Berlin 2005 – wissenschaftliches Programm

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DY: Dynamik und Statistische Physik

DY 34: Poster

DY 34.82: Poster

Montag, 7. März 2005, 15:30–18:00, Poster TU D

Interaction Between Dendritic Doublon Tips — •Oliver Wittwer und Jörg Bilgram — Laboratorium für Festkörperphysik, ETH, CH 8093 Zürich, Switzerland

In our experiments we investigate in situ three dimensional pattern formation of xenon crystals during free growth. Well known morphologies are dendrites, dendritic doublons and seaweed. We also observe triplons and quadruplons. The transition from dendrite to dendritic doublon has gained interest since it has been discovered in metallic samples [1]. Transitions between these morphologies can be initiated in our experiments by changing the temperature distribution in the environment of a growing crystal [2].

During the growth of dendritic doublons the two tips are mutually interacting. Three different behaviors induced by this interaction can be observed: 1) Stabilization of the growth velocity of the two tips. 2) Multiple tip splitting. 3) Periodic oscillations in growth velocity where the amplitude is increasing with time. The amplitude is in the range of 20 % of tip velocity. These oscillations have to be compared with the growth velocity of a freely growing isolated dendrite where fluctuations in growth rate (mainly due to pixel noise) are below ± 1.5 % of tip velocity at the same experimental conditions.

[1] K. Dragnevski, R. F. Cochrane, and A. M. Mullis, Phys. Rev. Lett. 89, 215502 (2002)

[2] I. Stalder and J. H. Bilgram, Europhys. Lett. 56, 829 (2001)