Demonstration of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>8</mml:mn><mml:mo>×</mml:mo><mml:mrow><mml:msup><mml:mrow><mml:mn>10</mml:mn></mml:mrow><mml:mrow><mml:mn>18</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi/><mml:mi mathvariant="normal">photons</mml:mi><mml:mi mathvariant="normal">/</mml:mi><mml:mi mathvariant="normal">second</mml:mi></mml:math>peaked at 1.8 Å in a relativistic Thomson scattering experiment

$7.6\ifmmode\times\else\texttimes\fi{}{10}^{6}$ x-ray photons per 3.5 ps pulse are detected within a 1.8--2.3 \AA{} spectral window during a proof-of-principle laser synchrotron source experiment. A 600 MW ${\mathrm{CO}}_{2}$ laser interacted in a head-on collision with a 60 MeV, 140 A, 3.5 ps electron beam. Both beams were focused to a $\ensuremath{\sigma}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}32\ensuremath{\mu}\mathrm{m}$ spot. Our next plan is to demonstrate ${10}^{10}$ x-ray photons per pulse using a ${\mathrm{CO}}_{2}$ laser of $\ensuremath{\sim}1\mathrm{TW}$ peak power.