Particle Acceleration and Plasma Heating due to Cyclotron Subharmonic Wave

本课题的目的是详细研究我们发现的频率为（n/2）i的回旋次谐波的共振加热特性，在1985财政年度，我们继原先研究的3/2 i共振加热的模拟之后，又进行了5/2 i共振加热的模拟。这项工作是应实验人员的要求进行的。5/2和3/2共振加热之间没有发现任何质的区别，因此，这两种加热机制在本质上是相同的，自1986年以来，MTT的Porkolab试图从与我们不同的角度解释这种加热机制。他提出的机制被命名为非线性朗道阻尼，其特征在于虚波的出现。因此，它在国际上是有争议的，因此我们需要重新审视我们对加热机制的说法。首先，我们证实了它的加热速率随时间的变化具有非线性过程的特征。第二w 关于我们 采用多重时间标度方法，得到了平均粒子轨道的解析解。第三，我们观察到虚波的存在。然而，与泵浦波相比，它的振幅在波能量中约为10%，并且如此之小，以至于虚拟波仅影响约10%的加热。因此，我们认为，本文认为，频率为=（n/2）_i的波在离子粒子轨道的相空间中共振地形成岛，由于粒子被捕获在这个岛中，离子被有效地加速; i层是由于这种俘获而提高离子加速效率的结果，但如果这种加热机制是由单粒子俘获现象引起的，那么加热应该在早期达到饱和。另一方面，如果存在某种能量弛豫机制，这种机制就可以被认为是真正的加热机制，为了验证等离子体中是否存在这种能量弛豫机制，我们在磁场和等离子体密度均匀的简单系统中进行了模拟。我们测试了两种情况：一种是弱的情况，另一种是大振幅的情况。在任一情况下，未观察到加热的饱和。这意味着简单的等离子体系统本身包含着某种能量弛豫机制。最后，我们证明了等离子体中的微小碰撞就是这种能量弛豫机制的结果。少

The purpose of this project is that the property on the resonant heating due to cyclotron subharmonic wave of frequency = (n/2) _i discovered by us is examined in detail.In 1985 fiscal year, we have carried out the simulation on 5/2 _i resonant heating, succeeding the simulation on 3/2 _i resonant heating, originally studied. This work has been requested by the experimentalists. Any qualitative differences are not found out between the 5/2 and 3/2 resonant heating, and therefore, these two heating mechanisms are the same in essence.Since 1986, Porkolab at MTT has attempted to explain this heating mechanism from the different aspect from ours. The mechanism proposed by him is named the nonlinear Landau damping and is characterized by appearance of the virtual wave. Therefore, it is controversial in the world and thus we have needed to reexamine our claim on the heating mechanism.First, we have confirmed that its heating rate in time has shown a feature of the nonlinear process. Second w … More e have an analytical solution of the averaged particle orbit by adopting the method of the multi-time scaling. Third we have observed the existence of the virtual wave. However, its amplitude is about 10 % in the wave energy compared with the pump wave and is so small that the virtual wave affects the heating by only about 10 %. Therefore, the rest part of the heating should be by interpreted in terms of the cyclotron subharmonic heating.Our original claim is that the wave of frequency = (n/2) _i forms islands resonantly in phase space of the ion particle orbit and ion is accelerated efficiently due to a particle trapping in this island and that the resonant feature of the energy deposition around = (n/2) _i layer is the result of the ion acceleration efficiency enhancement due to this trapping.If this heating mechanism results from the phenomenon of the single particle trapping, however, heating should be saturated in an early time. If some energy relaxation mechanism exists, on the other hand, this mechanism can be considered as a true heating mechanism.In order to see whether the energy relaxation mechanism exits in plasma or not, we have carried out the simulations in the simple system where the magnetic field and the plasma density are uniform. We have tested two cases: One is the weak and the other is the large amplitude case. In either case, the saturation of the heating is not observed. This means that the simple system of plasma itself involves some enegy relaxation relaxation mechanism. Finally we have shown that the very small binary collision in plasma owes to this energy relaxation mechanism. Less