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| MOAAU01 | First Lasing in Seeding Configuration at 160 nm Using High order Harmonic Generated in gas on the FEL of the SCSS Prototype Accelerator | |
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| Coherent radiation has been observed at 160 nm, 54 nm and 32 nm (respectively fundamental, 3rd and 5th non linear harmonics) by seeding the 5th harmonic of a Ti: Sa laser (800 nm, 50 mJ, 10 Hz, 100 fs) generated in a Xe gas cell inside the FEL of the SCSS (SPring-8 Compact Sase Source, Japan) Prototype Accelerator. In this configuration, the external source is focalized at the beginning of the first in-vacuum undulator section (300 periods, 15 mm of period) in order to interact properly with the electron beam (150 MeV, 0.3 nC, 10 Hz, 1 ps). The details of the experimental set-up will be given. With one undulator section, high amplification levels and shortening of the spectral width compared to the spontaneous emission have been measured. When adding the second undulator section, saturated signal is apparently observed. The measurements are then compared with time dependant simulations using PERSEO and GENESIS included in SRW. Finally, perspectives offered by seeding an FEL with High order Harmonics Generated in gas, following this first experimental demonstration, will be derived for 4th generation light sources in the soft X-ray range. | ||
| MOAAU02 | Lasing of a Cherenkov FEL Driven by a Low Electron Beam Current | |
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We have designed and constructed a compact (0.5 x 1.5 m), 100 kV Cerenkov FEL operating at around 20 to 25 GHz*. The electron beam is produced by a gridded thermionic electron gun, which yields a maximum current of about 500 mA. This current is injected into a cylindrical waveguide lined with Al2O3 and about 60 % of the beam is transported through the lined waveguide section. A transported current of only 250 mA was sufficient to observe lasing. The total power generated for an interaction length of 25 cm was about 3 W. Although not designed as an oscillator, reflections at various positions along the waveguide provide a low-Q resonator. The power observed was in good agreement with results obtained with a model of the CFEL when reasonable values are used for beam quality, resonator feedback and liner fluctuations**. Measurement of the tuning with voltage showed excellent agreement with theory, and indicates operation at the fundamental TM01 mode as well as on higher order modes.
* Proceedings of the 2004 FEL Conference, Trieste, Italy, 2004, p314-317** J. Appl. Phys. 100, 053108 (2006) |
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| MOAAU03 | First Lasing of the Elettra Storage-Ring Free-Electron Laser in Seeded Configuration | |
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| We report the first lasing of the Elettra storage-ring free-electron laser operated in “single-pass” seeded configuration. The external seed was provided by a Ti:Sa laser tuned at 780 and 390 nm, with adjustable repetition rate (10 Hz – 1kHz) and pulse duration (100 fs or 1 ps). We have obtained intense coherent radiation in the spectral range between 130 and 260 nm. Harmonic pulses are characterized by high peak power (orders of magnitudes above spontaneous radiation) and very good stability (fluctuations of few percent). The signal is transform limited. The Elettra optical klystron is made of independent APPLE-type undulators. This allows complete freedom in the choice of light polarization. Presently, all the above features make the Elettra free-electron laser in seeded configuration a unique light source, which is attractive for several user experiments. | ||
| MOAAU04 | First Lasing of FELICE | |
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| After a short description of the new beam line FELICE for intra-cavity experiments at the FELIX facility, first measurements of the laser characteristics after the observation of first lasing on 11 August, will be presented. | ||
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| MOBAU01 | Self-Force-Derived Mass of an Electron Bunch | 1 |
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| The properties of Lorentz transformations for energy and momentum in electromagnetic systems are illustrated in a simple example involving a short electron bunch moving in a bending magnet. The famous 4/3 problem in electromagnetic mass is discussed. | ||
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| MOBAU02 | Technology Challenges Towards Short-Wavelength FELs | 9 |
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| Since the very first proposal of high-gain FELs for the X-ray wavelength regime it was obvious that realization of such a device, potentially rewarding revolutionary science opportunities, would impose extraordinary challenges in terms of accelerator physics and technology. The talk will review the major steps that had to be taken to finally construct an FEL user facility for soft X-rays. Also, a few issues will be pointed out that are to be addressed in order to make full profit of the FEL principle at X-ray wavelengts. | ||
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