Abstract
Laser–solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging. A bright, energetic X-ray pulse can be driven from a small source, making it ideal for high resolution X-ray radiography. By limiting the lateral dimensions of the target we are able to confine the region over which X-rays are produced, enabling imaging with enhanced resolution and contrast. Using constrained targets we demonstrate experimentally a $(20\pm 3)~\unicode[STIX]{x03BC}\text{m}$ X-ray source, improving the image quality compared to unconstrained foil targets. Modelling demonstrates that a larger sheath field envelope around the perimeter of the constrained targets increases the proportion of electron current that recirculates through the target, driving a brighter source of X-rays.
Highlights
High intensity laser pulses rapidly ionize and accelerate electrons in laser–solid interactions, driving a multi-megaampere current of relativistic electrons into the target[1,2,3]. This electron current produces a bright source of bremsstrahlung radiation as it propagates, which has long been used as a source for radiography[4,5,6,7,8,9,10,11] and as a diagnostic for the internal electron current[12,13,14,15]
High energy laser pulses (>100 J) offer the potential of single-shot acquisition through larger industrial samples when combined with thick (>10 μm) high-Z targets due to the high flux of energetic X-rays produced during the interaction
We report on results from a recent experimental campaign using constrained targets to reduce the X-ray emission area and drive a bright X-ray source through increased refluxing of hot electrons and increase the flux by ∼50% compared to unconstrained foil targets of comparable thickness
Summary
High intensity laser pulses rapidly ionize and accelerate electrons in laser–solid interactions, driving a multi-megaampere current of relativistic electrons into the target[1,2,3] This electron current produces a bright source of bremsstrahlung radiation as it propagates, which has long been used as a source for radiography[4,5,6,7,8,9,10,11] and as a diagnostic for the internal electron current[12,13,14,15]. Using laser-driven X-ray sources as a backlighter in inertial confinement fusion has been an area of study, where experimental investigations have demonstrated a bright Kα emission with the side profile of the target as the source[16, 21,22,23]. We report on results from a recent experimental campaign using constrained targets to reduce the X-ray emission area and drive a bright X-ray source through increased refluxing of hot electrons and increase the flux by ∼50% compared to unconstrained foil targets of comparable thickness
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