本論文主要進行的工作是建置一個僅有環向磁場的教學用微小型托克馬克，並且利用單極蘭摩爾探針去驗證電漿是否約束住電漿。現在組建完成的微小型托克馬克包含幾個物件，分別為圓柱狀的真空腔、交流電源供應器、環型磁場線圈、脈衝形成網路、單極蘭摩爾探針。圓柱狀真空腔的材質為玻璃管，玻璃管直徑為30 cm高度為45 cm。點燃電漿之前會先在真空腔內部通入氬氣並將壓力維持在10^(-1) torr，由交流電源供應器提供振幅~ 1-kV頻率為20 kHz交流電壓，通過真空腔上的電子饋通來產生電漿。此外，環型線圈是由8組AWG-8 導線製成，每組環型線圈的高為400 mm，寬為250 mm的矩形，並且環型線圈作用是用於產生環向磁場。脈衝形成網路系統包含了如下幾個物件，分別為觸發盒、脈衝產生器、火花間隙開關、四階脈衝形成網路。觸發盒是用於觸發脈衝產生器，產生-8.0±0.4 kV的負高電壓，用來觸發火花間隙開關。最終當火花間隙開關運作時，四階脈衝形成網路會釋放出脈衝電流，用於驅動環型磁場線圈。經由放電電流測試，當四階脈衝形成網路的充電電壓為500 V時，釋放出的平均脈衝電流大小為760±80 A，電流寬度為0.9218±0.0004 ms，當此電流驅動環型磁場線圈時，並在距離微小型托克馬克中心處2.5 cm的地方會產生448±5 G的磁場。在未來我們會將四階脈衝形成網路的充電電壓提供到1 kV時，預期可以產生平均~ 1.4 kA的脈衝電流來驅動環型磁場線圈，在距離微小型托克馬克中心2.5 cm處時產生876 G的磁場，供給2.45 GHz的微波，可以透過電子迴旋共振加熱(electron-cyclotron resonance heating (ECH))的方式加熱電漿。最後，我們使用單極蘭摩爾探針去量測電漿特性，在單極蘭摩爾探針上施加0 ~ 50V 的電壓，我們發現沒有環向磁場時，量測到來自電漿的電流大小為4.25~4.89 uA，當有環向磁場產生時，量測到來自電漿的電流大小為0.93~1.61 uA，這顯示了環向磁場約束了電漿，使得更多的電子撞擊單極蘭摩爾探針，造成來自電漿的電流下降，也就是說電漿被環向磁場約束住。關鍵字:托克馬克、磁侷限核融合、蘭牟爾探針、環向磁場、脈衝形成網路。

In this thesis, we built a mini Tokamak with toroidal magnetic field only. A single Langmuir probe was used to verify that the plasma was confined by the toroidal magnetic field. To date, the mini Tokamak consists of a cylindrical vacuum chamber, an AC high-voltage power supply, a set of toroidal magnetic field coils, a pulsed-forming network (PFN), and a single Langmuir probe. The cylindrical vacuum chamber is made of a quartz tube. The diameter of the chamber is 30 cm and the height is 45 cm. The chamber is filled with Ar with a pressure of 10^(-1) torr. To generate the plasma, the AC high-voltage power supply with a ~ 1-kV AC voltage, and a frequency of 20 kHz is used to provide the AC voltage through an electrical feedthrough. Further, 8 rectangular toroidal field coils made of AWG-8 wires with a width of 250 mm and a height of 400 mm are used to generate the toroidal magnetic field. Furthermore, the PFN system is used to provide the pulsed current to drive the toroidal magnetic field coils. The PFN system includes a trigger box, a pulse generator, a spark-gap switch, and the four-stage PFN. The trigger box is used to trigger the pulse generator. The pulse generator generated the pulse with a peak voltage of -8.0±0.4 kV to trigger the spark-gap switch. When the spark-gap switch is activated, the pulse current is delivered to the toroidal field coils. From the discharge test, the four-stage PFN charged to 500 V provided an average current of 760±80 A with a width of 0.9218±0.0004 ms. In other words, a pulse magnetic field of 448±5 Gauss at r = 2.5 cm was generated. In the future, we will charge the PFN to 1 kV and generate the pulsed current of ~ 1.4 kA for toroidal magnetic field coils. Then, the expected toroidal magnetic field will be 876 G at r ≈ 2.5 cm. Therefore, with 2.45-Ghz microwave, electron-cyclotron resonance heating (ECH) can be used for heating the plasma. Finally, the single Langmuir probe with a bias voltage of 0~50 V was used to measure the plasma characteristics. We found that the current flowing into the probe was 4.25~4.89 uA and 0.93~1.61 A without and with toroidal magnetic field, respectively. It indicated that the toroidal magnetic field confined the plasma and more electrons hitting the single Langmuir probe so that the current was reduced. In other words, the plasma was confined by the toroidal magnetic field.
Keyword: Tokamak、Magnetic confinement fusion (MCF)、Langmuir probe、Toroidal magnetic field、Pulse-forming network.

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