Making spectral shape measurements in inverse Compton scattering a tool for advanced diagnostic applications.

Interaction of relativistic electron beams with high power lasers can both serve as a secondary light source and as a novel diagnostic tool for various beam parameters. For both applications, it is important to understand the dynamics of the inverse Compton scattering mechanism and the dependence of the scattered light's spectral properties on the interacting laser and electron beam parameters. Measurements are easily misinterpreted due to the complex interplay of the interaction parameters. Here we report the potential of inverse Compton scattering as an advanced diagnostic tool by investigating two of the most influential interaction parameters, namely the laser intensity and the electron beam emittance. Established scaling laws for the spectral bandwidth and redshift of the mean scattered photon energy are refined. This allows for a quantitatively well matching prediction of the spectral shape. Driving the interaction to a nonlinear regime, we spectrally resolve the rise of higher harmonic radiation with increasing laser intensity. Unprecedented agreement with 3D radiation simulations is found, showing the good control and characterization of the interaction. The findings advance the interpretation of inverse Compton scattering measurements into a diagnostic tool for electron beams from laser plasma acceleration.

High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter.

Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields and the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. We benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution.

High resolution energy-angle correlation measurement of hard x rays from laser-Thomson backscattering.

Thomson backscattering of intense laser pulses from relativistic electrons not only allows for the generation of bright x-ray pulses but also for the investigation of the complex particle dynamics at the interaction point. For this purpose a complete spectral characterization of a Thomson source powered by a compact linear electron accelerator is performed with unprecedented angular and energy resolution. A rigorous statistical analysis comparing experimental data to 3D simulations enables, e.g., the extraction of the angular distribution of electrons with 1.5% accuracy and, in total, provides predictive capability for the future high brightness hard x-ray source PHOENIX (photon electron collider for narrow bandwidth intense x rays) and potential gamma-ray sources.

A tapered undulator experiment at the ELBE far infrared hybrid-resonator oscillator free electron laser.

A tapered undulator experiment was carried out at the ELBE far-infrared free electron laser (FEL). The oscillator FEL makes use of a hybrid optical resonator. The main motivation was to see whether the presence of a dispersive medium in the form of a waveguide in the resonator has any effect on the outcome. The FEL saturated power and the wavelength shifts have been measured as a function of both positive as well as negative undulator field amplitude tapering. In contrast to the typical high-gain FELs where positive tapering proves beneficial for the output power we observed an improvement of performance at negative taper. During the same experiments we studied the characteristics of the detuning curves. The width of the curves indicates a maximum small signal gain for zero taper while the output peak power increases with negative taper. The saturated power output, the detuning curve characteristics, and the wavelength shifts agrees with the theoretical predictions. Details of the experiment are presented.

From shell to cell: neutron scattering studies of biological water dynamics and coupling to activity.

An integrated picture of hydration shell dynamics and of its coupling to functional macromolecular motions is proposed from studies on a soluble protein, on a membrane protein in its natural lipid environment, and on the intracellular environment in bacteria and red blood cells. Water dynamics in multimolar salt solutions was also examined, in the context of the very slow water component previously discovered in the cytoplasm of extreme halophilic archaea. The data were obtained from neutron scattering by using deuterium labelling to focus on the dynamics of different parts of the complex systems examined.

Liquid-like water confined in stacks of biological membranes at 200 k and its relation to protein dynamics.

Confined water is of considerable current interest owing to its biophysical importance and relevance to cryopreservation. It can be studied in its amorphous or supercooled state in the "no-man's land", i.e., in the temperature range between 150 and 235 K, in which bulk water is always crystalline. Amorphous deuterium oxide (D(2)O) was obtained in the intermembrane spaces of a stack of purple membranes from Halobacterium salinarum by flash cooling to 77 K. Neutron diffraction showed that upon heating to 200 K the intermembrane water space decreased sharply with an associated strengthening of ice diffraction, indicating that water beyond the first membrane hydration layer flowed out of the intermembrane space to form crystalline ice. It was concluded that the confined water undergoes a glass transition at or below 200 K to adopt an ultraviscous liquid state from which it crystallizes to form ice as soon as it finds itself in an unconfined, bulk-water environment. Our results provide model-free evidence for translational diffusion of confined water in the no-man's land. Potential effects of the confined-water glass transition on nanosecond membrane dynamics were investigated by incoherent elastic neutron scattering experiments. These revealed no differences between flash-cooled and slow-cooled samples (in the latter, the intermembrane space at temperatures <250 K is occupied only by the first membrane hydration layers), with dynamical transitions at 150 and 260 K, but not at 200 K, suggesting that nanosecond membrane dynamics are not sensitive to the state of the water beyond the first hydration shell at cryotemperatures.

Proton channel hydration and dynamics of a bacteriorhodopsin triple mutant with an M-state-like conformation.

The hydration and dynamics of purple membranes (PM) containing the bacteriorhodopsin (BR) triple mutant D96G/F171C/F219L were investigated by neutron diffraction coupled with H(2)O/D(2)O exchange and by energy-resolved neutron scattering. The mutant, which is active in proton transport (Tittor et al. in J. Mol. Biol. 319:555-565, 2002), has an "open" ground-state structure similar to that of the M intermediate in the photocycle of the wild type (wt) (Subramaniam and Henderson in Nature 406:653-657, 2000). The experiments demonstrated an increased proton channel hydration in the mutant PM compared with wt PM, in both high (86%) and low (57%) relative humidity. We suggest that this is due to the smaller side chains of the mutant residues liberating space for more water molecules in the proton channel, which would then be able to participate in the proton translocation network. PM thermal dynamics has been shown to be very sensitive to membrane hydration (Lehnert et al. in Biophys. J. 75:1945-1952, 1998). The global dynamical behaviour of the mutant PM on the 100-ps time scale, as a function of relative humidity, was found to be identical to that of the wt, showing that the "open" BR structure and additional water molecules in the proton channel do not provide a softer environment enabling increased flexibility.

Thermal motions in bacteriorhodopsin at different hydration levels studied by neutron scattering: correlation with kinetics and light-induced conformational changes.

Bacteriorhodopsin (BR) is a transmembrane protein in the purple membrane (PM) of Halobacterium salinarum. Its function as a light-driven proton pump is associated with a cycle of photointermediates which is strongly hydration-dependent. Using energy-resolved neutron scattering, we analyzed the thermal motions (in the nanosecond-to-picosecond time range) in PM at different hydration levels. Two main populations of motions were found that responded differently to water binding. Striking correlations appeared between these "fast" motions and the "slower" kinetic constants (in the millisecond time range) of relaxations and conformational changes occurring during the photocycle.

Luminosity of bragg crystal diffraction spectrometers with flat and focusing crystals.

Analytical approximations for calculations of the luminous efficiency of Bragg crystal diffraction spectrometers with flat and focussing crystals are derived. The given approximative formulas are in good agreement with ray-tracing calculations presented in an earlier work. Influences of the geometric source dimensions on the luminous efficiency are discussed for both spectrometer types mentioned.

Ray tracing for crystal-diffraction spectrometers with position-sensitive detectors.

Ray tracing calculations for crystal-diffraction spectrometers with position-sensitive detectors are done. After describing fundamentals of the ray tracing formalism, the paper presents selected results for a given spectrometer geometry. The developed method allows a three-dimensional representation of diffraction reflections as well as a matrix display of the recorded events in the detector plane. Applying the formalism of Monte Carlo simulation it is possible to calculate other important quantities, such as the resolving power and luminosity of the analyzed spectrometer.

[Comparative studies of bronchial secretion in children with chronic, nontuberculous lung diseases. 1. Methodico-technical studies of secretion collection and interpretation of the results]. / Vergleichende Bronchialsekretuntersuchungen bei Kindern mit chronischen, nichttuberkulösen Lungenerkrankungen. 1. Mitteilung: Methodisch-technische Untersuchungen zur Sekretgewinnung und Interpretation der Befunde.

The aim of the present study was to estimate different proteins in 166 bronchial secretions from 63 children with chronic nontuberculous lung diseases. In a first publication some methodological problems as the age of patients, the position of the bronchoscope, the bronchoscopic and bronchographic situation resp. and the mode of extraction are analysed. With increasing age the concentration of sIgA is elevated - in contrast to the IgG concentration. Only in severe diseases albumin declines with increasing age. Some variations in the concentration of proteins have been observed in relation to the position of the bronchoscope and in regard to a repeated extraction of bronchial secretions. No important differences in the concentration of proteins have been found in secretions obtained during diverse days. The different protein patterns in the bronchial secretions could be explained only partly by variations in the course of diseases.

[Comparative studies of bronchial secretions in children with chronic, nontuberculous lung diseases. 2. The detection of IgA, sIgA, IgG, IgM and albumin]. / Vergleichende Bronchialsekretuntersuchungen bei Kindern mit chronischen, nichttuberkulösen Lungenerkrankungen. 2. Mitteilung: Zum Nachweis von IgA, sIgA, IgG, IgM und Albumin.

The aim of the present study was to estimate some proteins in bronchial secretions from children with chronic nontuberculous lung diseases. In 166 samples from 63 children the immunoglobulins IgA, sIgA, IgG, IgM and albumin were measured. With rising deterioration of the state of the disease IgG, IgA and albumin were found to be increased, maximal values were observed in patients with dark altered mucosa. With increasing duration of the disease and in comparison with relapsing and deforming bronchitis IgA and sIgA are elevated in patients with chronic bronchitis. The other proteins had a decreasing tendency. In comparison with the later states of illness in sucklings with beginning of the lung disease IgA and sIgA could be estimated less frequently.

[Comparative studies of bronchial secretions in children with chronic, nontuberculous lung diseases. 3. The detection of lysozyme, transferrin, alpha 1-antitrypsin, alpha 2-macroglobulin, haptoglobin and alpha 1-acid glycoprotein]. / Vergleichende Bronchialsekretuntersuchungen bei Kindern mit chronischen, nichttuberkulösen Lungenerkrankungen. 3. Mitteilung: Zum Nachweis von Lysozym, Transferrin, Alpha 1-Antitrypsin, Alpha 2-Makroglobulin, Haptoglobin, Alpha 1-saures Glykoprotein.

In 166 bronchial secretions from 63 children with chronic nontuberculous lung diseases lysozyme, transferrin, alpha 1-antitrypsin, alpha 2-macroglobulin, haptoglobin and alpha 1-acid glycoprotein were estimated. In patients with hard bronchoscopic or bronchographic alterations a reduction of lysozyme, alpha 1-antitrypsin and alpha 2-macroglobulin could be found. These proteins were measured more frequently in cases with dark altered mucosa. Moreover no relation could be found between transferrin, alpha 1-antitrypsin and alpha 2-macroglobulin and the outbreak of the diseases. -In bacterial contaminated secretions transferrin could be demonstrated more frequently in comparison with sterile bronchial secretions.