Oleg Malyshev - Academia.edu (original) (raw)

Papers by Oleg Malyshev

Damping rings are important subsystems of the International Linear Collider (ILC). In this paper,... more Damping rings are important subsystems of the International Linear Collider (ILC). In this paper, we consider the vacuum specifications that and consider possible vacuum system design solutions for these rings. Our aim is to find the optimum approach to the vacuum system technology in order to achieve the required vacuum levels with reasonable conditioning time. It turns out that the optimum vacuum design uses a NEG coated tubular vacuum chamber. In this case, since almost all inner surface of vacuum chamber will be NEG coated, the gas density along the beam does not depend on the choice of material for a vacuum chamber. The choice of vacuum chamber material between stainless steel, aluminium and copper is then driven by beam impedance, thermal conductivity requirement and cost.

Superconducting coatings for superconducting radio frequency (SRF) cavities is an intensively dev... more Superconducting coatings for superconducting radio frequency (SRF) cavities is an intensively developing field that should ultimately lead to acceleration gradients better than those obtained by bulk Nb RF cavities. ASTeC has built and developed experimental systems for superconducting thin-film deposition, surface analysis and measurement of Residual Resistivity Ratio (RRR). Nb thin-films were deposited by magnetron sputtering in DC or pulsed DC mode (100 to 350 kHz with 50% duty cycle) with powers ranging from 100 to 600 W at various temperatures ranging from room temperature to 800 °C on Si (100) substrates. The first results gave RRR in the range from 2 to 22 with a critical temperature Tc  9.5 K. Scanning electron microscopy (SEM), x-ray diffraction (XRD), electron back scattering diffraction (EBSD) and DC SQUID magnetometry revealed significant correlations between the film structure, morphology and superconducting properties.

The RF chamber wal quality. Ther material, sur the RF su University ha one face can flat plate. T... more The RF chamber wal quality. Ther material, sur the RF su University ha one face can flat plate. T network an approximatel If one cons factor Q0 of a where H is th of the cavi frequency of of a cavity b sample) whi otherwise h conveniently where G is defined as an sample and sample and c dissipated ov CE RES FO

Lawrence Berkeley National Laboratory, 2010

As part of the international Linear Collider (ILC) collaboration, we have compared the electron c... more As part of the international Linear Collider (ILC) collaboration, we have compared the electron cloud (EC) effect for different Damping Ring (DR) designs respectively with 6.4 km and 3.2 km circumference and investigated the feasibility of a shorter damping ring with respect to the electron cloud build-up and related beam instability. The studies for a 3.2 km ring were carried out with beam parameters of the ILC Low Power option. A reduced damping ring circumference has been proposed for the new ILC baseline design SB2009 [1] and would allow to considerably reduce the number of components, wiggler magnets and costs. We discuss the impact of the proposed operation of the ILC at high repetition rate 10 Hz and address the necessary modifications for the DRs. We also briefly discuss the plans for future studies including the luminosity upgrade option with shorter bunch spacing, the evaluation of mitigations and the integration of the CesrTA results into the Damping Ring design.

Bulk niobium cavities are widely employed in particle accelerators to create high accelerating gr... more Bulk niobium cavities are widely employed in particle accelerators to create high accelerating gradient despite their high material and operation cost. Advancements in technology have taken bulk niobium close to its theoretical operational limits, pushing the research to explore novel materials, such as niobium based alloys. Nitrides of niobium offer such an alternative, exhibiting a higher Tc compared to bulk niobium. Replacing then the niobium with a material with better thermal conductivity, such as copper, coated with thin films of nitrides in a multilayer S-I-S would lead to improved performance at reduced cost. Physical vapour deposition (PVD) is currently used to produce these coatings, but it suffers from lack of conformity. This issue can be resolved by using chemical vapour deposition (CVD), which is able to produce high quality coatings over surfaces with a high aspect ratio. This project explores the use of CVD techniques to deposit NbN thin films starting from their chl...

Non-Evaporable Getter (NEG) coating has been used for years in many particle accelerators due to ... more Non-Evaporable Getter (NEG) coating has been used for years in many particle accelerators due to its advantages like evenly distributed pumping speed, low thermal outgassing, and low photon, electron and ion stimulated desorption yields. Although NEG coating has been tested at room temperatures intensively, there is little data on its behaviour at cryogenic temperatures. Tests in this environment are important for the Future Circular Collider (FCC) study and other accelerator facilities where the operational conditions of the beam screen are restricted to cryogenic temperatures. This work will provide some preliminary results on NEG properties at low temperatures, e.g. pumping speed and capacity, as well as its behaviour under electron bombardment, where electron stimulated desorption (ESD) yields will be calculated. The ternary TiZr-V coating, deposited with dense and columnar structure, will be the first material to be tested at cryogenic temperatures in ASTeC Daresbury laboratory...

An ongoing study on the superconducting thin films for future superconducting RF cavities require... more An ongoing study on the superconducting thin films for future superconducting RF cavities requires an intense testing of various superconducting properties. We have designed, built and tested a new facility for complex superconducting thin film testing that includes: (1) RRR measurement with and without magnetic field, (2) planar and (3) tubular magnetic field penetration experiments, (4) a superconducting coaxial resonator for bulk niobium and superconducting thin film characterisation. The system is based on a closed cycle refrigerator, eliminating the need for liquid helium, thus making it simple and safe to operate. The details of the design and commissioning will be presented at the conference. INTRODUCTION The ASTeC team working on thin film superconducting RF (TF SRF) is developing the UK capability to coat TF SRF cavities. To meet this ambition, the team is working in a few directions: − Surface preparation before deposition (material choice, cleaning, polishing, etc.); − Th...

Bulk niobium cavities are widely employed in particle accelerators to create high accelerating gr... more Bulk niobium cavities are widely employed in particle accelerators to create high accelerating gradient despite their high material and operation cost. In order to reduce this cost, thin layer of niobium are deposited on a copper cavity, which has lower material cost with higher availability and more importantly higher thermal conductivity. The coating of superconducting cavities currently is synthesized by physical vapour deposition (PVD) method which suffers from lack of conformity. By using chemical vapour deposition (CVD) and plasma enhanced chemical vapour deposition (PECVD) it is possible to deposit thin Nb layers uniformly with density very close to bulk material. This project explores the use of PECVD / CVD techniques to deposit metallic niobium on copper using NbCl5 as precursor and hydrogen as a coreagent. The samples obtained were then characterized via SEM, TEM, SAD, XRD, XPS, and EDX as well as assessing their superconductivity characteristics (RRR and Tc) All the sampl...

The production of superconducting coatings for radio frequency cavities is a rapidly developing f... more The production of superconducting coatings for radio frequency cavities is a rapidly developing field that should ultimately lead to acceleration gradients greater than those obtained by bulk Nb RF cavities. Optimizing superconducting properties of Nb thin-films is therefore essential. Nb films were deposited by magnetron sputtering in pulsed DC mode onto Si (100) and MgO (100) substrates and also by high impulse magnetron sputtering (HiPIMS) onto Si (100), MgO (100) and polycrystalline Cu. The films were characterised using scanning electron microscopy, x-ray diffraction and DC SQUID magnetometry.

Non-evaporable getter (NEG) coating has been used for years in many particle accelerator faciliti... more Non-evaporable getter (NEG) coating has been used for years in many particle accelerator facilities due to its evenly distributed pumping speed, low thermal outgassing, and low photon and electron stimulated desorption yields. We have previously demonstrated that quaternary Ti-Zr-Hf-V coating deposited from an alloy wire has the lowest desorption yields, the highest sticking probability and sorption capacity. In this work, we explore the single element targets which are widely available and can be produced in a form of a wire that is easy to apply for a uniform coating of various shapes of vacuum chamber. Single metal Zr coatings have been tested to find a more efficient and cheaper way of producing the NEG-coated vacuum chambers. Two samples coated with Zr of dense and columnar structure were analysed and results of the pumping properties are reported. The results show that pure Zr coating could be an economic solution, despite not being as effective as can be achieved with quatern...

The source and transport system of the Karlsruhe Tritium Neutrino experiment (KATRIN) must provid... more The source and transport system of the Karlsruhe Tritium Neutrino experiment (KATRIN) must provide a significant reduction of tritium flow and gas density. It comprises a 10-m-long windowless source tube, where the tritium gas is injected, followed by a differential pumping system and a cryogenic pumping system. The primary challenge of the analysis is that the gas flow changes from a viscous flow regime inside the source tube to a transitional flow regime at the first pumping stage, and to a molecular flow regime at the remaining stages of the differential pumping system and further downstream. A strong molecular beaming effect must be considered. This paper presents the results of calculations of gas density and flow for the complete source and differential pumping system. It is shown that a total flow-rate reduction factor of 1.4·10 can be attained, which is one of the prerequisites to achieve extreme-high vacuum conditions in the spectrometers used in the downstream end of the e...

Civil and Environmental Engineering Reports

The features of the tectonic structure together with the geological and geomorphological zoning o... more The features of the tectonic structure together with the geological and geomorphological zoning of Kyiv city are highlighted in the article. Particular attention is paid to the floodplains of the Dnieper River, which were formed by the hydraulic fill method. As a rule, such sites were created for new constructions and were quickly built up with low rise buildings, the bases of which were made using such hydraulic soils. Completed engineering-geological investigations of sites after hydraulic filling and observation of the base deformation over time allowed setting of the basic regularity and rules for construction on such territories. The ongoing development of the city has also covered these territories, where high-rise buildings, shopping malls, and other buildings are actively being built, and the loads from these must be transferred to reliable bases.

Civil and Environmental Engineering Reports, Sep 26, 2017

This paper describes a series of pile tests in sand. T-cross and square cross section piles were ... more This paper describes a series of pile tests in sand. T-cross and square cross section piles were jacking by static vertical load with a vibration. Special tests were carried out to examine the influence of T-cross section pile form on it bearing capacity, and the results of comparison bearing capacity on one cub meter of T-cross and square cross section jacking piles in the same ground conditions are described. The jacking vertical static load, sizes of displacements and compaction zones of a ground around a shaft of the experienced piles were investigated.

Physical Review Accelerators and Beams

Cheminform, 2010

ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Proceedings of International Conference on Particle Accelerators, 1993

Experimental measurements of photodesorption coefficients of HZ, CH4, CO and CO2 are being done t... more Experimental measurements of photodesorption coefficients of HZ, CH4, CO and CO2 are being done to obtain data necessary to predict the vacuum performance of the Collider. Experiments have been done or are planned for warm tubes (i.e. room temperature), cold tubes (i.e. 4.2 K) and liner conligurations (i.e. 4.2 K, 20 K and 80 K). Two synchrotron radiation beamlines have been constructed on the VEPP-2M storage ring at BINP, Russia. The photon critical energy is 284 eV, as in the SSC Collider, angle of incidence is 10 mrad. To date approximately fifteen warm beam tubes have been tested, including electrodeposited Cu, high purity bulk Cu and Nitronic 40 SS, several cleaning procedures, with and without in-situ baking and with and without magnetic field. The maximum integrated photon dose was achieved was 2~102~ photons/m on the high intensity beamline. Several experiments have been done on the VUV ring at BNL to check a subset of the BINP data and to extend the integrated photon flux up to lO= photons/m, or 100 days of SSC operation. The data from the warm experiments will be used to evaluate the best tubes to be used in the more time consuming cold experiments.

Lawrence Berkeley National Laboratory, 2010

Bulk niobium cavities are widely employed in particle accelerators to create high accelerating gr... more Bulk niobium cavities are widely employed in particle accelerators to create high accelerating gradient despite their high material and operation cost. In order to reduce this cost, thin layer of niobium are deposited on a copper cavity, which has lower material cost with higher availability and more importantly higher thermal conductivity. The coating of superconducting cavities currently is synthesized by physical vapour deposition (PVD) method which suffers from lack of conformity. By using chemical vapour deposition (CVD) and plasma enhanced chemical vapour deposition (PECVD) it is possible to deposit thin Nb layers uniformly with density very close to bulk material. This project explores the use of PECVD / CVD techniques to deposit metallic niobium on copper using NbCl5 as precursor and hydrogen as a coreagent. The samples obtained were then characterized via SEM, TEM, SAD, XRD, XPS, and EDX as well as assessing their superconductivity characteristics (RRR and Tc) All the sampl...