Comparison of Multistage Gyroamplifiers Operating in the Frequency-Multiplication Regime With Gyroamplifiers Operating at a Given Cyclotron Harmonic

The harmonic multiplying operation in a gyrotron traveling-wave amplifier (gyro-TWA) permits magnetic field reduction and frequency multiplication. This study presents a comparative analysis of fourth-harmonic multiplying gyro-TWAs with three schemes of operation. An improved mode-selective circuit using circular waveguides with various radii provides the rejection points within the range of operating frequencies to suppress the competing modes of gyro-TWAs. The simulated results reveal that gyro-TWAs are the most susceptible to the fundamental-harmonic TE11 competing mode, regardless of the operating scheme, and that the mode-selective circuit can provide an attenuation of more than 20 dB to suppress the competing modes. The amplification of the waves in a gyro-TWA depends on the lengths of the sections, and the simulated results show that the gain increases for all schemes, as the length of the lossy section or the length of the copper section increases. All schemes exhibit nearly the same saturated output powers and bandwidths; however, the saturated gain of the scheme at a high frequency multiplication ratio is less than that of the scheme at a low frequency multiplication ratio. Extensive numerical calculations of power and gain scaling are conducted for all schemes.

show abstract

Comparative analysis of terahertz fourth-harmonic gyro-TWAs and multiplying gyro-TWAs with axis-encircling electron beams

Yeh

Luo

Huang

et al. 2020

AIP Advances

View full text Add to dashboard Cite

The harmonic operation in a terahertz gyrotron traveling-wave amplifier (gyro-TWA) permits a reduced magnetic field, whereas a harmonic multiplying gyro-TWA enables magnetic field reduction and frequency multiplication. This study comparatively analyzes the 400-GHz fourth-harmonic gyro-TWAs and fourth-harmonic multiplying gyro-TWAs with axis-encircling electron beams. This property of the gyro-TWAs with axis-encircling electron beams enables us avoid the appearance of the majority of the competing modes. According to the simulation results obtained using multi-mode codes, the attenuating severs suppress the remaining competing modes. In the case of a harmonic gyro-TWA containing a sever section, the copper-section start-oscillation length is significantly influenced by a decrease in the sever-section radius when compared with an increase in the sever-section length. Furthermore, a stable fourth-harmonic TE41-mode gyro-TWA containing sever sections is proposed. We propose fourth-harmonic TE41-mode multiplying gyro-TWAs, where the drive stages operate in the fundamental-harmonic TE11 mode to reduce the frequency of the drive wave. We subsequently develop a stable fourth-harmonic multiplying gyro-TWA with sever sections in the drive and amplified stages to avoid the competing modes and enhance the output power. The stable high-gain fourth-harmonic gyro-TWA can yield a peak output power of 2.7 kW at 400.6 GHz with a saturated gain of 75 dB and a bandwidth of 0.7 GHz for a 75-kV and 2-A electron beam with an axial velocity spread of 3%. Furthermore, a peak output power of 1.7 kW can be obtained by the fourth-harmonic multiplying gyro-TWA at 400.4 GHz with a saturated gain of 57 dB and a bandwidth of 0.4 GHz. Subsequently, we calculate the power and gain scaling for the harmonic gyro-TWA and harmonic multiplying gyro-TWA.

show abstract

Comparison of Multistage Gyroamplifiers Operating in the Frequency-Multiplication Regime With Gyroamplifiers Operating at a Given Cyclotron Harmonic

Cited by 6 publications

References 32 publications

Gyromultiplier with sectioned cavity

Gyromultiplier with sectioned cavity

Comparative analysis of fourth-harmonic multiplying gyrotron traveling-wave amplifiers operating at different frequency multiplications

Comparative analysis of terahertz fourth-harmonic gyro-TWAs and multiplying gyro-TWAs with axis-encircling electron beams

Contact Info

Product

Resources

About