V. A. Isaev

Three-dimensional electrochemical phase formation

Abstract The formation of a three-dimensional electrodeposit by the nucleation, growth and overlap of a new phase under potentiostatic conditions is analysed. The development with time of the charge, current density and electrode coverage by the deposit is examined. Methods of obtaining the nucleation and growth parameters are proposed.

Galvanostatic nucleation and growth under diffusion control

A theory is proposed for galvanostatic three-dimensional nucleation and growth of new phase clusters controlled by diffusion of depositing ions in the bulk of the electrolyte to the clusters surface. The mathematical model is used to calculate the time dependences of the overpotential, number, and size of clusters formed on the electrode.

Non-steady-state electrochemical nucleation under potentiostatic conditions

Abstract The kinetics of electrochemical nucleation at constant overpotential have been analysed. The influence of the concentration change of single adatoms (monomers) on the process of nucleation is considered. The Fokker–Planck kinetic equation was solved accounting for this effect. Expressions were derived for the number of nuclei, for the nucleation rate and for the nucleation induction time.

Galvanostatic phase formation

The results of a theoretical study on initial stages of electrodeposition under galvanostatic conditions are presented. The model of three-dimensional nucleation and growth under these conditions is developed. This model is used to calculate the times dependences of the overpotential, number of clusters formed on the electrode, and nucleation rate. The peculiarities of nucleation and growth kinetics are analyzed.

High Power Accelerator R&D at the NRL 11.424‐GHz Magnicon Facility

An 11.424‐GHz magnicon amplifier has been jointly developed by the Naval Research Laboratory and Omega‐P, Inc. as an alternative technology to klystrons for powering a future X‐band linear collider. This paper will discuss its background, operating principles, and results to date, as well its present status as part of a facility for collaborative research on accelerator‐related technologies that require high‐power 11.424‐GHz radiation. Two collaborative research programs are currently under way using the magnicon output. The first, a collaboration with Omega‐P, Inc. and the Institute of Applied Physics, is investigating active microwave pulse compressors using plasma switch tubes. The second, a collaboration with Argonne National Laboratory and SLAC, is investigating dielectric‐loaded accelerating (DLA) structures, with the ultimate goal of developing a compact DLA accelerator.

Angular dependence of quartz fiber calorimeter response

Abstract A small quartz fiber calorimeter prototype with copper absorber has been assembled and tested at ITEP as a first test of a “0 degree” component of the RD-40 R&D program. Calibration and monitoring of each tower response was performed using the positions of single photoelectron peaks as well as the response to minimum ionizing particles incident at an angle of 45°. The response of the prototype to 4 GeV electrons as a function of beam angle with respect to the quartz fibers was studied in the range from 0° to 90°. The test results are compared to the GEANT based Monte Carlo (MC) simulations.

A plasma switch based on TE02 → TE01 round waveguide mode conversion for high-power X-band microwave compressors

A new type of a plasma switch is proposed, which provides Q-switching of the energy storage cavity of a high-power microwave compressor and ensures high electric strength in all stages of compressor operation. In a compressor with this switch, the energy is accumulated on the TE02 mode and extracted on the TE01 round-waveguide mode. The principle of operation of the proposed switch is based on a sharp increase in the TE02 → TE01 mode conversion coefficient during plasma generation in an electrically controlled gas-filled discharge tube arranged in the switch. The high electric strength of the switch is ensured by placing the discharge tube surface at the node of a standing wave field formed in the switch.

Effect of metal coating on the optical losses in heated optical fibers

The effect of heating in air on the optical losses in metal-coated fibers has been studied. Two fibers were drawn from the same silica preform and coated by different metals (copper and aluminum). Dependences of a change in the optical losses on the temperature were measured in a 20–400°C range at a 50°C step. The optical losses of metal-coated fibers heated to temperatures below 300°C change mostly due to the microbending contribution. At temperatures above 300°C, the main contribution to increasing optical losses is due to the absorption on OH groups. It is established for the first time that the contribution to optical losses due to the OH groups is much more pronounced in Al-coated fibers than in Cu-coated ones. In addition, the Al-coated fibers exhibit growth in the optical losses above 300°C due the absorption on molecular hydrogen.

Electrochemical nucleation and growth of silicon in the KF-KCl-K2SiF6 melt

The work related to the study of the initial stages of the silicon electrodeposition on the glassy carbon electrode in molten KF-KCl-K2SiF6 was performed. The silicon nucleation and growth process was investigated using cyclic voltammetry, chronoamperometry, and scanning electron microscopy. It was shown that the electrocrystallization process occurs by the instantaneous nucleation with diffusion-controlled growth under the studied conditions. The Scharifker-Hills theoretical model was used to calculate the nucleation density and the diffusion coefficient of depositing ions.

Three-dimensional nucleation and growth under galvanostatic conditions

The nucleation and growth of new phase clusters have been studied under galvanostatic conditions. Time dependences of the overpotential, number, and size of clusters formed on the electrode have been calculated from a model of the electrocrystallization process.