Evidence for microbunching "sidebands" in a saturated free-electron laser using coherent optical transition radiation.

We report the first measurements of z-dependent coherent optical transition radiation (COTR) due to electron-beam microbunching at high gains ( >10(4)) including saturation of a self-amplified spontaneous emission free-electron laser (FEL). In these experiments the fundamental wavelength was near 530 nm, and the COTR spectra exhibit the transition from simple spectra to complex spectra ( 5% spectral width) after saturation. The COTR intensity growth and angular distribution data are reported as well as the evidence for transverse spectral dependencies and an "effective" core of the beam being involved in microbunching.

Exponential gain and saturation of a self-amplified spontaneous emission free-electron laser.

Self-amplified spontaneous emission in a free-electron laser has been proposed for the generation of very high brightness coherent x-rays. This process involves passing a high-energy, high-charge, short-pulse, low-energy-spread, and low-emittance electron beam through the periodic magnetic field of a long series of high-quality undulator magnets. The radiation produced grows exponentially in intensity until it reaches a saturation point. We report on the demonstration of self-amplified spontaneous emission gain, exponential growth, and saturation at visible (530 nanometers) and ultraviolet (385 nanometers) wavelengths. Good agreement between theory and simulation indicates that scaling to much shorter wavelengths may be possible. These results confirm the physics behind the self-amplified spontaneous emission process and forward the development of an operational x-ray free-electron laser.

First Observation of z-Dependent Electron-Beam Microbunching Using Coherent Transition Radiation.

We report the first measurements of the electron-beam microbunching z dependence in a self-amplified spontaneous-emission (SASE) free-electron laser (FEL) experiment by the observation of visible wavelength coherent transition radiation (CTR). In this case the fundamental SASE wavelength was at 537 nm, and the CTR exhibited an exponential intensity growth similar to the SASE radiation. In addition, we observed for the first time structure in the CTR angular distribution patterns that may be useful for optimizing SASE FEL performance.

The ontogenesis of skin and organ characteristics in the Syrian golden hamster. III. Ontogenetic and intraspecific allometry for strain and sex as well as body weight- and age-dependent correlations.

The allometric relations, i.e. bodily characteristics, body weight-relationships as well as age-dependent organ and biochemical data were studied in a total of 464 golden hamsters of both sexes of an acromelanic white inbred and agouti coloured outbred strain. In the 3 age sections studied (I = day 1-20, II = day 25-100, III = day 110-365) the body weight- and age-dependent relations were found to be altered between and within the various characteristics. The body weight correlations predominated in the case of organ weights and skin muscle thickness. By contrast, age correlations were seen above all in the skin compartments with cyclic growth, hair follicle density and reticular thickness in the age sections I and II. Papillary thickness showed a positive relation to body weight and age after weaning, but no long-term relations were observed with both plasma insulin and blood glucose levels. The allometric behaviour of skin compartments could be explained particularly by thermoregulatory and "geometric" similarities and that of the organs by metabolic and other similarities. Most sex and strain differences in the absolute data, except for the kidney and adrenal weights, disappeared on allometric analysis and were thus mainly due to differences in body weight. For long-term toxicological investigations, the documentation of age and body weight as well as the determination of ontogenetic allometry is a "must".

The ontogenesis of skin and organ characteristics in the Syrian golden hamster. I. Skin compartments and subcutaneous adipocytes.

The quantitative relations between the 4 skin compartments [epidermis, stratum (str.) papillare, str. reticulare, panniculus carnosus], the hair follicle density and adipocyte size were investigated histometrically in a total of 464 golden hamsters of both sexes of the acromelanic white inbred strain Bio 1.5 and agouti coloured outbred strain Han:AURA. The overall regular course of ontogenesis from the 1st to the 365th day of life showed discontinuous impairments of the skin layer thickness in the shoulder and sacral region due to the spontaneous growth cycles of hair. Active phases of hair growth could be determined on days 15-25, 50-60 and 80-110 from measurements of the hair follicle density as well as skin thickness. In particular, the thickness of the str. reticulare was closely correlated to the growth cycles. By contrast, the epidermis, str. papillare and skin muscle thickness showed an age-dependent development. Also, no correlation was found between the size of inguinal adipocytes and hair growth cycle, which is in contrast to the data from the literature for small laboratory rodents. Only differences in skin muscle thickness could be found in the sites studied in the shoulder and sacral regions. Overall, the skin compartments, the skin follicle density and adipocyte size were found to be stable to effects such as animal strain, sex and skin localization.