The Linac Coherent Light Source (LCLS) previously demonstrated FEL operations over the energy range 280 eV to 11.2 keV in the fundamental. As part of the LCLS-II upgrade, in 2020 we resumed operation with an all-new undulator complex, replacing the previous system with a pair of dedicated, variable-gap hard and soft X-ray undulators driven by the 120 Hz LCLS normal conducting (NC) linac.
Starting in Run 21, we will begin operation of the new LCLS-II high-rate, superconducting (SC) linac driver, pushing the envelope in average brightness for ultrafast x-ray science. As we ramp up this exciting new capability, SC linac delivery begins with soft x-ray programs delivering ultrashort pulses at greatly increased rates. See the Run 21 information above for more information.
New undulator systems also enable a much wider photon energy range. With the existing NC linac (120 Hz), 200 eV to 25 keV has been achieved in the fundamental with pulse energies of 0.5-2 mJ and up, depending on the pulse duration and photon energy. Pulse length can be varied from 10 fs to 50 fs for hard X-rays, while for soft X-rays the range is extended to 250 fs. Shorter pulses, < 10 fs, with a reduced number of photons per pulse can also be provided via specialized operating modes.
Prior advanced capability beyond SASE has also been recommissioned with the NC linac. For users who require a monochromator, seeded hard X-ray beams can provide 2 to 4 times more photons per unit bandwidth than SASE beams with similar pulse durations. Seeded beams are available from 4.5 keV to 11 keV and 0.4-1.2 keV in the HXR and SXR range, respectively, with tune up from a SASE beam taking about 30 minutes. The LCLS NC linac is also capable of providing two-color operating modes, where multiple FEL pulses are produced with about 1% photon energy separation, in both the hard and soft X-ray regimes.
Users are encouraged to review LCLS instrument descriptions and contact LCLS instrument scientists to discuss technical capabilities and proposed experiments.