Abstract: The TESLA linear Collider would rely on superconducting structures at 1,3 GHz with a gradient of 25 MV/m and an unloaded quality factor at temperatures of 2 K.
However Nb Technology asks for superfluid e cooling systems. The use of a higher critical temperature superconductors would allow to adopt the simpler 4,2 K cryogenics.
V3Si has a reported Tc value of 17 K and RRR values up to 80 …. it follows –>
Author: Klaus Schirmer
Author: Matthias Bäcker ; Type of thesis: Foreign Institute Thesis
Due to their unique properties, plasmas have found a broad range of applications in biotechnology and biomedicine, including surface modification of implants and instruments by plasma activation or the deposition of specific diamond-like- and biocompatible structures. A completely new field is the investigation of plasma interaction with biological tissues and the exploration of potential applications.
In contrast to low pressure plasmas, atmospheric pressure plasmas can be operated more conveniently at ambient air and do not require costly vacuum systems. However, the physical properties of a plasma alter significantly with increasing pressure. Therefore, there is a steadily increasing interest in plasma-needles in recent years. These plasma- needles operate stably at atmospheric pressure without producing (filamentary) arcs, but are restricted to their size. Arcs can develop temperatures of several thousand degrees Kelvin and are therefore undesired. The construction of plasma-needle arrays can compensate the reduced effectiveness of a single plasma-needle. The low temperature of the back- ground gas and comparable high electron density of such plasma-needles offer manifold applications.
The objective of this work is the setup of a new atmospheric plasma device for the exploration of its diverse applications with focus on biomedical applications. With the help of comparable work and on the basis of preliminary experiments, a new plasma-needle has been fabricated. Subsequent, that plasma-needle was initially characterized and experimentally tested for thin film deposition and surface modification and is ready for tests on bacteria inactivation.
At first, a review of the state-of-the-art and current research on plasma-needles and their biomedical applications is given. The following two chapters deal with the basics of plasma physics, the experimental setup and the diagnostic tools as well as the principle of the plasma-needle. The results of the different measurements are presented and discussed in chapter five.
The following diagram is intended to help understanding the different steps of the work progress. After an introductory literature review, preliminary experiments with different plasma sources were executed. Thereupon, a prototype was constructed, which then was characterized and tested on two different possible applications, surface activation and carbon film deposition.
Author: Anila Gottschling ; Type of thesis: Foreign Institute Thesis
Abstract: Superconducting technology is becoming the standard route for supplying power to high-energy particle beams. Radiofrequency (RF) electric fields provide the motive power for high-energy accelerators. Superconducting Radio Frequency structures which are used for acceleration of low velocity ions are successfully operating in HERA at DESY (Germany), LEP at CERN (Switzerland) TRISTAN at KEK (Japan). A superconducting booster has the advantage that preserves the good quality of tandem beams and at the same time operating in CW (continuous work) mode has the capability to accept a high percentage of injected tandem current. The BCS surface resistance decreases rapidly at resonators of low frequencies and this permits operating at a temperature of 4,2 K (i.e. avoiding the use of expensive superfluid helium). The low b accelerating structures have been under development in the last two decades and this is related to their employment in energy boosters for …. please download the pdf file Continue reading
Author: MARION RIBEDEAU ; Type of thesis: Foreign Institute Thesis
Abstract: Continue reading
Author: Klaus Schirmer ; Type of thesis: Foreign Institute Thesis
Abstract: The TESLA linear Collider would rely on superconducting structures at 1,3 GHz with a gradient of 25 MV/m and an unloaded quality factor at temperatures of 2 K. However Nb Technology asks for superfluid e cooling systems. The use of a higher critical temperature superconductors would allow to adopt the simpler 4,2 K cryogenics. V3Si has a reported Tc value of 17 K and RRR values up to 80 …. it follows –> Continue reading
Author: ZHANG YAN ; Type of thesis: Foreign Institute Thesis
Abstract: Superconducting technique has been widely applied to linac particle accelerators for more than two decades. Cryogenic RF performance of SC cavities has been improved a lot due to improvement on purification of SC material, as well as SC cavity design, fabrication and surface treatment techniques. The Sputtering technique of SC cavities provided another chance to particle accelerators: the cost of cavity fabrication greatly decreased, while the performances of sputtering coated niobium cavities are competitive with those of bulk material SC cavities.
In this thesis some important features of RF cavities are briefly introduced; the difference in design of a SC cavity and that of a normal conducting cavity are indicated. The design parameters of a 144 MHz SC QWR and an 1.5GHz monocell spherical cavity are presented. The SC material for cavity fabrication, and measurement method of SC cavity are introduced, then the fabrication and surface treatment technique of SC cavities are discussed.
The application of sputtering technique in SC cavities is a recent development of SRF technique. After nearly two decades study, the sputtering coated niobium film SC cavities achieved a cryogenic RF performance close to that of bulk niobium cavities. The thesis introduced various sputtering techniques on this purpose from preliminary glow discharge, discusses the LNL, Peking University and Australia National University’s QWR sputtering configurations, and introduces LNL’s surface treatment technique for copper substrate cavity.
In the study of niobium sputtering for 1.5GHz monocell spherical cavity, different magnetron configurations were tried and measured a large amount of sputtered niobium samples. By improving the magnetron configuration and surface treatment technique of the substrate cavity, sputtered niobium cavities with better RF performance were obtained. It was found out that substrate surface treatment takes a very important role in the sputtering of a SC cavity, as sample measurement cannot give out helpful information of the RF performance, the study with substrate Continue reading
Author: JUERGEN BRODERS ; Type of thesis: Foreign Institute Thesis
Abstract: A cylindrical postmagnetron has been designed for sputtering Niobium films into 1,5 Ghz monocell Copper cavities of the TESLA-type.
For sputtering 1.5 GHz monocells we built a cylindrical post-magnetron . The idea under such a design was the search of high sputtering rates and high thickness uniformity of the coating sampled along the cavity profile. Higher sputtering rates respect to classical cylindrical magnetron are possible when sputtering from the whole target surface. The advantage is twofold: the fraction of impurities trapped in the film linearly decreases versus deposition rate, moreover the deposition takes shorter time.
On the other side for the classical cylindrical magnetron, when the discharge is switch on, plasma do not live simultaneously on the whole target surface, instead it is strictly confined onto the target surface portion where ionizing electrons are trapped by magnetic field lines. A large portion of target surface, the one just outside of the magnetic trap, reaches high temperatures as well, but there is not sputtering from it, unless the electromagnet is moved toward this region.
On the basis of our experience on cylindrical magnetrons of such a design, we have observed that films untouched by plasma have systematically worse purity than films immersed in the discharge. This problem becomes not important for postmagnetrons,since the whole target surface is sputtered simultaneously. When designing a post-magnetron two choiceswere possible: a) the cathode must follow the profile of the cavity, keeping the magnetic field lines constantly parallel to the target. End losses being avoided by an electrostatic mirror outside of the cavity. In this case the shape of the target is rather complicated since to get into the narrow bore of the cutoff,it must be collapsible. b) the cathode is a straight tube and
the magnetic field follows the shape of the cavity. Continue reading