The different startup modes of a reversed-field pinch (RFP) are examined and compared. The RFP startup is not the same as startup of other toroidal devices such as the tokamak because of the spatial and temporal variations of the toroidal field and the reversed toroidal field in the outer region of the pinch near the wall. In matched mode startup, used in many RFP experiments today, the toroidal flux is held constant during the current rise, with the field reversal occurring before the peak current. This mode, with its short rise time, has a low volt-second (V⋅s) input but requires a high toroidal voltage to reach a specific current in a relatively short time. In a ramped current mode, alow current RFP discharge is ramped to its final peak value. The toroidal flux needed as the current rises is generated by a dynamo action. This slower startup mode can be driven by a lower voltage but requires more V⋅s input than the matched mode. Different startup modes in the ZT-40M experiment at Los Alamos are compared and an analytic expression is given for characterizing the V⋅s contributions. The resistive component of the toroidal loop voltage during the current rise in ramped discharges is found to depend on theta (Θ = Bpol(wall)/Bϕave)- At a theta of ≅ 1.45, the resistive voltage has a minimum and it has been possible to reduce the V⋅s input by as much as 40% in ramp discharges by keeping theta close to this value.
反场箍缩（RFP）的不同启动模式被考察并比较。RFP的启动与其他环形装置（如托卡马克）的启动不同，因为环向磁场在箍缩外部区域靠近壁处存在空间和时间上的变化及反向。在匹配模式启动中（目前许多RFP实验采用此方式），环向磁通在电流上升期间保持恒定，而磁场反向发生在峰值电流之前。该模式上升时间短，伏秒（V⋅s）输入较低，但要在较短时间内达到特定电流则需要较高的环向电压。在爬升电流模式中，低电流RFP放电被爬升至最终峰值。随着电流上升所需的环向磁通由发电机效应产生。这种较慢的启动模式可由较低电压驱动，但所需的V⋅s输入比匹配模式更多。洛斯阿拉莫斯国家实验室的ZT-40M实验中比较了不同启动模式，并给出了表征V⋅s贡献的解析表达式。发现爬升放电中电流上升期间环向电压的电阻分量取决于theta（Θ = Bpol(壁面)/Bϕ平均）。当theta约为1.45时，电阻电压达到最小值，并且通过使theta保持接近该值，爬升放电中的V⋅s输入最多可减少40%。