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Zawartość zarchiwizowana w dniu 2022-12-23

Generation of ultra-high power spatially coherent radiation using two-dimensional distributed feedback

Cel

An important collaboration between Russian and European scientists from the group lead by Professor A.D.R. Phelps of the University of Strathclyde, UK, Professor N.S. Ginzburg of the Institute of Applied Physics RAS (IAP RAS), Nizhny Novgorod, Russia, Professor A. Arzhannikov of Budker Institute of Nuclear Physics RAS (BNIP RAS), Russia and Professor M. Thumm of the Research Center Karlsrhue, Germany, plans to look at the long-standing problem of controlling the oscillating dynamics and the provision of spatial coherence of radiation from a large size active medium. A new approach aimed at solving this problem is to use multi-dimensional distributed feedback, which may be realised in multi-periodical Bragg structures. For an active media, that is spatially extended along two co-ordinates, such as a relativistic electron beam of either sheet or annular geometry, it is proposed that novel two-dimensional (2D) distributed feedback be used to generate ultra-high power spatially coherent.
The potential of novel 2D Bragg resonators as compared with traditional 1D resonators will be studied. It is important to note that 1D Bragg resonators are used to select a single resonant cavity mode with the correct longitudinal index and have been used widely in FEM experiments to obtain narrow-frequency generation, but in all previous experiments the diameter of the microwave systems (D) did not exceed the wavelength of the radiation (lambda) by more than D/lambda ~ 2 to 4 and the radiation power was limited to 50MW in the millimetre wavelength region of the electromagnetic spectrum. A further increase in the output power in coherent radiation requires an increase in the transverse size of the system to prevent beam instability and RF-breakdown, however traditional 1D Bragg resonators lose mode selectivity with increasing transverse size resulting in a dramatic reduction in efficiency and spectral purity. The use of two-dimensional distributed feedback to synchronise radiation in the transverse dimension will enable high efficiency to be maintained as the transverse size of the gain medium is increased. Theory has already given very promising predictions of 2D Bragg resonator excitation by large size electron beams to provide powerful spatially-coherent radiation emission from a source even when D/lambda ~10 to 1000.
In the framework of the INTAS grant theoretical and experimental studies of novel FEM-oscillators operated with 2D distributed feedback, including single-module and multi-module schemes will be conducted. The possibility of generating high power coherent radiation based on different beam/wave interaction mechanisms (FEM, Cyclotron resonance masers, Cherenkov masers) will be investigated. The potential of using 2D feedback in quantum lasers and semiconductor devices will also be studied theoretically. Two main 2D distributed feedback geometry's (planar and co-axial) will be explored in two separate FEM experiments: a sheet electron beam FEM-experiment based at BINP RAS and a co-axial FEM-oscillator based at the University of Strathclyde collaborating with scientists form IAP RAS and the Research Centre Karlsrhue. The transverse coherence and spectral purity of the electromagnetic radiation generated in a 2D Bragg FEM will be measured and compared with a traditional 1D Bragg FEM.
The INTAS proposal "Generation of ultra-high power spatially coherent radiation using two-dimensional distributed feedback" aims to verify that 2D Bragg reflectors can be used to control and manipulate electromagnetic radiation, when the transverse size of the active medium exceeds the radiation wavelength by orders of magnitude. Experiments will be conducted to investigate narrow-band millimetre wavelength FEM-oscillators which are expected to provide spatially coherent single-mode generation when D/lambda ~ 10 to 50. The possibility of increasing the transverse size of the system to achieve ultra-high power level millimetre wave radiation will be studied and a narrow-band 4-mm FEM with output power up to 10 GW would be designed. First operation of a two-beam FEM synchronised by 2D distributed feedback is also planned to demonstrate the potential of the novel feedback mechanism to synchronise radiation from an active media in the form of a multi-layer structure, e.g. extended along both transverse co-ordinates.
As a result hundreds of MW to GW coherent radiation power may be achieved and it is anticipated that the radiation power will continue to scale with the transverse size of the active medium. Demonstration of enhanced mode stability and spectral purity from large-scale gain media has potentially wide applications in all situations where increased power levels of coherent radiation are needed. The concept of two-dimensional distributed feedback with suitable scaling of dimensions also offers great potential for new applications from microwave to infrared and optical frequencies. There are many areas of physics that would benefit from such enhanced sources, for example accelerators, ionosphere and fusion plasma diagnostics and investigation of non-linear properties of materials.

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Koordynator

University of Strathclyde
Wkład UE
Brak danych
Adres
107 Rottenrow
G4 0NG Glasgow
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