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J. Bahrdt

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2 papers
title: Short period, high field cryogenic undulator for extreme performance x-ray free electron lasers
format: journal article
publisher: APS
year: 13 July 2010
8 authors: F.H. O'Shea | Gabriel Marcus | J. B. Rosenzweig | Michael Scheer | Johannes Bahrdt | Raphael Weingartner | Andreas Gaupp | Florian Gruner
abstract: Short period, high field undulators can enable short wavelength free electron lasers (FELs) at low beam energy, with decreased gain length, thus allowing much more compact and less costly FEL systems. We describe an ongoing initiative to develop such an undulator based on an approach that utilizes novel cryogenic materials. While this effort was begun in the context of extending the photon energy regime of a laser-plasma accelerator based electron source, we consider here implications of its application to sub-fs scenarios in which more conventional injectors are employed. The use of such low-charge, ultrashort beams, which has recently been proposed as a method of obtaining single-spike performance in x-ray FELs, is seen in simulation to give unprecedented beam brightness. This brightness, when considered in tandem with short wavelength, high field undulators, enables extremely high performance FELs. Two examples discussed in this paper illustrate this point well. The first is the use of the SPARX injector at 2.1 GeV with 1 pC of charge to give 8 GW peak power in a single spike at 6.5 � with a photon beam peak brightness greater than 1035??photons/(s?mm2?mrad2??0.1%??BW), which will also reach LCLS wavelengths on the 5th harmonic. The second is the exploitation of the LCLS injector with 0.25 pC, 150 as pulses to lase at 1.5 � using only 4.5 GeV energy; beyond this possibility, we present start-to-end simulations of lasing at unprecedented short wavelength, 0.15 �, using 13.65 GeV LCLS design energy.

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title: The BESSY FEL Project
format: conference proceeding
conference: FEL 2001 23rd
year: 2002
20 authors: M. Abo-Bakr | W. Anders | J. Bahrdt | R. Bakker | W. Eberhardt | B. Faatz | R. Follath | A. Gaupp | M. v. Hartrott | E. Jaeschke | D. Kraemer | P. Kuske | M. Martin | R. Mueller | H. Prange | Sven Reiche | W. Sandner | F. Senf | I. Will | G. Wustefeld
abstract: Berliner Elektronenspeicherring-Gesellschaft fur Synchrotronstrahlung (BESSY) plans to construct a linac-based single-pass FEL as an addition to its existing third generation storage-ring-based light-source. The project aims to obtain an FEL-based user-facility that covers the VUV and soft X-ray spectral range (20 eV less than or equal to homega less than or equal to 1 keV). At present, the design stage is funded as a collaboration between BESSY, DESY, the Hahn-Meitner-Institute in Berlin, and the Max-Born-Institute in Berlin. This stage focuses on optimization of the FEL as a user light-source, both with respect to its capabilities and in its performance. Important issues are: stability, seeding options of the SASE FEL, wavelength-tunability, synchronization with external laser sources and, on a longer time-scale, the generation of ultra-short (< 20 fs RMS) optical pulses.

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