Direct observation of confined states in metallic single-walled carbon nanotubes

We investigated the local density of states (LDOS) of extended individual metallic single-walled carbon nanotubes using low-temperature scanning tunneling spectroscopy. We observed that the LDOS oscillates with energy close to the Fermi level. The oscillation period of about 50 meV varies with position on the nanotube. Maps of the LDOS reveal that the peaks in the oscillation are related to confined states. The widths of the peaks increase with increasing distance from the Fermi level.BN/BionanoscienceApplied Science

Measurements and simulations of seeded electron microbunches with collective effects

Measurements of the longitudinal phase-space distributions of electron bunches seeded with an external laser were done in order to study the impact of collective effects on seeded microbunches in free-electron lasers. When the collective effects of Coulomb forces in a drift space and coherent synchrotron radiation in a chicane are considered, velocity bunching of a seeded microbunch appears to be a viable alternative to compression with a magnetic chicane under high-gain harmonic generation seeding conditions. Measurements of these effects on seeded electron microbunches were performed with a rf deflecting structure and a dipole magnet which streak out the electron bunch for single-shot images of the longitudinal phase-space distribution. Particle tracking simulations in 3D predicted the compression dynamics of the seeded microbunches with collective effects

Technical Design of the XUV Seeding Experiment at FLASH

The Free electron laser at Hamburg FLASH operates in the Self Amplified Spontaneous Emission SASE mode, delivering to users photons in the XUV wavelength range. The FEL seeding schemes promise to improve the properties of the generated radiation in terms of stability in intensity and time. Such an experiment using higher harmonics of an optical laser as a seed is currently under construction at FLASH. The installation of the XUV seeding experiment sFLASH is going to take place in fall 2009. This includes mounting of new variable gap undulators upstream of the existing SASE undulators, building the XUV seed source as well as installation of additional photon diagnostics and electron beam instrumentation. In this contribution the layout of sFLASH will be discussed together with the technical design of its major component

Photon Diagnostics for the Seeding Experiment at FLASH

Starting from next year the technical feasibility of a direct seeding scheme at 30 and 13 nm will be studied at the Free electron LASer in Hamburg FLASH . During a major shutdown the SASE FEL facility will be upgraded and it is planned to install in addition a high harmonic generation HHG seed laser, a new chain of 10m variable gap undulators and a dedicated commissioning beamline for photon diagnostics and pilot time resolved pump probe experiments. Besides demonstrating successful seeding at short wavelength, the project aims for time resolution in the 10 fs range to study ultrafast processes by combining the naturally synchronized FEL and optical seed laser pulses. After the extraction of the radiation in a magnetic chicane, a short branch will accommodate intensity and beam monitors and a high resolution spectrometer. The intensity monitor detects scattered photons from a gold mesh on a shotto shot basis using micro channel plates MCP and XUV diodes. It is designed to detect photons several orders of magnitude apart in flux, i.e. spanning the wide range from spontaneous emission up to the seeded FEL radiation at gigawatt power level. Simulations of this device are presented as well as calibration measurements carried out at FLAS

Proceedings of the 39th International Free-Electron Laser Conference

The European XFEL is a high-repetition rate facility that generates high-power SASE radiation pulses in three beamlines. A joint upgrade project, with Finnish universities, to equip the SASE3 beamline with a chicane has been recently approved to generate two SASE pulses with different photon energies and temporal separation. In this work we report the status of the project, its expected performance, and recent experimental results. Additionally, we discuss methods to diagnose the properties of the generated radiation.The European XFEL is a high-repetition rate facility that generates high-power SASE radiation pulses in three beamlines. A joint upgrade project, with Finnish universities, to equip the SASE3 beamline with a chicane has been recently approved to generate two SASE pulses with different photon energies and temporal separation. In this work we report the status of the project, its expected performance, and recent experimental results. Additionally, we discuss methods to diagnose the properties of the generated radiation.The European XFEL is a high-repetition rate facility that generates high-power SASE radiation pulses in three beamlines. A joint upgrade project, with Finnish universities, to equip the SASE3 beamline with a chicane has been recently approved to generate two SASE pulses with different photon energies and temporal separation. In this work we report the status of the project, its expected performance, and recent experimental results. Additionally, we discuss methods to diagnose the properties of the generated radiation.The European XFEL is a high-repetition rate facility that generates high-power SASE radiation pulses in three beamlines. A joint upgrade project, with Finnish universities, to equip the SASE3 beamline with a chicane has been recently approved to generate two SASE pulses with different photon energies and temporal separation. In this work we report the status of the project, its expected performance, and recent experimental results. Additionally, we discuss methods to diagnose the properties of the generated radiation.The European XFEL is a high-repetition rate facility that generates high-power SASE radiation pulses in three beamlines. A joint upgrade project, with Finnish universities, to equip the SASE3 beamline with a chicane has been recently approved to generate two SASE pulses with different photon energies and temporal separation. In this work we report the status of the project, its expected performance, and recent experimental results. Additionally, we discuss methods to diagnose the properties of the generated radiation.The European XFEL is a high-repetition rate facility that generates high-power SASE radiation pulses in three beamlines. A joint upgrade project, with Finnish universities, to equip the SASE3 beamline with a chicane has been recently approved to generate two SASE pulses with different photon energies and temporal separation. In this work we report the status of the project, its expected performance, and recent experimental results. Additionally, we discuss methods to diagnose the properties of the generated radiation.</p