Introduction Rhenium-186 (t1/2 = 3.72 d) is very attractive for use as a theranostic agent in targeted radionuclide therapy (Eβ max = 1.072 MeV (> 76.6 %); Eγ = 137.2 keV)1. Previously published investigations of high specific activity 186Re production have utilized the 186W(p,n)186Re or 186W(d,2n)186Re reactions2-5. Our group is interested in the refinement and scale-up of the production of high specific activity 186Re by cyclotron irradiations of 186W with deuterons; including investigations of the most suitable target material. WO3 has been successfully used as a target material in proton irradiations by two other groups4,5. Further, the physical properties of WO3, such as the reported monoclinic with Pc space group, body centered cubic crystal structure6 and melting point of 1473 °C, made for an attractive target material as sintered and other more structurally robust pressed pellet target preparations could be explored. Thus, this study reports on the characterization and suitability of WO3 as a full-thickness target material for the deuteron production of 186Re. Materials and Methods Assessments of WO3 for target material suitability and structural integrity were made on thick targets (~1 g) prepared using both commercially available and converted WO3 by either uniaxially pressing (13.8 MPa) of powdered WO3 into an aluminum target support or by placing sintered WO3 pellets (1105 °C for 12 hours) into an aluminum target support. In some experiments, WO3 pellets were prepared by dissolution of Wmetal with H2O2, then treatment with 1.5 M HCl. The recovered hydrated WO3 was calcinated at 800 °C for 4 hours, allowed to cool to ambient temperature, pulverized with a mortar and pestle, uniaxially pressed at 13.8 MPa into pellets with a 13 mm die, and subsequently sintered in a tube furnace under flowing Ar at 1105 °C for 3, 6, and 12 hours. Material characterization and product composition analyses were conducted with SEM, EDS, XRD, Raman spectroscopy, and visible photoluminescence spectroscopy. Thick WO3 targets were irradiated for 10 min at 10 µA with nominal extracted deuteron energies of 17 MeV. Gamma-ray spectroscopy was per-formed to assess production yields and radionuclidic byproducts at least 24 hours post EOB. Results While the color of the commercially available WO3 is slightly different (dull, pale green) than the brighter more yellow color of the chemically processed WO3, X-ray diffraction spectrometry (XRD) indicated the two samples were virtually identical. Attempts to determine how the duration of the sintering process (at 1105 °C) affects the chemical/physical nature of the pellet yielded surprising results. In contrast to the characteristic annealed appearance of sintered material, grains of the WO3 sample appeared more densely packed, but not sintered to one another as had been seen during higher temperature (1550 °C) reductions of WO3 irrespective of the time interval used. Full-thickness pressed or sintered pellets of WO3 were found to disintegrate upon irradiation with the deuteron beam, allowing for the direct irradiation of the aluminum target body producing 24Na as a contaminant. Upon retrieval of the target support it was observed that the WO3 had vaporized, discoloring the surface of the well in the target support and coating the walls of ~61 cm (24 inches) of the terminal portion of the beamline, which then required decontamination. We believe that these observations are the result of outgassing oxygen species that subsequently reacted with the aluminum target support. While these findings are in sharp contrast with the successful production yields and isolations previously reported by both Shigeta et al. and Fassbender et al., we believe that these differences are attributable to differences in target design (previous studies utilized an en-closed target with cooling in front of and behind the target) necessitated by the configuration of our target station. Conclusions. The physical properties of powdered WO3, including its lower melting point and more suitable compressibility than powdered Wmetal, seemed to enhance the structural integrity of a WO3 pellet (whether pressed or sintered). However, when compared to our recent successes with the use of Wmetal based targets, the disappointing degradation of our WO3 targets when irradiated with the incident deuteron beam has led us to believe that Wmetal is the more viable target material for 186Re production in our facility.

Introduction A new high current (up to 50 kW) solid target irradiation system is being built. While retaining the same beam power capability of the previous target generation, the system is a totally new design with many improvements, simplified constriction, more reliable operation and a novel approach to target handling, beam collimation and beam diagnostic. Unlike the previous, three-part soldered target, the new target is fabricated from a single piece of metal. Material and Methods The target (or rather the target-material holder) is a single metal plate (usually copper or silver) incorporating the seals and the cooling channels (FIG. 1). The target is placed in the beam at 7°. Depending on target material and coolant flow the target can handle beam powers up to 50 kW (FIG. 2). Target transfer (utilizing a special shuttle) is pneumatic. Part of the transfer pipe is shown above the target station. Except the target o-rings (a part of each target) there are no elastomer seals in the system; all is of soldered/welded construction and metal seals. Sectional view (FIG. 3.) shows that target in place in the chamber. The target and the chamber are electrically insulated from the rest of the system, thus forming a Faraday cup for accurate current measurement. The collimator is formed of a two part silver casting. It is designed to handle up to 10 kW of beam power. Four-sector silver mask in front of the collimator allows precise beam cantering. The collimator parts were cast using 3D printed wax patterns. This allowed to create a complex pattern of cooling channels that are difficult to produce by machining (FIG. 4.) All the actions of target shuttle landing and the target placing are performed by three air cylinders. All three are fitted with Vespel SP22 (Du Pond) seals. Unlike previous systems that used mechanical grabbers to manipulate the target, low vacuum is employed to hold the target during removal from the shuttle and placing in the irradiation chamber. This greatly simplifies the operation and is more reliable. The pneumatic transfer system is using two vacuum producer to transfer the target shuttle between the target station and the hotcell. Both landing terminals in the target station and hotcell, as well as the transfer line itself, are under negative pressure preventing any spread of contamination. The hotcell landing terminal incorporates a fully automatic target-material dissolution system. After landing, the target is removed from the shuttle and the active face pressed against a reaction vessel where the dissolution takes place (FIG. 5.) All the functions of target transfer, placing and manipulations are controlled by a simple PLC (FMD88-10 PLC, Triangle Research) Results and Conclusion While intended mostly for cladding with metallic target materials, a special version of the target was designed to handle salts or oxides that can be fused and retained in grooves on the target face (FIG. 6.) Despite the poor thermal conduc-tivity of most of those materials, this target can handle high beam currents. FIGURE 7 shows a thermal modelling of the cen-tral 10×25 mm segment of the target (highest heat flux region under a Gaussian beam). Copper target with rubidium chloride fused in 0.8 mm wide and 1.7 mm deep grooves and spaced by 0.5 mm (60% coverage). Beam of 70 MeV energy and 400 μA intensity is collimated 20 % (320 μA on target). Cooling-water flow is set to 25 l/min. Cladding the target face with a thin metallic layer can help containing the target material. This process is currently under development. Most aspects of the system operation and con-striction were successfully used in the previous “generations” of targets in the last 30 years. The new system will provide improved performance with a simpler and more reliable design, lower maintenance and lower consumables cost. FIGURE 8 shows the “4th generation” system and target (2005). Dozens variants of this design are in use all over the world.

Introduction Zr-89 is a useful radionuclide for radiolabeling proteins and other molecules.1,2 There are many reports of cyclotron production of 89Zr by the 89Y (p,n) reaction. Most irradiations use thin metal backed deposits of Y and irradiation currents up to 100 µA or thicker amounts of Y or Y2O3 with ~ 20 µA irradiations.3,4 We are working to develop high specific activity 89Zr using a low energy 11 MeV cyclotron. We have found that target Y metal contains carrier Zr and higher specific activities are achieved with less Y. The goal of this work was to optimize yield while minimizing the amount of Y that was irradiated. Material and Methods All irradiations were done using a Siemens Eclipse 11 MeV proton cyclotron. Y foils were used for the experiments described here. Y2O3 was tried and abandoned due to lower yield and poor heat transfer. Yttrium metal foils from Alfa Aesar, ESPI Metals and Sigma Aldrich, 0.1 to 1 mm in thickness, were tested. Each foil was irradiated for 10 to 15 minutes. The targets to hold the Y foils were made of aluminum and were designed to fit within the “paper burn” unit of the Siemen’s Eclipse target station, allowing the Y target body to be easily inserted and removed from the system. Several Al targets of 2 cm diam. and 7.6 cm long were tested with the face of the targets from 11, 26 or 90o relative to the beam to vary watts cm−2 on the foil. The front of the foils was cooled by He convection and the foil backs by conduction to the Al target body. The target body was cooled by conduction to the water cooled Al sleeve of the target holder. Results and Conclusion The best target was two stacked, 0.25 mm thick, foils to stop beam. 92% of the 89Zr activity was in the front 0.25 mm Y foil. With the greatest slant we could irradiate up to 30 µA of beam on tar-get. However, the 13×30 mm dimensions of the foil was more mass (0.41 g) and lower specific activity than was desired. Redesign of the target gave a target 90o to the beam with 12×12 mm foils (0.15 g/foil) that were undamaged with up to 30 µA irradiation when two foils were used. This design has a reduction in beam at the edges of ~10%. With this design, a single Y foil, 0.25 mm thick sustained over 31 µA of beam and a peak power on target of 270 watts cm−2. The product was radionuclidically pure 89Zr after all 89mZr and small amounts of 13N produced from oxygen at the surface had decayed (TABLE 1). Our conclusion is that the optimum target is a single 0.25 mm thick Y foil to obtain the greatest specific activity at this proton energy. This produces 167 MBq of 89Zr at EOB with a 15 minute and 31 µA irradiation. We are continuing to redesign the clamp design to reduce losses at the edge of the beam.

Introduction Rhenium-186 (t1/2 = 3.72 d) is very attractive for use as a theranostic agent in targeted radionuclide therapy (Eβ max = 1.072 MeV (> 76.6 %); Eγ = 137.2 keV)1. Previously published investigations of high specific activity 186Re production have utilized the 186W(p,n)186Re or 186W(d,2n)186Re reactions2-5. Our group is interested in the refinement and scale-up of the production of high specific activity 186Re by cyclotron irradiations of 186W with deuterons; including investigations of the most suitable target material. WO3 has been successfully used as a target material in proton irradiations by two other groups4,5. Further, the physical properties of WO3, such as the reported monoclinic with Pc space group, body centered cubic crystal structure6 and melting point of 1473 °C, made for an attractive target material as sintered and other more structurally robust pressed pellet target preparations could be explored. Thus, this study reports on the characterization and suitability of WO3 as a full-thickness target material for the deuteron production of 186Re. Materials and Methods Assessments of WO3 for target material suitability and structural integrity were made on thick targets (~1 g) prepared using both commercially available and converted WO3 by either uniaxially pressing (13.8 MPa) of powdered WO3 into an aluminum target support or by placing sintered WO3 pellets (1105 °C for 12 hours) into an aluminum target support. In some experiments, WO3 pellets were prepared by dissolution of Wmetal with H2O2, then treatment with 1.5 M HCl. The recovered hydrated WO3 was calcinated at 800 °C for 4 hours, allowed to cool to ambient temperature, pulverized with a mortar and pestle, uniaxially pressed at 13.8 MPa into pellets with a 13 mm die, and subsequently sintered in a tube furnace under flowing Ar at 1105 °C for 3, 6, and 12 hours. Material characterization and product composition analyses were conducted with SEM, EDS, XRD, Raman spectroscopy, and visible photoluminescence spectroscopy. Thick WO3 targets were irradiated for 10 min at 10 µA with nominal extracted deuteron energies of 17 MeV. Gamma-ray spectroscopy was per-formed to assess production yields and radionuclidic byproducts at least 24 hours post EOB. Results While the color of the commercially available WO3 is slightly different (dull, pale green) than the brighter more yellow color of the chemically processed WO3, X-ray diffraction spectrometry (XRD) indicated the two samples were virtually identical. Attempts to determine how the duration of the sintering process (at 1105 °C) affects the chemical/physical nature of the pellet yielded surprising results. In contrast to the characteristic annealed appearance of sintered material, grains of the WO3 sample appeared more densely packed, but not sintered to one another as had been seen during higher temperature (1550 °C) reductions of WO3 irrespective of the time interval used. Full-thickness pressed or sintered pellets of WO3 were found to disintegrate upon irradiation with the deuteron beam, allowing for the direct irradiation of the aluminum target body producing 24Na as a contaminant. Upon retrieval of the target support it was observed that the WO3 had vaporized, discoloring the surface of the well in the target support and coating the walls of ~61 cm (24 inches) of the terminal portion of the beamline, which then required decontamination. We believe that these observations are the result of outgassing oxygen species that subsequently reacted with the aluminum target support. While these findings are in sharp contrast with the successful production yields and isolations previously reported by both Shigeta et al. and Fassbender et al., we believe that these differences are attributable to differences in target design (previous studies utilized an en-closed target with cooling in front of and behind the target) necessitated by the configuration of our target station. Conclusions. The physical properties of powdered WO3, including its lower melting point and more suitable compressibility than powdered Wmetal, seemed to enhance the structural integrity of a WO3 pellet (whether pressed or sintered). However, when compared to our recent successes with the use of Wmetal based targets, the disappointing degradation of our WO3 targets when irradiated with the incident deuteron beam has led us to believe that Wmetal is the more viable target material for 186Re production in our facility.

Introduction A new high current (up to 50 kW) solid target irradiation system is being built. While retaining the same beam power capability of the previous target generation, the system is a totally new design with many improvements, simplified constriction, more reliable operation and a novel approach to target handling, beam collimation and beam diagnostic. Unlike the previous, three-part soldered target, the new target is fabricated from a single piece of metal. Material and Methods The target (or rather the target-material holder) is a single metal plate (usually copper or silver) incorporating the seals and the cooling channels (FIG. 1). The target is placed in the beam at 7°. Depending on target material and coolant flow the target can handle beam powers up to 50 kW (FIG. 2). Target transfer (utilizing a special shuttle) is pneumatic. Part of the transfer pipe is shown above the target station. Except the target o-rings (a part of each target) there are no elastomer seals in the system; all is of soldered/welded construction and metal seals. Sectional view (FIG. 3.) shows that target in place in the chamber. The target and the chamber are electrically insulated from the rest of the system, thus forming a Faraday cup for accurate current measurement. The collimator is formed of a two part silver casting. It is designed to handle up to 10 kW of beam power. Four-sector silver mask in front of the collimator allows precise beam cantering. The collimator parts were cast using 3D printed wax patterns. This allowed to create a complex pattern of cooling channels that are difficult to produce by machining (FIG. 4.) All the actions of target shuttle landing and the target placing are performed by three air cylinders. All three are fitted with Vespel SP22 (Du Pond) seals. Unlike previous systems that used mechanical grabbers to manipulate the target, low vacuum is employed to hold the target during removal from the shuttle and placing in the irradiation chamber. This greatly simplifies the operation and is more reliable. The pneumatic transfer system is using two vacuum producer to transfer the target shuttle between the target station and the hotcell. Both landing terminals in the target station and hotcell, as well as the transfer line itself, are under negative pressure preventing any spread of contamination. The hotcell landing terminal incorporates a fully automatic target-material dissolution system. After landing, the target is removed from the shuttle and the active face pressed against a reaction vessel where the dissolution takes place (FIG. 5.) All the functions of target transfer, placing and manipulations are controlled by a simple PLC (FMD88-10 PLC, Triangle Research) Results and Conclusion While intended mostly for cladding with metallic target materials, a special version of the target was designed to handle salts or oxides that can be fused and retained in grooves on the target face (FIG. 6.) Despite the poor thermal conduc-tivity of most of those materials, this target can handle high beam currents. FIGURE 7 shows a thermal modelling of the cen-tral 10×25 mm segment of the target (highest heat flux region under a Gaussian beam). Copper target with rubidium chloride fused in 0.8 mm wide and 1.7 mm deep grooves and spaced by 0.5 mm (60% coverage). Beam of 70 MeV energy and 400 μA intensity is collimated 20 % (320 μA on target). Cooling-water flow is set to 25 l/min. Cladding the target face with a thin metallic layer can help containing the target material. This process is currently under development. Most aspects of the system operation and con-striction were successfully used in the previous “generations” of targets in the last 30 years. The new system will provide improved performance with a simpler and more reliable design, lower maintenance and lower consumables cost. FIGURE 8 shows the “4th generation” system and target (2005). Dozens variants of this design are in use all over the world.

Eine wesentliche Voraussetzung für eine weitere Erhöhung der Speicherdichte von Magnetspeicherplatten ist, dass der Abstand zwischen den Schreib-Lese-Köpfen und der informationstragenden Magnetschicht der Platte von derzeit 20 nm weiter verringert wird. Dies bedeutet, dass die Deckschicht, die die magnetische Schicht der Platte und die Sensoren der Köpfe vor Korrosion und Verschleiß schützt, nicht dicker als 2 – 3 nm sein darf. Die bisher in der Festplattenfertigung magnetrongesputterten Kohlenstoffnitridschichten (CNx) bilden allerdings nur bis hinab zu einer Schichtdicke von etwa 4 nm eine ausreichend geschlossene Schicht und verlieren deshalb unterhalb dieser Grenze ihren Korrosionsschutz. Ein Beschichtungsverfahren, das auch im Sub-4-nm-Bereich noch ausreichend dicht geschlossene Schichten erzeugt ist die kathodische Vakuumbogenverdampfung (Cathodic Arc). Die mit diesem Verfahren abgeschiedenen amorphen Kohlenstoffschichten zeichnen sich zudem durch gute mechanische Eigenschaften aus. Dabei können die gegenüber den herkömmlichen Verfahren höher energetischen Teilchen viel tiefer in die oberste Atomlage eindringen und auf diese Weise eine eng mit der Unterlage verzahnte, dichte und glatte Schicht bilden. In der vorliegenden Arbeit wird eine gepulste Hochstrom-Bogenquelle zur Abscheidung von ultradünnen, harten Kohlenstoff-Schutzschichten auf Magnetspeicherplatten untersucht. Hierzu wurde eine speziell für diesen Einsatz modifizierte Hochstrom-Bogenquelle in eine Plattenfertigungsanlage bei IBM angeschlossen und in iterativen Schritten für einen kontinuierlichen Prozess einer industriellen Massenproduktion optimiert. Die Erzeugung eines homogen glatten Schichtdickenprofils über eine Substratoberfläche mit einem Durchmesser von 95mm konnte durch die Entwicklung eines magnetischen Multipolarrays erreicht werden. Die Partikelproblematik des Arc-Verfahrens konnte durch die Konstruktion und Optimierung eines magnetischen 120°-Plasmafilters, der die Partikel wirkungsvoll vom Plasmastrahl separiert, gelöst werden. Neben der technischen Weiterentwicklung der Hochstrom-Bogenquelle wurden die in der Produktionsumgebung erzeugten Kohlenstoffschichten hinsichtlich ihrer mechanischen und anwendungsspezifischen Eigenschaften untersucht und durch gezielte Wahl der Prozessparameter optimiert.

Introduction Zr-89 is a useful radionuclide for radiolabeling proteins and other molecules.1,2 There are many reports of cyclotron production of 89Zr by the 89Y (p,n) reaction. Most irradiations use thin metal backed deposits of Y and irradiation currents up to 100 µA or thicker amounts of Y or Y2O3 with ~ 20 µA irradiations.3,4 We are working to develop high specific activity 89Zr using a low energy 11 MeV cyclotron. We have found that target Y metal contains carrier Zr and higher specific activities are achieved with less Y. The goal of this work was to optimize yield while minimizing the amount of Y that was irradiated. Material and Methods All irradiations were done using a Siemens Eclipse 11 MeV proton cyclotron. Y foils were used for the experiments described here. Y2O3 was tried and abandoned due to lower yield and poor heat transfer. Yttrium metal foils from Alfa Aesar, ESPI Metals and Sigma Aldrich, 0.1 to 1 mm in thickness, were tested. Each foil was irradiated for 10 to 15 minutes. The targets to hold the Y foils were made of aluminum and were designed to fit within the “paper burn” unit of the Siemen’s Eclipse target station, allowing the Y target body to be easily inserted and removed from the system. Several Al targets of 2 cm diam. and 7.6 cm long were tested with the face of the targets from 11, 26 or 90o relative to the beam to vary watts cm−2 on the foil. The front of the foils was cooled by He convection and the foil backs by conduction to the Al target body. The target body was cooled by conduction to the water cooled Al sleeve of the target holder. Results and Conclusion The best target was two stacked, 0.25 mm thick, foils to stop beam. 92% of the 89Zr activity was in the front 0.25 mm Y foil. With the greatest slant we could irradiate up to 30 µA of beam on tar-get. However, the 13×30 mm dimensions of the foil was more mass (0.41 g) and lower specific activity than was desired. Redesign of the target gave a target 90o to the beam with 12×12 mm foils (0.15 g/foil) that were undamaged with up to 30 µA irradiation when two foils were used. This design has a reduction in beam at the edges of ~10%. With this design, a single Y foil, 0.25 mm thick sustained over 31 µA of beam and a peak power on target of 270 watts cm−2. The product was radionuclidically pure 89Zr after all 89mZr and small amounts of 13N produced from oxygen at the surface had decayed (TABLE 1). Our conclusion is that the optimum target is a single 0.25 mm thick Y foil to obtain the greatest specific activity at this proton energy. This produces 167 MBq of 89Zr at EOB with a 15 minute and 31 µA irradiation. We are continuing to redesign the clamp design to reduce losses at the edge of the beam.

In dieser Arbeit werden versilberte Hochstrom-Steckverbindungen mit Kontaktelementen betrachtet, die in der Elektroenergieversorgung bei Belastung mit Fehlerströmen im Bereich von 24 µs bis 5 s eingesetzt werden. Am Flach- und Rundeinbau der Kontaktelemente werden Kurzschlussversuche im Bereich von (0,01…5) s durchgeführt. Der Kurzschlussstrom erwärmt die Steckverbindung und die Kontaktelemente innerhalb dieser Zeit auf mehrere 100 °C und führt zu einer thermisch aktivierten Schädigung. Dabei baut sich die Kontaktkraft durch Spannungsrelaxation zum Teil ab, und es kann zum Verschweißen der Mikrokontakte und Blasenbildung durch lokales Ablösen der Be-schichtung kommen. Bei einer zu starken Schädigung kann ein sicherer Betrieb der Steckverbindung nicht mehr si-chergestellt werden. Daher werden für die Mechanismen der Schädigung Grenzwerte festgelegt und eine maximale Belastung definiert. Ausgehend von den experimentellen Untersuchungen wird ein Berechnungsmodell auf Basis der Finiten-Elemente-Methode weiterentwickelt. Ein vereinfachtes Widerstandsmodell der Punktkontakte abhängig von Kontaktkraft und Kontakthärte bildet dabei das Verhalten der Mikrokontakte nach. Da das Verhalten der Kontakthärte bei starker Erwärmung im ms-Bereich nur unzureichend erforscht ist, werden aus Experimenten näherungsweise die benötigten Parameter bestimmt. Mit dem erweiterten Berechnungsmodell ist es möglich, die thermische Wirkung praktischer Kurzschlussversuche nachzubilden. Eine wesentliche Erkenntnis ist, dass die Höhe des Stoßstroms zu Beginn des Kurzschlusses einen entscheidenden Einfluss auf die maximale Erwärmung hat. Bei sehr hohen Stoßströmen am Anfang eines Kurzschlusses wird der Kontaktwiderstand stark reduziert. Für den weiteren Verlauf des Kurzschlusses entsteht in den Kontakten daher weniger Wärme, als wenn diese Reduktion nicht stattfindet. Das bedeutet, dass DC-Kurzschlüsse unter Umständen zu einer höheren thermischen Belastung und mechanischen Schädigung führen können als AC-Kurzschlüsse mit gleichem Effektivwert. Experimente bestätigen diese Theorie. Dies gilt allerdings nur, wenn der Stoßstrom nicht zum sofortigen Verschweißen der Kontakte führt. Anhand der Erkenntnisse aus den Experimenten und Berechnungen werden Empfehlungen für die Auslegung und die Prüfung von Hochstrom-Steckverbindungen gegeben. Es zeigte sich, dass das für Prüfungen oft verwendete I2t-Kriterium bei Steckverbindungen nur sehr eingeschränkt anwendbar ist. Die Kurzschlussdauer kann damit nur um ca. (13…17) % verändert werden, ohne dass sich die Beanspruchung in der Prüfung unzulässig ändert. Alternativ schlägt die Arbeit das Ixt-Kriterium vor. Dieses lässt es bei bekannter Geometrie der Steckverbindung zu, einen Prüfstroms in einem vielfach größeren Zeitbereich einzustellen und erzeugt dabei eine vergleichbare thermische Beanspruchung oder mechanische Schädigung. Ein Erwärmen der Steckverbindung auf die maximal zulässige Betriebstemperatur vor dem Kurzschluss, was bei-spielsweise bei einem Fehler im realen Betrieb stattfinden kann, hat einen vergleichsweise geringeren Einfluss auf die Erwärmung und die mechanische Schädigung. Hintergrund ist, dass die Vorerwärmung zu einer Reduktion der Kon-takthärte führt und damit große Kontaktflächen erzeugt, die einen geringen Kontaktwiderstand haben. Hierdurch entsteht weniger Verlustleistung, was die Erwärmung der Steckverbindung reduziert. Aus den gewonnen Erkenntnissen werden Empfehlungen für die Auslegung, Prüfung und die Modellierung des Kurz-schlussverhaltens von Steckverbindungen mit Kontaktelementen für die Elektroenergieversorgung abgeleitet. / In this thesis, silver plated plug-in connectors for electrical power supply under short time current load are investigat-ed. The duration of the short time or short circuit current load is between 24 µs and 5 s. Both flat and round model plug-in connectors are stressed with the short time current. This current heats the plug and socket as well as the contact elements by several hundred Kelvin, which can lead to thermally induced damages. These may include a reduction of the contact force, welding of the contact points and blistering of the coating. If the damage is too severe, safe operation at the rated continuous current may not be able after the short circuit. Thus, limiting loads are defined which ensure a safe operation. Based on the experiments, a finite element model is refined. A simplified model of contact points is used to imple-ment the contact behaviour. This model implements the overtemperature in the contacts, the contact hardness and the contact force into the calculation. In fact, few data for load in the range of milliseconds are available on this matter. Hence, experiments are used for an approximation of the required parameters. The refined model allows for a good correlation between experiments and calculated data. A key finding is that the magnitude of peak current at the beginning of the short circuit has a decisive influence on the maximum heating. In case of a very high peak current at the beginning of a short circuit, the contact resistance is greatly reduced. For the further course of the short-circuit, therefore, less heat is generated in the contacts than if this reduction did not take place. This means that DC short circuits can under certain circumstances lead to higher thermal stress and mechanical damage than AC short circuits with the same RMS value. This is only valid if the peak current does not heat the contact points up to their welding temperature. Experiments confirm this theory. Recommendations for the dimensioning and testing of high current connectors are given on the basis of the experi-ments and the calculations. It was shown that the I²t-criterion, which is often used for altering the test duration in recommended standards, can only be applied to a very limited extent. The short circuit duration can only be changed by about (13…17) % or otherwise the severity of the mechanical damage is likely to change as well. As an alternative, it is proposed to use the newly introduced Ixt-criterion. If the geometry of the connector is known, this criterion allows alternating the short circuit duration in a broader range without major changes in the severity of the test. In a real world application, short circuits may occur while the connectors are under heavy load, which means that at the beginning of the short time current, the connector is preheated. Tests showed that this has only a minor impact on the temperature rise and the mechanical damage of the contact elements. The reason for this behaviour is that, due to the preheating, the hardness of the contact material drops and the contact area is enlarged. This results in a comparatively lower contact resistance and less power loss is generated. This reduces the influence of the higher start-ing temperatures to a certain degree. On the basis of the findings, recommendations are derived for the design, testing and modelling of the short-circuit behaviour of connectors with contact elements for electrical power supply.

Eine wesentliche Voraussetzung für eine weitere Erhöhung der Speicherdichte von Magnetspeicherplatten ist, dass der Abstand zwischen den Schreib-Lese-Köpfen und der informationstragenden Magnetschicht der Platte von derzeit 20 nm weiter verringert wird. Dies bedeutet, dass die Deckschicht, die die magnetische Schicht der Platte und die Sensoren der Köpfe vor Korrosion und Verschleiß schützt, nicht dicker als 2 – 3 nm sein darf. Die bisher in der Festplattenfertigung magnetrongesputterten Kohlenstoffnitridschichten (CNx) bilden allerdings nur bis hinab zu einer Schichtdicke von etwa 4 nm eine ausreichend geschlossene Schicht und verlieren deshalb unterhalb dieser Grenze ihren Korrosionsschutz. Ein Beschichtungsverfahren, das auch im Sub-4-nm-Bereich noch ausreichend dicht geschlossene Schichten erzeugt ist die kathodische Vakuumbogenverdampfung (Cathodic Arc). Die mit diesem Verfahren abgeschiedenen amorphen Kohlenstoffschichten zeichnen sich zudem durch gute mechanische Eigenschaften aus. Dabei können die gegenüber den herkömmlichen Verfahren höher energetischen Teilchen viel tiefer in die oberste Atomlage eindringen und auf diese Weise eine eng mit der Unterlage verzahnte, dichte und glatte Schicht bilden. In der vorliegenden Arbeit wird eine gepulste Hochstrom-Bogenquelle zur Abscheidung von ultradünnen, harten Kohlenstoff-Schutzschichten auf Magnetspeicherplatten untersucht. Hierzu wurde eine speziell für diesen Einsatz modifizierte Hochstrom-Bogenquelle in eine Plattenfertigungsanlage bei IBM angeschlossen und in iterativen Schritten für einen kontinuierlichen Prozess einer industriellen Massenproduktion optimiert. Die Erzeugung eines homogen glatten Schichtdickenprofils über eine Substratoberfläche mit einem Durchmesser von 95mm konnte durch die Entwicklung eines magnetischen Multipolarrays erreicht werden. Die Partikelproblematik des Arc-Verfahrens konnte durch die Konstruktion und Optimierung eines magnetischen 120°-Plasmafilters, der die Partikel wirkungsvoll vom Plasmastrahl separiert, gelöst werden. Neben der technischen Weiterentwicklung der Hochstrom-Bogenquelle wurden die in der Produktionsumgebung erzeugten Kohlenstoffschichten hinsichtlich ihrer mechanischen und anwendungsspezifischen Eigenschaften untersucht und durch gezielte Wahl der Prozessparameter optimiert.