Ten-Megawatt Pulsed Gyrotron with a 1-cm Wavelength and a 50% Efficiency

Kulagin

Мануилов

et al. 2007

Radiophys Quantum El

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We propose a method of increasing the pitch factor and decreasing the spread of rotational velocities of helical electron beams (HEBs) formed in nonadiabatic magnetron-injection guns of gyroresonant devices. The method is based on the effect of a special diaphragm mounted at the starting point of the transport channel on the process of formation of the laminar electron beam. The diaphragm located at one of the trajectory minima has such a diameter that it cannot be bent around by electrons with minimum rotational velocities. Such electrons land on it, whereas the remaining electrons pass further, moving in an increasing magnetic field. Then the electrons with the maximum rotational velocities reflect from the magnetic mirror adiabatically and land on the other side of the same diaphragm. Thus, the electron beam in the cavity contains electrons with a smaller resulting spread of rotational velocities. In the region of the HEB formation, the accumulation of the space charge of reflected electrons is eliminated, and the shielding of the electric field at the cathode is reduced, which eventually leads to an increase in the HEB pitch factor. Using such a diaphragm in the regime of current limitation by the space charge, the HEB with a high pitch factor (about 1.4) and a velocity spread acceptable for gyrotron applications (lower than 30%) was formed.

Section: Introductionmentioning

confidence: 99%

Experiments on the formation of an intense helical electron beam under conditions of picking-up of the electrons reflected from the magnetic mirror

Kulagin

Мануилов

et al. 2007

Radiophys Quantum El

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“…Measurements in the operation regime (accelerating voltage 280 kV and beam current 60 A) also showed a greater velocity spread, which obviously did not match the high efficiency of the gyrotron (50%, see. [3]) based on the analyzed HEB. We attributed this mismatch to the high (and different for the two analyzers) coefficient of electron reflection from the analyzer electrodes.…”

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confidence: 99%

Study of the magnetic analyzer of relativistic helical electron beams

Zaitsev

Radiophys Quantum Electron

Kulagin

et al. 2006

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681.7The paper presents the results of studying the analyzer of helical electron beams experimentally. The analyzer is based on separation of electron velocity fractions in the adiabatically growing magnetic field. Optimization of the analyzer design to minimize the amount of electrons reflected from the analyzer elements made it possible to practically eliminate the systematic error in measurements of the velocity spread and pitch-factor.Recently, gyroresonance devices (gyrotrons and gyroklystrons) have advanced noticeably into the range of electron energies from 300 to 500 keV. Their efficient operation requires helical electron beams (HEBs) with a high pitch factor (relation of the oscillatory electron velocity to the longitudinal one) and a low electron velocity spread. We propose a special analyzer to measure the noted parameters of the beam under conditions where the traditional modeling of the trajectories in the region of lower voltages [1] is inaccurate due to the dependence of the electron mass on the electron energy. In this analyzer, electrons are separated over their transverse velocities by using an adiabatically growing magnetic field directly in the operation regime of HEB formation [2].The magnetic analyzer was tested in the modeling regime (see [2]) by comparing the obtained results with the data of the traditional electrostatic analyzer. Both analyzers showed similar values of the pitch factor of the measured beam. However, the magnetic analyzer demonstrated a significantly greater spread of electrons over transverse velocities as compared with the electrostatic one. Measurements in the operation regime (accelerating voltage 280 kV and beam current 60 A) also showed a greater velocity spread, which obviously did not match the high efficiency of the gyrotron (50%, see.[3]) based on the analyzed HEB. We attributed this mismatch to the high (and different for the two analyzers) coefficient of electron reflection from the analyzer electrodes. Below the results of the experiments are described, which confirmed this assumption and made it possible to eliminate the drawbacks of the analyzer design that hindered adequate measurements of the beam parameters.

“…Therefore, the high-order TE mp modes with nonzero azimuthal indices m, which have long been used in gyrotrons [7], are rather attractive. Both electric and magnetic fields of such modes on the cavity walls are relatively small compared with the fields in the zone of interaction with the electron beam.The possibility of creating a high-order nonsymmetric-mode gyroklystron is supported by the results of our previous studies such as development of the method allowing us to reach a high-frequency electricfield intensity of 150 kV/cm on the electrodynamic-system wall [8], creation of a magnetron-injection gun forming a helical electric beam (with an accelerating voltage of 280 kV and a current of 60 A) with a pitch factor of 1.3 for the case of acceptable electron spread over transverse velocities [9], and testing the output cavity in the active-oscillator mode where the output power exceeding 10 MW is obtained at a frequency of 30 GHz for the TE 53 mode and the radiation duration equal to the supply-voltage duration [10,11]. 3 4 5 2 1 7 10 8 9 6 Fig.…”

mentioning

confidence: 99%

“…The possibility of creating a high-order nonsymmetric-mode gyroklystron is supported by the results of our previous studies such as development of the method allowing us to reach a high-frequency electricfield intensity of 150 kV/cm on the electrodynamic-system wall [8], creation of a magnetron-injection gun forming a helical electric beam (with an accelerating voltage of 280 kV and a current of 60 A) with a pitch factor of 1.3 for the case of acceptable electron spread over transverse velocities [9], and testing the output cavity in the active-oscillator mode where the output power exceeding 10 MW is obtained at a frequency of 30 GHz for the TE 53 mode and the radiation duration equal to the supply-voltage duration [10,11]. to exclude the self-excitation of parasitic modes and optimize the operating-mode coupling with the output waveguide.…”

mentioning

confidence: 99%

Pulsed high-order volume mode gyroklystron

Zaitsev

Radiophys Quantum Electron

Kuzikov

et al. 2005

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We present the results of studies of a gyroklystron with the TE 53 output mode. A 30-dB gain is obtained at a frequency of 30 GHz for an output power of 5 MW, efficiency 25%, pulse duration 0.4 ms, and amplification bandwidth 40 MHz.1. At present, the development of multimegawatt gyroklystrons is mainly aimed at the international program of creating new-generation electron-positron colliders [1]. The majority of such gyroklystrons [2-6] use the TE 01 or TE 02 modes as operating ones for which the axisymmetric electric field on the cavity wall is zero, which is favorable from the electric-strength viewpoint. However, such modes fail to eliminate the risk of thermal "fatigue" of the cavity walls in the pulsed-periodic regime. Moreover, the TE 0p modes (with axisymmetric fields) compare unfavorably with modes of other types if the radial index p increases. Therefore, the high-order TE mp modes with nonzero azimuthal indices m, which have long been used in gyrotrons [7], are rather attractive. Both electric and magnetic fields of such modes on the cavity walls are relatively small compared with the fields in the zone of interaction with the electron beam.The possibility of creating a high-order nonsymmetric-mode gyroklystron is supported by the results of our previous studies such as development of the method allowing us to reach a high-frequency electricfield intensity of 150 kV/cm on the electrodynamic-system wall [8], creation of a magnetron-injection gun forming a helical electric beam (with an accelerating voltage of 280 kV and a current of 60 A) with a pitch factor of 1.3 for the case of acceptable electron spread over transverse velocities [9], and testing the output cavity in the active-oscillator mode where the output power exceeding 10 MW is obtained at a frequency of 30 GHz for the TE 53 mode and the radiation duration equal to the supply-voltage duration [10,11]. 3 4 5 2 1 7 10 8 9 6 Fig. 1. * zaitsev@appl.sci-nnov.ru † Deceased.