Due to an isolated error in the 3D simulation parameters, the laser energy and intensity (calculated using the energy) values were incorrectly stated as 10.9 J and 3×10²² W cm⁻², respectively, in Sections 3.3, 7 and 8. The correct values are 39.8 J and 1.1×10²³ W cm⁻². Similarly, the values stated for the higher energy case, 109 J and 3×10²³ W cm⁻² in Section 7, should be 398 J and 1.1×10²⁴ W cm⁻², respectively.

The conversion efficiencies (which are calculated using the laser energy) shown in Figures 9(d)–9(f) are corrected by multiplying by a constant factor of 0.273. With corrected energies, the synchrotron conversion efficiencies in Section 3.3 now become 4.32%, 4.50% and 1.67% for x_f = 0, z_R and −z_R, respectively, corresponding to changes of +4% and −61% for the positive and negative defocus, respectively.

This error does not affect the conclusions of the article.