Ultracold ions wake in dusty plasmas

Abstract

Motivated by the recent experimental realization of ultracold dusty plasma (2019 Sci. Rep. 9 3261), we present the results of particle-in-cell simulation with Monte-Carlo-collisions for wake behind a dust particle due to focusing of ions at superfluid helium temperature (∼2 K). Dynamical screening (wakefield) defines structural and dynamical properties of charged dust particles in plasmas such as phase transition, crystal formation, vibration modes (waves) etc. Here, we delineate in detail the dependence of wake strength on the streaming velocity of ions and on the ion-neutral charge exchange collision frequency (neutrals density) in the ultracold dusty plasma. Lowering the temperature to ultracold level leads to a wake pattern behind a dust particle that completely differs from the wake at normal conditions. For wide range of parameters, most remarkable features of the wakefield are (i) the formation of wake pattern with two maxima split in transverse to ion flow direction in the downstream area, (ii) pronounced inverse V shape of the wakefield closely resembling the wake in quark-gluon plasma and dense quantum plasma (warm dense matter), and (iii) the inter-dust attraction region in transverse direction. The latter shows that molecule-like interaction between dust particles is realized in ultracold dusty plasmas. These observations show a fundamental difference of ultracold dusty plasma physics from well studied complex plasmas at normal conditions.

Screening of a test charge in a free‐electron gas at warm dense matter and dense non‐ideal plasma conditions

“…This manifests itself in wakefield effects [ 32–34,77–79 ] that are well known in many fields of plasma physics, including dusty plasmas. [ 80–82 ] The study of wakefields around a projectile in quantum plasmas was, so far, restricted to the case r s < 1, due to lack of reliable data for the dynamic local field correction at r s > 1. Recently, Dornheim et al [ 62 ] have developed an effective static approximation for the dynamic local field correction, which provides highly accurate results for electronic properties.…”

Ion energy-loss characteristics and friction in a free-electron gas at warm dense matter and nonideal dense plasma conditions

“…As a final note, we mention that the attraction between like-charged ions is well known in situations out of equilibrium such as in streaming quantum plasmas at < 1. This manifests itself in wakefield effects [32][33][34][74][75][76] that are well known in many fields of plasma physics, including dusty plasmas [77][78][79] . The study of wakefields around a projectile in quantum plasmas was, so far, restricted to the case < 1, due to lack of reliable data for the dynamic local field correction at > 1.…”

Ring dust structures in a weak inhomogeneous magnetic field

“…A voltage is applied to the electrodes, which are located in the lateral branches of the tube. Aluminium oxide (Al 2 O 3 ) particles (density 3.987 g∕cm 3 ) with a size of 1 − 4 𝜇𝑚 were used for the dust structures creation. Dust particles are inside a container located in the side branch of the discharge tube on the anode side.…”

“…Dusty plasma occurs in space and astrophysical environments (e.g., star formation regions, atmospheres and planet rings, and others) and it is actively investigated under laboratory conditions. [1][2][3] In recent decades, the activity of studying dusty plasmas under the influence of weak and strong external magnetic fields has been growing, since magnetic fields play a crucial role in many plasma systems, such as fusion and astrophysical plasmas. The presence of a magnetic field in plasma experiments can have significant impact on such phenomena as plasma drift, [4] dust particle charge fluctuations, [5] dust particle crystallization, [6] filamentation, [7,8] and dust grid patterning.…”