Development of a millimeter wave, frequency tunable gyrotron using a permanent magnet system

研制了一种新型、紧凑、高次谐波的回旋管，它具有绕轴电子束和永磁体系统，它基于一种相对较新但研究较少的原理--大轨道回旋管。由于这种器件具有更大的模式分离和选择性，与传统的回旋管相比，可以更容易地获得高次谐波下的单模工作。该装置已被优化为在回旋频率的四次谐波下工作，适合作为毫米波光谱的辐射源。用永磁体代替超导磁体具有操作维护方便、经济、重量小、体积小、供电简单等优点。所有这些有利的特性使所开发的回旋管适用于其他一些需要100 GHz左右的强大便携式辐射源的领域。一种理论研究…在此基础上，对电子束形成和束场相互作用进行了计算机模拟，以研究回旋管在较宽的参数空间内的工作，并选择最佳的工作条件。考虑到可用电源(加速电压在35-40千伏范围内，束流1-1.5安)和可获得的磁场(约1T)的限制，计算结果被用来确定对整个系统的要求。作为计算机辅助设计(CAD)的结果，已经开发出高性能的电子光学系统。它是基于一种新型的电子枪，它使用磁场的逐渐(而不是突然)反转来形成具有适当参数的绕轴电子束。电子光学系统的结构在迭代过程中被优化，在此过程中，电极的几何形状和磁场分布都被改变，以寻找最优的组合。利用实际测量的永磁体内部的磁场分布进行了最终设计，虽然计算得到的场分布与实测场分布有明显的偏差，但基本的束流质量参数(速度比、速度散布和束流波纹)都接近要求。为了修正实际磁体产生的磁场分布，我们计划在最终设计中加入一组额外的线圈进行微调，目前该设计已接近完成。磁路由高级NdFeB永磁体组成。它包括轴向(在谐振腔区域)和径向(在枪和集电极区域)磁化段。利用ELF/MAGIC程序对磁路系统进行了计算机辅助设计。永磁体由信越化学有限公司生产和测量。整个回旋管将由位于北诺夫哥罗德的俄罗斯科学院应用物理研究所制造。较少

A novel, compact, high harmonic gyrotron with axis-encircling electron beam and permanent magnet system has been developed.It is based on a relatively new and less studied principle known as large-orbit gyrotron (LOG). Due to the greater mode separation and, hence, selectivity in such devices a single mode operation at higher harmonics can be obtained easier compared with the conventional gyrotrons. The device has been optimized for operation at the fourth harmonic of the cyclotron frequency and is suitable as a source of radiation in the millimeter wave spectroscopy. The use of a permanent magnet instead of superconducting one has several clear advantages such as easier and more economical operation and maintenance, smaller weight and dimensions, simple power supply. All these advantageous characteristics make the developed gyrotron applicable to a number of other fields where powerful portable sources of radiation with frequency around 100 GHz are needed. A theoretical investigations … More based on a computer simulations of both electron beam formation and beam-field interaction have been performed in order to study the operation of the gyrotron in a broad parameter space and to select the optimum conditions. The results were used to specify the requirements to the entire system taking into account the limitations which stem from the available power supply (accelerating voltages in the range 35-40 kV, beam currents 1-1.5 A) and attainable magnetic field (about 1 T).As a result of a computer-aided design (CAD) a high performance electron-optical system has been developed. It is based on a novel type of electron gun which uses a gradual (instead of abrupt) reversal of the magnetic field to form axis-encircling electron beams with appropriate parameters. The configuration of the electron-optical system has been optimized in an iterative process during which both the geometry of the electrodes and the magnetic field distribution were varied searching for a superior combination. The final design has been carried out using the measured magnetic field distribution inside the real permanent magnet.Although there is a noticeable deviation between calculated and measured field profiles the basic beam quality parameters (velocity ratio, velocity spread and beam ripple) are close to the required. In order to correct the field distribution produced by the real magnet we plan to include a set of additional coils for fine tuning in the final design which is near completion now.The magnetic circuit consists of a high-grade NdFeB permanent magnet. It includes axially (in the region of the resonant cavity) and radially (in both gun and collector regions) magnetized segments. The computer aided design of the magnetic system has been carried out using the ELF/MAGIC code. The permanent magnet has been produced and measured by Shin-Etsu Chemical Co. Ltd. The whole gyrotron tube will be fabricated by the Institute of Applied Physics of the Russian Academy of Sciences in N.Novgorod. Less