為研究磁化電漿中由電子梯度所導致之約電子尺度大小的擾動，本研究研發了具有截止頻率為一百萬赫茲、空間解析度為四毫米的寬頻蘭摩爾探針。在磁化電漿實驗中(MPX)，此探針可滿足電子梯度溫度擾動所需之解析度。此探針可同時量測離子飽和電流及浮動電壓之擾動。
於本研究中我們還完成了可用來計算平面模型下的電子梯度擾動的色散關係式的程式碼，並以磁化電漿實驗的參數代入計算，估得此儀器中產生之電子梯度擾動的頻率約為一百萬赫茲。
我們將寬頻蘭摩爾探針應用在磁化電漿實驗上並試圖量測擾動訊號。對離子飽和電流及浮動電壓二個物理量，寬頻蘭摩爾探針都量測到頻率約為四千赫茲的低頻擾動。值得一提的是，此四千赫茲的擾動訊號只在大磁鏡比時才被偵測到。頻譜分析顯示，此擾動是由交換不穩定所造成。然而此探針並沒有在電子梯度擾動的頻率範圍量到顯著的訊號，這可能是因為我們創造的電漿的電子梯度不夠大。而色散關係式得出的結果同意了這個推論：計算結果顯示電子梯度模式在此次實驗中是穩定的。
利用高能(約三十千瓦)的磁控管系統，我們近期內已開始了電子自旋加熱的實驗，預期此加熱方式可創造很大的電子梯度，使電子梯度模式變的不穩定。

We developed wide band Langmuir probe (WBLP) system to experimentally study electron scale turbulence associated with electron temperature gradient (ETG) mode in magnetized plasma. WBLP is equipped with high cutoff frequency of 1 MHz and spatial resolution of 4 mm which satisfies required resolution to diagnose the ETG instability in a magnetic mirror plasma device, MPX (Magnetized Plasma eXperiment). WBLP can simultaneously measure fluctuations of ion saturation current and floating potential.
A numerical solver of dispersion relation of electrostatic wave in slab geometry including the ETG mode was developed. Parameter survey of this dispersion equation predicts frequency of ~1MHz as the frequency range of the ETG mode in MPX.
We applied WBLP to the magnetized plasma experiment and attempted measurement of fluctuation signal. WBLP detected low-frequency fluctuation signal with frequency of 4 kHz in both ion saturation current and floating potential channels. The low –frequency fluctuation was observed when the magnetic mirror ratio was large. From frequency analysis, it was found that the fluctuation can be explained by flute instability. However WBLP did not obtain significant level of fluctuation signal in frequency band of the ETG mode. This may be attributed to shallow temperature gradient of the plasmas. This conjecture agrees with a result of calculation of the dispersion relation. The calculation indicates the ETG mode in this experiment was stable.
We have most recently initiated electron cyclotron heating (ECH) experiment by utilizing a high power (30kW) magnetron system. It is expected that the ECH produces steep gradient of electron temperature and destabilize ETG mode.

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