= Solution
State a radiation-width convention. For rms Gaussian-equivalent single-electron undulator radiation take $\sigma_r=\sqrt{\lambda L}/(4\pi)$ and $\sigma_r'=\sqrt{\lambda/L}$, so the diffraction emittance is $\lambda/(4\pi)$. These give 11.3 micrometres and 70.7 microradians. Convolve independent <electron> and radiation widths in quadrature. The total <photon> source is then
$$
\boxed{\Sigma_x\simeq78.3\ \mu\mathrm m,\quad\Sigma'_x\simeq80.6\ \mu\mathrm{rad},\quad\Sigma_y\simeq13.7\ \mu\mathrm m,\quad\Sigma'_y\simeq70.8\ \mu\mathrm{rad}.}
$$
Some approximate undulator width conventions differ by order-one factors; these must be kept consistent in the following brightness comparison.
Back to article page
