(Color online) Shot-to-shot variation in electron energy spectrum at various plasma densities. Laser parameters , . The spectrometer axis is at the top of each image (marked by ), electrons are deflected downwards according to their energy. The shots were taken with collimation angle , giving energy resolution at and at . The brightness of the image is proportional to the charge incident on the screen (false color). The color scale for each density is normalized to the peak signal for that density.
(Color online) Variation in electron beam energy (circles, left axis) and percent FWHM energy-spread (squares, right axis) with plasma density. The curves shows the linear estimate for maximum energy . The error bars on the beam energy represent the standard deviation from the mean value over a series of shots.
Fluctuation of electron beam parameters as a function of plasma densities. (a) Standard deviation of electron beam peak energy . (b) Standard deviation of relative energy-spread . (c) Root mean square pointing fluctuation . (d) Standard deviation of electron charge as measured in the monoenergetic peak on the electron spectrometer (black squares) and as measured with a beam profile monitor for (gray circles) .
(Color online) Percentage of shots showing monoenergetic spectra as a function of laser energy for three plasma densities. Diamonds: ; circles: ; squares: . Dotted lines represent for a threshold vector potential of .
(Color online) Results from a 2D PIC simulation with OSIRIS for the Astra Gemini system. , , , , , (a) Electron density profile after the laser has propagated . (b) Laser transverse intensity profile (integrated along ) as a function of propagation distance. (c) Electron energy spectrum after propagation.
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