共查询到20条相似文献,搜索用时 578 毫秒
1.
S. O. Kuznezov V. I. Malygin 《Journal of Infrared, Millimeter and Terahertz Waves》1991,12(11):1241-1252
The output radiation of a gyrotron has the form close to the Gaussian beam. Knowing parameters of the wave beam along its way from a gyrotron to an object permits one to optimize the transmission losses. By this, the structure of the wave beam can be recorded with an infrared camera in several cross-sections of the beam. Real gyrotron wave beam is approximated with high precision by the Gaussian beam. 相似文献
2.
G. F. Brand 《Journal of Infrared, Millimeter and Terahertz Waves》1999,20(6):1207-1219
In previous papers we have shown how beams of millimeter-wavelength electromagnetic radiation with phase singularities can be generated by diffraction from a specially-configured forked blazed grating. Here we consider how the hollow conical beam output of a gyrotron is diffracted by this kind of grating. Two applications are considered; using the grating (a) as a single-element quasioptical antenna to convert the output into a well-collimated gaussian-like beam and (b) as a device to enable the estimation of the fractions in oppositely-rotating modes in the gyrotron output. 相似文献
3.
An improved design for quasi-optical mode conversion of whispering gallery mode gyrotron radiation 总被引:1,自引:0,他引:1
A. W. Möbius J. A. Casey K. E. Kreischer A. Li R. J. Temkin 《Journal of Infrared, Millimeter and Terahertz Waves》1992,13(8):1033-1063
Results are reported of a theoretical and experimental investigation of a quasi-optical mode converter for the transformation of whispering gallery mode gyrotron output into a linearly polarized Gaussian like beam. The mode converter consists of a helically cut waveguide launcher, similar to that originally proposed by Vlasovet al, followed by a focusing mirror. Theoretical results using aperture field methods indicate that the length of the waveguide launcher is of critical importance in providing a confined radiation pattern. Experimental results on the radiation pattern were obtained for several launcher lengths using a 0.6 MW, 149 GHz pulsed gyrotron operating in the TE16,2 mode. Radiation pattern results for the optimum launcher length agree well with theoretical calculations using the Stratton-Chu aperture radiation theory for unperturbed waveguide modes. A mirror focusing in the azimuthal direction was designed by a geometrical optics approach to focus the radiation coming from the launcher. Good focusing with 91.4% efficiency (power in the focused beam divided by gyrotron power) was found experimentally using the combined launcher and mirror with the pulsed gyrotron. These results indicate that quasi-optical antennas are useful for transforming high order, high frequency gyrotron modes into directed beams in free space. 相似文献
4.
准光模式变换器是大功率输出回旋管的关键部件.采用高转换效率的准光模式变换器可以横向输出电磁波,增大收集极的尺寸,提高回旋管的输出功率,提高整管效率.该文设计的回旋管内置准光模式变换器由Denisov辐射器天线和四个反射镜组成,输入频率为94GHz,模式为TE6,2模.采用耦合波理论分析和优化了Denisov辐射器内的场分布,并根据矢量绕射理论编制数值模拟程序计算了各个反射镜上的场分布,其输出功率转换效率达97.2%.利用三维全波仿真软件feko6.0进行对比分析,最后加工所设计的结构并内置于回旋振荡管进行热测实验,结果表明其输出场分布与理论计算结果基本一致. 相似文献
5.
V. V. P. Singh E. Borie A. K. Sinha B. N. Basu H. N. Bandopadhyay 《Journal of Infrared, Millimeter and Terahertz Waves》2000,21(4):485-504
This paper investigates the possibility of using Silicon Nitride Composite (Kyocera SN-287) as single-disc, edge-cooled window for gyrotrons operating below 200 kW CW in the frequency range 28-42 GHz. Rotationally symmetric TE0n, and TEM00 Gaussian modes of rf transmission through the window have been considered. Analysis performed using a one dimensional (1D) finite difference (FD) code reveals that thermal stresses developed due to non-uniform temperature distribution on the disc surface are well within manageable limits for a 200 kW 42 GHz gyrotron proposed for some ECRH applications. For industrial gyrotrons, for microwave material processing and operating at a maximum power level of 100 kW CW, Si3N4 windows may be a cost effective replacement for sapphire windows. It is found that a TE02 profile results in lower peak temperature at the window disc in comparison to a Gaussian beam profile and allows the use of smaller discs. 相似文献
6.
J. W. Radder K. M. Likin F. S. B. Anderson D. T. Anderson 《Journal of Infrared, Millimeter and Terahertz Waves》2008,29(4):360-372
The HSX oversized, mode-converting ECRH transmission line has been upgraded to a hybrid system to increase launched microwave power and reduce electrical arcing. Filtering of high-order, spurious modes ensures efficient coupling to a Gaussian beam for optimal electron heating. A Vlasov mode converter and two phase-correcting ellipsoidal mirrors convert the TE02 gyrotron output mode to a symmetric, linearly polarized, microwave beam. A swappable twist reflector plate rotates beam polarization for 2nd-harmonic X-mode or fundamental O-mode ECRH. Long distances are traversed by coupling the beam to a dual-mode (TE11?+?TM11), smooth, circular cross-section waveguide. This system has been successfully tested without arcing for 50 ms pulses and over 100 kW of launched power. Analysis of the microwave beam for 50 kW, 2 ms microwave pulses reveals agreement with predicted beam shapes at two beam locations. The new system has also demonstrated increased plasma stored energy for ECRH plasmas with equal launched power. 相似文献
7.
Sung Gug Kim Ashwini Sawant Ingeun Lee Dongsung Kim MunSeok Choe Jong-Hyo Won Jungho Kim Joonho So Won Jang EunMi Choi 《Journal of Infrared, Millimeter and Terahertz Waves》2016,37(3):209-229
A high-power W-band gyrotron has been designed and performance tested in Korea, with an output power in the range of tens of kilowatts. The gyrotron consists of a diode-type electron gun operating at 40 kV, a TE6,2 mode interaction cavity, and a mode converter for producing a highly Gaussian output mode beam. Presented here are the detailed component design procedure and the experimental results of the gyrotron’s performance evaluation. A maximum power of 62 kW was achieved with an efficiency of 22 %, and a highly Gaussian output beam was observed. The gyrotron’s output beam is analyzed, and its transmission through an oversized waveguide is discussed. This gyrotron is the first gyrotron developed in Korea with high power greater than 10 kW and high frequency greater than 90 GHz. 相似文献
8.
S. N. Spark A. D. R. Phelps P. R. Winning 《Journal of Infrared, Millimeter and Terahertz Waves》1991,12(8):885-894
The extended frequency tuning range of the Strathclyde University gyrotron is demonstrated. The gyrotron consisted of a field-immersed, field emission cold cathode and a shaped anode cavity. The cavity was oversized with an ill-defined boundary at one end. This system could therefore support the oscillation of a very large number of TEpqs modes. The maser was thus highly tunable via differential mode excitation. A heterodyne technique was used to demonstrate the maser oscillation in the Ka-band (26.5–40GHz), with the maser oscillating at 35GHz in the TE01 mode. Previous to this a quasi-optical diffraction grating spectrometer was used to show the maser was oscillating under different conditions respectively, single and multi-mode in the W-band (75–110GHz) and multi-mode in the G-band (140–220GHz). To control the output beam a quasi-optical mode converter has been successfully developed. This converts various TEpq modes into a Gaussian beam. Studying the output of the maser, the mm-wave pulse has been shown to consist of a ~100ns envelope containing ~2ns pulses spaced ~5ns apart. Although this behaviour may have several explanations, some of the most recent code simulations predict this behaviour as a result of mode beating in the complex transient start-up of the maser oscillation. Since this gyrotron not only supports many transverse modes, but also several longitudinal modes, such beating is a likely consequence. 相似文献
9.
The cyclotron autoresonance maser (CARM) is considered as a possible source of millimetre and submillimetre coherent radiation with large average power. At present the most acute problems of CARM creation are the formation of a curvilinear relativistic electron beam with a small spread of velocities and mode discrimination. Two kinds of electron-optical systems can be used: a magnetron-injection gun (gyrotron type) and a quasi-Pierce gun with undulator (kicker). Undesirable gyrotron modes in CARM can be suppressed by choosing a proper operating regime. The main schemes of electron-optical and electrodynamic systems were verified in preliminary experiments with CARM. In short pulse operation a power of 30-50 MW was obtained at wavelengths of 4-4 mm and 6 mm with an efficiency 8-10%. Calculations show that CARM with average power 1-10MW at 1-2 mm is realizable. 相似文献
10.
A low-power tunable quasi-optical gyrotron was designed for driving free electron laser amplifiers in the frequency ránge of 220–270 GHz. The gyrotron cavity consisted of a spherical mirror and a plane slotted mirror to produce a Gaussian radiation output beam. Output powers of 1–10 kW were obtained in the 4 cm length cavity by a few amperes of electron beams with a voltage of 30 kV. 相似文献
11.
低电压频率可调太赫兹回旋管在生物医学和波谱学等领域具有重要应用。文章分析了超低电压(<1 kV)下采用传统开放腔互作用电路的330 GHz 回旋管输出功率和频率调谐特性,探讨了超低电压下由于电子相对论效应减弱而导致的回旋管中电子注-波互作用耦合强度降低的问题。在此基础上,针对330 GHz 超低电压回旋管提出了一种改进的互作用电路结构,其下倾式尾端结构有助于增大反向波幅度,提高弱相对论电子注与电磁波之间的耦合强度,从而提高回旋管的输出效率及频率调谐带宽。非线性模拟结果表明,在低至0.3 kV 的超低电压下,采用此种互作用电路结构仍可获得大于1 W 的连续波输出功率及22 GHz 的连续调谐带宽,峰值输出效率大于7%。 相似文献
12.
13.
David S. Tax Eunmi M. Choi Ivan Mastovsky Jeffrey M. Neilson Michael A. Shapiro Jagadishwar R. Sirigiri Richard J. Temkin Antonio C. Torrezan 《Journal of Infrared, Millimeter and Terahertz Waves》2011,32(3):358-370
We present an internal mode converter (IMC) design for a 1.5 MW, 110 GHz gyrotron operating in the TE22,6 mode. The launcher, designed using the codes Surf3d and LOT, converts the cavity waveguide mode into a nearly pure Gaussian
beam. The Gaussian beam output from the launcher is shaped by a series of 4 smooth, curved mirrors to provide a circular output
beam with a flat phase front at the gyrotron window. By employing smooth mirrors rather than mirrors with phase correcting
surfaces, such an IMC is less sensitive to alignment issues and can more reliably operate with high efficiency. The IMC performance
was verified by both cold test and hot test experiments. Beam pattern measurements in each case were in good agreement with
theoretical predictions. The output beam was of high quality with calculations showing that the Gaussian Beam content was
95.8 ± 0.5% in both hot and cold test. 相似文献
14.
H. Richter N. Rothbart H.-W. Hübers 《Journal of Infrared, Millimeter and Terahertz Waves》2014,35(8):686-698
Terahertz quantum-cascade lasers (QCLs) are very promising radiation sources for many scientific and commercial applications. Shaping and characterizing the beam profile of a QCL is crucial for any of these applications. Usually the beam profile should be as close as possible to a fundamental Gaussian TEM00 mode. In order to completely characterize the laser beam the power and the wavefront have to be measured. We describe methods for characterizing the beam properties of QCLs. Several QCLs with single-plasmon waveguide and emission frequencies between 2 and 5 THz are investigated. The beam profiles of these lasers are shaped into almost fundamental Gaussian modes using dedicated lenses. The beam propagation factor M2 is as low as 1.2. The wavefront is measured along the axis of propagation with a THz Hartmann sensor. Its curvature behaves as expected for a Gaussian beam. The applied methods can be transferred to any other THz beam. 相似文献
15.
Highly Efficient Quasi-Optical Mode Converter for a Multifrequency High-Power Gyrotron 总被引:2,自引:0,他引:2
Prinz O. Arnold A. Gantenbein G. Ying-hui Liu Thumm M. Wagner D. 《Electron Devices, IEEE Transactions on》2009,56(5):828-834
A highly efficient quasi-optical mode converter with a bandwidth of 38 GHz has been designed and tested. The mode converter combines low-diffraction losses and a Gaussian mode content up to 97% for a set of nine modes in the range of 105 to 143 GHz for a 1-MW CW gyrotron. This was achieved using a dimpled-wall waveguide antenna (launcher), one quasi-elliptical mirror, and two toroidal mirrors. The optimization of the launcher was done using coupled-mode theory. The simulation results show a well-focused Gaussian beam for all nine operating modes. The curvature radii of the toroidal mirrors were determined by Gaussian mode transformation (ABCD-law) and subsequently optimized for a multimode operation. The simulations of the quasi-optical mode converter are based on the electric field integral equation and, thus, are 3-D. Experimental low-power measurements show close agreement with predictions. 相似文献
16.
17.
The mode-matching technique (MMT) is used to compute the electromagnetic fields, stored energy, and input admittances of a gyrotron cavity coupled to one or more waveguides. The method is based on matching the cavity and waveguide eigenmodes across the cavity apertures and accommodates cavity walls of finite conductivity. The MMT is used in the gyrotron problem because fields in and near the aperture must be computed accurately, and because the eigenmode decomposition is advantageous for inclusion of an electron beam. Irrotational modes are part of the complete set of orthogonal vectors required to expand an H-field in an open cavity, but were excluded in most gyrotron literature; here, this is corrected. The MMT is numerically implemented for cavities of rectangular and circular cross section. Coupling between different modes in a gyrotron cavity through external and ohmic losses is demonstrated. A coupled (complex) cavity gyrotron design is analyzed using MMT. The energy and modal spectra of the cavity are computed, demonstrating the mode selective properties of the design 相似文献
18.
高次谐波太赫兹回旋管的多模工作研究 总被引:1,自引:1,他引:0
为了发展大功率、实用性强的太赫兹辐射源,文中对太赫兹回旋管中多个二次谐波工作模式的注波互作用进行了理论和实验研究,分析不同参数下多个二次谐波工作模式单模振荡的条件.实验研究结果表明,在二次谐波工作状态下,通过调节工作磁场、电流等参数,在单管中实现了四个不同频率0.391、0.404、0.416、0.423 THz,千瓦级以上输出功率的太赫兹波辐射. 相似文献
19.
针对170 GHz兆瓦级回旋管短脉冲实验对蓝宝石输能窗的实际要求,分析了蓝宝石窗传输高斯波束的反射和吸收特性,优化设计了低反射、低损耗蓝宝石输能窗的工程方案。对研制的蓝宝石窗部件进行微波冷测,驻波比(VSWR)小于1.1,验证了蓝宝石窗的低反射特性;计算结果表明该结构的最大输出平均功率阈值为590 W。对使用该蓝宝石窗研制的170 GHz回旋管进行测试,验证了理论计算的功率阈值,为大功率回旋管蓝宝石输能窗的实际应用提供了依据。 相似文献
20.
T. Saito T. Nakano H. Hoshizuki K. Sakai Y. Tatematsu S. Mitsudo I. Ogawa T. Idehara V. E. Zapevalov 《Journal of Infrared, Millimeter and Terahertz Waves》2007,28(12):1063-1078
A 300 GHz CW gyrotron FU CW I has been developed and installed in the Research Center for Development of Far-Infrared Region, University of Fukui as a power source of a high frequency material processing system. Its performance was tested and the maximum power of 1.75 kW / CW has been attained at the beam voltage of 15 kV and the beam current of 1A. The maximum window power efficiency of 15.5% has been obtained at the cathode voltage slightly lower than 15 kV. This gyrotron is designed to deliver a Gaussian beam after mode conversion from the oscillation mode TE22,8 in the cavity with a complex of an internal radiator and beam shaping mirrors. The detailed measurement with an infrared camera has confirmed that a Gaussian beam is radiated when the magnetic field strength B c at the cavity is adjusted at a proper value. However, within a range of B c , the output power is emerged into multiple directions, which suggests simultaneous oscillation of competing cavity modes. 相似文献