Parameters

Parameters Update

The Linac Coherent Light Source (LCLS) previously demonstrated FEL operations over the energy range 280 eV to 11.2 keV in the fundamental. With 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. Then in Run 21, we began operation of the original LCLS-II high-rate, superconducting (SC) linac driver, pushing the envelope in average brightness for ultrafast x-ray science with an electron beam energy of up to 4 GeV. With this exciting new capability, SC linac operation began with soft x-ray programs delivering ultrashort pulses at greatly increased rates.

Now with LCLS Run 26-27, we offer capabilities to soft and hard X-ray instruments using only the LCLS NC linac at 120 Hz while the SC accelerator undergoes a major energy upgrade through the LCLS-II-HE (High Energy) Project to push its performance and photon energy reach even further for future runs.

Upgraded undulator systems have also enabled 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.

In Runs 23 and 25 we focused on the steady ramp of high-rate capability for soft X-ray users with the 4 GeV SC linac. SXR pulses with hundreds of microjoules in continuous trains of multiple kHz are available, with photons per pulse varying with photon energy.

Prior advanced capability beyond SASE has also been recommissioned. For high-rate, SC linac users on the SXR undulator, sub-fs, lower photon number XLEAP pulses have been successfully delivered. For NC linac users who require a monochromator, seeded hard X-ray beams can provide up to 5 times more photons per unit bandwidth than SASE beams with similar pulse durations. Seeded beams are available from 4.5 keV to 12 keV HXR range, with first 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.