Nils Berglund | Trajectories in a mass spectrometer @NilsBerglund | Uploaded October 2024 | Updated October 2024, 3 minutes ago.
This remake of the video youtu.be/O837373mq-Y with particle trajectories was requested by viewers. The simulation illustrates the principle of a mass spectrometer, which is a device allowing to sort charged particles according the their mass/charge ratio.
The particles injected on the left side have an random radius, a mass proportional to their radius squared, and a constant positive charge. There is a constant electric field, directed from left to right, that accelerates the particles. In the middle of the simulation region, there is a constant magnetic field, perpendicular to the simulation plane. The particles interact via a Lennard-Jones potential, and are subject to a viscous drag, in order to avoid numerical instability. The Coulomb interaction between particles has been turned off, however, since otherwise they would not stay in the bins at the right (in practice, one uses more elaborate ways to collect the separated particles).
The particles' acceleration, resulting from the Lorentz force, is proportional to the ratio between their charge and their mass. Therefore, lighter particles are deflected more, and tend to land in lower bins than heavier particles.
The video has two parts, showing the same simulation with two different representations.
With trajectories: 0:00
Without trajectories: 2:44
The particles' color depends on their size.
To save on computation time, particles are placed into a "hash grid", each cell of which contains between 3 and 10 particles. Then only the influence of other particles in the same or neighboring cells is taken into account for each particle.
The Lennard-Jones potential is strongly repulsive at short distance, and mildly attracting at long distance. It is widely used as a simple yet realistic model for the motion of electrically neutral molecules. The force results from the repulsion between electrons due to Pauli's exclusion principle, while the attractive part is a more subtle effect appearing in a multipole expansion. For more details, see en.wikipedia.org/wiki/Lennard-Jones_potential
Render time: 3 minutes 7 seconds with tracers
2 minutes 15 seconds without tracers
Compression: crf 23
Color scheme: Turbo, by Anton Mikhailov
gist.github.com/mikhailov-work/6a308c20e494d9e0ccc29036b28faa7a
Music: "Dusty Finger" by DJ Williams@djwmusic
Current version of the C code used to make these animations:
github.com/nilsberglund-orleans/YouTube-simulations
https://www.idpoisson.fr/berglund/software.html
Some outreach articles on mathematics:
https://images.math.cnrs.fr/auteurs/nils-berglund/
(in French, some with a Spanish translation)
#molecular_dynamics #mass_spectrometer
This remake of the video youtu.be/O837373mq-Y with particle trajectories was requested by viewers. The simulation illustrates the principle of a mass spectrometer, which is a device allowing to sort charged particles according the their mass/charge ratio.
The particles injected on the left side have an random radius, a mass proportional to their radius squared, and a constant positive charge. There is a constant electric field, directed from left to right, that accelerates the particles. In the middle of the simulation region, there is a constant magnetic field, perpendicular to the simulation plane. The particles interact via a Lennard-Jones potential, and are subject to a viscous drag, in order to avoid numerical instability. The Coulomb interaction between particles has been turned off, however, since otherwise they would not stay in the bins at the right (in practice, one uses more elaborate ways to collect the separated particles).
The particles' acceleration, resulting from the Lorentz force, is proportional to the ratio between their charge and their mass. Therefore, lighter particles are deflected more, and tend to land in lower bins than heavier particles.
The video has two parts, showing the same simulation with two different representations.
With trajectories: 0:00
Without trajectories: 2:44
The particles' color depends on their size.
To save on computation time, particles are placed into a "hash grid", each cell of which contains between 3 and 10 particles. Then only the influence of other particles in the same or neighboring cells is taken into account for each particle.
The Lennard-Jones potential is strongly repulsive at short distance, and mildly attracting at long distance. It is widely used as a simple yet realistic model for the motion of electrically neutral molecules. The force results from the repulsion between electrons due to Pauli's exclusion principle, while the attractive part is a more subtle effect appearing in a multipole expansion. For more details, see en.wikipedia.org/wiki/Lennard-Jones_potential
Render time: 3 minutes 7 seconds with tracers
2 minutes 15 seconds without tracers
Compression: crf 23
Color scheme: Turbo, by Anton Mikhailov
gist.github.com/mikhailov-work/6a308c20e494d9e0ccc29036b28faa7a
Music: "Dusty Finger" by DJ Williams@djwmusic
Current version of the C code used to make these animations:
github.com/nilsberglund-orleans/YouTube-simulations
https://www.idpoisson.fr/berglund/software.html
Some outreach articles on mathematics:
https://images.math.cnrs.fr/auteurs/nils-berglund/
(in French, some with a Spanish translation)
#molecular_dynamics #mass_spectrometer
