Application of the magnetron sputtering technique for the deposition of niobium onto copper RF cavities for particle accelerators – Master Thesis Andrii Tsymbaliuk

Author: Andrii Tsymbaliuk ; Type of thesis: Master Thesis
Abstract: Niobium cavities will be used for super conductive particle accelerators. One of the main challenges is replacing Nb bulk cavities onto Cu cavities, sputtered by the thick Nb layer. In order to improve technology of vacuum sputtering Nb onto copper cavities, the researching work was held.
Many research institutions have studied the sputtering technology applied to complex substrates. The development of the deposition of Niobium onto copper cavities started at CERN from 1980, as a method to replace bulk cavities. Then, at Legnaro National Laboratories (LNL), since 1987 it has been studied the bias diode sputtering in order to deposit Niobium onto copper QWRs for the construction of ALPI accelerator, obtaining positives results: good film uniformity and good performance but lower deposition rates in comparison with other techniques such as magnetron sputtering technique. The magnetron sputtering is a deposition technique widely used in the thin film industry because of advantages of this method.
In the Legnaro National Laboratories were developed three different types of cavities: TESLA-type 9-cell RF cavities, Quarter Wave Resonators, 6 GHz cavities. For each type different magnetron sputtering technique is applied. The aim of the investigation is to analyse the influence of the different magnetron configurations on the Nb sputtering for every type of the developed cavities.

Upgrading of silver edible coatings on cardamom seeds – Master Thesis Vanessa Andreina Garcia Diaz

Author: Vanessa Andreina Garcia Diaz ; Type of thesis: Master Thesis
Abstract: In this work, Cardamom seeds were coated with silver by the Magnetron Sputtering technique. Twenty (20) processes were tested in different ways with wet and dry treatments and then sputtered. The wet treatment was made in order to reduce the size of a sugar buffer coating of the seeds, while surface treatments were applied to improve the aspect of the seeds. The parameters of deposition were 0,2 and 0,15 A of current for the cathode, 5×10-3 mbar pressure of work and the other parameters depend on the samples. The aim of the work was based on obtaining cardamom seeds with a silver coating that has silver appearance and small size. The ideal aspect of the seeds and their sizes are to be similar to the usual Cardamom seeds on the market. For this reason the seeds had a sugar and water layer that avoid degassing from the seeds. A dissolution of this covering was made to reduce their sizes (wet process) and a dry tumbling treatment was applied before deposition process to improve the coating.

Chemical and electrochemical treatments for accelerating cavities – Master Thesis Eduard Chyhyrynets

Author: Eduard Chyhyrynets ; Type of thesis: Master Thesis
Abstract: During my master course I worked mainly in chemical laboratory to proceed chemical and electrochemical treatment protocols that involve several steps, and they vary from Niobium 6 GHz cavities to modeling square copper samples.
My main task was dedicated to the learning different techniques, that were applied to the problem of ARIES project, that makes the second part of this thesis. Here is the list of techniques: electropolishing, chemical polishing, cleaning processes and SEM, EDS, profilometer equipment.
To investigate the role of the substrate in the SRF performances, several surface treatments were applied to a certain amount of copper samples. Here is a list of the treatments involved: chemical polishing, electropolishing, combination of chemical and electrochemical treatment and to mechanical treatment (tumbling). The quality of the sample’s surface were studied and evaluated by visual observation, under SEM, EDS, profilometer and by calculating average removal thickness.
The protocol optimization was done on flat samples in order to study the critical points of the processes and avoid wasting the real samples. In the nearest future, the quality of the work will be evaluated by comparing the performance of Nb thin film on different substrate preparation.

Brazing of Alumina/304 Stainless Steel for rotating joint applications – Master Thesis Davide Carniani

Author: Davide Carniani; Type of thesis: Master Thesis
Abstract: Mechanical face seal is a type of seal widely used in rotating equipment. They apply in all instances where movement is required, from robotics to automotive. Among the many existing fields of application, pumping systems are quite demanding in terms of performance, especially when the device has to be used in harsh environments.
The aim of the project was the development of the process for alumina (Al2O3) and 304 stainless steel in one piece for the realization mechanical systems (mechanical face seals) working in chemically aggressive environments.
Vacuum brazing technique was selected as joining technique to overcome incompatibility in the nature of chemical bonds of the materials involved. Home-made copper-based active brazing alloy (ABA) prepared starting from powders and binder was used to join two materials. A custom oven heated by IR-lamp until 1000°C was used to perform the brazing process.
The objective of the work was to study the process parameters: time of brazing, ramps of heating and cooling, temperature of brazing, issues in the join of chemically and thermo-mechanically different materials, amount of ABA to be applied and types of the binder.
Particular attention was given to the binder, changing the ease of brazing paste application and paste stability during storage, which are important factors for the industrialization of the process.
The process developed was shown to provide good integrity of the samples produced.

Innovative PVD technologies for depositing superconducting Nb films into TESLA-type 9-cell RF cavities for particle accelerators – Giorgio Keppel PhD Thesis

Author: Giorgio Keppel; Type of thesis: PhD Thesis
Abstract: Superconducting radiofrequency resonators have become standard components inside particle accelerators. This paper proposes the research and development of copper cavities internally coated with a niobium thin film, as an alternative to the niobium bulk cavities. This R&D work is part of the ISIDE experiment, of the National Institute of Nuclear Physics, and has been carried out at the Legnaro laboratories. Specifically, at the Material Science and Technologies for Nuclear Physics Service of INFN, it has been built a new system for coating, via magnetron sputtering, a thin film of superconducting niobium inside the TESLA-type 9-cell copper resonators. The work was divided into two main areas. A first phase consisted on the design of a sputtering configuration for coating superconductive cavities based on the construction of a vacuum system using a 3D CAD software and FEM simulations in order to verify the final structure of the vacuum system. Parallel to this a phase for the construction of the induction heating apparatus was followed. Afterward, the assembly of the vacuum system was performed, with connected vacuum tests, and followed by the commissioning of the induction and pumping systems. A second phase, however, focused on the study of coating configurations, particularly on the benefits and/or problems that each configuration can lead. This study ended with the design of four different coating configurations; which will be short-tested in order to check the most suitable for coating the 9-cell copper cavity with good uniformity and excellent superconducting properties. The most promising configuration is definitely the last taken into account, which involves the use of the inductor to heat the cavity during the process and the use of an innovative cylindrical magnetron with a rotating magnet pack inside that confine the plasma on the target surface. The target consists on a Niobium tube, and the study of the magnetic configuration and at the same time rotation of magnet pack permit to have a constant deposition rate along the whole cavity (high cathode erosion rate in the cavity cell regions and low cathode erosion rate along cavity cut-off). Even if the work is still evolving and the deposition tests are just starting, what as been performed is definitely innovative and original; up to now, in literature, there are no reports of coating performed by coupling the induction heating with the magnetron sputtering. The development of a plant that allows coupling these two technologies is the main aim of this work.