Search

A high resolution online grating spectrometer has been set up at the free electron laser in Hamburg FLASH at DESY in Hamburg. This new photon diagnostic device allows to parasitically measure the spectral distribution of the FEL laser pulses on a single shot basis and therefore gives complementary spectral and temporal pulse information for user experiments and FEL operation. The spectrometer combines a plane mirror and two plane variable line spacing (VLS) gratings and is installed at the non-monochromized beamline branch at FLASH. In contrast to a standard grating the blaze angle is optimized for the zero-order radiation transferred to the experimental stations, leaving approximately 1–10% intensity for recording the wavelength in the spectrometer. The detector, an intensified CCD camera imaging the dispersed beam on a Ce:YAG crystal, can follow the focal plane of the gratings covering a wavelength ranging from 6 to 60 nm. The resolving power of the spectrometer is expected to range from 500 to 8000 depending on the FEL wavelength.

At the vacuum ultraviolet (VUV) free electron laser in Hamburg (FLASH) an infrared (IR) beamline is being built to allow novel pump-and-probe experiments combining coherent IR pulses with the FEL radiation in the VUV spectral range. It will provide useful IR radiation generated by a purpose built undulator over the wavelength range from 200 μm to 10 μm and possibly even shorter. The commissioning of the beamline has started this summer and first light will be delivered to the experimental hall by autumn 2007. Another important application of the beamline will be electron diagnostics of the longitudinal charge distribution of the electron bunches.

FLASH has been a user facility since 2005, delivering radiation in the wavelength range between 7 and 47 nm using the SASE principle. After the present upgrade, the wavelength range is extended to 4.45 nm. With the third harmonic accelerating module in place to linearize the longitudinal phase space, the stability and reproducibility of the machine is substantially improved. The user requests for beam time by far exceeds the time available. In order to increase user beam time and to improve the radiation properties delivered to users, a major extension of the user facility called FLASH II has been proposed by DESY in collaboration with the HZB. FLASH II is a seeded FEL in the parameter range of FLASH. As logical continuation, the seeding with HHG which started with sFLASH will result in direct seeding. Because in the foreseeable future there will probably not be HHG seed lasers available at high repetition rates down to wavelengths of 4 nm, a cascaded HGHG scheme is proposed to produce short wavelengths. After a first design report, the project now enters its technical design phase. During this time, the FLASH beam parameters after the present upgrade 2009/2010 will be characterized and the present design will be re-evaluated and adjusted. In addition, start-to-end simulations will complete the simulations which have been performed so far, including a design of the extraction area.

Ultra-fast laser sources have revolutionized many fields in science. As technology improves, new applications can be made accessible. The OPCPA technique has shown potential to be the key technology for future amplifier systems, but hasn’t achieved a breakthrough such as Ti:Sapphire laser technology, mostly due to the complex pump amplifier design. We present an operationally stable OPCPA system that might turn the tide for OPCPA technology. This first prototype system will be used in the accelerator environment at the FLASH free electron laser at DESY in Hamburg. The envisioned key parameters for this amplifier are >1 mJ pulse energy with a repetition rate of 100 kHz and a pulse duration of

A stigmatic spectrometer for the 2.5–40 nm extreme-ultraviolet (EUV) region has been realized. The design consists of a grazing-incidence spherical varied-line-spaced grating with flat-field properties and of a spherical mirror mounted in the Kirkpatrick–Baez configuration that compensates for the astigmatism. The spectrum is acquired on a fluorescent screen and intensified CCD detector that can be moved along the spectral focal curve to select the spectral region to be acquired. This stigmatic design has also spectral and spatial resolution capability for extended sources. The spectral and spatial resolution of the system has been characterized by using the emission from a hollow-cathode lamp or a laser-produced plasma. At present, the instrument is installed at the vacuum–ultraviolet free-electron-laser (VUV FEL) at DESY for the spectral monitoring of the FEL beam in the 20–40 nm region.

We present an overview of the vacuum‐ultraviolet free electron laser (VUV FEL) user facility at DESY comprising the layout of the experimental hall, radiation transport to the experimental area, as well as photon beam diagnostics. In general, diagnostics of the FEL radiation is particularly challenging due to the laser’s unique properties such as extremely high peak powers and short pulse lengths. Yet, pulse‐resolved characterization of the photon beam is essential for most user experiments. In order to monitor important parameters like radiation pulse intensity, spectral distribution, etc. new concepts have been developed allowing efficient use of the new source.

The report presents results of experimental and analytical studies of certain energy transfer mechanisms and rates in high-energy gas flows. The immediate application is to generate kinetic data to aid in the prediction of the radiation emitted by hypervelocity vehicle flowfields, radiation from high altitude rocket plumes, how shocks, and shock layers around the vehicles. The present report gives data on a newly discovered vibration-to-electronic (V-E) energy transfer process in CO, creating strong UV signal on the CO 4th Positive Bands. This process has been found to be mediated by small amount of free electrons in the flow. Analogous processes populating radiating excited electronic states of NO, CN, and C2 are also presented. In a complementary phase of the work, production of highly vibrationally excited N2 in cold plasmas and the measurement of vibrational level populations by spontaneous Raman spectroscopy is reported.