JC: Stefan: Highly radiative shock experiments driven by GEKKO XII

In this paper, recent results obtained on highly radiative shocks generated in a xenon .lled gas cell using the GEKKO XII laser facility are presented. Data show extremely high shock velocity (.150 km/s) never achieved before in gas. Preliminary analyses based on theoretical dimensionless numbers and numerical simulations suggest that these radiative shocks reach a new radiative regime where the radiative pressure plays a role in the dynamics and structure of the shock. A major effect observed is a strong anisotropic emission in the downstream gas. This unexpected feature is discussed and compared to available 2D radiation hydrodynamic simulations.
http://www.springerlink.com/content/n152166384177217/
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DM extraordinaire: Will & Henry:Talk and Poster presentation for Toulouse and Erice

Will: Poster Erice Summer school: Compression of multi-millijoule pulses using circular polarization with a differentially pumped hollow-fiber

We have compared the performance of a hollow-fiber pulse compression system using both statically filled and differentially pumped configurations. The fibre is seeded using 3mJ, carrier-envelope phase stabilized pulses with either linear or circular polarization. We have found that the most desirable performance of the system is achieved by combining the use of circularly polarized pulses with differential pumping. In this case, a significantly higher energy transmission was measured at 1bar helium pressure, compared with the transmissions for differential pumping with linear polarization, and for both polarization cases under static fill. For a differentially pumped fiber, the broadest spectra were found at 3bar for both polarizations. Linear and circular polarizations both produced spectra supporting sub-4-fs pulse durations, but a higher energy transmission was observed in the circularly polarized case. The performace of the system is improved by differential pumping and circularly polarized pulses as a result of reduced ionization and self-focusing at the fiber entrance. We envisage that our technique will be useful for increasing the energy of few-cycle pulses, for strong field experiments at higher intensities.

Henry: Talk Toulouse FASTQUAST YEP meeting: High-order Harmonic generation from plasma plumes at KHz repetition rate

I am giving my first scientific talk outside of imperial at the YEP meeting in Toulouse in just under a couple of weeks. So I would like to run through the presentation I plan to give and get your feedback. In this talk I will be presenting the some of the resent progress we have with HHG for plasma plumes at KHz repetition rate, including the presence of Quantum path signature and resonant enhancement of certain harmonics from particular tarjets.
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JC: Felix: Attosecond control of electron-ion recollision in high harmonic generation

We show that high harmonic generation driven by an intense near-infrared (IR) laser can be temporally controlled when an attosecond pulse train (APT) is used to ionize the generation medium, thereby replacing tunnel ionization as the first step in the well-known three-step model. New harmonics are formed when the ionization occurs at a well-defined time within the optical cycle of the IR field. The use of APT-created electron wave packets affords new avenues for the study and application of harmonic generation. In the present experiment, this makes it possible to study harmonic generation at IR intensities where tunnel ionization does not give a measurable signal.
http://iopscience.iop.org/1367-2630/13/3/033002/
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DM: Jon: Programme Grant: Getting started on the Attosecond Electron Dynamics Programme: the 1st 6 months

note: 12:00 sharp start!

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JC: Rashid: Attosecond emission from chromium plasma

We present the first measurement of the attosecond emission generated from underdense plasma produced on a solid target. We generate high-order harmonics of a femtosecond Ti:sapphire laser focused in a weakly ionized underdense chromium plasma. Using the .Reconstruc- tion of Attosecond Beating by Interference of Two-photon Transitions. (RABITT) technique, we show that the 11thto the 19thharmonic orders form in the time domain an attosecond pulse train with each pulse having 300 as duration, which is only 1.05 times the theoretical Fourier transform limit. Measurements reveal a very low positive group delay dispersion of 4200 as2. Beside its fundamental interest, high-order harmonic generation in plasma plumes could thus provide an intense source of attosecond pulses for applications.
http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-19-4-3677
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DM: Tsuneto: Development of CEP-stabilized high power CPA/OPA lasers and direct generation of highly phase-matched isolated attosecond pulses

One of the most crucial issues for the present attophysics is to increase the pulse energy of isolated attosecond pulses (IAP.s). For this purpose, there are two crucial experimental challenges to demonstrate; one is to develop multi-mJ few cycle lasers with a stabilized carrier-envelope phase (CEP) and the other is to achieve the phase-matching highly between the few cycle pulses and high harmonics of them. In this talk, I will present our research activities on both challenges. First, I will present our recent results of RIKEN based on our TW-class 2-cycle laser system (5 fs, 780 nm, 5 mJ, 1 kHz). Recently, we have stabilized CEP of this system with two feedback loops and by blocking mechanical vibrations on the laser system thoroughly. Through the phase matching process, we could select the supercontinuum component of the harmonics without any use of bandpass filters such as Mo/Si mirrors. By using a heterodyne interferometry using mixed gases, we verified that we could select IAP directly. Second, I will briefly introduce our recent results at Imperial College London on constructing a CEP-stabilized high power OPA (optical parametric amplification) laser. CEP-stabilized seed pulses were generated using type II DFG of different frequency components of the supercontinuum generated with a hollow fiber compression technique, and the seed pulses were amplified by two-stage OPA.s. Final output pulses had a pulse energy of 500 μJ, pulse duration of 40fs, and tunable wavelength from 1300-1800 nm. As the first demonstration of this handmade laser, we could generate high harmonics up to 47th using a tube target filled with Xe gas.
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JC: Stefan: Study of high Mach number laser driven blast waves in gases

A series of experiments were performed examining the evolution of blast waves produced by laser irradiation of a target immersed in gas. Blast waves were produced by illumination of wires by 1 kJ, 1 ns laser pulses from the Z-Beamlet laser at Sandia National Laboratories. The blast waves were imaged by probe laser pulses at various times to examine the trajectory, radiative precursor, and induced perturbations on the blast wave front. Well de.ned perturbations were induced on the blast wave front with arrays of wires placed in the gas and the results of the experiments are compared to the theoretical predictions for the Vishniac overstability. It is found that the experimental results are in general agreement with these theoretical predictions on thin blast wave shells and are in quantitative agreement in the simplest case.
http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PHPAEN000017000011112104000001&idtype=cvips&prog=normal
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