impact_parameter_perp¶
-
plasmapy.formulary.
impact_parameter_perp
(T: Unit("K"), species: (<class 'plasmapy.particles.particle_class.Particle'>, <class 'plasmapy.particles.particle_class.Particle'>), V: Unit("m / s") = <Quantity nan m / s>) -> Unit("m")¶ Distance of closest approach for a 90 degree Coulomb collision.
Parameters: - T (Quantity) – Temperature in units of temperature or energy per particle, which is assumed to be equal for both the test particle and the target particle
- species (tuple) – A tuple containing string representations of the test particle (listed first) and the target particle (listed second)
- V (Quantity, optional) – The relative velocity between particles. If not provided,
thermal velocity is assumed: \(\mu V^2 \sim 2 k_B T\)
where
mu
is the reduced mass.
Returns: impact_parameter_perp – The distance of closest approach for a 90 degree Coulomb collision.
Return type: Raises: ValueError
– If the mass or charge of either particle cannot be found, or any of the inputs contain incorrect values.UnitConversionError
– If the units on any of the inputs are incorrectTypeError
– If T, or V are not Quantities.RelativityError
– If the input velocity is same or greater than the speed of light.
Warns: - ~astropy.units.UnitsWarning – If units are not provided, SI units are assumed
- ~plasmapy.utils.RelativityWarning – If the input velocity is greater than 5% of the speed of light.
Notes
The distance of closest approach, impact_parameter_perp, is given by [1]
\[b_{\perp} = \frac{Z_1 Z_2}{4 \pi \epsilon_0 m v^2}\]Examples
>>> from astropy import units as u >>> T = 1e6*u.K >>> species = ('e', 'p') >>> impact_parameter_perp(T, species) <Quantity 8.3550...e-12 m>
References
[1] Francis, F. Chen. Introduction to plasma physics and controlled fusion 3rd edition. Ch 5 (Springer 2015).