| Paper | Title | Page |
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| MOPPH056 | Generation of Attosecond X-ray Pulses with a Multi-Cycle Two-Color ESASE Scheme | 114 |
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Generation of attosecond x-ray pulses is attracting much attention within the x-ray free-electron laser (FEL) user community. Several schemes have been proposed based on manipulations of electron bunches with extremely short laser pulses. In this paper, we extend the attosecond two-color ESASE scheme* to the long optical cycle regime using a detuned second laser** and a tapered undulator. Both lasers can be about ten-optical-cycle long, with the second laser frequency detuned from the first one in order to optimize the contrast between the central and side current spikes. A tapered undulator can be used to mitigate the degradation effect of the longitudinal space charge force in the undulator*** as well as to suppress the FEL gain of all side current spikes. Simulations using the LCLS parameters show a single attosecond x-ray spike of ~100 attosecond can be produced with a good contrast ratio.
* A. A. Zholents and G. Penn, Phys. Rev. ST Accel. Beams 8, 050704 (2005). |
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| TUPPH048 | Recent Results of the SPARC Project | 359 |
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| The SPARC project foresees the realization of a high brightness photo-injector to produce a 150-200 MeV electron beam to drive 500 nm FEL experiments in various configurations. The SPARC photoinjector is also the test facility for the recently approved VUV FEL project named SPARX. The second stage of the commissioning, that is currently underway, foresees a detailed analysis of the beam matching with the linac in order to confirm the theoretically prediction of emittance compensation based on the “invariant envelope” matching , the demonstration of the “velocity bunching” technique in the linac and the characterisation of the spontaneous emission radiation in the SPARC undulators. In this paper we report the experimental results obtained so far. | ||
| TUPPH080 | FEL Emissions at 160 nm in Seeded Configuration on the SCSS Test Accelerator | 429 |
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| Recently it has been proved that seeding a Free-Electron Laser with Harmonics Generated in gas can drastically improve the properties of the light emission and in particular the temporal coherence, which is quite limited in the Self-Amplified Spontaneous Emission configuration. Here, the impact of the seed level on the FEL emission has been characterized at 160 nm on the SCSS Test Accelerator. Actually, at extremely low level of HHG injection (0.5 pJ, 10 W), i.e. approximately ten times the effective noise power of the SASE emission, the FEL emission starts to be amplified and the number of spikes decrease. Then, the FEL energy per pulse begins clearly proportional to the HHG energy per pulse. More specifically for a seed power (<175 W) 230 times larger than the effective SASE noise power, the FEL spectrum exhibits a stable quasi Gaussian shape. As it is theoretically feasible to generate XUV harmonics which can be dominating with a similar factor, one can imagine High Gain Harmonic Generation configurations with only two or three stages for reaching wavelengths of a few nanometers. |