Sisira James

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The newly commissioned Orion laser system has been used to study dense plasmas created by a combination of short pulse laser heating and compression by laser driven shocks. Thus the plasma density was systematically varied between 1 and 10  g/cc by using aluminum samples buried in plastic foils or diamond sheets. The aluminum was heated to electron(More)
An analysis of an electron spectrometer used to characterize fast electrons generated by ultraintense (10^{20}Wcm^{-2}) laser interaction with a preformed plasma of scale length measured by shadowgraphy is presented. The effects of fringing magnetic fields on the electron spectral measurements and the accuracy of density scale-length measurements are(More)
The heating of solid foils by a picosecond time scale laser pulse has been studied by using x-ray emission spectroscopy. The target material was plastic foil with a buried layer of a spectroscopic tracer material. The laser pulse length was either 0.5 or 2 ps, which resulted in a laser irradiance that varied over the range 10(16)-10(19) W/cm(2).(More)
We report new experimental results obtained on three different laser facilities that show directed laser-driven relativistic electron-positron jets with up to 30 times larger yields than previously obtained and a quadratic (∼E_{L}^{2}) dependence of the positron yield on the laser energy. This favorable scaling stems from a combination of higher energy(More)
Plasma expansion following the interaction of an intense laser beam with the inner surface of gold hohlraums, emulating conditions relevant to indirect drive inertial confinement fusion (ICF), has been investigated by a radiographic technique which employs a beam of laser-accelerated protons. This probing technique has made it possible to measure the(More)
The onset of filamentation, following the interaction of a relatively long (τ(L)≃1  ns) and intense (I(L)≃5×10(14)  W/cm(2)) laser pulse with a neopentane filled gas bag target, has been experimentally studied via the proton radiography technique, in conditions of direct relevance to the indirect drive inertial confinement fusion scheme. The density(More)
The ORION laser facility is one of the UK's premier laser facilities which became operational at AWE in 2010. Its primary mission is one of stockpile stewardship, ORION will extend the UK's experimental plasma physics capability to the high temperature, high density regime relevant to Atomic Weapons Establishment's (AWE) program. The ORION laser combines(More)
We have developed a high-resolution x-ray spectrometer for measuring the shapes of spectral lines produced from laser-irradiated targets on the Orion laser facility. The instrument utilizes a spherically bent crystal geometry to spatially focus and spectrally analyze photons from foil or microdot targets. The high photon collection efficiency resulting from(More)
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