336 research outputs found
Statistical properties of the radiation from SASE FEL operating in a post-saturation regime with and without undulator tapering
We describe statistical and coherence properties of the radiation from x-ray
free electron lasers (XFEL) operating in the post-saturation regime. We
consider practical case of the SASE3 FEL at the European XFEL. We perform
comparison of the main characteristics of the X-ray FEL operating in the
post-saturation regime with and without undulator tapering: efficiency,
coherence time and degree of transverse coherence.Comment: 6 pages, 5 figure
A possible upgrade of FLASH for harmonic lasing down to 1.3 nm
We propose the 3rd harmonic lasing in a new FLASH undulator as a way to
produce intense, narrow-band, and stable SASE radiation down to 1.3 nm with the
present accelerator energy of 1.25 GeV. To provide optimal conditions for
harmonic lasing, we suggest to suppress the fundamental with the help of a
special set of phase shifters. We rely on the standard technology of
gap-tunable planar hybrid undulators, and choose the period of 2.3 cm and the
minimum gap of 0.9 cm; total length of the undulator system is 34.5 m. With the
help of numerical simulations we demonstrate that the 3rd harmonic lasing at
1.3 nm provides peak power at a gigawatt level and the narrow intrinsic
bandwidth, 0.1% (FWHM). Pulse duration can be controlled in the range of a few
tens of femtoseconds, and the peak brilliance reaches the value of 10^31
photons/(s mrad^2 mm^2 0.1%BW). With the given undulator design, a standard
option of lasing at the fundamental wavelength to saturation is possible
through the entire water window and at longer wavelengths. In this paper we
briefly consider additional options such as polarization control, bandwidth
reduction, self-seeding, X-ray pulse compression, and two-color operation. We
also discuss possible technical issues and backup solutions.Comment: arXiv admin note: text overlap with arXiv:1205.250
Prospects for CW and LP operation of the European XFEL in hard X-ray regime
The European XFEL will operate nominally at 17.5 GeV in SP (short pulse) mode
with 0.65 ms long bunch train and 10 Hz repetition rate. A possible upgrade of
the linac to CW (continuous wave) or LP (long pulse) modes with a corresponding
reduction of electron beam energy is under discussion since many years. Recent
successes in the dedicated R&D program allow to forecast a technical
feasibility of such an upgrade in the foreseeable future. One of the challenges
is to provide sub-Angstrom FEL operation in CW and LP modes. In this paper we
perform a preliminary analysis of a possible operation of the European XFEL in
the hard X-ray regime in CW and LP modes with the energies of 7 GeV and 10 GeV,
respectively. We consider lasing in the baseline XFEL undulator as well as in a
new undulator with a reduced period. We show that, with reasonable requirements
on electron beam quality, lasing on the fundamental will be possible in
sub-Angstrom regime. As an option for generation of brilliant photon beams at
short wavelengths we also consider harmonic lasing that has recently attracted
a significant attention
A hard x ray split and delay unit for the HED experiment at the European XFEL
For the High Energy Density HED experiment [1] at the European XFEL [2] an x ray split and delay unit SDU is built covering photon energies from 5 keV up to 20 keV [3]. This SDU will enable time resolved x ray pump x ray probe experiments [4,5] as well as sequential diffractive imaging [6] on a femtosecond to picosecond time scale. Further, direct measurements of the temporal coherence properties will be possible by making use of a linear autocorrelation [7,8]. The set up is based on geometric wavefront beam splitting, which has successfully been implemented at an autocorrelator at FLASH [9]. The x ray FEL pulses are split by a sharp edge of a silicon mirror coated with multilayers. Both partial beams will then pass variable delay lines. For different photon energies the angle of incidence onto the multilayer mirrors will be adjusted in order to match the Bragg condition. For a photon energy of h amp; 957; 20 keV a grazing angle of amp; 952; 0.57 has to be set, which results in a footprint of the beam 6 amp; 963; on the mirror of l 98 mm. At this photon energy the reflectance of a Mo B4C multi layer coating with a multilayer period of d 3.2 nm and N 200 layers amounts to R 0.92. In order to enhance the maximum transmission for photon energies of h amp; 957; 8 keV and below, a Ni B4C multilayer coating can be applied beside the Mo B4C coating for this spectral region. Because of the different incidence angles, the path lengths of the beams will differ as a function of wavelength. Hence, maximum delays between 2.5 ps at h amp; 957; 20 keV and up to 23 ps at h amp; 957; 5 keV will be possibl
First Observation of Self-Amplified Spontaneous Emission in a Free-Electron Laser at 109 nm Wavelength
We present the first observation of Self-Amplified Spontaneous Emission
(SASE) in a free-electron laser (FEL) in the Vacuum Ultraviolet regime at 109
nm wavelength (11 eV). The observed free-electron laser gain (approx. 3000) and
the radiation characteristics, such as dependency on bunch charge, angular
distribution, spectral width and intensity fluctuations all corroborate the
existing models for SASE FELs.Comment: 6 pages including 6 figures; e-mail: [email protected]
PENGARUH PENAMBAHAN CACAHAN LIMBAH PLASTIK JENIS HIGH DENSITY POLYETHYLENE (HDPE) PADA
Waste is a very complex problem in urban area. Plastic waste is increasing every year. Kupang with population of 291,794 people generate waste reaches 926 m3/day. Organic waste to 700 m3 and inorganic waste about 226 m3.
Concrete is planned by strength quality 25 MPa. Based on the analysis in this study obtained that concrete flexural strength value increased due to the addition of HDPE plastic shredded into the concrete, with chopped levels are added to the concrete at 0%, 0.50% and 0.90% .0,70%. Flexural strength value of normal concrete without the addition of shredded plastic (0%) is 4.12 MPa, flexural strength of concrete with the addition of shredded plastic 0.50% is 4.30 MPa increased 4.37% from normal concrete flexural strength, flexural strength of concrete with the addition of shredded plastics 0.70% is 4.21 MPa increased 2.19% from the normal concrete flexural strength and flexural strength of concrete with the addition of shredded plastic 0.90% is 3.94 MPa decreased 3.64% of flexural strength normal concrete
Isolated terawatt attosecond hard X-ray pulse generated from single current spike
Isolated terawatt (TW) attosecond (as) hard X-ray pulse is greatly desired for four-dimensional investigations of natural phenomena with picometer spatial and attosecond temporal resolutions. Since the demand for such sources is continuously increasing, the possibility of generating such pulse by a single current spike without the use of optical or electron delay units in an undulator line is addressed. The conditions of a current spike (width and height) and a modulation laser pulse (wavelength and power) is also discussed. We demonstrate that an isolated TW-level as a hard X-ray can be produced by a properly chosen single current spike in an electron bunch with simulation results. By using realistic specifications of an electron bunch of the Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL), we show that an isolated, >1.0 TW and similar to 36 as X-ray pulse at 12.4 keV can be generated in an optimized-tapered undulator line. This result opens a new vista for current XFEL operation: the attosecond XFEL
AN OPTION OF HIGH CHARGE OPERATION FOR THE EUROPEAN XFEL
Abstract The 1.3 GHz superconducting accelerator developed in the framework of TESLA and the European XFEL project holds the potential to accelerate high charge electron beams. This feature has been successfully demonstrated during the first run of the free electron laser at the TESLA Test Facility with lasing driven by electron bunches with a charge of up to 4 nC. Currently DESY and the European XFEL GmbH perform revision of the baseline parameters for the electron beam. In this report we discuss a potential option of operation of the European XFEL driven by high charge (1 nC to 3 nC) electron beams. We present the results of the production and characterization of high charge electron bunches. Experiments have been performed at PITZ and demonstrated good properties of the electron beam in terms of emittance. Simulations of the radiation properties of SASE FELs show that application of high charge electron beams will open up the possibility to generate radiation pulse energies up to the few hundred milli-Joule level
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