Early Planet Formation: A Facility to Study the Time Evolution and Equilibrium States of Multitudes of Interacting sub-millimeter to centimeter Dust and Ice Aggregate Ensembles

行星的形成发生在新形成的恒星周围的吸积盘（原行星盘）中。早期阶段由尘埃和冰聚集体的碰撞生长主导：最初微米大小的尘埃和冰颗粒碰撞，通过表面力粘在一起，形成更大的聚集体，这些聚集体是进一步生长的种子。直到毫米级的碰撞都是由粘性相互作用主导的。然而，亚毫米到毫米/厘米大小的尘埃和冰聚集体碰撞的结果直到今天还不清楚，甚至假设在毫米/秒到厘米/秒的圆盘中典型的碰撞速度是一个碰撞障碍。这可能会阻止进一步的增长（不再粘），也可能是有益的（由较大的机构清扫小聚集体）。因此，行星形成的中间阶段还没有得到充分的理解。最近发现，在实验室中，通过努森压缩机效应使尘埃和冰聚集体悬浮在表面上，可以实现毫米/秒到厘米/秒范围内的亚毫米到几厘米尘埃和冰聚集体的自由碰撞。悬浮的尘埃和冰聚集体之间以mm/s到cm/s的碰撞是经常（每秒几次）可观察到的，并且可以在无限的时间段内获得粘附、弹跳和破碎的概率及其细节。因此，单次碰撞的细节，特别是一个系统的相互作用的尘埃或冰聚集体的时间演化到平衡态的实验accessibility. In内边缘和光学薄的部分的原行星盘尘埃聚集体的主机星星照射。最近还发现，聚集体受到一种能加速尘埃的电泳力的作用。在实验室中有大量的自由悬浮的聚集体，可以进行电泳的研究。在这个项目中，我们在实验室中进行了有和没有电泳影响的碰撞实验：数千个自由相互作用的亚毫米到厘米的尘埃和冰聚集体的时间演化在实验室中是第一次很容易获得的，这将在这里详细研究。

Planetary formation takes place in accretion disks (protoplanetary disks) around newly formed stars. The early phase is dominated by collisional growth of dust and ice aggregates: The initially micron sized dust and ice particles collide, stick together by surface forces and form larger aggregates which are the seeds for further growth. Up to millimeter size collisions are dominated by sticky interactions. However, the outcome of collision of sub-mm to mm/cm sized dust and ice aggregates is till this date unclear, even a emph(boucing barrier) is postulated for the typical collision velocities in a disk of mm/s to cm/s. This might prevent further growth (no more sticking) or might also be beneficial (sweep-up of the small aggregates by larger bodies). Hence, the intermediate stage of planet formation is not sufficiently understood.It was recently discovered that free collisions of sub-mm to several cm dust and ice aggregates within the mm/s to cm/s regime can be realized in the laboratory by levitating aggregates over a surface by a Knudsen compressor effect. Collisions between the levitating dust and ice aggregates with mm/s to cm/s are frequently (several per second) observable and probabilities for sticking, bouncing and fragmentation and their details can be gained over unlimited periods of time. Hence, the details of single collisions and espacially the time evolution towards equilibrium states of a system of multitudes of interacting dust or ice aggregates are experimental accessible.At the inner edge and at the optically thin parts of protoplanetary disks dust aggregates are irradiated by the host star. It was also just recently discovered that aggregates are subject to a photophoretic force which accelerates the dust. Having multitudes of free levitating aggregates in the laboratory, studies of photophoresis are possible.In this project we carry out collision experiments in the laboratory with and without the influence of photophoresis: The time evolution of thousands of free interacting sub-mm to cm dust and ice aggregates is easily accessible in the laboratory for the first time which will be studied in detail here.