Project P6: Collision properties of solids in debris disks at low to moderate impact velocities

碎片盘是由于星子之间的碰撞而形成的，其中碰撞体部分破碎。由于星子及其碎片的强度决定了它们的大小分布，因此研究在碎片盘条件下原行星阶段生长的固体的碰撞结果是必要的。熔化或烧结效应对于不太大的星子来说是相当不重要的，因此碰撞体应该是（亚）微米大小的尘埃和冰粒的聚集体，它们由范德华力和偶极子力结合在一起。我们将在实验室中研究在原行星阶段在碎片盘条件下形成的尘埃和冰聚集体的碰撞物理。特别是，我们将推导出碎片的起始速度，最大碎片等于碰撞体质量一半的速度，碎片的尺寸分布作为冲击速度的函数，以及质量-速度相关性以及灰尘和冰聚集体在mm到dm尺寸范围内碎片的速度矢量分布。为了实现这些目标，我们将利用布伦瑞克实验室现有的实验装置，使碰撞速度达到~ 1米/秒到~ 1000米/秒。因此，我们将推导出一个碎片盘尘埃和冰聚集体的经验碰撞模型，该模型将直接用于P1、P2和P3。除此之外，我们还将为P5提供宽孔隙度范围的样品，进一步研究其光学性质。

Debris disks form due to collisions among planetesimals in which the colliding bodies are partly fragmented. As the strength of the planetesimals and their fragments determines the size distribution, it is essential to study the collisional outcome of solids grown at the protoplanetary phase under the conditions of debris disks. Melting or sintering effects are rather unimportant for not too large planetesimals so that the colliding bodies should be aggregates of (sub-)micrometer-sized dust and ice particles, which are held together by van der Waals and dipole forces. We will investigate in the laboratory the collision physics of dust and ice aggregates formed at the protoplanetary phase under the conditions of debris disks. In particular, we will derive the onset velocity for fragmentation, the velocity at which the largest fragment equals half the mass of the colliding bodies, the size distribution of fragments as a function of impact velocity, and the mass-velocity correlation as well as the velocity-vector distribution of the fragments for dust and ice aggregates in the mm to dm size range. To achieve these goals, we will utilize existing experimental setups in the Braunschweig laboratory with which collision speeds between ~ 1 m/s and ~ 1000 m/s can be achieved. As a result, we will derive an empirical collision model for debris-disk dust and ice aggregates that will be directly usable in P1, P2, and P3. On top of that, we will also provide samples in a wide porosity range for P5 for further investigation of their optical properties.