TY  - JOUR
AU  - Helml, W.
AU  - Maier, A. R.
AU  - Schweinberger, W.
AU  - Grguraš, I.
AU  - Radcliffe, P.
AU  - Doumy, G.
AU  - Roedig, C.
AU  - Gagnon, J.
AU  - Messerschmidt, M.
AU  - Schorb, S.
AU  - Bostedt, C.
AU  - Grüner, F.
AU  - DiMauro, L. F.
AU  - Cubaynes, D.
AU  - Bozek, J. D.
AU  - Tschentscher, Thomas
AU  - Costello, J. T.
AU  - Meyer, Michael
AU  - Coffee, R.
AU  - Duesterer, Stefan
AU  - Cavalieri, A. L.
AU  - Kienberger, R.
TI  - Measuring the temporal structure of few-femtosecond free-electron laser X-ray pulses directly in the time domain
JO  - Nature photonics
VL  - 8
IS  - 12
SN  - 1749-4893
CY  - London [u.a.]
PB  - Nature Publ. Group
M1  - PUBDB-2015-01020
SP  - 950 - 957
PY  - 2014
N1  - (c) Macmillan Publishers Limited. Post referee full text in progress. Embargo full text 6 months from 24 November 2014.
AB  - Short-wavelength free-electron lasers are now well established as essential and unrivalled sources of ultrabright coherent X-ray radiation. One of the key characteristics of these intense X-ray pulses is their expected few-femtosecond duration. No measurement has succeeded so far in directly determining the temporal structure or even the duration of these ultrashort pulses in the few-femtosecond range. Here, by deploying the so-called streaking spectroscopy technique at the Linac Coherent Light Source, we demonstrate a non-invasive scheme for temporal characterization of X-ray pulses with sub-femtosecond resolution. This method is independent of photon energy, decoupled from machine parameters, and provides an upper bound on the X-ray pulse duration. We measured the duration of the shortest X-ray pulses currently available to be on average no longer than 4.4 fs. Analysing the pulse substructure indicates a small percentage of the free-electron laser pulses consisting of individual high-intensity spikes to be on the order of hundreds of attoseconds.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000345818600015
DO  - DOI:10.1038/nphoton.2014.278
UR  - https://bib-pubdb1.desy.de/record/206556
ER  -