Static ECE Tomography

磁流体动力学（MHD）不稳定性和扩散机制是核聚变研究中的重要物理问题，电子回旋辐射（ECE）具有强度与电子温度成正比、频率与磁场成正比的优点，可以连续测量局部电子温度，是研究上述问题的有力工具，特别是，由于ECE具有很高的测量精度，因此，ECE具有很好的应用前景。在高温、高密度聚变等离子体中，压力驱动的MHD不稳定性变得更加重要，这些不稳定性往往是局部的，气球模是典型的例子，研究局部MHD不稳定性的理想工具是像照相机一样的二维ECE成像或三维ECE成像（摄像机+频率）。为此，需要一个象电视摄像机那样的二维微波探测器。在本研究中，我们研制了一个平面型微波探测器的元件。该元件的二维成像阵列是一个二维微波探测器。该探测器是一个GaAs芯片，包括一个蝴蝶结天线，一个肖特基势垒二极管（SBD）混频器和一个异质结双极晶体管（HBT）中频放大器。该器件采用单片微波集成电路（MMIC）工艺在GaAs衬底上制作而成。该器件在中频处有大于10 GHz的平坦响应。在紧凑螺旋系统（CHS）中，用聚乙烯透镜从探测器的前侧聚焦ECE，并利用90 GHz的本振产生的本振波（LO），200 mW雪崩管振荡器从背面聚焦，中频经三级放大器放大（共96 dB），并分为4个带通滤波器（1，2，34 GHz），带宽0.3GHz，在T_e= 600 eV，n_e= 2 × 10 ~（-3）/cc的情况下，直流电平为800 mV，信号电平为5 mV<13>，这一结果为ECE成像诊断技术的发展迈出了重要的一步。

Important physics issues of the nuclear fusion research are magnetohydrodynamic (MHD) instabilities and diffusion mechanism.Electron cyclotron emission (ECE) has advantage that the intensity is proportional to the electron temperature and the frequency is proportional to the magnetic field.Since the local electron temperature can be continuously measured with ECE, ECE is the strong tool to study the above issues.Especially, the pressure driven MHD instabilities become more important in the high temperature and the high density fusion plasma.These are often localized.The ballooning mode is the typical example.Ideal tool for the localized MHD instability is the two dimensional ECE imaging like a camera or the three dimensional ECE imaging (camera+frequency).A two dimensional microwave detector like TV camera is necessary for this purpose.In this research we have developed an element of the plane type microwave detector.A two dimensional imaging array of the element is a two dimensional microwave detector.This detector is a GaAs chip including a bow-tie antenna, a Shottky barrier diode (SBD) mixer and a heterojunction bipolar transistor (HBT) IF amplifier.This device is made using the monolithic microwave integrated circuit (MMIC) technology on GaAs substrate.This device has a flat response about the intermediate frequency of more than 10 GHz.The ECE from the plasma in the compact helical system (CHS) is successfully measured with this detector.ECE is focused using a polyethylene lens from the front side of the detector and the local wave (LO), which is generated by the 90GHz, 200mW IMPATT oscillator is focused from the back side.The intermediate frequency is amplified using 3-stage amplifier (total 96dB) and is divided to 4 band-pass-filters (1, 2, 34GHz) with band width of 0.3GHz.The DC level is 800mV while the signal level is 5mV in the case of T_e=600eV and n_e=2x10^<13>/cc.This result is the most important step in the development of the ECE imaging diagnostics.