Internal transport barriers (ITBs), marked by a steep density profile, even stronger peaking in the pressure profile and reduction of core transport are obtained in Alcator C-Mod. They are induced by the use of off-axis D(H) ICRF (ion cyclotron range of frequencies) power deposition. They also arise spontaneously in Ohmic H-mode plasmas once the H-mode lasts for several energy confinement times. Recent studies have explored the limits for forming, maintaining and controlling these plasmas. The C-Mod provides a unique platform for studying such discharges: the high density (up to 8 × 1020 m−3) causes the ions and electrons to be tightly coupled by collisions with Ti/Te = 1, and the plasma has no internal particle or momentum sources. The ITBs formed in both Ohmic and ICRF heated plasmas are quite similar regardless of the trigger method. Control of impurity influx and heating of the core plasma in the presence of the ITB have been achieved with the addition of central ICRF power, in both Ohmic H-mode and ICRF induced ITBs. Control of the radial location of the transport barrier is achieved through manipulation of the toroidal magnetic field and plasma current. A narrow region of decreased electron thermal transport, as determined by sawtooth heat pulse analysis, is found in these plasmas as well. Transport analysis indicates that reduction of the particle diffusivity in the barrier region allows the neoclassical pinch to drive the density and impurity accumulation in the plasma centre. Examination of the gyro-kinetic stability indicates that the density and temperature profiles of the plasma core are inherently stable to long-wavelength drift mode driven turbulence at the onset time of the ITB, but that the increasing density gradients cause the trapped electron mode to play a role in providing a control mechanism to ultimately limit the density and impurity rise in the plasma centre.
内部输运垒（ITBs），其特征是密度分布陡峭，压强分布峰值更强，芯部输运减少，已在Alcator C-Mod中获得。它们是通过使用离轴D(H) ICRF（离子回旋频率范围）功率沉积诱导产生的。它们也在欧姆H模等离子体中自发出现，只要H模持续数个能量约束时间。近期研究已探索了形成、维持和控制这些等离子体的极限。C-Mod为研究此类放电提供了独特平台：高密度（高达8 × 10²⁰ m⁻³）使离子和电子通过碰撞紧密耦合，且Ti/Te = 1，等离子体没有内部粒子或动量源。在欧姆加热和ICRF加热等离子体中形成的ITBs，无论触发方式如何，都相当相似。在存在ITB的情况下，通过添加中心ICRF功率，已实现了对杂质流入的控制和芯部等离子体的加热，这在欧姆H模和ICRF诱导的ITBs中均如此。输运垒的径向位置通过操纵环向磁场和等离子体电流来控制。在这些等离子体中也发现了一个窄区域，其中电子热输运减少，这是通过锯齿热脉冲分析确定的。输运分析表明，垒区粒子扩散率的降低使得新经典箍缩能够驱动芯部等离子体中的密度和杂质积累。回旋动理学稳定性分析表明，在ITB形成时，芯部等离子体的密度和温度分布对长波长漂移模驱动的湍流固有稳定，但密度梯度的增加会使俘获电子模发挥作用，提供一种控制机制，最终限制芯部等离子体中的密度和杂质上升。