Untersuchungen zum Betriebsverhalten eines Waermerohres mit fluessigem Stickstoff

A heat pipe with axial grooves was operated with nitrogen, and its performance was analyzed with a view to several different parameters. To simplify the test set-up, the cold zone of the pipe profile is cooled with liquid nitrogen instead of a small cooler. Further, the performance of the heat pipe was also tested at different angles of inclination, i.e. in gravitational or counter-gravitational direction. (orig.)Ziel dieser im Rahmen einer Diplomarbeit durchgefuehrten Untersuchungen ist es, ein Waermerohr mit Axialrillenprofil mit Stickstoff als Waermetraeger in Betrieb zu nehmen und das Betriebsverhalten unter verschiedenen Parametern zu untersuchen. Die Kaltzone des Rohrprofiles soll dabei zur Vereinfachung des Testaufbaus durch fluessigen Stickstoff anstelle eines Kleinkuehlers gekuehlt werden. Als Waermequelle in der Verdampfungszone dient eine elektrische Heizung. Ausserdem soll das Waermerohr auch unter verschiedenen Auslenkungen in Betrieb entgegen oder in Richtung der Schwerkraft untersucht werden. (orig.)Available from TIB Hannover: RA 831(3123) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Entwicklung integrierter supraleitender Flussquantenoszillatoren fuer ultra-empfindliche submm-Wellenempfaenger auf der Basis der Nb- und NbN-Technologie Abschlussbericht

SIGLEAvailable from TIB Hannover: F00B1415+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

SQUID2000 - HTS-SQUID-Modul fuer den Biomagnetismus, die zerstoerungsfreie Pruefung und die geomagnetische Exploration Abschlussbericht

SIGLEAvailable from TIB Hannover: F00B1321+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman

HTS rf-SQUID-Planargradiometer mit langer Basislaenge fuer die Inspektion von Flugzeugfelgen

An important task in the field of nondestructive evaluation (NDE) of aircraft components is the reliable detection of small cracks hidden very deep in the material. This will become even more important in the future, because the thickness of aircraft parts is going to increase further. Conventional eddy current testing systems reach their limit here, whereas SQUIDs (Superconducting QUantum Interference Devices) show an excellent sensitivity for the low excitation frequencies needed. As it is required to suppress large magnetic disturbances without magnetic shielding, a gradiometer SQUID is utilized for these measurements. By calculations, it is proved in this work that an optimum signal-to-noise ratio is reached when the baseline of the SQUID gradiometer is enlarged from the so far used 3.6 mm to about 10 mm. However, an enhancement of the baseline leads to a significant increase of the SQUID inductance and hence of the white noise. Consequently, the SQUID sensor cannot be operated reliably in the flux locked loop any more. It is shown that the inductance may be reduced significantly by placing a superconducting cover strip on top of the gradiometer slit. Thus, the gradiometer slit cannot be penetrated by magnetic flux any more. Calculations of the goemetric and kinetic inductance confirm that a distinct reduction of the inductance can be reached this way. Furthermore, the calculations show that it is possible to raise the baseline to 9 mm without an increase of the inductance, compared to an uncovered gradiometer with 3.6 mm baseline. (orig.)Available from TIB Hannover: RA 831(3779) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Herstellung und Charakterisierung von Detektoren im Materialsystem AlGaAs/GaAs

As a general model for III/V semiconductors the preparation and properties of GaAs/AlGaAs detectors were studied. For the preparation of the semiconductor materials a flexible molecular beam epitaxy device was constructed. Research work mainly aimed at the avalanche effect in pure GaAs diodes and in AlGaAs/GaAs staircase diodes and included the characterization of direct current properties and noise behaviour. Field-dependence of the ionization coefficients could be described within a large temperature region using the model by Wolff. Alpha beam experiments revealed the potentials of AlGaAs/GaAs p-i-n diodes as this layer detectors in high-performance physics. (WEN)SIGLEAvailable from TIB Hannover: RA 831(2845) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Plasmaabscheidung von mikrokristallinem Silizium Merkmale und Mikrostruktur und deren Deutung im Sinne von Wachstumsvorgaengen

The microstructure of microcrystalline silicon (#mu#c-Si:H) grown in a low-temperature (<or#approx#400 C) PECVD process was investigated in dependence on the process parameters and the choice of the substrate material. For characterization, Raman spectroscopy, X-ray diffraction, atomic force microscopy and transmission electron microscopy were applied. It is shown that a stationary growth is observed in the long term structural evolution of the thin films. The characteristics of this stationary growth can be described in relation to the crystallinity of the microcrystalline samples, irrespective of the details of plasma processing and the nature of the substrate. This also applies for the initially homoepitaxial growth on Si(100), which transforms to disordered growth under similar structural changes when compared to low-temperature MBE growth. A catalytic role of hydrogen during grain epitaxy is suggested therefore and existing models for the growth of #mu#c-Si:H are extended in order to explain for the formation of (111) facets, planar defects on (111) planes and a preferred crystallographic orientation. The present study evidences limitations for tailoring the structural properties of #mu#c-Si:H according to technical demands. E.g. the columnar morphology and the formation of structural defects limit the extent of coherent crystalline domains. Their sizes cannot be influenced significantly by the choice of the plasma parameters and the substrate material. (orig.)148 refs.Available from TIB Hannover: RA 831(3753) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Entwicklung und Realisierung von HTSL-Mehrlagenstrukturen Abschlussbericht

Within the project (no.: 13N6793/8) the micro shadow mask technique was established to be used as a standard patterning technique for HTS-ramptype Josephson junctions. The indicated advantage of this technique could not be confirmed. Furthermore interface engineered ramp type junctions showed improved properties compared to micro shadow patterned junctions. A cryogenic laser microscope was developed at the IPM in Nishny Novgorod, builded up in ISI in the Forschungszentrum Juelich and tested successfully. The microscope can be operated at 80 K and gives an accuracy of 2 #mu#m in the position. Multilayer flux transformer used in combination with rf-SQUIDs and complex arrays of Josephson junctions prepared on bicrystall-substrates were analyzed using this microscope. Weak points in the crossover of the multiturn flux transformer were detected. Mathematical simulation on coplanar resonators for rf-SQUIDs gave an excellent agreement between calculation and experiment. Single phase HTS thin films with no loss in quality could not be realized using sputtering technique. The change in the sputter target is responsible for this effect. On sapphire bicrystall substrates no work was realized. On r-cut sapphire substrates covered with an epitaxial bufferlayer (f.e. YSZ) excellent HTS-thin films could be realized. (orig.)Available from TIB Hannover: F99B267 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Allotaxie: Ein neues Verfahren zur Herstellung von Eisendisilizid- und Siliziumdioxid-Heterostrukturen in Silizium

Epitaxial growth of Si/SiO_2/Si and Si/FeSi_2/Si heterostructures by molecular beam allotaxy and subsequent annealing were investigated. The heterostructures were characterized by rutherford backscattering spectroscopy, by the channeling method and by resistance measurements using the van der pauw method. By allotaxy of FeSi_2 metallic and semiconducting buried FeSi_2 layers of preferred FeSi_2 parallel Si(111) orientation are obtained. In the Si-O system, however, epitaxial silicon growth is hampered by the oxygen. (WEN)SIGLEAvailable from TIB Hannover: RA 831(2869) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Experimentelle Untersuchungen zur Wechselwirkung von HTSL-Josephson-Kontakten in kleinen Netzwerken

The mutual interactions of high-T_c grain boundary Josephson junctions in different types of small arrays have been investigated experimentally. Among the different possible dynamical states in Josephson arrays, the totally phase locked state is the most interesting and, for high frequency oscillator applications, most important state. The approach to use simple one-dimensional, antenna-coupled series arrays of up to 100 junctions was only partially successfull, because of deficiensies of state-of-the-art high-T_c technology. Two dimensional (2d) arrays have been shown theoretically to be most tolerant against spread in junction parameters. Therefore small 2d arrays of 4 x 4 junctions were fabricated and characterised via dc-measurements. The synchronisation of these arrays was extremely sensitive on external magnetic field. This might be a consequence of vortex motion in the arrays. Nevertheless, phase locking of up to 16 high-T_c junctions was demonstrated by dc-measurements for the first time. (orig.)SIGLEAvailable from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Entwicklung einer Mehrlagen-Technologie zur Herstellung von kryoelektronischen Schaltungen mittels Laserablation mit gekreuzten Plasmen Abschlussbericht

Within the project (no.: 13N63601) a novel patterning technique was developed. The technique called micro shadow mask technique give the possibility to prepare in a multilayer-HTS-device the bottom layer with beveled edges during the deposition process. The dimension of the micro shadow mask is defined by a standard photolithographic process down to a linewidth of 2 #mu#m. For the moment this method is in use only in Juelich. It will give new aspects in the preparation of SNS-ramp-type Josephson-junctions. The whole work was performed with the pulsed laser deposition using crossed flux technique. Furthermore a cryogenic laser microscope was developed at the IPM in Nishny Novgorod, builded up in ISI in the Forschungszentrum Juelich and tested successful. This microscope will be used to analyze complex HTC-devices prepared in ISI. For the improvement of rf-SQUID's multilayer thin film capacitors were realized and studied concerning the response frequency. The integration of HTC / insulator / HTC capacitors was not successful using high frequency compatible materials as an insulator. In the frame of this project the realization of such capacitors failed. (orig.)SIGLEAvailable from TIB Hannover: F97B1296+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman