Abstract
Pulsed beams of energetic x-rays and neutrons from intense laser interactions with solid foils are promising for applications where bright, small emission area sources, capable of multi-modal delivery are ideal. Possible end users of laser-driven multi-modal sources are those requiring advanced non-destructive inspection techniques in industry sectors of high value commerce such as aerospace, nuclear and advanced manufacturing. We report on experimental work that demonstrates multi-modal operation of high power laser-solid interactions for neutron and x-ray beam generation. Measurements and Monte Carlo radiation transport simulations show that neutron yield is increased by a factor ~2 when a 1 mm copper foil is placed behind a 2 mm lithium foil, compared to using a 2 cm block of lithium only. We explore x-ray generation with a 10 picosecond drive pulse in order to tailor the spectral content for radiography with medium density alloy metals. The impact of using >1 ps pulse duration on laser-accelerated electron beam generation and transport is discussed alongside the optimisation of subsequent bremsstrahlung emission in thin, high atomic number target foils. X-ray spectra are deconvolved from spectrometer measurements and simulation data generated using the GEANT4 Monte Carlo code. We also demonstrate the unique capability of laser-driven x-rays in being able to deliver single pulse high spatial resolution projection imaging of thick metallic objects. Active detector radiographic imaging of industrially relevant sample objects with a 10 ps drive pulse is presented for the first time, demonstrating that features of 200 μm size are resolved when projected at high magnification.
Highlights
IntroductionOf the many regimes of plasma acceleration discussed in the literature, the interaction of a short (~ several ps) laser pulse (with irradiance ILλ2 > 1018 W μm cm−2) with a solid foil generating an electron pulse with high peak current (MA) transporting through to the rear surface of the target, has become a robust and reliable source of ions and x-rays
We demonstrate the unique capability of laser-driven x-rays in being able to deliver single pulse high spatial resolution projection imaging of thick metallic objects
We have demonstrated an increase in laser-driven neutron yield of a factor ~2 across the neutron energy range 1–5 MeV by utilising a stacked proton catcher design and presented tuning of the x-ray spectral emission for single-pulse high spatial resolution projection imaging of industrially relevant objects while using a newly-developed active detector screen
Summary
Of the many regimes of plasma acceleration discussed in the literature, the interaction of a short (~ several ps) laser pulse (with irradiance ILλ2 > 1018 W μm cm−2) with a solid foil generating an electron pulse with high peak current (MA) transporting through to the rear surface of the target, has become a robust and reliable source of ions and x-rays. We present a short portfolio of laser-driven x-ray radiograph images that demonstrate the unique and highly applicable nature of these sources for non-destructive inspection of large industrial objects These demonstration experiments are crucial for guiding continuing research into establishing mechanisms for control and optimisation, indicating the avenues that should receive more effort in our goal to fully harness and broaden their application potential. This work complements the breadth of applications demonstrated with laser acceleration from gas targets [11,12,13] and strengthens the multi-modal source offering of laser drivers
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