Spectroscopic investigations of transient processes in self-pulsing microdischarges

对于常压下微等离子体的应用，器件的长期稳定性是前提条件。因此，通常倾向于在稳定的均匀发光模式下操作。对于微等离子体的稳定运行来说，理解从辉光到受限弧光(GAT)的过渡等瞬变过程是至关重要的。等离子体动态过程在几个显著不同的时间尺度上的非线性可能导致在操作模式之间周期性地出现类似的转变。这里研究的微等离子体阵列在微秒时间尺度上显示自脉冲，而微尺度大气压等离子体喷流在毫秒尺度上显示脉冲。就像时间尺度一样，对这种脉冲起源的解释也是不同的。局部热不稳定性可能与介电表面亚稳态或载流子的局部积累一样重要。结合空间和相位分辨光学发射光谱和多光子激光诊断，周期性允许访问其他自毁操作模式，具有高时间分辨率和灵敏度。诊断将与自脉冲频率同步，从而允许研究稳定的运行模式、其间的转换和潜在的不稳定性。

For application of microplasmas at atmospheric pressure long-term stability of the devices is a prerequisite. Thus, operation in the stable homogeneous glow mode is often favored. Understanding of transient processes such as the transition from glow to the constricted arcing operation (GAT) is crucial for stable operation of microplasmas. Non-linearities in the plasma dynamic processes on several significantly different time scales may lead to a periodical appearance of similar transitions between operation modes. The microplasma arrays investigated here show self-pulsing on a micro-second timescale whereas the microscaled atmospheric pressure plasma jet pulses on a millisecond scale. As different as the timescales are the interpretations for the origins of this pulsing. Local thermal instabilities may contribute as much as the local accumulation of metastables or charge carriers at dielectric surfaces. Combined with space and phase resolved optical emission spectroscopy and multi-photon laser diagnostics, the periodicity allows to access otherwise self-destructing operation modes with high temporal resolution and sensitivity. Diagnostics will be synchronized to the self-pulsing frequency allowing the investigation of the stable operation modes, the transitions in between and the underlying instabilities.