共查询到20条相似文献,搜索用时 31 毫秒
1.
A. Fernández W. Kasparek K. Likin R. Martín 《International Journal of Infrared and Millimeter Waves》2001,22(5):649-660
TJ-II plasma start-up and heating are made by electron cyclotron resonance waves at the second harmonic of the electron cyclotron frequency. Two quasi-optical transmission lines transmit the microwave power of the gyrotrons to the vacuum vessel. The first line launches the microwave power under fixed injection geometry, i.e. there is no possibility to change the launching angle and the wave polarization. The second line has a moveable mirror installed inside the TJ-II vessel. To get high absorption efficiency and a narrow energy deposition profile the internal mirror focuses the wave beam at plasma center.To get more flexibility in the experiments on heating and current drive the first transmission line needs to be upgraded. The design is presented in this paper. The new launching antenna includes an internal mirror to focus the beam and to change the injection angle. Both launchers are then symmetrical. A polarizer consisting of two corrugated mirrors is used to get any wave polarization. Two mirrors with an array of coupling holes and calorimetric measurements of the energy absorbed in the barrier window allow the estimation of the microwave power launched into the TJ-II. 相似文献
2.
I. Ogawa Y. Miyake T. Idehara S. Sabchevski 《International Journal of Infrared and Millimeter Waves》2002,23(1):1-19
A novel focusing mirror based on the shifting of the beam phase according to the Gaussian beam optics enabled us to realize a focusing elements with different focal lengths in different directions and to convert the gyrotron output into a Gaussian-like beam. In this paper, we compare the quality of beams produced by the new system (which includes novel mirrors) and a conventional system consisting of a quasi-optical antenna, an ellipsoidal mirror and two parabolic cylinder mirrors. 相似文献
3.
Michael P. Perkins Rong Cao Jeffrey M. Neilson Ronald J. Vernon 《International Journal of Infrared and Millimeter Waves》2007,28(3):207-218
A four-mirror internal quasi-optical mode converter designed for a CPI gyrotron is discussed. Many improved methods were used
in designing the mode converter. The launcher was designed and analyzed using the TOL and Surf3d codes developed by CCR. Mirrors
1 and 2 were designed using analytic surfaces to shape the general wavefront curvature of the beam radiated from the launcher.
Mirrors 3 and 4 were iteratively designed using improved techniques that produced smooth mirror surfaces. Good agreement was
found between theory and low-power cold-test measurements. The fraction of power coupled between the target Gaussian beam
and the output of mirror 4, inferred from measurements, was 0.990. The stray radiation from the internal quasi-optical mode
converter, inferred from measurements, was only 1.9% of the total power radiated from the launcher. This resulted in a high
overall system efficiency of 97.0%, which is greater than previous designs. 相似文献
4.
X. Yang O. Drumm A. Arnold E. Borie G. Dammertz K. Koppenburg B. Piosczyk D. Wagner M. Thumm 《International Journal of Infrared and Millimeter Waves》2003,24(10):1599-1608
The quasi-optical mode converter for a frequency step-tunable gyrotron which consists of a dimpled-wall antenna (Denisov-type launcher) and a beam-forming mirror system has been optimized for 9 modes from TE17,6 at 105 GHz to TE23,8 at 143 GHz. The first mirror is a large quasi-elliptical focusing one; the second and third are phase-correcting mirrors with a non-quadratic shape of the surface. The results of calculations show that for these modes the Denisov-type launcher has a well-focused beam with low diffraction losses, and the radiation pattern presents an almost identical field shape for all modes considered. A multi-mode optimization of the phase-correcting mirrors with two different methods has been tested. The simulations show that the phase-correcting mirrors can be used for broadband operation in the frequency range from 105 GHz up to 143 GHz in the various design modes. This quasi-optical mode converter can achieve efficiencies of 94%-98% for converting the rotating high-order cylindrical cavity modes into the usable fundamental Gaussian mode. 相似文献
5.
I. Ogawa T. Idehara M. Pereyaslavets W. Kasparek 《International Journal of Infrared and Millimeter Waves》1999,20(4):543-558
Gaussian optics can be used to design a quasi-optical system converting the TE06 mode output (f=388 GHz) of a submillimeter wave gyrotron into a well-collimated, linearly-polarized free-space beam with a circular cross-section. A quasi-optical antenna produces a main beam with an elliptical cross-section, which is then converted by two mirrors into a well-collimated beam with a circular cross-section. 相似文献
6.
P. R. Winning S. N. Spark A. D. R. Phelps 《International Journal of Infrared and Millimeter Waves》1991,12(6):629-648
A series of electron cyclotron masers (ECMs) has been designed and successfully operated in the frequency range of 6 to 200 GHz over the past 10 years at Strathclyde University. The current Mk. VI ECM operated between 35–200 GHz, the TE
0 1
0
mode (35.2 GHz) being the lowest order cavity mode excited. Investigation of this ECM and quasi-optical converter combination was made to establish to what extent a Gaussian beam could be produced from the TE
0 1
0
gyrotron cavity mode.An antenna of the Vlasov (step-cut radiator) configuration was chosen and successfully developed in a series of low-power experiments up to the W-band frequency regime. The low-power experiments demonstrated that such an antenna system could be constructed and operated in the Ka-band frequency region without resorting to high precision quasi-optical components. The final version of the quasi-optical antenna was externally coupled to the output window of the maser and a plane polarized pencil beam was successfully obtained from the combined maser/Vlasov antenna mode converter.A theoretical model involving a single TE
0n
0
input mode was chosen to analyse the output beam characteristics from the Vlasov antenna system. Comparison was made between the single mode theoretical model and the experimental results obtained from the maser. 相似文献
7.
High-frequency gyrotron operation in the TE611 whispering gallery mode is reported. Powers as high as 112 kW and an efficiency as high as 25.4 percent have been obtained. In addition to the TE611 mode, ten other fundamental modes with frequencies between 133.9 and 216.4 GHz were observed. A quasi-optical antenna for whispering gallery modes has been tested for the TE611 mode. The combination of this antenna and a reflector produces a well-collimated linearly polarized RF beam suitable for electron cyclotron resonance heating (ECRH) or plasma diagnostics. The experimental conversion efficiency was determined to be 89 percent, and the cross polarization was down by 25 dB. A new quasi-optical transmission line employing this antenna has also been tested with the gyrotron. The absence of mode competition for the TE611 mode, as well as the efficient conversion of the output radiation into a linearly polarized Gaussian-like beam, substantiates the arguments for operation in surface modes in high-power gyrotrons. The implications of quasi-optical antennas for megawatt gyrotron window design are discussed. 相似文献
8.
Alvaro Gonzalez Yoshinori Uzawa Yasunori Fujii Keiko Kaneko 《Infrared Physics & Technology》2011,54(6):488-496
The ALMA Band 10 (787–950 GHz) receiver is a dual-polarization heterodyne system based on NbTiN superconducting technology. The coupling of energy from the secondary mirror of the ALMA Cassegrain antenna to the Superconductor–Insulator–Superconductor (SIS) mixers used for down-conversion is achieved by a frequency-independent optical system composed of two elliptical mirrors to focus and redirect the incoming radiation, a wire-grid to separate orthogonal linear polarizations and two corrugated horns, one for each polarization and SIS mixer. In this paper, we present the ALMA Band 10 tertiary optics design and evaluate its performance by quasi-optical techniques, Physical Optics simulations and measurements. Detailed results of secondary aperture efficiency and beam-squint are provided. The characterization procedure described in this paper can be used for any optical system at around 1 THz. 相似文献
9.
Takanari Yasui Takeshi Ohtsuka Tetsu Suzuki Shigeki Okajima Kazuya Nakayama Mitsuru Tomioka Katsuhiro Kamimura Takeo Namekata Hiroaki Minamide Hiromasa Ito 《International Journal of Infrared and Millimeter Waves》2006,27(2):199-210
A new, wide-band, high-speed and high-sensitivity THz detector has been developed. The prototype detector consists of a parabolic
cylindrical mirror, a long wire antenna and a Schottky barrier diode. Direct detection measurements have shown a stable sensitivity
of 150 ± 50 V/W for 1–2 THz without any adjustments. The long wire antenna was fixed at the focus of parabolic cylindrical
mirror then it has been realized less operation steps, easy coupling to the external THz signals and a dramatic enhancement
in the practicality of this system. The optically polished mirror and frosted surface one showed comparable sensitivities,
thus easy polishing and less cost mirror fabrication can be applied for this system. The radiation pattern showed a maximum
radiation angle of approximately 23° with its dominant main lobe, which was attributed to the wire antenna character and confirmed
good agreements with classical antenna theory. 相似文献
10.
11.
A. A. Bogdashov A. V. Chirkov G. G. Denisov D. V. Vinogradov A. N. Kuftin V. I. Malygin V. E. Zapevalov 《International Journal of Infrared and Millimeter Waves》1995,16(4):735-744
A new approach for the design of a quasi-optical gyrotron mode converter is proposed. It is based on the synthesis of quasi-optical mirrors using diffraction (Helmholtz-Kirchhoff) integrals. First application of such a method we already described in [1, 2]. Now a more powerful technic is used to provide optimal distributions of the wave beam field. It is shown that by means of specially shaped mirrors parameters of the main converter are enhanced strongly. In this paper we review the search for the optimal scheme of the converter, present and compare results of calculations and measurements of the gyrotron wave beam. 相似文献
12.
This paper describes an experimental study of a quasi-optical cavity to be used in qyrotrons. The cavity configuration was designed so that its output wave could pass into a quasi-optical transmission line. The test cavity was coaxially composed of a pair of annular mirrors, one of which was a curved conical mirror and the other was a plane mirror having a radial slot array for wave output. A mode excited in the cavity at 56.4 GHz was observed by detecting the radiation wave that leaked out through the slotted mirror. It was shown that the present slotted mirror served as a partially and uniformly transparent mirror to radiate the output wave with the same mode as in the cavity. 相似文献
13.
I. Ogawa T. Idehara A. Sakai K. Yoshida T. Tsuchida K. Kawahata A. Ejiri H. Iguchi K. Tanaka K. Matsuoka R. Akiyama M. Osakabe S. Okamura T. Minami C. Takahashi W. Kasparek 《International Journal of Infrared and Millimeter Waves》1998,19(5):727-736
Intense submillimeter wavelength radiation (f=354 GHz, P=110 W) from Gyrotron FU II is converted into a well-collimated, linearly-polarized beam by a quasi-optical transmission line consisting of a quasi-optical antenna and several mirrors. The observed focusing of the beam agrees with calculations based on the Huygens equation. We have used this intense beam to study low frequency density fluctuations by plasma scattering in Compact Helical System (CHS) plasmas at the National Institute for Fusion Science. 相似文献
14.
Jiayu Chen Zheng Liang Yongchuan Zhang Ziqiang Yang 《International Journal of Infrared and Millimeter Waves》2000,21(10):1563-1567
A novel Smith-Purcell FEL with a relativistic electron beam of middle energy and a quasi-optical resonator composed of diffraction grating and three mirror reflector is described in this paper. Coherent radiation with peak power of tens of KW at 3 mm waveband is successfully detected from an experimental facility characterized by beam energy of 400-500 KeV, pulse length of 70 ns, pulse beam current of 0.2 KA, and pulse guide magnetic field of up to 1.2 T. 相似文献
15.
张文 李宁蒋玲 缪巍林镇辉 姚骑均史生才陈健 吴培亨S.I.Svechnikov Yu. B. Vachtomin S. V. Antipov B. M. voronov G. N. Gol'tsman 《中国物理快报》2007,24(6):1778-1781
A quasi-optical superconducting NbN hot-electron bolometer (HEB) mixer is measured in the frequency range of 0.5-2.5 THz for understanding of the frequency dependence of noise temperature of THz coherent detectors. It has been found that noise temperature increasing with frequency is mainly due to the coupling loss between the quasioptical planar antenna and the superconducting HEB bridge when taking account of non-uniform distribution of high-frequency current. With the coupling loss corrected, the superconducting HEB mixer demonstrates a noise temperature nearly independent of frequency. 相似文献
16.
Huiyun Wu Haotong Ma Xiaojun Xu Jinbao Chen Yijun Zhao 《Optical and Quantum Electronics》2013,45(1):1-9
Improving power coupling efficiency of beam uplink propagation in a relay mirror system is under extensive research in recent years. A typical model of the relay mirror system is established and theory of beam shaping used to improve power coupling efficiency of the relay mirror system is analyzed in detail. A reduced-scale experimental relay mirror system is founded, which has the same Fresnel number as uplink propagation in the relay mirror system with 1.0 m-caliber transmitter and 30?km propagation distance. Phase distribution of the source is optimized by using the stochastic parallel gradient descent algorithm. The experimental results showed that power coupling efficiency of uplink propagation in the reduced-scale relay mirror system was improved from 72.67 to 87.88 % by beam shaping and the bucket power proportion in 5 pixels at the target was improved from 45.49 to 52.78 %. 相似文献
17.
D. V. Vinogradov 《International Journal of Infrared and Millimeter Waves》1995,16(11):1945-1963
The surface of an inclined mirror, which converts Gaussian beams with simple astigmatism hase been found within the quasi-optical approximation. The beam reflected from the found mirror was examined. Power losses of the reflected beam, when the beam is incident on a selective system, which transmits a Gaussian beam of one polarization only have been found. 相似文献
18.
Yijun He Quanrang Yang 《International Journal of Infrared and Millimeter Waves》1993,14(11):2371-2378
A uniform high-frequency solution is presented for the diffraction by a dielectric spherical mirror by a Gauss beam. Using the complex source-point theory, the radial field of quasi-optical power combiner is obtained. The E or H plane patterns of the combiner are calculated. 相似文献
19.
A. W. M?bius J. A. Casey K. E. Kreischer A. Li R. J. Temkin 《International Journal of Infrared and Millimeter 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
20.
N. L. Aleksandrov A. V. Chirkov G. G. Denisov D. V. Vinogradov W. Kasparek J. Pretterebner D. Wagner 《International Journal of Infrared and Millimeter Waves》1992,13(9):1369-1385
The excitation of very high-order modes in circular waveguides has been performed in a cavity with a connected up-taper with a geometry similar to those used in gyrotrons. A Gaussian beam was coupled to the cavity which was made translucent by an array of holes. With the help of a special optics, the amplitude as well as the phase distribution of the beam was matched to the mode to be excited in the resonant cavity. By simple rotation of one mirror to adjust the phase distribution together with the change of frequency to match the resonance condition, a large number of modes could be produced with one experimental set-up. Field measurements in the output waveguide show a high mode purity of the radiation and confirm the calculations. The method can be used for cold tests of electrodynamic systems operating with these modes, e.g. quasi-optical converters for gyrotrons. 相似文献