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Planar Free Electron Maser and Non-Linear Effects

#2209


Generation and Amplification of Microwave Radiation Pulses in High-Power FEM with Two-Dimensional Distributed Feedback and Non-Linear Effects at High Radiation Intensity

Tech Area / Field

  • PHY-RAW/Radiofrequency Waves/Physics

Status
3 Approved without Funding

Registration date
23.05.2001

Leading Institute
Budker Institute of Nuclear Physics, Russia, Novosibirsk reg., Akademgorodok

Supporting institutes

  • Russian Academy of Sciences / Institute of Applied Physics, Russia, N. Novgorod reg., N. Novgorod\nVNIITF, Russia, Chelyabinsk reg., Snezhinsk

Collaborators

  • University of New Mexico / The University of New Mexico / Department of Electrical and Computer Engineering, USA, NM, Albuquerque\nForschungszentrum Karlsruhe Technik und Umwelt / Institut für Hochleistungsimpuls und Mikrowellentechnik, Germany, Karlsruhe\nUniversity of Strathclyde, UK, Glasgow

Project summary

Introduction and Overview.

The main project objective is to elaborate the concept for creation of a generator of coherent microwave radiation pulses with large electromagnetic flux cross section that allows to reach extremely high (1-10 GW) power. Other objective that is important for practical applications is to produce such power for 4-mm radiation pulses with a few microseconds duration and as a result to obtain hundreds of joules in a single pulse. Realization of these objectives is planned on the base of the scheme of a planar free electron maser (FEM) using a sheet electron beam and two-dimensional distributed feedback. This scheme was proposed and partially studied theoretically and experimentally in the framework of ISTC Project # 531. To confirm fundamental ideas that underlie such planar maser the specialized ELMI device was created in INP under support of the Project # 531. Microsecond pulses of 4-mm radiation with energy content about 100 J were obtained in the experiments at this device. Now researches on planar FEM are being continued. As further expansion of these researches we propose the idea to create a high-power microwave generator as a set of planar masers immediately adjacent to each other, operating in-phase and thereby combined into a single technical device with multilayer electrodynamic structure. To provide oscillation phase synchronism therewith, interchange of some portion of energy stored in resonators is suggested. Theoretical study of single planar maser as an amplifier showed the achievability of good radiation synchronism at the output with gain factor up to 50 dB. This demonstrates prospects for generators with planar multichannel structure, as the line of researches in the problem of high power generation in mm-radiation. Theoretical research on generation of radiation in such structure will be a major part of work under the project. The initial experimental confirmation of the chosen approach is suggested to be performed at ELMI device by combining two planar masers into a single device.

To turn researches on planar masers from the area of fundamental science into the sphere of practical implementations it is expected that we continue our work on developing energy recuperator for a sheet electron beam and elaborate realization principles for frequency mode operation of such device. Since plasma processes occur at electrodynamic system elements in vacuum and in the Earth’s atmosphere at high power flux densities then the major part of work under the project is suggested to be concentrated on investigation of these processes and their influence on space-time evolution of radiation.

High-power generators of mm-radiation are promising for use in scientific researches and practical applications. The sphere of potential applications comprises protection of objects from lightning during thunderstorm, atmosphere purification and ozone layer regeneration, energy transmission between satellites in outer space, hot plasma production in thermonuclear reactors. They are also hold much promise for clearing concrete caps of nuclear reactors, establishing conditions for unique chemical reactions and micro-grain ceramics synthesis. In such situation this activity on creating high-power generators of microwave radiation and their use for solving global problems for the benefit of mankind may be the sphere of fruitful activities of Russian scientists engaged early in weapon development.

Expected Results and their Application.

The proposed project refers to the category of fundamental researches since its main objective is the elaboration of generation principles for coherent radiation fluxes with large cross section and extremely high power for millimeter and submillimeter wavelength. Generation of microsecond pulses of 4-mm radiation with energy content of hundreds of joules will be a result of practical significance.

In the previous researches we showed that the scheme of a planar maser with two-dimensional distributed feedback is quite adequate to the problem of increasing one of cross section dimensions of generated electromagnetic radiation flux up to values, more than two orders larger than the wavelength magnitude on the retention of high degree of space coherence. In this project we need to solve the problem of power build-up in the radiation flux through the cross section build-up in another coordinate by combining several planar FEMs in a single device. The elaboration of fundamentally novel approach to relativistic beam recuperator based on resonance between cyclotron and bounce motions of electrons is the addition to this problem. Foundations of this approach were laid by the previous project. Occurrence and development of plasma formation in the cross section of high-power flux of microwave radiation can take place both in vacuum cavity of generator itself and under radiation propagation in the atmosphere. The influence of plasma occurrence on generation and propagation of radiation will be studied both theoretically and experimentally.

As the result of this project fulfillment the following problems are expected to be solved:

– the fundamental problem to create a power coherent radiation flux with large cross section by combining several planar FEMs with two-dimensional distributed feedback in a single device will be solved.


– novel approach to relativistic beam recuperator based on resonance between cyclotron and bounce motions of electrons will be elaborated.
– non-linear effects in high-power flux of microwave radiation associated with plasma occurrence and development in its cross section will be studied.

Meeting ISTC Goals and Objectives.

Participation of weapon scientists and specialists in elaboration of new principles of generation of coherent microwave radiation with extremely high power as well as searching new designs of generators of such radiation allows those people to be perted gradually to scientific activity in unmilitary branches and become integrated into international scientific community, which is wide in this research area. Since application of high-power microwave radiation is promising in the area of ecological safety, high technologies and energetics of the future in a great number of industrialized countries, then weapon scientists gain the opportunity to present results of their researches in this important sphere at international level. The persion of weapon scientists from defence researches to this sphere began earlier on – during previous ISTC project on planar maser fulfillment where they took an active part.

Scope of Activities.

The project is directed to comprehensive solution of the problem of generation and application of extremely power (the level of few gigawatts) 4-mm radiation. This problem will be solved in the framework of four large tasks.

The first one is theoretical and experimental studies of two-dimensional distributed feedback in 4-mm planar maser when operating in generator and regenerative amplifier regimes. The studies must point advantages and disadvantages for each of these two regimes. INP and IAP joint efforts will be directed to analytical solution of the problem, and VNIITF will play a leading role in numerical simulation. Experiments will be pursued at ELMI device constructed in INP under ISTC project partially support. Results of these researches will be presented at international conferences and published in journals and reports. The work on this problem will be mainly completed to the beginning of the third year of works under this project.

The second task will be dedicated to the research of the possibility of cophased operation of several planar masers in parallel by the use of distributed feedback. This is a principally new step in development of the idea for use of distributed feedback in three-dimensional electrodynamic systems. Participants’ duties will be allocated just as in the first task. For this task fulfillment deep reconstruction of ELMI device is suggested in INP for the purpose of creating two masers operating in parallel and combined in a single generator of cophased radiation. Accelerator diode manufacture will be completed during the first year, and units for two-channel generator of 4-mm radiation by the end of the second year. Acceptance certificate will be processed through test reports. Results of theoretical and experimental researches will be represented in reports and scientific publications.

The creation of generators of high-power pulse microwave radiation and its use in practice assume to research non-linear effects in radiation flux as the result of plasma occurrence under microwaves breakdown. The third task of this project will be dedicated to this. Numerical models elaborated in VNIITF under Project #531 will be widely used for computer simulations of this problem. Special diagnostic complex will be developed both for mm-radiation and occurring plasma to study these effects.

The solution of the fourth task connected with technical aspects arising in development of high-power microwave radiation sources, needed for practical use, comprises a considerable part of works under this project. In this section the development of energy recuperator for utilized beam, which is based on resonance between cyclotron and bounce motions of electrons, is proposed. Preprints and protocols of finished assembly tests will be used as reporting documents. Another technical problem is to elaborate the concept of microwave generator operating in regime of small sequence of microsecond pulses. Results of this problem development will be represented in preprints and reports on the project.

Role of Foreign Collaborators.

We assume an active exchange of information on the Project implementation with collaborators. We affirm our readiness to submit additional annotations of reports (submitted to ISTC) to collaborators. Collaborators can exercise efficient control of obtained results and take part in technical inspection of activities under the Project . Joint participation in workshops on the Project as well as in international conferences (FEL, AFEL, BEAM’s and EUROEM) and meetings are supposed. Direct cooperation with the Institute for Pulsed Power and Microwave Technology (Karlsruhe, Germany) in development of planar Bragg reflectors will be developed. Close cooperation with Strathclyde University (Glasgow, UK) in the theory of distributed feedback is expected.

Technical Approach and Methodology.

The adopted main approach to scientific researches includes revealing of strategic problems and solving them by use of flexible combining of analytical investigation, numerical simulation and well equipped physical experiment. One of such problems is application of distributed feedback to attain spatially coherent radiation fluxes generated in two- and three-dimensional electrodynamic structures with sizes several orders larger than the radiation wavelength. Analytical investigation makes possible mainly to formulate model equations and boundary conditions. Then these equations are solved by numerical methods on the base of modern computers. For solving electrodynamics problems and for calculating the structure of electromagnetic fields in resonators with complicated geometry we suppose to use direct numerical simulation. In its turn experiments in INP are pursued at recently constructed ELMI device equipped with modern diagnostic system that is based on analog-digital technique and computers. Non-linear effects under radiation propagation in vacuum and the Earth’s atmosphere associated with plasma occurring in fluxes of high-power microwave radiation is the other problem to be solved in the Project. In connection with this problem the computer codes have been already developed in VNIITF and a series of solutions describing plasma behavior under different conditions have been obtained. In the Project we are going to construct a model describing plasma influence on radiation and a self-consistent solution for the system: high-power radiation – non-linear medium of propagation. High power level of microwave radiation generated at ELMI device gives opportunity to carry out experiments on this Project problem. The next problem concerns technical aspects of high-power generators of microwave radiation. It will be solved through computing various assemblies of these devices, then designing by computer methods, manufacturing by high-technology processes at mechanical shops and, finally, finished product testing.


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