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Abstract: The LCLS beam is meant for a single user, but the baseline undulator is longenough to serve two users simultaneously. To this end, we propose a setupcomposed of two elements: an X-ray mirrors pair for X-ray beam deflection, anda 4 m-long magnetic chicane, which creates an offset for mirrors pairinstallation in the middle of the baseline undulator. The insertable mirrorspair can separate spatially the X-ray beams generated in the first and in thesecond half of the baseline undulator. Rapid switching of the FEL amplificationprocess allows deactivating one half and activating another half of theundulator. As proposed elsewhere, using a kicker installed upstream of the LCLSbaseline undulator and an already existing corrector in the first half of theundulator, it is possible to rapidly switch the X-ray beam from one user toanother. We present simulation results for the LCLS baseline, and show that itis possible to generate two saturated SASE X-ray beams in the whole 0.8-8 keVphoton energy range in the same baseline undulator. These can serve two users.Our technique does not perturb the baseline mode of operation of the LCLSundulator. Also, the magnetic chicane setup is very flexible, and can be usedas a self-seeding setup too. We present simulation results for the LCLSbaseline undulator with SHAB. One can produce monochromatic radiation at the2nd harmonic as well as at the 1st. We describe an efficient way for obtainingmulti-user operation at the LCLS hard X-ray FEL. To this end, a photon beamdistribution system based on the use of crystals in the Bragg reflectiongeometry is proposed. The reflectivity of crystal deflectors can be switchedfast enough by flipping the crystals with piezoelectric devices. Monochromatichard X-rays can then be distributed among 6 independent experiments, therebyenabling 6 users to work in parallel in the near and far experimental halls.



Autor: Gianluca Geloni, Vitali Kocharyan, Evgeni Saldin

Fuente: https://arxiv.org/







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