Category: Master Thesis

Author: Li Jin Hai ; Type of thesis: Master Thesis
Abstract: The superconductor accelerator cavity is one of the most important and perspective technology for an advance accelerator. For example, the International Committee for Future Accelerators decided that the Linear Collider design had been based on the superconductor technology. Moreover, the accelerator operating with continue wave (CW) mode must use the superconductor technology in stead of the normal conductor technology, such as the Accelerator-driven sub-critical reactor system (ADS), the Accelerator Transmutation of Waste (ATW), the Accelerator Production of Tritium (APT), and so on.
In order to meet all kinds of application, the scientific world interest is now focus on further developments of new resonant cavities fabrication techniques to reduce cost and improve the performance of the accelerator cavity. To realize this object, one of the important methods is to pursue research on new materials. The goal will be the achievement of superconducting cavity working better the Nb ones at 4.2K. For example, the better parameters of the Tc, the surface resistance, the critical field Hc and the Q value are needed.
Up to now, the most possible candidate is Nb3Sn. The Nb3Sn has not only the better superconductivity parameters, but also the stable property and the easy fabrication. There are two methods to fabricate the superconductor cavity with the Nb3Sn, which are including the diffusion method and the multilayer deposition method. In the thesis, we focus on the multilayer deposition method, and …… Continue reading →

Author: Jahanfar Hanieh ; Type of thesis: Master Thesis
Abstract: 

The economic damages in the world because of corrosion are considered as one of the problems in economic developments . The global economic damages of corrosion is in the scale of billion dollars . Just in the US in one year the total economic damage because of corrosion is around a half of billion dollars ! .
As much as corrosion is dangerous and considerable, protection against corrosion is important which is seriously followed by researchers .
The word protective usually refers to the corrosion . The corrosion of metals typically takes place in the reinforced concrete. It happens when there is an anode where oxidation occurs, and a cathode where reduction occurs.
Considering the importance of protection against corrosion , my thesis project was started with one of the best methods of protection which is thin film deposition and with one of the most interesting protective material which is CeO2 .
Also its necessary to mention that another projects have been done in the superconductive laboratory of INFN in Legnaro with the object of deposition of CeO2 thin film as a protector but in the last project the used target has been CeO2 target and just a certain sputtering technique has been used so we decided to compare different sputtering techniques which was possible through using different power supplies and comparing them, with a more industrial target .This is why we chose Ce target and 4 different kinds of power supplies as DC, AC ,RF and Pulsed DC to be compared through using the main system which was reactive magnetron sputtering . By using the mentioned 4 power supplies and comparing them the most important parameters have been deposition rate and film stoichiometry as sensitive functions of reactive gas partial pressure .
Meanwhile as one of the examples of corrosion is oxidation of the copper coins we chose protection of coins as the main application for my thesis. Circulating mintage of copper coins (Like 1 , 2 or 5 cents) just in Italy have been around 400 million coins in 2009 . If we multiply this circulation to the cost of mintage new coins to be replaced with old ones which are usually effected by corrosion we can estimate a big economic damage in Italy because of corrosion So we decided to specifically apply our protection method to the Euro copper coins as a reasonable application. Continue reading →

Author: Chirkov Dmytro Vasiliovych ; Type of thesis: Master Thesis
Abstract: The main aim of this work is try to electrodeposit metallic niobium films from room-temperature ionic liquids.
Nowadays electrochemical surface treatment is one of the most used approaches in industry.
Aqueous solutions has been the most widely used process mainly because of advantages such us low cost, non-flammability, high solubility of electrolytes, high conductivities resulting in low ohmic losses, high solubility of metal salts and high rates of mass transfer. However, despite these advantages there are several limitations in using aqueous solutions such as limited potential windows, gas evolution processes that can result in hydrogen embrittlement, passivation of substrates, electrodes and deposits, and the necessity for hazardous complex agents such as cyanide, causing environmental contamination. These are the reasons why new non-aqueous solutions to electrodeposit niobium have been researched.
One of the main limitations in using aqueous solutions is their narrow electrochemical window. The major reason for carrying out electrodeposition in non-aqueous electrolytes (such as conventional organic solvents, molten salts or ionic liquids) is water and air stability and the wide electrochemical window of these media.
Alternatively, also high temperature molten salts have been used extensively for niobium electrodeposition. They have wide potential windows, high conductivities and high solubility for metal salts. In fact, they have most of the advantages of aqueous solutions and overcome most of the limitations of aqueous solutions, but their one major limitation is the very high temperature (more than 750°C).
Therefore, the alternative to high temperature molten salts was an ionic substance that melts at a low temperature. Over the last few decades, room temperature ionic liquids have been widely studied in various scientific fields due to their interesting properties, such as negligible vapour pressures, high chemical and thermal stability, acceptable intrinsic ionic conductivity and wide potential window.
Ionic liquids are molten salts with melting points below 100°C and they consist entirely of cations and anions. The development of ionic liquids, especially air and water stable types, has attracted extensive attention since they have outstanding physical properties.
The aim of this work will be the analysis of available literature data in order to have precise knowledge about niobium behavior in the different electrolytes and to get new information about possible electrolytes based on ionic liquids. Continue reading →

Author: Atroshchenko Konstantin ; Type of thesis: Master Thesis
Abstract: International Committee for Future Accelerators recommended that the Linear Collider design has to be based on the superconducting technology. And this is the reason why the international scientific society directed efforts to improving superconductive technology and reducing its cost.
In this work, in the framework of researching a valid alternative to Nb for RF superconducting cavities, thin film Nb3Sn has been investigated. The goal will be the achievement of superconducting cavities working better than the Nb ones at 4.2 K.
In order to improve the existing technology of substrates coating by thermally diffused Nb3Sn a new high temperature annealing technology has been developed. In the first part of the work, is given the short theoretical review of RF superconductivity, main superconductors that are used to be a good alternative to a pure Nb and fundamentals of the induction heating theory. Second part is dedicated to the existing double furnace technology, developed in the superconductivity lab in LNL. The influence of preliminary surface treatments like glow discharge of the sample, anodization and chemical etching on the quality of thermally diffused Nb3Sn was studied. And in the third part is given the description of the new induction heating system, suggested for annealing of the 6 GHz cavities. Also in the third part we will go through the results of coating samples and cavities with thermally diffused Nb3Sn with high temperature annealing and the results of the RF – test.
Finally, it is important to mention, that from the very beginning of investigation the induction heating for annealing 6 GHz cavities it became clear that the technology has an enormous potential in producing thermally diffused Nb3Sn. Continue reading →

Author: Yin Meng ; Type of thesis: Master Thesis
Abstract: Particle physics is now at the threshold of great discoveries. The experiments with particle accelerators and observations of the cosmos have focused attention on phenomena that can not be explained by the standard theory. The technology based on superconducting niobium accelerating cavities can reach a high expenditure of energy by many orders of magnitude lower than that of normal-conducting copper cavities. Even taking into account the power spent to maintain the temperature of liquid helium, the net gain in economic terms is still unassailable.
The sputtering technology was chosen first in the pure diode configuration and subsequently in the magnetron configuration. High Power Impulse Magnetron Sputtering (HIPIMS) is an evolution of the magnetron technique which relies on 100μs high voltage pulses of the order of 1 kV compared to the 300 V of the standard DC magnetron process. During the pulse a huge power density is deposited onto the target, of the order of a few kW/cm2 compared to a few W/cm2 of the standard DC process, producing a highly dense plasma in which also the Nb atoms are partially ionized. These can in turn be attracted to the substrate with a suitable bias. A further advantage of the technique lies in the fact that no hardware changes are required compared to a standard DC biased magnetron system, except for the obvious replacement of the power supply.
In this work, an R&D effort has been undertaken to study the HIPIMS, to improve it and understand the correlation between the parameters applied and the film morphology, the superconducting properties and the RF film quality.
The experiment system is based on the NEW HIGH-RATE SYSTEM for the deposition cavity 1.5 GHz. The experimental details and the measurements of the characteristics of the deposited films are described. Even though the work is still in progress, all of the partial results from now on have been analyzed and commented, in order to extrapolate all the information. The final results are a global overview of the HIPIMS techniques for Nb on 1.5Hz superconducting cavity. Suggestions for future efforts have been included as part of the conclusions. Continue reading →

Author: Acosta Gabriela ; Type of thesis: Master Thesis
Abstract: The subject of present Master Work is the thermomechanical design of a high power neutron converter for the SPIRAL2 Facility, which is being developed in collaboration with the INFN – Italy and GANIL – France.
The main objective is description of an general overview about the project and its main goals. The SPIRAL2 is a linear particle accelerator for the production of high intensity exotic ion beams. It will be under operation in the existing installations of the GANIL Institute in Caen, France. Therefore a neutron converter target has been designed and it must produce 1014 fissions/second, at a working temperature up to 1850°C. Available deuteron beam for the operation of this accelerator has a power up to 200 kW and all the calculations and tests around the main critical elements of the neutron converter module are explained in the next sections of this document. Continue reading →

Author: Rupp Vitalii Volodymyrovych ; Type of thesis: Master Thesis
Abstract: Electropolishing is one of the oldest electrochemical techniques which is widely adapted in industry. Since many years electropolishing has been growing and from day to day it fills more and more niches in different fields of science and technology. Among possible Surface Treatments, electropolishing occupies a key role, because it is the cleanest way for removing hundreds of microns of material. Most galvanic processes start their life from water solutions. Electropolishing is not an exception, even now Nb electropolishing based on water solution with sulfuric and hydrofluoric acids is the most used. Literature results with this standard mixture are excellent,
however the EP of thousands of cavities could become an industrial nightmare from the point of view of security at work. HF is not like other highly corrosive acids: if, by accident, it gets in contact with skin, pain is not felt, but F- ions begin to pass through, searching for the bone calcium.
Since many years world’s science has been interested in ionic liquids and it is not for nothing. A green chemistry based on ionic liquids has come to the fore, and at INFN-LNL laboratories was done the first Niobium electropolishing by a harmless mixture of Choline Chloride and urea heated around 150°C.
In my work I will try to study influence of adding to the mixture some regulators. While it has already been showed the possibility of Nb dissolving with electropolishing effect,I will try to find recipe for technological Nb electropolishing. My second goal is to have ready a
recipe to application on 6 GHz cavities. Continue reading →

Author: Lytovchenko Oleksiyi ; Type of thesis: Master Thesis
Abstract: Photovoltaics constitutes a new form of producing electric energy that is environmentally clean and very modular. In stand-alone installations, it must use storage or another type of generator to provide electricity when the sun is not shining.
Photovoltaics is very suitable as the power supply for remote communication equipment. Its use is increasing rapidly to produce electricity in grid-connected houses and buildings in industrialized countries, despite a 5 to 10 times higher cost than conventional electricity. Crystalline Si technology, both monocrystalline and multicrystalline is today clearly dominant, with about 90% of the market.
Thin-film technology is one of the candidates to take over from Si technology. There are many technological options regarding thin-film materials and methods of deposition but their primary claim to the throne currently occupied by Si is that they can be ultimately produced at much lower cost. Copper oxide is a good candidate for low cost photovoltaic element. It is non toxic and has high absobtion in visible spectra of light. In order to improve it performance doping methods and “partner” component for hetero- or homo –junction have to be studied.
In summary, it is very likely that photovoltaics will become in the next half century an important source of world electricity. Public support and global environmental concerns will keep photovoltaics viable, visible, and vigorous both in new technical developments and user applications. Nations which encourage photovoltaics will be leaders in this shining new technology, leading the way to a cleaner, more equitable twenty-first century, while those that ignore or suppress photovoltaics will be left behind in the green, economic energy revolution. Continue reading →

Author: Gonzalez, Winder A. ; Type of thesis: Master Thesis
Abstract: 

Vacuum coating processes use a vacuum environment and an atomic or molecular condensable vapor source to deposit thin films, typically less than 5µm in thickness. An example of such a process is magnetron sputtering where material is removed from a solid target by ion bombardment and deposited on a substrate in atomic layers. It is one of the most flexible and controllable methods of generating a metal vapour in vacuum. Applications include low friction coatings for tools, antireflective coatings on glass, semiconductors, decorative coatings e.g. bath taps, touch panel screens, car headlamps, telescope mirrors and coatings for photovoltaics.
A magnetron sputtering source is composed by a cathode, an anode and a combined electric and magnetic field. There are various types of magnetron depending on the application and the target efficiency required. Each type requires an optimized design of magnetic field to ensure operation of the magnetron source. As the price of raw materials becomes higher, the efficiency of the usage of the deposition materials also becomes an important concern.
The purpose of a magnetic field in a sputtering plasma is to increase the efficiency of ionization by capturing electrons emitted from the target to enlarge the rate of the collisions between electrons and neutral gas atoms. The lack of uniformity of the magnetic field produces a non-uniform plasma density, hence differential sputtering rates across the surface of the target. It is obvious that increasing uniformity of the magnetic field will improve the uniformity of the erosion of the target.
This thesis shows the setup of a d.c. magnetron sputtering configuration for a 4″ diameter Copper target, based on a computational study of different magnetic confinements, as well as with an optimization …..
of the erosion sputtered from the target. Continue reading →

Author: SERGEY SYNECHKO ; Type of thesis: Master Thesis
Abstract: Continue reading →