Heidelberg 2015 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 62: Poster: Quantum Optics and Photonics III
Q 62.78: Poster
Donnerstag, 26. März 2015, 17:00–19:00, C/Foyer
Temporal coherence properties of FLASH at λ = 31.7 nm — •Paul Möllers1, Sebastian Roling1, Peter Üffink1, Sven Toleikis2, Michael Wöstmann1, and Helmut Zacharias1 — 1Westfälische Wilhelms-Universität Münster — 2DESY, Hamburg
Free electron lasers (FEL) based on Self-Amplified Spontaneous Emission (SASE) emit partially coherent radiation that enables among others the performance of diffractive imaging experiments. Especially for these experiments a precise knowledge of the coherence properties is of utmost importance. With the split-and-delay unit (SDU) at beamline BL2 at FLASH the temporal coherence at λ = 31.7 nm is measured for the present accelerator configuration including a 3rd harmonic phase shifter. For the generation of saturated SASE radiation electron bunches with a bunch charge of Q = 0.33 nC are accelerated to E = 457.6 MeV. The FLASH pulses with a pulse energy of 16.5 µJ are split by the sharp edge of a wavefront beam splitter in the SDU. One of the partial beams can be delayed with respect to the other by moving the delay stage. Both partial beams are then overlapped on a CCD-camera. At zero delay interference fringes occur with a visibility of V = 0.82. The visibility decreases as expected when the delay of one beam with respect to the other is increased. A Gaussian function can be fitted to the data yielding a coherence time of τc = 4.7 fs.