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arXiv · 1411.2134

Compact tunable Compton x-ray source from laser-plasma accelerator and plasma mirror

Hai-En Tsai·Xiaoming Wang·Joseph Shaw·Zhengyan Li·Alexey V. Arefiev·Xi Zhang·Rafal Zgadzaj·Watson Henderson·V. Khudik·G. Shvets·M. C. Downer
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Abstract

We present an in-depth experimental-computational study of the parameters necessary to optimize a tunable, quasi-monoenergetic, efficient, low-background Compton backscattering (CBS) x-ray source that is based on the self-aligned combination of a laser-plasma accelerator (LPA) and a plasma mirror (PM). The main findings are: (1) an LPA driven in the blowout regime by 30 TW, 30 fs laser pulses producesnot only a high-quality, tunable, quasi-monoenergetic electron beam, but also a high-quality, relativistically intense (a0~1) spent drive pulse that remains stable in profile and intensity over the LPA tuning range. (2) A thin plastic film near the gas jet exit retro-reflects the spent drive pulse efficiently into oncoming electrons to produce CBS x-rays without detectable bremsstrahlung background. Meanwhile anomalous far-field divergence of the retro-reflected light demonstrates relativistic "denting" of the PM. Exploiting these optimized LPA and PM conditions, we demonstrate quasi-monoenergetic (50% FWHM energy spread), tunable (75 to 200 KeV) CBS x-rays, characteristics previously achieved only on more powerful laser systems by CBS of a split-off, counter-propagating pulse. Moreover, laser-to-x-ray photon conversion efficiency ~6e12 exceeds that of any previous LPA-based quasi-monoenergetic Compton source. Particle-in-cell simulations agree well with the measurements.

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Hai-En Tsai, Xiaoming Wang, Joseph Shaw, Zhengyan Li, Alexey V. Arefiev, Xi Zhang, Rafal Zgadzaj, Watson Henderson, V. Khudik, G. Shvets, M. C. Downer. 2015-01-14. Compact tunable Compton x-ray source from laser-plasma accelerator and plasma mirror. https://doi.org/10.1063/1.4907655

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