Experimental measurement of the confinement potential between a two-particlevertical dust chain*

A dust particle in a 2D crystal structure or 1D chain structure is confined by forces from the
environment, including the interaction force between neighboring particles. This force can be
simplified by modeling it as a linear recovering force, f = kdx , which results from a parabolic
confinement potential kΔx²/2 . The force constant k = mω₀² depends on the experimental
conditions with m the dust mass and ω₀ the dust resonance frequency. Properties of the dusty
plasma system, such as the ion focusing effect downstream of particles in a flowing plasma, alter
the shape of the confining potential. In this case, accurately modeling the force between the
particles requires including higher-order, nonlinear terms. This presentation will discuss
employing probability distribution function and mean square displacement techniques to obtain
the non-linear force terms by analyzing dust particle position fluctuations. As an application, we
will analyze the linear thermal expansion coefficient of a two-particle vertical chain.