一种新型的强流相对论等离子回旋管

本文介绍了一种新型的强流相对论器件——强流相对论等离子回旋管。叙述了在强流相对论性器件中填充等离子体实现空间电荷补偿的原理,及苏联科学院普通物理所在3cm波段获得的实验结果。     

0.42THz频率连续可调同轴回旋管

作为目前工作在太赫兹频段输出功率最大的辐射源之一回旋管的功率可达到数十千瓦. 传统太赫兹回旋管一般为点频工作,难以满足动态核极化核磁共振等多方面技术需要。采用机械调节的方式,实现了带宽为2GHz中心频率为0.42THz二次谐波频率连续可调同轴回旋管,通过非线性理论分析发现,在不改变工作磁场条件下,在调节带宽范围内,可实现大于8kW的功率输出.     

兆瓦级回旋管单级降压收集极横向磁扫描系统的仿真

对170 GHz兆瓦级回旋管单级降压收集极横向磁扫描系统进行了仿真.采用单级降压收集极一方面回收了废电子注的部分活跃能量同时提升总输出效率超过55%.横向磁扫描系统的引入扩展了废电子注轨迹长度至1100 mm,使收集极表面热耗散保持在技术允许范围内.此外仿真得到了扫描信号的调制深度以及横向线圈数的最优结果 38. 9%和6,以及可接受的最大平均功率值117. 1 W/cm~2.为了确保在实际工作中的安全性和可行性,设计了轴向开槽的收集极冷却系统,利用软件ANSYS开展了收集极的热和流体分析.得到收集极内外表面的最高温度各自为156. 09℃和140. 35℃.进水口和出水口的水温范围分别为20～26. 68℃和38. 01～58. 56℃.     

大功率毫米波回旋管发射机的设计

阐述了利用新型大功率毫米波器件回旋管研制大功率毫米波雷达发射机的系统方案及设计难点。根据回旋管放大器的组成和特点,讨论了发射机中应用的全固态调制器等关键技术及其设计方法。指出了目前回旋管发射机存在的问题。     

Review of quasi-optical gyrotron development

There is currently a need for megawatt average power sources of 100–600 GHz radiation for electron cyclotron heating of fusion plasmas. One of the leading candidates for such a source, the conventional wave guide cavity gyrotron,⁽¹⁾ has produced impressive output powers and efficiencies at frequencies up to about 300 GHz. However, this gyrotron configuration is limited at high frequencies by high ohmic heating and problems with transverse mode competition due to the highly overmoded configuration, and with beam collection, since the beam must be collected along a section of the output waveguide. The quasi-optical gyrotron (QOG), first proposed in 1980 by Sprangle, Vomvoridis, and Manheimer,⁽³⁾ features an open resonator formed by a pair of spherical mirrors instead of a waveguide resonator and has the potential for overcoming each of these limitations. The resonator mirrors can be well removed from the beam-wave interaction region, allowing a large volume for the interaction and low ohmic heating densities at the mirrors. The beam direction is transverse to the resonator so that beam collection is separate from the output waveguide. This geometry is particularly well suited to the use of a depressed collector for electron beam energy recovery. The QOG operates in the lowest-order transverse (TEM_ool) Guassian mode of the resonator, higher-order transverse modes being effectively suppressed by higher diffraction losses. This paper reviews recent progress toward the development of high-power quasi-optical gyrotrons for ECRH of fusion plasmas. It includes an overview of gyrotron theory in terms of normalized variables as they apply to the quasi-optical gyrotron for operation both in the fundamental and the higher harmonics. Scaling equations for the output power and resonator mirror heating by the RF are given. The design tradeoffs between annular and sheet electron beams are discussed as is the issue of beam space-charge depression in the open resonator. Recent advances in the analysis and design of QOG configurations capable of efficient and stable single-mode operation are discussed, showing the possibility of achieving 50% transverse efficiency in highly overmoded resonators. The application of a depressed collector is discussed as a means of recovering the energy in the axial motion of the spent electron beam and, thus, raising the output efficiency to near the transverse electronic efficiency. The problem of high field magnet design is addressed, for both fundamental and higher harmonic operations, the latter being necessary at very high frequencies. The design equations and tradeoffs are applied to the design of 1-MW, CW quasi-optical gyrotrons operating at 120 GHz, in the first and second harmonic at 280 GHz and in the second harmonic at 560 GHz. The output coupling for these 1 MW designs is 5–7% showing the potential for even higher powers per tube if sheet-beam electron guns can be developed. The estimated electronic efficiency of the fundamental harmonic designs is 23%, which leads to an output efficiency of 47% with the use of a depressed collector with a modest collection efficiency. The peak ohmic heating density is 500 kW/cm² in all the designs. This leads to resonator mirror separations ranging from 127 cm for 120-GHz design, to 232 cm for the 560-GHz, second harmonic design. Finally, a simple output system composed of'elliptical and parabolic mirrors is described that converts the output radiation from the resonator into a parallel, quasi-Gaussian beam. Experimental programs are reviewed as well, including the recent experiment at the Naval Research Laboratory that produced frequencies ranging from 95–130 GHz and powers up to 150 kW. Operation in a single mode was observed at powers up to 125 kW despite the resonator being highly overmoded. Comparison is made with the theoretically-predicted region of single-mode operation. Recent progress in the experimental characterization of QOG resontors is summarized.     

应用于动态核极化核磁共振的太赫兹回旋管

太赫兹波驱动的动态核极化核磁共振波谱技术能将信号灵敏度提高几个数量级,太赫兹回旋管可实现高功率输出,并有一定的频率调谐范围,符合核磁共振波谱系统对太赫兹辐射源的需求。介绍了应用于核磁共振波谱系统的频率可调太赫兹回旋管的发展,研究了多段式腔体结构以及频率可调太赫兹回旋管中工作电压和磁场与电子注质量的关系。在应用于动态核极化核磁共振的太赫兹频率可调回旋管工作时,多段式腔体结构明显优于传统三段式谐振腔。在设计太赫兹频率可调回旋管时,不仅要考虑改变工作电压或磁场导致的电子横纵速度比的变化,而且还要考虑改变工作电压或磁场导致的电子速度离散和引导中心半径离散的变化。     

140 GHz兆瓦级回旋管高斯模式输出窗设计

根据热核聚变用140 GHz回旋振荡管研制需要,对高斯模式输出窗进行研究。以化学气相沉积金刚石作为输出窗片的材料,通过理论分析,优化设计出低反射、低吸收高斯模式输出窗片的尺寸,获得窗片半径和厚度分别为46 mm和1.8 mm。通过理论分析各参数对高斯模式透射率的影响,并利用FEKO软件进行计算验证,获得高斯模式输出窗设计参数,从而为热核聚变用回旋振荡管的研究打下技术基础。     

大半径同轴谐振腔太赫兹回旋管研究

 为了发展大功率太赫兹辐射源,本文对大半径同轴谐振腔回旋管进行了理论和数值模拟研究,理论计算结果表明在同轴谐振腔中其角向对称的TE_0n模式的截止频率与n近似成正比关系,与内外导体之间的距离近似成反比关系.根据上述特点作者设计了一只大半径同轴腔0.3THz、TE₀₄模回旋管,数值计算和粒子模拟结果表明:大半径同轴谐振腔太赫兹回旋管与空心波导谐振腔回旋管相比具有很多优点:腔体尺寸相对较大,工作电流可以大幅度提高;其对称的TE_0n模式与非对称的TE_mn模式的间隔较大,有利于克服模式竞争.     

W波段边廊模回旋管Vlasov模式变换器的辐射场研究

采用几何光学模型详细研究了边廊模回旋管中Vlasov模式变换器的工作原理,利用等效像源模型结合矢量绕射理论分析了通过此模式变换器的辐射场.考虑W波段边廊模回旋管的具体参数,通过数值计算,讨论了通过Vlasov模式变换器后辐射波束的场分布特性.结果表明,Vlasov模式变换器将回旋管中的高阶边廊模式转换为自由空间的高斯模式,且远场的高斯场型较近场更好.