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When the viscous drag option is selected, each ion is subjected to
a drag force directed opposite to its motion. This drag force is proportional
to the velocity of the ion:
where b is the damping coefficient.
The viscous drag option is especially useful for two objectives:
- forming crystals
- achieving dynamic equilibrium in the heating cloud regime (recall
that stable equilibria in the heating regime are only attainable
in region
)
by attaining a configuration for which the heating rate equals the rate
of energy loss due to viscous damping (see file cloud9A.trp).
In ion-trapping experiments, laser cooling is typically used when extensive
cooling is required. Although velocity-selective laser-cooling is clearly a more complicated
process, several computational research groups, use the simple
frictional drag force employed by TrapApp as
a suitable ``first approximation'' to laser cooling.[21,12]
Wolfgang Christian
Fri May 12 10:36:01 EDT 1995