Coherence properties of the radiation from FLASH

FLASH is the first free electron laser user facility operating in the vacuum ultraviolet and soft x-ray wavelength range. Many user experiments require knowledge of the spatial and temporal coherence properties of the radiation. In this paper we present an analysis of the coherence properties of the radiation for the fundamental and for the higher odd frequency harmonics. We show that temporal and spatial coherence reach maximum close to the FEL saturation but may degrade significantly in the post-saturation regime. We also find that the pointing stability of short FEL pulses is limited due to the fact that non-azimuthal FEL eigenmodes are not sufficiently suppressed. We discuss possible ways for improving the degree of transverse coherence and the pointing stability.Comment: 17 pages, 19 figure

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

A Method for Ultrashort Electron Pulse Shape-Measurement Using Coherent Synchrotron Radiation

In this paper we discuss a method for nondestructive measurements of the longitudinal profile of sub-picosecond electron bunches for X-Ray Free Electron Lasers (XFELs). The method is based on the detection of the Coherent Synchrotron Radiation (CSR) spectrum produced by a bunch passing a dipole magnet system. This work also contains a systematic treatment of synchrotron radiation theory which lies at the basis of CSR. Standard theory of synchrotron radiation uses several approximations whose applicability limits are often forgotten: here we present a systematic discussion about these assumptions. Properties of coherent synchrotron radiation from an electron moving along an arc of a circle are then derived and discussed. We describe also an effective and practical diagnostic technique based on the utilization of an electromagnetic undulator to record the energy of the coherent radiation pulse into the central cone. This measurement must be repeated many times with different undulator resonant frequencies in order to reconstruct the modulus of the bunch form-factor. The retrieval of the bunch profile function from these data is performed by means of deconvolution techniques: for the present work we take advantage of a constrained deconvolution method. We illustrate with numerical examples the potential of the proposed method for electron beam diagnostics at the TESLA Test Facility (TTF) accelerator. Here we choose, for emphasis, experiments aimed at the measure of the strongly non-Gaussian electron bunch profile in the TTF femtosecond-mode operation. We demonstrate that a tandem combination of a picosecond streak camera and a CSR spectrometer can be used to extract shape information from electron bunches with a narrow leading peak and a long tail.Comment: 60 pages, 39 figure

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

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

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]