| Paper | Title | Page |
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| MOPCH051 | Operation of the First Undulator-based Femtoslicing Source | 154 |
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At the BESSY II storage ring, a source of sub-100-fs x-ray pulses with tunable polarization and excellent signal-to-background ratio has been constructed in 2004, based on laser-induced energy modulation ("femtoslicing"*) and subsequent angular separation of the short-pulse x-rays from an elliptical undulator. After commissioning and characterizing the source, short-pulse radiation is now routinely delivered for pump-probe applications. The paper summarizes the results from commissioning and operational experience as well as possible upgrade options.
*A. Zholents and M. Zoloterev, PRL 76 (1996), 912. |
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| MOPCH053 | Towards Sub-picoseconds Electron Bunches: Upgrading Ideas for BESSY II | 157 |
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Sub-picoseconds bunches were achieved with the BESSY low alpha optics, and their lengths were measured using Fourier Transform spectroscopy*. To avoid the coherent synchrotron radiation instability, the current in these short bunches has to be limited to theμampere level. An upgrade of the BESSY II rf gradient to much larger values is suggested to overcome this low current limitation by two orders of magnitude. Intense, picoseconds long bunches could then be achieved already at the regular user optics. The resulting short and very intense electron bunches are useful for generation of short x-ray pulses and powerful THz-radiation. Expected parameters of bunch length and current are discussed.
*J. Feikes et al. "Sub-Picoseconds Electron Bunches in the BESSY Storage Ring", EPAC'04, Luzerne (Switzerland), July 2004. |
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| MOPCH054 | Plans for the Generation of Short Radiation Pulses at the Diamond Storage Ring | 160 |
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| Diamond is a third generation light source under commissioning in Oxfordshire UK. In view of the increasing interest in the production of short radiation pulses, we have investigated the possibility to operate with a low-alpha optics, the use of a third harmonic cavity for bunch shortening and the implementation of a crab cavity scheme in the Diamond storage ring. The results of the initial accelerator studies will be described, including the modification of the beam optics, non-linear beam dynamics optimisation and choice of RF parameters for the crab cavity operation. The expected performance of these schemes will be summarised. | ||
| MOPCH055 | Circulation of a Short, Intense Electron Bunch in the NewSUBARU Storage Ring | 163 |
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| One new method is proposed which supplies synchrotron radiation light from a short and intense electron bunch. This method supplies a short and intense x-ray pulse and extremely strong coherent radiation in a long wavelength region to beam lines of a storage ring. SPring-8 linac supplied a short and intense 1.0 GeV electron beam to NewSUBARU storage ring. The electron bunch was compressed to 10ps (full width) from the normal condition (20ps full width) using ECS system. The pulse charge was 0.10nC/bunch and the energy spread was (±) 0.2 % (full width) at the injection point. The ring lattice was adjusted at a quasi-isochronous condition to keep the short bunch for many revolutions. The estimated linear and non-linear momentum compaction factors were -6·10-5 (the linear factor), 0.0 (the second order factor) and +0.9 (the third order factor). The bunch length was measured by a streak camera, and the coherent radiation was detected by a Shottky diode detector. The short bunch was successfully circulated for about 50 turns. | ||
| MOPCH056 | Development of High Brightness Soft X-ray Source Based on Inverse Compton Scattering | 166 |
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| Compact soft X-ray source based on inverse compton scattering have been developed at Waseda University. Using 1047nm laser light from Nd:YLF laser scattered off 4.2MeV electron beam generated from a photo-cathode rf-gun, we have already suceeded to generate the soft X-ray. The energy of this x-ray is included in the part of water window, in which absorption of water is much less than that of moleculars that organize a living body. Furthermore, this x-ray source has other features such as short pulse, proportional mono-energy and energy variableness. Because of these tures, the application to the biological microscope have been expected. However, the flux of x-ray is not satisfied for the biological microscope application. Therefore, to multiply a soft X-ray flux, we utilized multi-pass amplifier for the laser light and improved a collision chamber. In this conference, we will report the experimental results and future plans. | ||
| MOPCH057 | The Design of a 1.8 keV Compton X-ray Generator for a SC RF Linac at KAERI | 169 |
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| A quasi-monochromatic X-ray source based on the KAERI SC linac system has been designed and is being manufactured now. A 10 MeV 10 mA electron beam together with a 20 W 1.06 ?m laser beam will be used for 1.8 keV Compton X-ray generation with a few percentage of energy spread and 107 photons per second. A simple straight beamline was designed to deliver the electron beam with no degradation of its emittance and energy spread and to focus it to a proper size to produce the desired X-rays. We expect the first demonstration of 1.8 keV Compton X-ray generation in autumn 2006. | ||
| MOPCH058 | RF Photogun as Ultra Bright Terahertz Source | 0 |
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| Recently research into new terahertz (0.3 to 30 THz) light sources has gained a lot of interest. Especially compact sources capable of delivering high peak fields (~ 1 MV/cm), in a short pulse. To achieve this, we will use short relativistic electron bunches, created by photoemission and accelerated in an rf-photogun, to create THz light by means of coherent transition radiation. Because wavelengths smaller and comparable to the bunch length add up coherently, the intensity scales with N2, with N the number of electrons in the bunch. In the first experiments we expect to create THz light pulses with a bandwidth of 1 THz and 1 μJ per pulse. If such a light pulse is focused on a spot of radius 250 μm, this corresponds to peak electrical fields of 1 MV/cm. The eventual goal is to increase the bandwidth of the source, by creating shorter electron bunches. This will be accomplished by choosing a suitable radial laser profile, leading to ellipsoidal electron bunches, which can be focused and compressed very effectively. Eventually this will lead to THz pulses with a bandwidth of 10 THz and energy of 100 μJ. This corresponds to peak electrical fields of 10 MV/cm and higher. | ||
| MOPCH059 | From Pancake to Waterbag: Creation of High-brightness Electron Bunches | 0 |
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| Our recent insight is that, when creating high-brightness electron bunches, the major problem is not space charge density itself, but its distribution. Non-linear space charge effects lead to a decrease of brightness. We have a novel recipe of creating waterbag bunches (uniformly charged 3D ellipsoids), which have linear space charge fields. Because of these linear fields we have control of the Coulomb explosion of the bunches. Furthermore, using linear charged particle optics, waterbags can be compressed and focussed with conservation of brightness. Our recent simulations prove that it is possible to create such ideal waterbag bunches in practice. The recipe is to create at the cathode a pancake-like electron bunch with a "hemisphere" charge density distribution. During acceleration this pancake will evolve into a waterbag by its own space charge forces, if two conditions on the acceleration field and the surface charge density are fulfilled. These two conditions are leading to a parameter space, which is explored by simulations. We will present numerical simulations and the present status of the experimental realization. | ||
| MOPCH062 | Centroid, Size, and Emittance of a Slice in a Kicked Bunch | 172 |
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| A transversely kicked bunch will decohere due to, among other things, chromatic and amplitude-dependent tune shifts. The chromatic tune shift leads to correlation between transverse and longitudinal phase space. Such a correlation can be used for compressing synchrotron radiation of the bunch with adequate optics. In this report, we revise the decoherence calculation to derive the centroid and second moments of a beam slice in a kicked bunch, taking into account chromatic and nonlinear decoherence, but neglecting wakefield and radiation damping, etc. A simple formula for estimating slice bunch length (and potential pulse compression ratio) is given for the ideal situation. |