# München 2019 – wissenschaftliches Programm

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# P: Fachverband Plasmaphysik

## P 14: Complex and Dusty Plasmas II

### P 14.3: Vortrag

### Mittwoch, 20. März 2019, 11:55–12:10, HS 20

**Classic textbook experiment on entropy in binary complex plasmas** — •Frank Wieben and Dietmar Block — Institute of Experimental and Applied Physics, Kiel University, Kiel, Germany

In physics textbooks a classic example to illustrate the concept of entropy considers two systems that are brought into thermal contact. The change in entropy of the whole system is determined by the initial temperatures and heat capacities of the subsystems and the final temperature. To realize this gedankenexperiment turns out to be difficult since the entropy has to be measured and the two systems have to be brought into contact without creating entropy while removing the barrier itself. In two-dimensional complex plasmas the full phase space information is readily available and thermodynamic phenomena can be studied on the single particle level. In this contribution we reenact this textbook experiment and show that two particle species in a binary complex plasma can serve as two isolated subsystems where the isolation can be switched off instantaneously. Binary complex plasmas contain two particle species of different sizes and materials. The two subsystems are represented by the particle species which attain different temperatures in a laser heating scenario. Due to the nature of the laser forces acting on the particles the temperature ratio can be adjusted by variation of neutral gas pressure. The changes in entropy are determined from phase spaces and results of both experiment and numerical simulation are validated through the heat capacity. This work has been supported by the Deutsche Forschungsgemeinschaft (DFG) in the framework of SFB TR24, Project A3b and Research Grant BL555/3-1.