Ion Trapping Simulation Using High-Performance Fortran
by Susan Fischer, Davidson College, Physics Major
advisors: Ken Hawick and Paul Coddington, NPAC Research Scientists
Project conducted as part of the 1994 Research Experiences for
Undergraduates (REU) Program in High-Performance Computing
conducted by the Northeast Parallel Architecture Center (NPAC)
at Syracuse University.
A computational physics simulation which models the behavior of ions in a
``trap'' was developed to study behavior of ions within Paul traps and
Penning traps, which use electric and/or magnetic fields to confine ions.
The simulation was developed, tested, and
run in Fortran 90, with the intent of porting the application to
High-Performance Fortran when a complete compiler is available. Parts
of the code were tested on ``subset HPF.'' Development of the simulation
and analysis of results required several computationally intense
algorithms, including Gear and velocity-Verlet finite difference methods,
and repeated calculation of long-range interaction forces and potentials.
At this stage of testing, it appears that the
results of the simulation agree with theory.
What is ion trapping?
An ion trap, shown in the figure above, uses some
configuration of electric
and magnetic fields to confine ions to a very small (on the order of
0.001 mm) region of space.
Two types of traps are modeled by this simulation: the Paul trap, which
consists of a static electric potential and an oscillating electric
potential, and the Penning trap, which uses a static electric potential
to confine ions on the z-axis and a strong magnetic field
(up to 5 Tesla, 50000 times stronger than the earth's magnetic field!!)
to confine the radial position.
What are the motivations behind ion-trapping?
In a word, physics research.... confined particles are the ideal
subjects of experiments involving molecular and atomic spectroscopy,
quantum electrodynamics, and plasma behavior.
What do the ions do in an ion trap? What is interesting about
Well, that depends on the experimental conditions, or, in the case of
this simulation, on user-specified simulation parameters.
Depending on parameters which include:
the following behaviors are possible:
- mass of ions
- applied static potential & oscillating potential (Paul trap); applied
static potential & magnetic field (Penning trap)
- trap size
- number of ions
Click here for a summary of the current stage of the project....
- periodic oscillations
- chaotic oscillations
- ions escape
Click here for a detailed (.ps, 9 Mbytes) write-up of the project...
Click here for a detailed (.html, no pictures) write-up of the project...
Susan L. Fischer
Davidson College, North Carolina