Submillimeter-wave large-orbit gyrotron

Bratman, V. L.; Kalynov, Yu. K.; Мануилов, В. Н.; Самсонов, С. В.

doi:10.1007/s11141-006-0001-9

Cited by 30 publications

(9 citation statements)

References 13 publications

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“…Several successful terahertz range large orbit harmonic gyrotrons experiments have been carried out at resonant magnetic fields 10.5 -14 T [16,17]. The 3D PIC code MAGIC was used to simulate and optimize the design of the cusp electron beam source.…”

Section: Cusp Electron Gunmentioning

confidence: 99%

Design and simulation of a ∼390 GHz seventh harmonic gyrotron using a large orbit electron beam

Li¹,

He²,

Cross³

et al. 2010

J. Phys. D: Appl. Phys.

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Abstract. A~390 GHz harmonic gyrotron based on a cusp electron gun has been designed and numerically modelled. The gyrotron operates at the 7 th harmonic of the electron cyclotron frequency with the beam interacting with a TE 71 waveguide mode. Theoretical as well as numerical simulation results using the 3D Particle-In-Cell (PIC) code MAGIC are presented. The cusp gun generated an axis-encircling, annular shaped electron beam of energy 40 keV, current 1.5 A with a velocity ratio of 3. Smooth cylindrical waveguides have been studied as the interaction cavities and their cavity Q optimized for 390 GHz operation. In the simulations 600 W of output power at the design frequency has been demonstrated. [5,6]. The gyrotron is well known as a coherent millimeter wave source capable of high power and high frequency output which is extendable to the Terahertz (THz) frequency region. Recently a gyrotron achieved kilowatts of output power operated at the fundamental electron cyclotron frequency of 1 THz [7] by using a pulsed solenoid. However, continuous wave (CW) operation at such a frequency is a formidable task because of the large magnetic field (~40 T) that is required. As the output frequency increases, both larger magnetic fields and reduced interaction region size are needed when operating at the fundamental cyclotron frequency. An alternative approach to generate CW high frequency radiation is to work at higher cyclotron harmonics [8,9,10,11] which allow the use of larger cavity sizes and smaller magnetic fields by a factor of s, where s is the harmonic number. A CW high harmonic gyrotron operating at a frequency of~390 GHz at relatively lower B-field was designed and is presented in this paper. In this gyrotron cyclotron resonance takes place between the seventh harmonic of the electron cyclotron frequency (s = 7) and the TE 71 waveguide mode. A large orbit electron beam from a cusp gun is used to reduce the possibility of parasitic interactions. The small-signal theory of the beam-wave interaction was used to calculate the growth rate and the starting current. A smooth-bore cavity was designed with a suitable Q value by optimizing the angle of the output taper and the length of the cavity so that the starting current requirement is met. Finally, the beam-wave interaction of the gyrotron was simulated using the 3D Particle-In-Cell (PIC) code MAGIC and the results are presented. Keywords: Harmonic gyrotron, terahertz, large orbit electron beam

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Section: Cusp Electron Gunmentioning

confidence: 99%

Design and simulation of a ∼390 GHz seventh harmonic gyrotron using a large orbit electron beam

Li¹,

He²,

Cross³

et al. 2010

J. Phys. D: Appl. Phys.

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“…For comparatively low electron energy and beam current, the ratio g = v ⊥ /v of the rotational and translational velocities (pitch factor) and the cavity length L are increased up to 1.5 and 24λ, respectively, where λ is the radiation wavelength in free space. A favorable fact related to this change in parameters is significant narrowing of the cyclotron-resonance band and simplification of the solution of the mode-competition problem compared with the above-described experiment [25,26]. According to the calculations, the electron efficiency can reach 10% for the working current, which yields a total efficiency of 1.3% and an output power of about 0.7 kW with allowance for the ohmic loss.…”

Section: Log With a Radiation Frequency Of 1 Thzmentioning

confidence: 99%

“…After a number of experiments [23][24][25][26], LOGs operated at the shortest wavelength were created at the Institute of Applied Physics (IAP) of the Russian Academy of Sciences. In those devices, the electrodynamic system was a conventional (i.e., opened towards the collector) cylindrical gyrotron cavity, which has much better selective properties than the closed cavities used in [2,14,17].…”

Section: Small-and Large-orbit Gyrotronsmentioning

confidence: 99%

“…In that system, a beam with a particle energy of 250 keV, a current of 10 A, and a duration of 10 µs was formed and used to obtain single-frequency generation at the third and fourth cyclotron harmonics of the TE 3,2,1 and TE 4,2,1 modes with frequencies of 115 and 130 GHz, respectively, and an output power of about 100 kW. Modification of this electron-optical system allowed one to increase the adiabatic compression of the beam with the same particle energy, but for a lower current of 3 A, up to 4400 times and achieve generation at the TE 3,5,1 , TE 3,8,1 , and TE 3,9,1 modes in the frequency range 0.37-0.41 with a power of 10-20 kW [25,26] in a LOG with two different cavities at the third cyclotron harmonic.…”

Section: Small-and Large-orbit Gyrotronsmentioning

confidence: 99%

“…In contrast to the previous experiments [23][24][25][26], the scheme of the terahertz LOG (Fig. 3) includes a two-mirror quasioptical converter of the working mode to a wave beam.…”

Section: Log With a Radiation Frequency Of 1 Thzmentioning

confidence: 99%

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Large-orbit Subterahertz and Terahertz gyrotrons

Bratman

Kalynov

Мануилов

2009

Radiophys Quantum El

Self Cite

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We review briefly the main ideas and achievements in the field of physics related to shortwavelength large-orbit gyrotrons, in which the coupling of electrons with the working mode and the discrimination of parasitic modes in the case of resonance at the high cyclotron harmonic are more efficient compared with conventional gyrotrons. The results of studying a new large-orbit gyrotron with moderate electron energies of 50-80 keV and comparatively low magnetic fields of 10.5-14 T are presented. In this gyrotron, high-power single-mode generation was obtained at the second and third cyclotron harmonics in the frequency range 0.55-1.00 THz. The prospects of development and application of short-wavelength large-orbit gyrotrons are discussed. SMALL-AND LARGE-ORBIT GYROTRONSThe conventional gyrotron with many off-axis elec-B B a) b) Fig. 1. Projections of electron trajectories onto the cross section of the cavity in a conventional gyrotron at the fundamental cyclotron resonance (a) and in a LOG at the high cyclotron harmonic (b).tron beamlets [1] and the gyrotron with an axis-encircling electron beam [2] were proposed and demonstrated in 1965 and 1968, respectively. A type of the oscillator with an axis-encircling beam, in which electrons move along helical trajectories around the axis of an axisymmetric electrodynamic system, is called a large-orbit gyrotron (LOG). This name is related to the fact that the LOG is usually operated at the high cyclotron harmonic and, therefore, the magnetic field in it, for the same operating frequency, is lower and the Larmor radius of electrons is greater compared with the conventional "small-orbit" gyrotron which is operated at the fundamental cyclotron resonance or the second cyclotron harmonic (Fig. 1). In the case where the conventional gyrotron and the LOG are operated at the same resonant harmonic, the electron "orbit" in them is the same and is determined by the Larmor radius of the electron in the same magnetic field.It should be emphasized that the conventional gyrotrons are perfect oscillators which provide, in particular, a radiation power of 1 MW in the quasi-continuous-wave regime at a high frequency of 0.17 THz with an efficiency of 50% (see, e.g., [3,4]). Conventional gyrotrons also work in the submillimeter-wave range [5][6][7][8] and recently have been used to overcome a 1-THz frequency when operated at the fundamental cyclotron resonance [9] and the second cyclotron harmonic [10]. At the same time, despite their relatively long history, LOGs have been realized in a comparatively small number of experiments and are still at the stage of fundamental research. Nevertheless, LOGs are still fairly attractive for operation at the high cyclotron harmonics since they ensure a more efficient coupling of electrons with the working-mode field and,

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