b_perp

plasmapy.physics.transport.collisions.b_perp(T, particles, V=<Quantity nan m / s>)

Distance of closest approach for a 90 degree Coulomb collision.

T : ~astropy.units.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

particles : tuple

A tuple containing string representations of the test particle (listed first) and the target particle (listed second)

V : ~astropy.units.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.

b_perp : float or numpy.ndarray

The distance of closest approach for a 90 degree Coulomb collision.

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 incorrect

TypeError

If T, or V are not Quantities.

RelativityError

If the input velocity is same or greater than the speed of light.

~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.

The distance of closest approach, b_perp, is given by [1]

\[b_{\perp} =\]

rac{Z_1 Z_2}{4 pi epsilon_0 m v^2}

>>> from astropy import units as u
>>> T = 1e6*u.K
>>> particles = ('e', 'p')
>>> b_perp(T, particles)
<Quantity 8.35505011e-12 m>

[1]	Francis, F. Chen. Introduction to plasma physics and controlled fusion 3rd edition. Ch 5 (Springer 2015).