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Title |
Other Keywords |
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| MOPC029 |
Longitudinal Structure of Electron Bunches at the Micrometer Scale from Spectroscopy of Coherent Transition Radiation
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radiation, electron, linac, space-charge |
130 |
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- B. Schmidt, C. Behrens, S. Wesch
DESY, Hamburg
- H. Delsim-Hashemi, J. Rossbach, P. Schmüser
Uni HH, Hamburg
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At the free electron laser FLASH in Hamburg, a longitudinal bunch compression scheme is used resulting in a longitudinal current profile with a narrow leading spike. Part of this spike is responsible for producing high-intensity short FEL pulses via the SASE process. The width and the structure of the current spike, which are key parameters for the efficiency of the SASE process, are barely accessible to direct measurements in the time domain. Using an infrared multi-stage grating spectrometer, we have studied the spectral composition of coherent transition radiation from single electron bunches. The data show that the 'fundamental width' of the current spike is about 40 fs (fwhm) with prominent substructures down to the 10 fs scale. The intensity fluctuations of coherent radiation in the corresponding wavelength range are strongly correlated to the fluctuations of the FEL pulse energy. Extension of the method to the near infrared regime have revealed micro-structures with characteristic lengths from a few micrometers down to fractions of a micrometer. Their interrelation with the parameters of the electron beam and the compression system have been studied.
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| TUPP020 |
Analysis of Collective Effects at the Diamond Storage Ring
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impedance, single-bunch, simulation, storage-ring |
1574 |
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- R. Bartolini, C. Christou, R. T. Fielder, M. Jensen, A. F.D. Morgan, S. A. Pande, G. Rehm, C. A. Thomas
Diamond, Oxfordshire
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The Diamond storage ring has achieved its nominal operating current of 300 mA in multi-bunch mode and up to 10 mA in single bunch mode. Several collective instabilities have been observed and their dependence on machine parameters such as chromaticities, RF voltage and fill pattern have been investigated. We report here the analysis of the observed current thresholds and rise times of the instabilities compared with analytical estimates and tracking simulations. We also present the results of the MAFIA simulations performed with the aim of understanding the main contribution to the impedance of the ring and establishing a machine impedance database.
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| TUPP100 |
A Four-dimensional Vlasov Solver for Microbunching Instability in the Injection System for X-ray FELs
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simulation, electron, emittance, beam-transport |
1764 |
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- M. Migliorati, A. Schiavi
Rome University La Sapienza, Roma
- G. Dattoli
ENEA C. R. Frascati, Frascati (Roma)
- M. Venturini
LBNL, Berkeley, California
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The phenomenon of microbunching instabilty arises from small charge-density fluctuations in the electron bunches that are amplified by the combined effect of space charge and coherent synchrotron radiation as the beam travels through magnetic compressors. In order to study the coupled longitudinal and transverse beam dynamics we propose to develop a four-dimensional grid-based Vlasov solver. The goal is to give an accurate characterization of the microbunching instability seeded by the random noise present in the initial bunch distribution. Solving directly the Vlasov equation instead of using macroparticle simulations has the advantage of avoiding the statistical fluctuations due to a limited number of macroparticles. Because a Vlasov solver in a high dimension phase-space tends to be particularly time consuming, to be practical a code implementing this method should run on parallel processors. In this paper we report progress toward the realization of such a 4D Vlasov solver.
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| TUPP143 |
Collective Ionization by Attosecond Electron Bunches
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electron, plasma, target, ion |
1851 |
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- A. Ogata, T. Kondoh, K. Norizawa, J. Yang, Y. Yoshida
ISIR, Osaka
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Present accelerator technology has realized linac bunch length on the order of femtosecond. If the bunch length becomes onto the order of attosecond, its inverse is comparable to the ionization frequency; ionization potential divided by Plank's constant. The stopping power then becomes proportional to square of the number of bunch electrons. Such a bunch ionizes the target collectively. This collective, or coherent ionization will provide us plenty of applications including unknown ones at the present. This phenomenon has historically been expected in cluster beams, which can be regarded as ultra-short bunches. The present paper adapts formalism of stopping power of a medium characterized by a dielectric function against cluster beams to that against electron bunches. It then describes some numerical calculations on the collective ionization by the attosecond electron bunches.
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| WEPC064 |
The Possibility of Conversion of Hefei Light Source Storage Ring Into a Dedicated THz Radiation Source
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radiation, synchrotron, synchrotron-radiation, storage-ring |
2139 |
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- L. Wang, G. Feng, W. Li, L. Liu, C.-F. Wu, H. Xu, S. C. Zhang
USTC/NSRL, Hefei, Anhui
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In the future of National Synchrotron Radiation Laboratory, a new advanced VUV and soft X-ray light source would be contructed and provide synchrotron radiation with high brilliance and transverse coherence. At that time, the current HLS storage ring would be replaced by the new one. Instead of retire of the old ring, there is another case, that is upgrading current low energy storage ring as a dedicated THz light source. In this paper, the possibility of lattice upgrading were evaluated. And its performance was estimated according to exist theoretical model.
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| THPP089 |
Gamma Transition Jump for PS2
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betatron, optics, quadrupole, lattice |
3572 |
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- W. Bartmann, M. Benedikt, E. Métral, D. Möhl
CERN, Geneva
- S. Peggs
BNL, Upton, Long Island, New York
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The PS2, which is proposed as a replacement for the existing ~50-year old PS accelerator, is presently considered to be a normal conducting synchrotron with an injection kinetic energy of 4 GeV and a maximum energy of 50 GeV. One of the possible lattices (FODO option) foresees crossing of transition energy near 10 GeV. Since many intensity dependent effects can take place in both the longitudinal and the transverse planes a fast jump of gamma transition is necessary in order to pass the non-adiabatic region rapidly. The aim of the present paper is on the one hand to scale the gamma transition jump, used since 1973 in the PS, to the projected PS2 and on the other hand based on these results the analysis of the implementation and feasibility of a gamma transition jump scheme in a conventional FODO lattice.
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