Increasing the locking bandwidth of a waveguide-cavity oscillator through the use of a double-tuned circuit

The experimental 6 GHz Gunn oscillator consists of a TE101 waveguide cavity and a coupling slot, both being mechanically tunable in frequency. Fractional-bandwidth?voltage-gain products of approximately 0.2, corresponding to Qext = 10, were obtained. Comparison is made with other broadband injection-locked solid-state oscillators.     

Measurement of frequency shift in a gyrotron oscillator

A ballistic model of the interaction mechanism in gyrotron amplifiers and oscillators has been discussed in prior communications. It is the objective of the present contribution to support such purely theoretical investigations with some experimental evidence. In this connection it has been decided to measure the output frequency of a gyrotron oscillator and note its shift from the resonance frequency of the cavity when ‘cold’. According to the ballistic interaction model the frequency shift is a function of the beam current, the anode voltage and the axial magnetic field. It is shown that, except for a single parameter which depends on the exact value of the electromagnetic energy stored in the cavity, reasonable agreement can be achieved between theoretical predictions and the corresponding experimental results. A single-cavity gyrotron oscillator operating in a TE₀₂ mode has been used in the investigations.     

Axisymmetric quasi-optical gyrotron oscillator

An axisymmetric quasi-optical gyrotron (ASQUOTRON) is considered to realize a 10 MW, 150 GHz, CW oscillator required for an electron cyclotron resonance heating of a fusion plasma. The gyrotron has an axisymmetric mirror to be used as its optical cavity. It is shown that the axisymmetric mirror of relatively small radius (～20 cm) can be used in producing the 10 MW continuous wave with a tolerable mirror heat load (～0.5 kW/cm²). Considerations are also made on wave transmissions through the mirror and to a target.     

W波段三次谐波回旋振荡管的模拟与设计

研究了影响毫米波谐波回旋管互作用效率的多个因素,通过采用三次谐波工作,94 GHz回旋管的工作磁场降低到了1.185 T,使采用永磁体取代超导磁体成为可能.利用自洽非线性计算和粒子模拟研究了回旋振荡管的注-波互作用过程,发现了腔体品质因数与互作用效率的内在联系,研究了工作电压和电子注横纵速率比对耦合强度的影响,考虑了磁场渐变及电子注速度离散对互作用效率的影响,通过选择合理的工作模式和系统参数,当工作电压为40 kV、工作电流为12 A、电子注横向速度离散为3%时获得了95 kW的输出功率及19.7%的效率.当采用单级降压收集极后,效率可以进一步提高到39.2%.     

Study of the bandwidth characteristic of a non-reflection-type gyrotron TWA

With a set of equations for the self-consistent large-signal interaction derived in this paper, the bandwidth characteristics of a non-reflection-type gyrotron-TWA using a tapered waveguide and tapered magnetic field system have been analysed. Numerical calculations indicate that under defined conditions an instantaneous bandwidth of nearly 10 % at a center frequency of 35 GHz with a length of the order of only～8 cm of the rf interaction region could be achieved.     

PHASE-LOCKING OF HIGH POWER GYROTRON OSCILLATOR

The phase-locking process is studied for high-power gyrotron oscillator driven by an external signal. The phase-locking nonlinear differential equations are derived, and the condition of phase-locking is shown and analyzed. The phase-locking signal can be introduced after gyrotron oscillates into saturation or before it. Two different ways of inputting signal make markable influence on the phase-locking process, this phenomenon is discussed. In this paper, the numerical calculations and analysis are given for gyrotron TE13 mode.     

Low-frequency locking of a two-resonator parametric oscillator

Studies have been-made of a parametric oscillator pumped at frequency fp, with circuits resonant at fsoand fp-so, and an output taken at fp-so. The oscillator output frequency may be controlled by that of a small input signal applied at a frequency close to fso.     

W波段二次谐波回旋振荡器

针对谐波回旋管互作用效率低的问题, 以自洽非线性理论为基本工具, 系统地分析了三个关键因素, 即互作用腔体长度(Q值)、电子注的横纵速度比和工作电压对二次谐波互作用系统性能的影响.研究发现当工作磁场选择在硬激发区时, 通过综合调节电子注的横纵速度比和工作电压能够获得较高的互作用效率.基于自洽非线性理论优化设计了一个W波段二次谐波回旋振荡器, 粒子模拟(PIC)结果显示当电子注速度离散３％, 工作电压37 kV, 电流4 A时, 输出效率达到了39.5%.     

W波段低电压三次谐波回旋振荡管

回旋振荡管采用三次谐波工作方式的互作用磁场只有基波状态磁场的三分之一,可有效降低设计难度,具有广阔的应用前景。通过对三段式单腔结构的耦合系数、起振电流、高频场分布、模式竞争以及注波互作用研究,确定了工作模式为TE03的W波段低电压三次谐波回旋振荡管的基本工作参数;通过粒子模拟软件(PIC)模拟分析,在电子注电压、注电流及速度比分别为35 kV、4 A和1.6时,在93.7 GHz频点处获得15.57 kW的输出功率,效率约11.1%,且该管可在此工作模式下稳定工作。     

Formation and suppression of stationary and chaotic oscillations in a non-autonomous gyrotron backward-wave oscillator

Formation and suppression of chaotic oscillation modes in a non-autonomous gyrotron backward-wave oscillator is studied. It is shown that, in the considered system, developed chaotic oscillations and stationary single-frequency oscillations can be formed in a gyrotron tube upon variation in the frequency and power of an external signal. Domains in the plane of basic control parameters are found in which the considered oscillation modes of a non-autonomous gyrotron backward-wave oscillator are observed.     

Phase locking of a continuous-wave optical parametric oscillator to an optical frequency comb for optical frequency synthesis

A continuous-wave optical parametric oscillator (OPO) was phase locked to an optical frequency comb in the 830-nm region. The optical frequency of the OPO was controlled by changing the cavity length of the pump laser. The residual phase noise under phase locking was 220 mradrms and the energy concentration to the carrier was 95%. Furthermore, the optical frequency fluctuations of a free-running OPO were measured by using an optical frequency comb that was phase locked to an atomic clock. The measured fluctuations were around 10 MHz in an hour.     

BEAM-WAVE INTERACTION ANALYSIS IN THE COUPLED DOUBLE CAVITY GYROTRON OSCILLATOR

general equation of electron-wave synchronous interaction is obtained in gyrotron oscillator,in which the effects of guiding center drift and phase of RF field profile is considered.The interactionefficiency is calculated for the second harmonic operation of single TE_(021) mode for a double cavity gyrotronoscillator model,in which the RF field profile and operating parameters of the gyrotron oscillator areregulated in order to get optimum efficiency.It is shown that the efficiency of 53 percent can be obtained for a=1.5.The characteristic of the double cavity configuration is discussed.The bunching processes of thedouble cavities are compared with that of single cavity.The effects of guiding center drift and RF field profilephase on the beam-wave interaction are analysed.     

220 GHz共焦波导回旋振荡管的理论研究与模拟仿真

随着毫米波波段回旋管的研究深入,传统的封闭式圆波导谐振腔的弊端越发明显。根据回旋管非线性理论,设计了一只采用开放式准光谐振腔作为高频结构的回旋振荡管,其工作频率为220 GHz、工作电压为60 k V、电流为3 A、横纵速度比α为1.5、工作模式为HE06模。通过采用自主研发的三维粒子模拟软件CHIPIC对其进行数值模拟研究,分析其工作特性,并进一步优化参数。仿真结果表明:所设计的回旋管在磁场为8.57 T的条件下工作,可获得36 k W的峰值功率输出,输出功率效率可达20%。     

Theory of harmonic gyrotron oscillator with slotted resonant structure

A small signal theory is presented of the harmonic gyrotron oscillator with a slotted resonator. The magnetron-type wall structure has the effect of creating a strong harmonic field near the electron orbits and, as a result, greatly reducing the beam voltage and start-oscillation power required for harmonic operations. Characteristics of operation and methods of optimization are studied and numerically illustrated. It is shown that at a given harmonic the startoscillation beam power is lower at a lower beam voltage.     

140 GHz, TE22,6模式回旋振荡管高频谐振腔

通过数值计算方法,编程模拟了140 GHz, TE22,6模式回旋振荡管开放式缓变截面谐振腔的传播特性,计算出谐振腔的谐振频率和品质因数;利用CST软件对该高频谐振腔进行仿真计算,得到腔体内横截面的电场分布云图。通过实验和仿真软件得到的数据进行比较,两者有较好的一致性。测试结果表明,当磁场为5.48 T,电子注电流为28 A,电子注电压为68.6 kV时,TE22,6模式的平均输出功率为0.25 kW,峰值功率为0.56 MW。当磁场为5.68 T,电子注电流为27.6 A,电子注电压为69.12 kV时,回旋振荡管可同样工作于TE22,6,2模式,平均输出功率为0.21 kW,峰值功率为0.47 MW。     

An injection locking test for oscillator design

A simple injection-locking experiment for oscillator characterization is demonstrated. The measurements confirm theoretical treatments of injection locking.     

Second harmonic operation at 460 GHz and broadband continuous frequency tuning of a gyrotron oscillator

We report the short-pulse operation of a 460 GHz gyrotron oscillator both at the fundamental (near 230 GHz) and second harmonic (near 460 GHz) of electron cyclotron resonance. During operation in a microsecond pulse length regime with 13-kV beam voltage and 110-mA beam current, the instrument generates several watts of power in two second harmonic modes, the TE/sub 2,6,1/ at 456.15 GHz and the TE/sub 0,6,1/ at 458.56 GHz. Operation in the fundamental modes, including the TE/sub 0,3,1/ mode at 237.91 GHz and the TE/sub 2,3,1/ at 233.15 GHz, is observed at output powers up to 70 W. Further, we demonstrate broadband continuous frequency tuning of the fundamental modes of the oscillator over a range of more than 2 GHz through variation of the magnetic field alone. We interpret these results in terms of smooth transitions between higher order axial modes of the resonator. The 460 GHz gyrotron is currently being processed for continuous duty operation, where it will serve as a microwave source for sensitivity-enhanced nuclear magnetic resonance (dynamic nuclear polarization) studies at 16 T (700 MHz /sup 1/H), a field strength which is two-fold higher than has been accessible with previous technology.     

A new method of AM-PM conversion by using a locking oscillator

Phase modulated output can be obtained from an injection locked oscillator which has an amplitude modulated external force. The principle of AM-PM conversion and its experimental results are shown.