PLEIADES: A picosecond Compton scattering x-ray source for advanced backlighting and time-resolved material studies

Abstract

The PLEIADES ͑Picosecond Laser-Electron InterAction for the Dynamical Evaluation of Structures͒ facility has produced first light at 70 keV. This milestone offers a new opportunity to develop laser-driven, compact, tunable x-ray sources for critical applications such as diagnostics for the National Ignition Facility and time-resolved material studies. The electron beam was focused to 50 m rms, at 57 MeV, with 260 pC of charge, a relative energy spread of 0.2%, and a normalized emittance of 5 mm mrad horizontally and 13 mm mrad vertically. The scattered 820 nm laser pulse had an energy of 180 mJ and a duration of 54 fs. Initial x rays were captured with a cooled charge-coupled device using a cesium iodide scintillator; the peak photon energy was approximately 78 keV, with a total x-ray flux of 1.3ϫ10 6 photons/shot, and the observed angular distribution found to agree very well with three-dimensional codes. Simple K-edge radiography of a tantalum foil showed good agreement with the theoretical divergence-angle dependence of the x-ray energy. Optimization of the x-ray dose is currently under way, with the goal of reaching 10 8 photons/shot and a peak brightness approaching 10 20 photons/mm 2 /mrad 2 /s/0.1% bandwidth.

Three-dimensional time and frequency-domain theory of femtosecond x-ray pulse generation through Thomson scattering

“…For example, electron beam emittances as low as 1 mm mrad with bunch charges of several hundred pico-Coulombs have been demonstrated at Brookhaven National Laboratory [28]. For the calculations presented here, the particle dynamics code PARMELA was used to simulate the electron bunch production at the PLEIADES facility at LLNL [11]. The accelerator consists of several major components, including an S-band photocathode rf gun and four 2.5 m S-band accelerator sections.…”

Low-Intensity Nonlinear Spectral Effects in Compton Scattering

“…Rapid advances in terawatt-class laser technology [1] and high-brightness, high-gradient electron accelerators [2] are enabling the development of a new type of light source based on Compton scattering [3], where relativistic electrons interact with a coherent photon field to generate bright, ultrafast, tunable x-rays and γ-rays [4,5]. These compact sources are a natural complement to larger-scale 3 rd and 4 th generation light sources [6], and provide a mean to generate MeV-scale photons with unprecedented spectral brightness.…”

Optimal design of a tunable thomson-scattering based gamma-ray source

“…Also, the system becomes less sensitive to timing jitter; a slip in the relative timing of the two beams causes the interaction point to move longitudinally, but does not change the scaattering column densities. A more detailed discussion of this issue, with simulations, is found in [2].…”

“…Operating in the 10s-of-keV to few-MeV photon energy range, these source can surpass the brightness of synchrotrons by several orders of magnitude due to their straight-forward energy scaling [1]. LLNL has previously demonstrated [2] a bright Thomsonscattering source operating between 30 and 120 keV. This system was used, among other things, to carefully benchmark Compton-scattering simulation codes [3].…”