Untersuchungen zur Anwendung von mehrdimensionalen Korrelationsverfahren bei der Determination von Kanten mit hochauflösenden optischen Messmaschinen

Diese Arbeit untersucht, wie durch mikroskopische Bildserien mit unterschiedlichen Fokuspositionen Objekte sicherer lokalisiert oder charakterisiert werden können. Das vorgeschlagene Verfahren der extrafokalen Korrelation wird ausführlich in Simulationen und Experimenten an Kantenobjekten diskutiert. Abschließend erfolgt ein Ausblick für die Anwendung bei komplexeren Objekten. Einleitend wird die theoretisch bekannte kantenversteilernde Wirkung bei kohärenter Beleuchtung experimentell nachgewiesen und kritisch auf die Begriffe optisches Auflösungsvermögen und Schärfentiefe bei Mikroskopsystemen eingegangen. Zur Sicherstellung möglichst großer Rechenressourcen wird auf effektive Datenformate, schnelle Fourier-Transformationen und Parallelisierung eingegangen. An modifizierten Mikroskopsystemen konnte gezeigt werden, dass Korrelationsverfahren die sonst störenden Oszillationen an Kantenrändern vorteilhaft nutzen können, wenn die zur Korrelation benutzten Erwartungswerte diese Oszillationen berücksichtigen. Die Einbeziehung extrafokaler Bildebenen kann gleichfalls die Reproduzierbarkeit der Detektion von Kantenorten erhöhen, d. h. auch Bereiche außerhalb einer definierten Schärfentiefe können sinnvoll zur Determination eines Kantenortes genutzt werden, wenn der Gewinn an Information den Verlust durch das zunehmende Rauschen überwiegt. In bestimmten Parameterbereichen ist die extrafokale Korrelation mit Erwartungswerten der reinen Mittelung über benachbarten Bildebenen überlegen. Insbesondere bei kohärenter Beleuchtung sind reine Mittelungen der extrafokalen Korrelation unterlegen. Die extrafokale Korrelation, basierend auf der Suche nach der kleinsten Summe der Fehlerquadrate, ist zwar aufwendiger, aber oft erfolgreicher als die schnellere Fourier-Kreuzkorrelation. Das Verfahren der extrafokalen Korrelation kann auch seriell benutzt werden, um 2-dimensionale Verläufe von Kanten zu analysieren, was z. B. bei der Bestimmung von Strukturbreiten-Homogenitäten der Fall ist. Angerissen wird die Erweiterung des Verfahrens für komplexere Objekte, die am Beispiel der Kreisdurchmesserbestimmung in dieser Arbeit seriell bearbeitet wurde, da die notwendige 4-dimensionale Korrelation mit großen Datenmengen künftigen Rechnergenerationen vorbehalten bleibt. Im Anhang wird das Negativ-Kontrast-Misch-Verfahren als spezielle Methode zur Kontraststeigerung vorgestellt

5. Vorlesung (16.12.2017): Physik & Smartphone

Das Smartphone ist immer dabei. Kaum ein anderes technisches Gerät hat solch eine Präsenz erlangt. Kaum eines gebraucht Hochtechnologie und Physik so vielfältig und kompakt. Wir werden in das Innenleben der Smartphones schauen, wo uns träge Mini-Massen, Corioliskraft, Hall-Effekt, Drucksensoren, viel Funktechnik und anderes mehr begegnen. All dies benutzen wir und machen klassische Experimente der Physik mit dem Smartphone als »Stuntman«. Vieles des Gezeigten wird man zu Hause nachmachen können – aber Vorsicht auch ein Stuntman kann sterben

Combining super-resolution microcopy with neuronal network recording using magnesium fluoride thin films as cover layer for multi-electrode array technology

We present an approach for fabrication of reproducible, chemically and mechanically robust functionalized layers based on MgF2 thin films on thin glass substrates. These show great advantages for use in super-resolution microscopy as well as for multi-electrode-array fabrication and are especially suited for combination of these techniques. The transparency of the coated substrates with the low refractive index material is adjustable by the layer thickness and can be increased above 92%. Due to the hydrophobic and lipophilic properties of the thin crystalline MgF2 layers, the temporal stable adhesion needed for fixation of thin tissue, e.g. cryogenic brain slices is given. This has been tested using localization-based super-resolution microscopy with currently highest spatial resolution in light microscopy. We demonstrated that direct stochastic optical reconstruction microscopy revealed in reliable imaging of structures of central synapses by use of double immunostaining of post- (homer1 and GluA2) and presynaptic (bassoon) marker structure in a 10 µm brain slice without additional fixing of the slices. Due to the proven additional electrical insulating effect of MgF2 layers, surfaces of multi-electrode-arrays were coated with this material and tested by voltage-current-measurements. MgF2 coated multi-electrode-arrays can be used as a functionalized microscope cover slip for combination with live-cell super-resolution microscopy

Superconducting beam charge monitors for antiproton storage rings

A Cryogenic Current Comparator (CCC) is a new type of instruments for monitoring charged beams like ions or antiprotons. Using superconducting effects is it possible to create a nondestructive, contactless and easy to calibrate beam measurement system with a high current resolution in amplitude and time. The Meissner effect enables an effective magnetic shielding of the system. The screening current enables creation of DC-transformers and therefore a DC-current measurement system. The combination of two Josephson-junctions and coils form a superconducting quantum interference device (SQUID) in an analog magnetic feedback of the flux-locked loop (FLL), which is linearizing the SQUID’s transfer function. The performance of the CCC system opens beam currents range between 1 nA and 20 µA. Installations at the Antiproton Decelerator at CERN and GSI in Darmstadt shows a strong correlation between SEM/longitudinal-Schottky and CCC signals including the known spill pattern but with a better signal to noise ratio

Axial Cryogenic Current Comparator (CCC) for FAIR

The Cryogenic Current Comparator (CCC) is a superconducting device based on an ultrasensitive SQUID (fT range). Measuring the beam¿s azimuthal magnetic field, it provides a calibrated non-destructive measurement of beam current with a resolution of 10 nA or better, independent from ion species and without tedious calibrations procedure. The non-interceptive absolute intensity measurement of weak ion beams ( 1 µA) is essential in heavy ion storage rings and in transfer lines at FAIR. With standard diagnostics, this measurement is challenging for bunched beams and virtually impossible for coasting beams. To improve the performance of the detector several upgrades are under study and development: One is the investigation of a new type of CCC using an alternative magnetic shield geometry. The so-called ‘axial¿ geometry will allow for much higher magnetic shielding factor, an increased pick-up area, and a lower low frequencies noise component. Further improvements and optimizations of the detector will be presented. The CCC will be tested on the beamline at the end of 2023 allowing to define the best possible version for FAIR

Cryogenic Current Comparators as Low Intensity Diagnostics for Ion Beams

The Cryogenic Current Comparator (CCC) is a SQUID based superconducting device for intensity measurement, firstly proposed as a beam diagnostics instrument in the 90s at GSI. After prove of principle the CCC was introduced into other facilities, attesting great potential for high resolution measurements but at the same time considerable mechanical and cryogenics challenges and costs. In the course of plannings for FAIR the CCC has been revitalized. Systematic investigations started, involving commercially available SQUID systems, which led to improvements of detector and cryostat. The developments resulted in nA spill measurements at GSI (2014) followed by the installation of a CCC in CERN Antiproton Decelerator (AD), which has in the meantime become a key instrument. Since then optimization of the device is ongoing, with respect to various operating conditions, system robustness, current resolution and last but not least system costs. Alternative CCC versions with improved magnetic shielding have been developed as well as ¿Dual Core‘ versions for background noise reduction. We give an overview of CCC optimization and development steps, with focus on applications at GSI and FAIR

Cryogenic Current Comparators as Low Intensity Diagnostics for Ion Beams

The Cryogenic Current Comparator (CCC) is a SQUID based superconducting device for intensity measurement, firstly proposed as a beam diagnostics instrument in the 90s at GSI. After prove of principle the CCC was introduced into other facilities, attesting great potential for high resolution measurements but at the same time considerable mechanical and cryogenics challenges and costs. In the course of plannings for FAIR the CCC has been revitalized. Systematic investigations started, involving commercially available SQUID systems, which led to improvements of detector and cryostat. The developments resulted in nA spill measurements at GSI (2014) followed by the installation of a CCC in CERN Antiproton Decelerator (AD), which has in the meantime become a key instrument. Since then optimization of the device is ongoing, with respect to various operating conditions, system robustness, current resolution and last but not least system costs. Alternative CCC versions with improved magnetic shielding have been developed as well as ¿Dual Core‘ versions for background noise reduction. We give an overview of CCC optimization and development steps, with focus on applications at GSI and FAIR