Three-dimensional energy transfer of single particles in...
1
Three-dimensional energy transfer of single particles in dust-density waves 1 Institute of Physics, Ernst-Moritz-Arndt-University, Greifswald, Germany 2 IEAP Christian-Albrechts-University, Kiel, Germany Abstract Dust-density waves occur in a wide parameter regime and have been subject to research for many years. However, experimental access to the three-dimensional single particle motion was only gained recently. There, the particles that constitute the “dust-density wave” or “dust- acoustic wave” can be tracked in 3D on the kinetic level of individual particles. In this contribution we present measurements and simulations of the energy transfer between the different motion components of single particles participating in dust-density waves. Additionally, molecular-dynamics (MD) simulations describing particles in dust- density waves in a given force field have been performed. The energy transfer behavior in the experiment is compared to that from the simulations Financial support from the DLR under 50WM1138 and 50WM1538 is gratefully acknowledged. [1] Microgravity stereoscopy setup 3x Prosilica GE680 cameras @ 640x360 @ 260 Hz moveable camera rig allows adjustment of FoV calibration by imaging of a defined target-grid triangulation from two or three cameras reconstructs particle positions x y z Vertical cut featuring the dust-density waves. The field-of-view is highlighted by the red square. right camera top camera left camera observation- volume Non-orthogonal camera setup, moveable by stepper motors *1 1 2 2 1 M. Himpel , C. Killer , T. Bockwoldt , A. Piel , A. Melzer *[email protected] [1] M. Himpel, C. Killer, B. Buttenschön, A. Melzer; Phys. Plasmas 19, 123704 (2012) [2] M. Himpel, B. Buttenschön, A. Melzer; Rev. Sci. Instrum. 82, 053706 (2011) [3].M. Himpel et al., Phys. Plasmas 21, 033703 (2014) [4] J. Williams and E. Thomas, Phys. Plasmas 14, 063702 (2007) References [2,3] Microgravity measurements Simulated DDWs vs. measured DDWs Phase-resolved energy transfer Velocity distribution functions Wave appearance The kinetic particle energy in a DDW is found to be higher than the neutral gas temperature. The origin of high temperatures is probably the ion stream that heats the particles and the instabilities that lead to self-excited DDWs [4]. The question is, how much kinetic energy of the particles is transferred from the oscillatory to the transverse velocity components. Additionally, phase resolved investigations allow to find the location in the phase-space where the majority of the energy is transferred. velocity (m/s) ×10 -3 -4 -2 0 2 4 count (a.u.) 0 0.05 0.1 0.15 0.2 v x v y v z −20 −10 0 10 20 0 2000 4000 6000 8000 velocity (mm/s) count (a.u.) harmonic harmonic with noise Measured data: bimodal z- distribution shoulder hints to trapped particles Harmonic oscillator: two-peak distribution (without noise) bimodal distribution with Gaussian noise added MD-results: bimodal distribution with positive offset collisions transfer momentum to the v x and v components y phase (frames) a (m/s 2 ) -0.05 0 0.05 harmonic oscillator model results in too narrow peaks MD-simulation gives appropriate peak broadening due to the particle-particle repulsion harmonic oscillator peak is situated in the wave trough MD-velocity peak is closer to the wave crest, which better represents the measurement data harmonic oscillator features a drop of a located at the z wavecrest position MD-simulation features a smoother drop of the particle acceleration [2] Measurement Harmonic oscillator MD-simulation Particle number density Velocity Acceleration phase (frames) height (mm) 20 40 60 phase (frames) the measurements as well as the MD data show that the main energy is transfered to the transverse motion in the wave crest How much of the total energy is deposed in the transverse motion? MD: the transverse energy as a fraction of the total energy is dominant in the wave troughs Measurements: no significant signature present phase (frames) 10 20 30 E transverse /E total 0.08 0.1 0.12 0.14 0.16 phase (frames) 10 20 30 trans. energy (eV) 0.18 0.2 0.22 0.24 0.26 phase (frames) 10 20 30 E transverse (a.u.) 0.4 0.6 0.8 1 Reconstructed three-dimensional particle trajectories. The full phase space information allows detailed investigations regarding the particle motion. Singl particle tracking is done by using fluorescent tracer particles even particles participating in DDWs can be individually tracked approx. 2000 trajectories are reconstructed in each measurement (~10s)
Transcript of Three-dimensional energy transfer of single particles in...
-
Three-dimensional energy transfer of single particles in dust-density waves
1 Institute of Physics, Ernst-Moritz-Arndt-University, Greifswald, Germany2 IEAP Christian-Albrechts-University, Kiel, Germany
Abstract
Dust-density waves occur in a wide parameter regime and have been subject to research for many years. However, experimental access to the three-dimensional single particle motion was only gained recently. There, the particles that constitute the “dust-density wave” or “dust-acoustic wave” can be tracked in 3D on the kinetic level of individual particles.In this contribution we present measurements and simulations of the energy transfer between the different motion components of single particles participating in dust-density waves. Additionally, molecular-dynamics (MD) simulations describing particles in dust-density waves in a given force field have been performed. The energy transfer behavior in the experiment is compared to that from the simulations Financial support from the DLR under 50WM1138 and 50WM1538 is gratefully acknowledged.
[1]Microgravity stereoscopy setup
3x Prosilica GE680 cameras @ 640x360 @ 260 Hz moveable camera rig allows adjustment of FoV calibration by imaging of a defined target-grid triangulation from two or three cameras reconstructs
particle positions
xy
z
Vertical cut featuring the dust-density waves. The field-of-view is highlighted by the red square.
right camera
top camera
left camera
observation-volume
Non-orthogonal camera setup, moveable by stepper motors
*1 1 2 2 1M. Himpel , C. Killer , T. Bockwoldt , A. Piel , A. Melzer
[1] M. Himpel, C. Killer, B. Buttenschön, A. Melzer; Phys. Plasmas 19, 123704 (2012)
[2] M. Himpel, B. Buttenschön, A. Melzer; Rev. Sci. Instrum. 82, 053706 (2011)
[3].M. Himpel et al., Phys. Plasmas 21, 033703 (2014)
[4] J. Williams and E. Thomas, Phys. Plasmas 14, 063702 (2007)
References
[2,3]Microgravity measurements
Simulated DDWs vs. measured DDWs
Phase-resolved energy transfer
Velocity distribution functionsWave appearance
The kinetic particle energy in a DDW is found to be higher than the neutral gas temperature. The origin of high temperatures is probably the ion stream that heats the particles and the instabilities that lead to self-excited DDWs [4]. The question is, how much kinetic energy of the particles is transferred from the oscillatory to the transverse velocity components. Additionally, phase resolved investigations allow to find the location in the phase-space where the majority of the energy is transferred.
velocity (m/s) ×10 -3-4 -2 0 2 4
count (a
.u.)
0
0.05
0.1
0.15
0.2 v xv
y
vz
−20 −10 0 10 200
2000
4000
6000
8000
velocity (mm/s)
cou
nt
(a.u
.)
harmonicharmonic with noise
Measured data: bimodal z-
distribution shoulder hints to
trapped particles
Harmonic oscillator: two-peak distribution
(without noise) bimodal distribution
with Gaussian noise added
MD-results: bimodal distribution
with positive offset collisions transfer
momentum to the v xand v componentsy
phase (frames)
a (
m/s
2)
-0.05
0
0.05
harmonic oscillator model results in too narrow peaks
MD-simulation gives appropriate peak broadening due to the particle-particle repulsion
harmonic oscillator peak is situated in the wave trough
MD-velocity peak is closer to the wave crest, which better represents the measurement data
harmonic oscillator features a drop of a located at the zwavecrest position
MD-simulation features a smoother drop of the particle acceleration
[2]
Measu
rem
en
tH
arm
on
ic o
scilla
tor
MD
-sim
ula
tio
n
Particle number density Velocity Acceleration
phase (frames)
he
igh
t (m
m)
20
40
60
phase (frames)
the measurements as well as the MD data show that the main energy is transfered to the transverse motion in the wave crest
How much of the total energy is deposed in the transverse motion? MD: the transverse energy as a
fraction of the total energy is dominant in the wave troughs
Measurements: no significant signature present
phase (frames)
10 20 30
Etr
ansvers
e/E
tota
l
0.08
0.1
0.12
0.14
0.16
phase (frames)
10 20 30
tra
ns.
en
erg
y (
eV
)0.18
0.2
0.22
0.24
0.26
phase (frames)
10 20 30
Etr
ansv
ers
e (
a.u
.)
0.4
0.6
0.8
1Reconstructed three-dimensional particle trajectories. The full phase space information allows detailed investigations regarding the particle motion.
Singl particle tracking is done by using fluorescent tracer particles
even particles participating in DDWs can be individually tracked
approx. 2000 trajectories are reconstructed in each measurement (~10s)
Seite 1
