Schematic overview of the new LCLS and NEH layout with both accelerators [LCLS (red) and LCLS-II (blue)]. The LCLS-II X-ray laser is shown alongside the existing LCLS. LCLS uses the last third of SLAC's two-mile-long linear accelerator – a hollow copper structure that operates at room temperature and allows the generation of 120 X-ray pulses per second. For LCLS-II, the first third of the copper accelerator has been replaced with a superconducting one, capable of a repetition rate of up to 1 MHz. Future Far Hall layout changes for LCLS-II HE are not included.