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The paper presents the experimental results on generation of high power 4-mm-wave radiation in a two-channel planar free electron maser (FEM) with two-dimensional distributed feedback. This oscillator is driven by two relativistic electron sheet beams (1 MeV/1 kA/5 µs). At certain parameters of the experiment the two-dimensional distributed feedback circuit provides a well reproducible regime of the...
High-efficiency Ka-band FEM-oscillator was elaborated during the last few years in collaboration between JINR (Dubna) and IAP RAS (N.Novgorod). A schematic diagram of the JINR-IAP FEM experiments is shown in Fig.1. The induction linac LIU-3000 (JINR), which generates a 0.8 MeV / 200 A / 250 ns electron beam with a repetition rate of 1 Hz, drives the FEM-oscillator. Transverse velocity in the magnetically...
This paper describes experiments carried out at the ELMI-device on synchronous generation of 4-mm waves in a two-channel planar FEM with combined electrodynamic system. The results of spectral measurements are presented and discussed.
A new scheme of terahertz band FEL with hybrid Bragg resonator is proposed consisting of an advanced input Bragg mirror and a traditional output Bragg mirror. Advanced Bragg mirror exploiting the coupling between the two counter propagating modes and the cutoff one provides mode selection over the transverse index.
In experiments at ELMI-device (BINP, Novosibirsk) the operation of 4-mm free electron maser (FEM) with two dimensional distributed feedback was demonstrated. These results gave a base for development multichannel planar FEM with 2-D distributed feedback. In case of two channels jointed by special waveguide 2-D distributed feedback can be also used for two stage generation of submillimeter radiation...
In this paper the authors consider the planar model of the FEL with a hybrid resonator consisting of two Bragg structures with different operating features: an upstream (cathode-side) advanced and a downstream (collector-side) traditional Bragg reflectors. Mode control in the transverse direction is achieved in the upstream advanced Bragg reflector due to additional transverse electromagnetic energy...
Possibility of realization of terahertz planar FEL is demonstrated based on advanced Bragg reflectors exploiting the coupling between propagating and quasi cut-off modes. Such structure allows providing spatial coherence radiation on two coordinates for large oversize of interaction space.
Two-dimensional distributed feedback is an effective method of producing ultrahigh-power spatially coherent radiation from an active medium, that is spatially extended along two coordinates, including relativistic electron beams with sheet and annular geometry. This paper describes the progress in the investigations of planar and coaxial free-electron masers (FEMs) based on a novel feedback mechanism...
A planar narrow band Bragg reflector based on coupling of propagating and quasi-cutoff modes is considered. Coupled waves analysis together with direct numerical simulations demonstrate the operability of novel scheme up to THz frequency band.
Summary form only given as follows. For an active media, that is spatially extended along two coordinates, including relativistic electron beams with sheet and annular geometry, as well laser media, the use of two-dimensional (2D) distributed feedback is beneficial for providing spatial coherence of the radiation and, thus, can be used to increase the total radiation power. Such 2D feedback can be...
Summary form only given as follows. The JINR-IAP FEM-oscillator was elaborated during the last few years based on 0.8 MeV/200 A/250 ns linac LIU-3000 (JINR, Dubna). This 30-GHz FEM generates currently 20 MW/200 ns pulses with spectrum width of ~6 MHz and repetition rate of up to 1 Hz. The high efficiency and stability of the FEM was achieved by using reversed guide magnetic field regime and advanced...
Hybrid two-mirror scheme resonator are used which consists of 2D up-stream Bragg reflector and tradition 1D downstream Bragg reflector. In the frame of coupled-wave approach and direct 3D simulations (code CST MicroWave Studio) electrodynamics properties of two-mirror hybrid resonator are studied. It is demonstrated that above microwave system possesses high selectivity over both transverse and longitudinal...
Summary form only given. Three years ago we proposed a two-stage process for generation of sub-millimeter radiation based on stimulated intercavity scattering. A key feature of this process is to use two sheet beams with a few kiloampere currents that propagate in two parallel sheet channels connected by a special waveguide. First channel operates as a planar FEM-oscillator at 4-mm wavelength. Powerful...
Paper describes main features of a project of an experiment at ELMI-device on two-stage generation of submillimeter radiation pulses. In this experiment two parallel high current sheet beams will be used. Submillimeter waves generation is based on stimulated scattering of mm-waves accumulated in the resonator of a planar FEM-oscillator driven by one of these beams.
This paper describes main features of a project on two- stage generation of submillimeter radiation pulses at ELMI-device. In this project one sheet beam will drive 2D Bragg planar FEM in which intensive 4-mm radiation accumulated in the FEM resonator, is used for stimulated scattering on the another sheet beam.
The analysis of electrodynamic properties of two-dimensional (2D) Bragg resonators of planar and coaxial geometry realizing 2D distributed feedback was carried out in the frame of the coupled-mode approach and in 3D simulations taken into account. High selectivity of above structures is demonstrated for large Fresnel parameters. Formation of the high-Q eigenmodes in the vicinity of the Bragg resonance...
Sub-mm Bragg FEM (free-electron maser) is developed based on 0.8 MeV / 200 A linac. Present paper describes recent design and key elements of the oscillator. Results of the first experiments, which proved operability of novel FEM scheme, are described.
A 30 GHz commutator aimed to switch phase of 0.1-1 mks, 1-100 MW microwaves in pulse compression systems like SLED is suggested. The commutator in a form of circular (100 mm) Si-disk put on a surface of copper mirror is based on creation of thin photoconductive layer in high purity low-loss silicon. The photoconductivity is caused by means of Ti:Sa laser radiation (1-10 mJ, 0.1 ps) with wavelength...
A novel Bragg FEM scheme [1] is discussed in which an electron beam synchronously interacts with a propagating wave, and the latter is coupled to a quasi cut-off mode. This coupling is realized by either helical or asimuthally symmetric corrugation of the waveguide walls. The quasi cut-off mode provides feedback in the system leading to self-excitation of the whole system while the energy extraction...
A project to generate powerful sub-mm pulses in JINR-IAP FEM-oscillator driven by 0.8 MeV / 200 A linac is in progress. Present paper describes recent design and key elements of the oscillator.
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