Pickworth L, Suzuki-Vidal F, Smith RA, Skidmore J, Suttle L, Swadling GFet al., 2012, Optical Thomson scattering measurements of cylindrical wire array parameters, Physics of Plasmas, Vol: 19, Pages: 056303-1-056303-10, ISSN: 1070-664X

Journal article

Robbie SIO, Doyle HW, Symes DR, Smith RAet al., 2012, A study of ambient upstream material properties using perpendicular laser driven radiative blast waves in atomic cluster gases, HIGH ENERGY DENSITY PHYSICS, Vol: 8, Pages: 55-59, ISSN: 1574-1818

Journal article

Suzuki-Vidal F, Bocchi M, Lebedev SV, Swadling GF, Burdiak G, Bland SN, de Grouchy P, Hall GN, Harvey-Thompson AJ, Khoory E, Patankar S, Pickworth L, Skidmore J, Smith R, Chittenden JP, Krishnan M, Madden RE, Wilson-Elliot K, Ciardi A, Frank Aet al., 2012, Interaction of a supersonic, radiatively cooled plasma jet with an ambient medium, PHYSICS OF PLASMAS, Vol: 19, ISSN: 1070-664X

Journal article

Symes DR, Hohenberger M, Doyle HW, Smith RA, Moore AS, Gumbrell ET, Rodriguez R, Gil JMet al., 2011, Studying radiative shocks using laser driven blast waves in clustered gases, 4th International Conference on Superstrong Fields in Plasmas, Publisher: ELSEVIER SCIENCE BV, Pages: 186-188, ISSN: 0168-9002

Conference paper

Rodriguez R, Gil JM, Florido R, Rubiano JG, Mendoza MA, Martel P, Minguez E, Symes DR, Hohenberger M, Smith RAet al., 2011, Determination of the average ionization and thermodynamic regimes of xenon plasmas with an application to the characterization of blast waves launched in xenon clusters, HIGH ENERGY DENSITY PHYSICS, Vol: 7, Pages: 71-76, ISSN: 1574-1818

Journal article

Hohenberger M, Symes DR, Lazarus J, Doyle HW, Carley RE, Moore AS, Gumbrell ET, Notley MM, Clarke RJ, Dunne M, Smith RAet al., 2010, Observation of a Velocity Domain Cooling Instability in a Radiative Shock, PHYSICAL REVIEW LETTERS, Vol: 105, ISSN: 0031-9007

Journal article

Symes DR, Hohenberger M, Lazarus J, Osterhoff J, Moore AS, Faeustlin RR, Edens AD, Doyle HW, Carley RE, Marocchino A, Chittenden JP, Bernstein AC, Gumbrell ET, Dunne M, Smith RA, Ditmire Tet al., 2010, Investigations of laser-driven radiative blast waves in clustered gases, 2nd International Conference on High Energy Density Physics, Publisher: ELSEVIER SCIENCE BV, Pages: 274-279, ISSN: 1574-1818

Conference paper

Skopalova E, El-Taha YC, Zair A, Hohenberger M, Springate E, Tisch JWG, Smith RA, Marangos JPet al., 2010, Pulse-Length Dependence of the Anisotropy of Laser-Driven Cluster Explosions: Transition to the Impulsive Regime for Pulses Approaching the Few-Cycle Limit, PHYSICAL REVIEW LETTERS, Vol: 104, ISSN: 0031-9007

Journal article

Symes DR, Wegner U, Ahlswede H-C, Streeter MJV, Gallegos PL, Divall EJ, Smith RA, Rajeev PP, Neely Det al., 2010, Ultrafast gated imaging of laser produced plasmas using the optical Kerr effect, APPLIED PHYSICS LETTERS, Vol: 96, ISSN: 0003-6951

Journal article

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