On fundamental diffraction limitation of finesse of a Fabry-Perot cavity

We perform a theoretical study of finesse limitations of a Fabry-Perot (FP) cavity occurring due to finite size, asymmetry, as well as imperfections of the cavity mirrors. A method of numerical simulations of the eigenvalue problem applicable for both the fundamental and high order cavity modes is suggested. Using this technique we find spatial profile of the modes and their round-trip diffraction loss. The results of the numerical simulations and analytical calculations are nearly identical when we consider a conventional FP cavity. The proposed numerical technique has much broader applicability range and is valid for any FP cavity with arbitrary non-spherical mirrors which have cylindrical symmetry but disturbed in an asymmetric way, for example, by tilt or roughness of their mirrors.Comment: 15 pages, 10 figure

Optical Gravitational Wave Antenna with Increased Power Handling Capability

Fundamental sensitivity of an optical interferometric gravitational wave detector increases with increase of the optical power which, in turn, limited because of the opto-mechanical parametric instabilities of the interferometer. We propose to optimize geometrical shape of the mirrors of the detector to reduce the diffraction-limited finesse of unessential optical modes of the interferometer resulting in increase of the threshold of the opto-mechanical instabilities and subsequent increase of the measurement sensitivity. Utilizing parameters of the LIGO interferometer we found that the proposed technique allows constructing a Fabry-Perot interferometer with round trip diffraction loss of the fundamental mode not exceeding $5$~ppm, whereas the loss of the first dipole as well as the other high order modes exceed $1,000$~ppm and $8,000$~ppm, respectively. The optimization comes at the price of tighter tolerances on the mirror tilt stability, but does not result in a significant modification of the optical beam profile and does not require changes in the the gravity detector read-out system. The cavity with proposed mirrors is also stable with respect to the slight modification of the mirror shape.Comment: 5 pages, 4 figure

Diffraction losses of a Fabry-Perot cavity with nonidentical non-spherical mirrors

Optical cavities, with both optimized resonant conditions and high quality factors, are important metrological tools. In particular, they are used for laser gravitational wave (GW) detectors. In order to have high cavity powers in GW detectors, it is necessary to suppress the parametric instability and to reduce the loss in the arm caused by point absorbers by damping the resonant conditions of harmful higher order optical modes (HOOM). This can be achieved effectively by using non spherical mirrors in symmetric Fabry–Perot (FP) cavities by increasing roundtrip losses of HOOMs Ferdous F et al 2014 Phys. Rev. A 90 033826; Matsko A et al 2016 Phys. Rev. D 93 083010. FP cavities in most of the GW detectors have non-identical mirrors to optimize clipping losses and reduce thermal noise by reducing the beam size on one side of the cavity facing to the beam splitter and recycling cavities. We present here a general method to design non spherical non-identical mirrors in non-symmetric FP cavities to damp HOOMs. The proposed design allows us to suppress the loss of the arm power caused by point absorbers on test masses

Diffraction losses of a Fabry-Perot cavity with nonidentical non-spherical mirrors

Optical cavities with both optimized resonant conditions and high quality factors are important metrological tools. In particular, they are used for laser gravitational wave (GW) detectors. It is necessary to suppress the parametric instability by damping the resonant conditions of harmful higher order optical modes (HOOM) in order to have high cavity powers in GW detectors. This can be achieved effectively by using non spherical mirrors in symmetric Fabry-Perot (FP) cavities by increasing roundtrip losses of HOOMs. Fabry-Perot cavities in most of the GW detectors have non-identical mirrors to optimize clipping losses and reduce thermal noise by reducing the beam size on one side of the cavity facing to the beam splitter and recycling cavities. We here present a general method to design non spherical non-identical mirrors in non-symmetric FP cavities to damp HOOMs. The proposed design allows to the suppress the loss of the arm power caused by point absorbers on test masses.Comment: 12 pages, 10 figure

Mathematical modelling of the liquid atomization process by cocurrent gas flow

This paper focuses on the physical-mathematical model of liquid atomization in the spray pattern of an ejection nozzle. A flow field of a gas phase behind the nozzle section is computed using the Ansys Fluent package. Dynamics of molten metal droplets in the gas phase within a trajectory approach is calculated. Using the presented model, numerical calculation results are given

Защитные свойства Zr-содержащих конверсионных покрытий на цинке

The aim of the study is to develop an environmentally friendly chromium-free passivation technology for galvanized steel. Passivation of zinc coatings was carried out by deposition of conversion coatings from solutions containing ZrO(NO3)2, Na2SiF6 and oxidizer H2O2 or K2S2O8. The effect of the solution pH, the concentration of Na2SiF6 and the type of oxidizer on the protective properties of coatings was studied by the drop method and electrochemical method of linear voltammetry in 3 % NaCl using the full factor experiment 23 . The main effects and effects of the interaction of the studied factors for the darkening time of the droplet and the dissolution potential of zinc are calculated. The solution pH in the presence of the oxidizing agent K2S2O8 influences the both parameters in the most extent. Concentration of Na2SiF6 has a significant effect on the dissolution potential of zinc and the least effect on the darkening time of the droplet. An increase in the solution pH and the concentration of Na2SiF6 increases the protective properties of the coatings. Measurements of the mass loss and open circuit potential during the resource testing of conversion coatings in 3% NaCl showed an increase in the corrosion rate over time.Цель исследования − разработка экологически безопасной бесхромовой технологии пассивации гальванически оцинкованной стали. Пассивация гальванических цинковых покрытий проводилась осаждением на них конверсионных покрытий из растворов, содержащих ZrO(NO3)2, Na2SiF6 и окислитель H2O2 или K2S2O8. Изучалось влияние pH раствора, концентрации Na2SiF6 и типа окислителя на показатели защитных свойств покрытий методом капли и электрохимическим методом линейной вольтамперометрии в 3 %-ном NaCl с использованием полного факторного эксперимента 23 . Рассчитаны главные эффекты и эффекты взаимодействия исследованных факторов для времени потемнения капли и потенциала растворения цинка. Наибольшее влияние на оба показателя оказывает pH раствора в присутствии окислителя K2S2O8. Концентрация Na2SiF6 оказывает значительное влияние на потенциал растворения цинка и наименьшее влияние на время потемнения капли. Увеличение pH раствора и концентрации Na2SiF6 увеличивает показатели защитных свойств покрытий. Измерения потери массы и потенциала разомкнутой цепи в процессе ресурсных испытаний конверсионных покрытий в 3 %-ном NaCl показали возрастание скорости коррозии со временем

PROFESSIONAL TRAINING OF DENTISTS TO INCREASE ALVEOLAR BONE JAWS FOR DENTAL IMPLANTATION

Results of clinical trial in article are presented. The conducted sociological survey of 100 doctors of stomatologistssurgeons (76 men and 24 women) aged from 29 to 45 years, an experience of professional activity not less than 3 years after completion of training in the internship or clinical internship working in municipal (30 people), departmental (24 people) and private dental clinics and offices (46 people) the motivational component to performance of an osteal plasty of jaws is studied, and also the factors constraining introduction of methods of an osteal plasty in municipal and departmental stomatologic out-patient and polyclinic authorities are established. It is established that in municipal, departmental and private out-patient and polyclinic authorities to surgical activity in this direction 73, 3 %, 79, 2 % and 95, 7 % of dentists that was caused generally by desire of salary increase, respectively or desire of professional body height, and also other factors, respectively. It is emphasized that only 14 % of doctors of stomatologists-surgeons gain necessary knowledge of questions of jaw osteal plasty when training (professional retraining, improvement, clinical internship) in HIGHER EDUCATION INSTITUTIONS. Need of updating of training programs and thematic plans on the chairs which are carrying out professional retraining, improvement and (or) training of dentists in clinical internship concerning a surgical dentistry and maxillofacial surgery is noted